A treatise on prospecting : blowpiping, mineralogy, assaying, geology, prospecting, placer and hydraulic mining : with practical questions and examples and answers to questions

Name: A treatise on prospecting : blowpiping, mineralogy, assaying, geology, prospecting, placer and hydraulic mining : with practical questions and examples and answers to questions
Author: International Correspondence Schools

International Correspondence Schools

A treatise on prospecting : blowpiping, mineralogy, assaying, geology, prospecting, placer and hydraulic mining : with practical questions and examples and answers to questions

International Correspondence Schools · 1899 · Historical

A treatise on prospecting : blowpiping, mineralogy, assaying, geology, prospecting, placer and hydraulic mining : with practical questions and examples and…

Public-domain full text preserved in the Mountain Man Mining Library. Original source: archive.org.

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Copyright, 1890, by The Colliery Engineer Company.

BIowpipin)2r: Copyright, 1893, 1S94, 1H9H. by Thk Collikry E.NGirfGF.K Company.

Mineraloifv : Copyrijfht, 1H9S, 18H4, 189H, by TlIE COLLIRRY Hngineek COMl'ANY.

AssayinK : Copyright, IHfti, 1899, by THK CoLMERY KNGINKKR COMPANY.

(leolofefv : Copyright, 1895, 1898. by TiiE COLLIERY ENGINEER Company.

Prospecting: Copyright. 1893, 1895. 1898, by THE CoLLIEKY Knginefk ComI'ANY.

Placer and Hydraulic Mining: Copyright, 1897, by The Colliery Knc.inefr Company

Burr Printing House,

Frankfort And Jacob Streets,

New York.

Preface.

In this volume are included all the Instruction and Ques- tion Papers used in our Metal Prospectors* Scholarship. The information herein contained will enable the prospector to properly locate mining claims, to determine the value of minerals, and to recognize likely regions for prospecting and thus avoid working in wholly unproductive fields. Con- siderable attention is also devoted to the subject of Placer Mining. The Papers are here presented in a neat, concise form, so that they may be carried on trips and always be available for use. This volume gives more information, and gives it in simpler language, than any other book on this subject.

The method of numbering the pages, cuts, articles, etc., is such that each Paper is complete in itself ; hence, in order to make the indexes intelligible, it was necessary to give each paper and part a number. This number is placed at the top of each page, on the headline, opposite the page number; and to distinguish it from the page number, it is preceded by the printer's section mark, §. Consequently, a reference such as §37, page 12, would be readily found by glancing at the inside of the headlines until § 37 is found, and then looking through § 37 until page 12 is found. As this volume has been printed from the plates that were used to print the same Papers in our Metal Mining Course, the plates bear the same section numbers.

The Keys to the Question Papers have been placed at the end of the volume, following the Question Papers. When- ever it has been deemed inadvisable to answer a question, a reference to the proper article in the Instruction Paper has been given, the reading of which will enable the student to answer the question himself.

The International Correspondence Schools.

Contents.

Blowpiping. Section, Page,

Constitution of Matter 34 1

Chemical Elements 34 1

Formation of Chemical Compounds . . 34 44

Chemical Nomenclature 34 14

Blowpiping 34 19

Wet Tests 34 19

Apparatus for Blowpiping 34 21

Blowpipe Reagents 34 32

Examination of a Substance Before the

Blowpipe 34 36

Reduction of Metallic Oxides with Soda . 34 51 Table Showing Colors Imparted to the

Flame by Various Minerals 34 56 Table Showing Colors of Borax Beads in

Oxidizing Flame 34 58

Table Showing Colors of Borax Beads in

Reducing Flame 34 60

Tables Showing Color of Salt of Phos- phorus Beads in Oxidizing Flame . . 34 62 Table Showing Color of Salt of Phos- phorus Beads in Reducing Flame . . 34 64 Table of Characteristic Reactions of

Common Metallic Oxides 34 66

Mineralogy.

Minerals and Their Properties 35 1

Crystallography 35 11

Isometric System 35 12

Ki V

Vi Contents.

Mineralogy — Continued. Section. Page.

Tetragonal System 35 15

Orthorhombic System 35 17

Monoclinic System 35 19

Triclinic System 35 22

Hexagonal System 35 23

Distortion 35 26

Iron 35 27

Copper 35 34

Lead 35 42

Zinc 35 47

Silver 35 52

Gold 35 57

Coal 35 60

Metallic Ores of Secondary Importance . 35 63 Minerals of Secondary Importance . . 35 63 Table of Minerals of Secondary Impor- tance 35 64

Table of Minerals Sent with Blowpipe

Outfit 35 72

Precious Stones 35 80

Table of Precious Stones 35 82

(langue Minerals 35 88

AsSAYIX(i.

Methods of Analysis 36 1

Fire Assaying 36 5

Preparing the Sample 36 5

Weighing 36 10

Furnaces 36 20

Furnace Tools 36 25

Crucibles, Scoritiers, etc 36 28

Fluxes 36 32

Table of Crucible Charges for (iold and

Silver Ores 36 42

(lold and Silver Assav 36 4.5

Scorification Assav 36 4T

Tabic of Scorificr Charges 36 48

CONTENTS. vii

Assaying — Continued. Section. Pme.

Crucible Assay 30 (JO

Calculations 3G 06

Ores of Metallic Scales ;iO 08

Control Assays 30 73

Bullion Assays 30 75

Lead Assav 3(; S2

Wet Assays ' . . 30 85

Apparatus for Wet Assays 30 87

Iron Determination 30 1)3

Manganese Determination 30 111

Determination of Phosphorus 30 113

Lime Determination 30 118

Insoluble Matter and Silica 30 120

Copper Determination 30 124

Lead Determination 30 131

Zinc Determination ... 30 132

Sulphur Determination 30 135

Preparation of Reagents 30 137

Weights and Measures 30 142

GEOLO<iY.

Introductory 37 1

Dynamical Geology . . 37 2

Atmospheric Agencies 37 2

Aqueous Agencies 37

Igneous Agencies 37

Organic Agencies 37 30

Structural Geology :J7 32

Stratified Rocks 37 33

Unstratified or Igneous Rocks 37 4()

Plutonic or Massive Rocks 37 47

Volcanic or Eruptive Rocks 37 51

Structure Common to All Rocks . . 37 00

Mineral Veins and Ore Deposits .37 72

Fossils and Characteristics of the Periods 37

Economic Geology ... .37 100

Materials of Commercial Importance 37 100

viii CONTEXTS.

I )sn:ri i ;. Scctioti. Page.

I*r<*Iiiniii.'iry ICdnralion and Pr('j)araiin . ;{S 1

PrusprrlMis Out fit .'JS 5

hncalinii ul Plater Claims 3S

I.ntalini I.ndt* Claims Ji8 17

Tunmd Silrs 38 20

Mil! Silos . : :58 28

l.otaiin aiul Rocordinjj 38 21

l*ios|ir\'Unj; lor (irms and Pnvitnis Stones 38 31

r ndeu'jinn\l riospoolinji" 38 35

idlnu: 38 30

May;n\'lu Pusprr* ir-v 38 43

X ,

N

Blowpiping.

Constitution Of Matter.

1. It is eminently necessary that the student shall, before taking up the subject of Blowpiping, have some knowledge of the fundamental principles of Chemistry, and for that reason we will here briefly state for his benefit those which we deem most essential.

it

Chemical Elements.

2. A chemical element is a substance which can not be decomposed or divided into simpler substances by any known process. That is, a chemical element is the simplest, or ultimate, form of matter. There are at present (1898) seventy-four recognized elements, or substances that are, as far as we know, elementary. There is no good reason to suppose, however, that these knoivn elements comprise all the elementary substances in existence; in fact, the supposi- tion is rather to the contrary. New elements have been discovered from time to time in the past, the year 1894 witnessing the discovery of two — argon a gaseous element closely resembling nitrogen, and helium an element allied to uranium — and there are various scientific reasons for believing that there is still quite a number of undiscovered elements waiting for genius or accident to disclose them to the world.

It is quite possible that some of the substances which we consider elementary, and place in the list of elements, are

§34

2 Blowpiping. § 34

in reality compounds of two or more still unknown ele- ments.

3. The elements may be divided, like all other matter, into gaseous, liquid, and solid classes, according to their physical state at ordinary conditions of pressure and temper- ature.

The gaseous elements are hydrogen, oxygen, nitrogen, argon, chlorine, and fluorine. The first three were for- merly called Jixcd gdSis as they were supposed to remain in the gaseous state under all conditions, but in the last few years all of them, even hydrogen, the lightest, have been reduced to the form of liquids by the use of enormous pressures and very low temperatures, so that the term has lost its significance and is rapidly falling into disuse.

Only two of the known elements — bromine and mercury (quicksilver) — belong to the liquid class, and the former is very volatile and must be kept air-tight or it will rapidly evaporate at ordinary temperatures. The rest of the known elements are all solids under ordinary conditions.

4. The solid elements may be further classified as mi'tallic and non'metallu\ according to physical peculiarities. Carbon, phosphorus, arsenic, sulphur, boron, tellurium, selenium, iodine, and silicon rank as the non-metallic ele- ments, while the rest of the solid elements are considered metallic. Mercury, also, is classed as a metallic element.

5. The various elements combine among themselves to form chemical compounds, and the elements and their com- pounds constitute all the matter of the universe. By far the greater portion of the elements occur in nature only in combination, and of those that do occur in the elementary form, in the case of only a few — such as gold and platinum among the solids, and nitrogen among the gases — is this form the usual one; and, so far as is known, no element occurs invariably uncombined, or native. The combination of elements is discussed more at length in Arts. 1 1 to 24.

§34 Blowpiping. 8

Atoms And Molbculbs.

A molecule of any substance is the smallest portion of that substance that can exist independently and still preserve its identity. That is, if any attempt is made to still further subdivide the substance, the resultant parts will no longer be of the same character as the original sub- stance. Molecules are in turn made up of still smaller masses of one or more chemical clc merits called atoms.

7. An atom is the smallest portion of an element. With a few exceptions, atoms exist only /// combination with other atoms of the same or other elements, as a constituent of a molecule. (The molecules of mercury, zinc, and cadmium contain only one atom each.) ,

To illustrate the relation between molecules and atoms, we may draw a comparison between a molecule of any sub- stance and some familiar compound, say gunpowder. We will consider a grain of gunpowder as representing a mole- cule. Now, this grain of powder has certain well-defined characteristics, but if we give it sufficient heat it will at once explode, breaking up into gas and a certain amount of solid residue, and neither the gas nor the residue resembles the original gunpowder in the least; but, nevertheless, they were both constituents of the grain, and helped to give it its character; and to this extent they bear the same relation to the grains of gunpowder as the constituent atoms of a molecule do to the molecule.

8. Atomic Weight. — As an atom is a portion of an element, there must, of course, be as many different kinds of atoms as there are of elements; and as the elements themselves are not all of the same density, the weights of the atoms also are variable. Atoms are infinitesimal, and mil- lions of them are necessary to make a particle that is visible to the eye; so, of course, it is impossible to obtain the actual weight of a single atom. The relative weights of the atoms of the known elements have been determined, however, within very close limits. The atomic weight (also known as the combining: relglit) of an element is the ratio of the

4 Blowpiping. § 31

weight of an atom of that clement to the weight of an atom of hydrogen. Hydrogen, being the lightest known element, is taken as the standard for determining atomic weights, and the weight of its atom is considered as unity, or 1.

9. Molecular Weight. — The weight of a molecule of any substance, cither elementary or compound, is, of course, equal to the sum of the weights of the atoms composing it; therefore the molecular i'eigtit of the substance is the sum of the atomic zcdghis of all the elements composing it, each multiplied by the number of atoms of that element in a molecule of the substance. Plements have both atomic and molecular weight, the latter being usually either two, or some simple multiple of two, times the former, as, with only a few exceptions (see Art. 7), a molecule contains at least two atoms; but compounds can have only molecular weight, as they immediately lose their identity as com- pounds if they are broken up into their elements.

Symbols.

lO. For convenience in writing chemical formulas and equations, the various elements may be represented by their chemical symbols. These symbols are merely the initials or an abbreviation of the name of the element, either English or Latin. Table I gives a list of the known elements, and opposite each element is its chemical symbol and atomic or combining weight. The non-metallic elements in the table are printed in heavy type.

Formation Of Chfmicai. Compounds.

CHBMICAI. FOR Mt' I. AS ANI> KOUATIONS.

11, To save the time and trouble of writing out in full the names of compounds, and to facilitate chemical calcula- tions, a svstem of chemical notation has been devised in which the various elements are represented by their symbols, and their relative proportions by subscripts and coefficients.

§34

Blowpiping.

Table I

Names Of Blbmbnts, Their Symbols And Combining

Weights.

Svm- bol.

Combi- i

ning I

Weight '

Aluminum

Antimony (stibium).

Argon

Arsenic

Barium

Bismuth

Boron

Bromine

Cadmium

Caesium

Calcium

Carbon

Cerium

Chlorine

Chromium

Cobalt

Copper (cuprum). . . ,

Erbium

Fluorine

Gadolinium

Gallium

Germanium

Glucinum

Gold (aurum)

Helium

Hydrosen

Indium

Iodine

Iridium

Iron (ferrum)

Lanthanum

Iad (plumbum)

Lithium

Magnesium

Manganese

Mercury

(hydrargyrum) Molyb<lenum

Al

Sb

A

As

Ba

Bi

B

Br

Cd

Cs

Ca

Ce

a

Cr

Co

Cu

E

F

Gd

G

Ge

Au

He

H

In

Ir

Fe

La

Pb

Ain Jfo

K

?)4.oo

13S.30

:?)4.oo

55.f)0

Neodymium

Nickel

Niobium

Xitroijen

Osmium ' . .

Oxyien

Palladium

Phosphorus . . .

Platinum

Potassium (kalium). Proseodymium

Rhodium.

Rubidium

Ruthenium

Samarium

Scandium

Selenium

Silicon

Silver (argentum). . Sodium (natrium). .

Strontium

Sulphur

Tantalum

Tellurium

Terbium

Thallium

Thorium

Thulium ..'.

Tin (stannum) . . . .

Titanium

Tungsten (wolfram)

Uranium

Vanadium

Ytterbium.

Yttrium

Zinc

Zirconium

Sym- bol.

Combi*

ninir Weight.

Av

Nb

N

Os

Pd

P

Pt

K

Pr

Rh

Rb

Rh

Sm

Sc

Se

Si

Ak

Art

Sr

S

Pa

Te

Tr

Pi

Ph

Pu

1)9.40

Sn

Pi

W

U

I'

Yb

y

Zn

Zr

Note. — The elements Neodymium and Proseodymium always occur together, and so they are called Didymium in the tables on blowpipe reactions.

6 Blowpipixg. § 34

1 2. Subscript*. — Subscripts are small figures placed after and slightly below the symb<ls of the different ele- ments of a compound, to indicate the projxjrtion (by volume) of each present, or the number of atoms of each in a mole- cule of the compound. Thus, the formula for sul- phuric acid, indicates that the acid is made up of hydrogen, sulphur, and oxygen, in the proportion of parts (by volume) of hydrogen, 1 of sulphur (when no subscript is given, the subscript 1 isunderstofKl), and 4 of oxygen; or, that a mole- cule of is made up of 2 atoms of //, 1 of and 4 of O. The formula of water (HO) tells the observer at once that water is two-thirds hydrogen and one-third oxygen, by volume. The advantages of such a svstem of notation are obvious. In reading formulas, the subscripts are read, as they are written, after the symbol of the element they modify; thus, is read two, .S', O four."

13 If a parenthesis is placed around the symbols of a group of elements, and a subscript written after the paren- thesis, the subscript multiplies everything within the paren- thesis. Thus, (sesquisulphate of iron) might also characteristic of the sulphates, and acts, in replacing and being replaced by other elements, like a single element, and hence is written in parenthesis, with a subscript correspond- ing to the subscript of a single element whose place it fills. Hy so doing, compounds can be assigned to their proper class — sulphates, hydrates, etc. — at a glance; while the other method, removing the parenthesis and multiplying the various subscripts, would lead to considerable confusion.

A radical is a group of elements (characteristic of a class of compounds) which acts like a single element in replacing or being replaced by elements or in combining with other radicals. As a rule, radicals can not exist by themselves, as the atoms of the elements composing ihem are not com- bined in such j)rop<rtions as lo form stable molecules, and hence the radicals must either break down so as to form stable molecules or thev must combine with each other or

§ 34 Blowpiping 7

with elements so as to form stable compounds. The radical of sulphuric acid, has already been mentioned, and it is this that occurs in sulphates. The radical of nitric acid and the nitrates is NO, and that of the hydrates or hydro- oxides is OH. Thus, ANOis silver nitrate; barium nitrate; KOH is potassium hydrate, and Ca{OH) is calcium hydrate. The radical HO seems to combine with itself to form a compound, H-O-O-H, or which is called hydric peroxide.

14. Coefficient. — Coefficients are numbers placed before symbols of free elements, or formulas of compounds, to indicate the relative amounts of substances under consid- eration. Coefficients may be illustrated as follows : When we wish to write two molecules of water we write 2//,C, or when we wish to write two molecules of hydrochloric acid we write 2HCl the coefficient applying to the entire formula.

15. Chemical affinity is the tendency which all elements possess (to a greater or less degree) to combine with each other and so form chemical compounds. This tendency or attraction is not a constant force, but varies between the different elements; for instance, there is prac- tically no affinity between gold and oxygen, but iron rusts or oxidizes in moist air. The affinity between chlorine and hydrogen is so great that if they are merely mixed and exposed to light (not flame) they will explode with great violence and unite to form hydrochloric acid. The affinity of fluorine for hydrogen is even more intense, and light is not necessary to produce combination and explosion when the elements are mixed.

16. A chemical reaction is a change in the arrangement of the atoms of two or more compounds or molecules so as to form different compounds or molecules. Chemical reac- tions are due to the difference in affinity of the various elements, and usually involve several elements or compounds. These reactions may be represented by chemical equations.

8 Blowpiping. § 34

one side of the chemical equation being composed of the factors which enter into the reaction, and the other side of the factors resulting from the reaction, each factor being preceded by its proper coefficient.

Ordinarily, if two elements or compounds that have an affinity for each other are brought together, they unite to form a new compound; but in some cases this union will not take place at ordinary temperatures or under ordinary con- ditions, and in such cases heat, electricity, or some other agency may be necessary to facilitate the union. As an illustration : If two volumes of hydrogen gas and one volume of oxygen gas are mixed at ordinary temperatures, they would remain in the gaseous condition indefinitely, but should their temperature be elevated, or should the mixture be brought into contact with a flame, they will immediately imite to form water, the formula for which is II fi.

Chemical reactions may be considered under the three following heads: Direct union or synthesis, displace- ment, and substitution or exclianne.

1 1. Direct union or synthesis takes place when an element in the free state comes into contact with another element for which it has considerable affinity, and the two combine to form a chemical compound. In the same way two compounds (or an element and a compound) may unite to form a single new compound. As illustrations of direct union or synthesis, we may mention the formation of water by the union of oxygen and hydrogen, as has already been mentioned. The reaction in this case may be represented by the equation

27/4- c; ///;

but on account of the fact that this reaction does not take

place at ordinary temperatures, some people write the

equation

2//+ c; + heat 77/7

Another illustration of direct union or synthesis has already been mentioned in the formation of hydrochloric acid, the reaction for which may be represented by the equation

H-\-Cl=HCl

§ 34 Blowpiping. 9

The converse of direct union or synthesis is the breaking up or disintegration of simple compounds into their con- stituent elements. Analytical chemistry depends upon the breaking up of the compounds to determine their nature. Many compounds, such as carbonates, sulphides, etc., can be decomposed by heat alone, while others are decomposed by electric currents; as, for instance, water may be decom- p)osed into oxygen and hydrogen, and various metallic salts may be decomposed into the metal and free acid by means of electric currents.

18. Displacement takes place when a free element comes in contact with a compound containing some element for which the free element has a greater affinity than the other constituents of the compound. The free element will immediately form a combination with the element for which it has affinity, and the other element or elements of the compound will be set free or forced to form new com- pounds. This may be illustrated as follows: If metallic zinc and hydrochloric acid be brought into contact in the proportion of two molecules of hydrochloric acid to one of zinc, the reaction illustrated by equation I will take place.

I. Zn + 2//a Zn CI, + 2//

It is by this means that hydrogen gas is usually made in the laboratory. If metallic zinc be brought into contact with a solution of sulphate of copper, the reaction illustrated in equation II will take place.

II. CtiSO -{-Zn ZfiSO + Cu

This reaction is employed for the precipitation of metallic copper, and metallic iron may be substituted for the zinc, in which case sulphate of iron and free copper would be the result. The latter method is frequently employed for the precipitation of copper from mine waters containing sul- phate of copper in solution, the mine waters being led into tanks containing scrap iron. The scrap iron is changed into sulphate of iron (green vitriol) and the copper deposited

10 Blowpiping. § 34

as metallic copper, the sulphate of iron going into the solu- tion and being carried away by the water.

1 9. Substitution or exchange takes place when two compounds come together, the elements of which are so constituted that some of them have a tendency either to exchange places with a portion of those in the other com- pound or else to unite and form new compounds. If lime- stone be brought into contact with hydrochloric acid, the reaction shown in equation III will take place.

III. CaCO + 2//C7= CaCl, + CO + HO

The results of this equation are calcium chloride, carbon dioxide, or carbonic acid gas, as it is sometimes called, and water. This is the reaction commonly used in the labora- tory for obtaining carbon dioxide. Another illustration of this class of reactions is shown in equation IV, in which case iron sesquioxide is treated with sulphuric acid, and the resulting compounds will be sesquisulphate of iron and water.

20. All chemical reactions are included in the prece- ding classification. Occasionally, when a compound is robbed of any of its constituents, the affinity between the remaining elements is not sufficient to keep them together, and they will break up independent of the original reaction.

21. Combining PoiJ-er. — It has been found that the elements always combine in certain definite proportions, and in all the elements which are gases or can be com- bined when in the gaseous state, it has been found that these proportions are by volume; and from investigations which have been carried on, it is fair to assume that all ele- ments combine in proportions by volume when in the gaseous state.

For instance, if one volume of H (hydrogen) combines with one volume of CI (chlorine), they will form two volumes of hydrochloric acid, HCL This law always holds, and each element has a certain combining or holding power; that is,

§ 34 Blowpiping. 11

its atoms can hold in combination or combine with a certain number of atoms of other elements.

Hydrogen has been taken as the standard by which to measure or compare this combining power. The combining power of the various elements is found to range from an equivalent of one atom of hydrogen up to as high as an equivalent of seven atoms of hydrogen. Those that can hold one atom of hydrogen are called monads; if the ele- ment combines with or replaces the equivalent of two atoms of hydrogen or other monad elements, it is called a dyad, and is said to have a valence of two; if it combines with or replaces the equivalent of three atoms of hydrogen, it is called a triad, and has a valence of three; if it combines with four atoms, it is called a tetrad; with five atoms, a pentad; with six atoms, a hexad; and with seven atoms, a heptad.

22. Equivalence or valence may be defined as that property of an element by virtue of which its atom may hold a definite number of other atoms in combination. Hydrogen is always used as a standard for measuring valence.

Hydrogen always has the same valence, while several of the other elements combine in two or more proportions; but if an element has an odd valence, its valence will usually increase or decrease in multiples of two, and hence remain odd; as, for instance, chlorine has valences of one, three, five, and seven, but not two, four, and six, while sulphur has even valences of two, four, and six, but never an odd valence.

To make valence somewhat plainer, it may be stated somewhat as follows: The combining power of the elements may be represented by bonds, and these may be illustrated graphically by short lines. The lines represent the number of bonds and not their direction. H has but one bond, while oxygen has two and carbon four, as illustrated below:

12 Blowpiping. § 34

In a chemical compound, all the bonds are supposed to be satisfied.

23. Radicals have free bonds on account of the fact that the elements composing them are not completely satis- fied, and it is for this reason that they act as elements; for instance, if one atom of hydrogen and one atom of oxygen be combined, we may assume that they would take the position shown below :

in which there is still a free bond, but now if this same H-0- radical be combined with a similar radical, we may assume that they would take the position :

Ho-O-H

in which a free bond of each radical would be satisfied by that of the other, and the formula would become as noted in Art. 13. If to the HO radical we add one atom of hydrogen in place of the other HO radical, we would have obtained the formula H-O-H or which would be water.

24. Nascent State. — By experiment in regard to the molecular weight of gases, it has been found that in hydro- gen gas the atoms are not free, but the molecule is com- posed of two atoms, as //-//, or //,. In the same way the molecules of oxygen gas are composed of two atoms 0—0, or O. (See Art. 7.) It is evident that the forces necessary to hold these molecules together must reduce their ability to combine with other elements; i. e., before oxygen gas can combine with another element, the molecule which is composed of two atoms of oxygen mtist be broken up so that the atoms will ])e set free. The same is true in regard to hydrogen gas, and in this case the reaction may be well illustrated as follows : If ferric chloride be treated with hydrogen gas by passing the gas from a gener- ator through a solution of the ferric chloride, no change whatever in the condition of the chloride will occur, but if the solution of ferric chloride contain free acid — as, for

§ 34 Blowpiping. 13

instance, hydrochloric acid — and then zinc be added to the solution, the reaction that will take place between the zinc and the free hydrochloric acid will be illustrated by equa- tion V.

V. Zn + IHCI ZnCl + %H

but in this case the hydrogen at the moment it is freed will be in an atomic form; that is, it will not be combined into the molecules composed of two atoms of hydrogen, and hence it is free to form any compound that it may. This free hydrogen will combine with ferric chloride as illustrated in equation VI.

It will be seen that this reaction liberates hydrochloric acid from the ferric chloride and reduces the ferric chloride to ferrous chloride. Now, in certain chemical reactions it is desirable to have a solution of iron in the ferrous state, and this may be accomplished as shown by the reactions above. After the reaction is once started, the hydro- chloric acid freed from the ferric chloride would decompose more zinc, and the reaction would be continuous so long as ferric chloride, zinc, and free acid be present.

The fact that the elements are more active at the moment they are freed has led chemists to call this state of an element the nascent state (nascent means being born).

For an experiment to illustrate this, it is well to use a solu- tion of potassium permanganate, which has a dark-red color. If hydrogen from the generator be passed into this solution, no reaction will occur, even though free acid be present, but if zinc and acid be added to the solution, so as to form hydrogen in the solution, the nascent hydrogen will immediately combine with the potassium permanganate to form a colorless solution. The ferric-chloride solution is only slightly yellow, and hence it requires a test to deter- mine the moment at which all the ferric salt has been reduced to a ferrous salt.

14 Blowpiping. § 34

Chemical Nomenclature.

25. In the naming of the chemical elements, the only attempt made at system is in restricting the use of the termination -;/;;/ to the metallic elements, and even to this there are two exceptions, selenium and tellurium; these two elements were originally supposed to be metallic, and the names have not been altered since their non-metallic character was recognized.

In the naming of compounds, however, a definite system has been adopted by which the name of the compound is made to indicate its composition.

26. Binary CompoundH. — The simplest of chemical compounds are those containing only two elements — binary compounds. Such compounds are made up either of a metal and a non-metal or of two elements replaceable by a metal and non-metal respectively, and which may, therefore, for purposes of comparison, be considered as metallic and non-metallic. Thus, hydrogen is replaceable in all acids by metals, and in many of its chemical characteristics resem- bles the metallic elements. Sulphur and arsenic in some compounds are non-metallic in character and in others they have all the chemical characteristics of metals.

27. In binary compounds, the name of the non-metal gives the name to the class, the termination -/V/<* being sub- stituted for the concluding syllable or syllables of the name of the element. Thus, compounds of a metallic element with oxygen are oxides; with sulphur, sulpJiidcs ; with chlorine, c/iloridts, etc. The specific name of the ccn- pound is derived from the metallic element; thus, copper oxide, iron sulphide, silver chloride. Frequently, however, the same elements combine in more than one proportion. Thus, we have two oxides of iron, FeO and Fi\C\, and cor- responding sulphates, chlorides, etc. There are several ways of denominating such compounds. Usually we use the Latin name of the metallic constituent and substitute for the final syllable or syllables the suffix -ic in the names of the compounds in which the proportion of the non-metallic

§ 34 Blowpiping. 15

constituent is largest, and -ous in the names of the com- pounds having smaller proportions of the non-metallic con- stituent. Thus, FeO is the formula for {errous oxide; Fcfi for ferr/V oxide; SO is sulphur(7//j oxide or anhydride; SO is sulphur/r oxide or anhydride, etc. In the higher com- pounds, the same system is also used : CrSO is chromt7j sulphate ; chrom/V sulphate, etc.

28. The use of the names of the Greek and Latin numer- als as prefixes to the class names of the compounds, instead of the suffixes given above, is quite common. The Greek prefixes mono-, di- /r/-, teira- punta- hexa- etc. are most frequently used; thus, FcS is ;;/(7;/(7sulphide of iron; /v5„ //sulphide, etc. The Latin prefixes //;//-, bi-y tcr- qiiadro- etc. are used interchangeably with the Greek, a monowX- phide and a /////sulphide being identical ; or a //oxide and a ///oxide. The prefix /r(7/c?- is frequently applied to the class name of the one of two or more compounds of the same ele- ment which contains the lowest proportion of the non-metal, and per- to the one containing the highest proportion. Thus, SnCl is/n;/t;chloride of tin, or stannous chloride, and SnCl is /d'rchloride of tin, or stannic chloride.

29. Iron, aluminum, chromium, manganese, nickel, and cobalt form, besides the regular series of oxides and corre- sjxnding compounds in which the valence of the metals is even — two, four, and six — another series in which the valence is apparently odd — three — called .ye'.y(////oxides, sesqui- sulphates, etc., the combining proportion of the non-metal to the metal being as 3 to 2; as/t/?3, (chromium sesquihydrate — or chromic hydrate — two volumes of OH being equivalent to one of O), etc.

30. A compound in which the metallic constituents are in less than the normal proportion (in other words, in which the valence of the metallic element is less than its minimum normal valence) is distinguished by the profix sub- to its class name. Thus, in suboxide of copper {CtiO), copper, which is ordinarily a dyad or tetrad, has an apparent valence of 1.

16 Blowpiping. § 34

31 Acids*. — An acid is a compound of hydrogen with one or more other elements, in which the hydrogen is replace- able, wholly and in part, by a metallic element or a group of elements equivalent to a metal. As a class, acids have a sour {acid) taste, and most of them turn certain vegetable colors red — notably in the case of blue litmus, which gives a very delicate test for the presence of an excess of acids.

Certain oxides, when dissolved in water, combine with it chemically and form acids. Oxides having this property are called anhydrides, a term meaning containing no water or hydrogen. " The following equation illustrates the reac- tion between sulphuric anhydride and water:

SO + HO H,SC\ (sulphuric acid)

The term acid is sometimes used in reference to anhy- drides, as carbonic acid gas " but this usage is being abandoned.

32. Acids containing oxygen are called oxy-acids or oxacids to distinguish them from a group of binary acids containing no oxygen, which are known as hydr acids — hydrochloric acid (HCl), hydriodic acid {HI), hydrofluoric acid {HF), hydrosulphuric acid or sulphureted hydrogen (//,.V), etc.

When an element forms more than one oxacid, the termination -ous is applied to the name of the acid in which the proportion of the oxygen to the characteristic element is smaller (or, to be more exact, to the one in which the characteristic element has the lower valence, the distinction depending rather upon valence than actual proportion), and 'ic to the more highly oxidized acid.

33. Bases. — A base is a compound — usually an oxide or a hydrate of a metallic element, or of a radical equivalent to a metal — which is chemically opposed to acids in all its reactions and characteristics. Certain bases in which the distinctive chemical characteristics are very marked are called alkalies. They neutralize acids, restore the blue color to litmus reddened by acids, and turn yellow turmeric

§ 34 Blowpiping. 17

paper to a reddish-brown color. The most familiar alkalies are caustic soda and caustic potash (sodium and potassium hydrates — NaOH and KOH) and ammonia (ammonium hydrate — NHjOH). The metallic constituents of these compounds belong to a group known as the alkali metals consisting of sodium, potassium, lithium, rubidium, caesium, and the metallic radical ammonium The metals of this group and their oxides combine with great readiness with water, forming strongly alkaline hydrates — all except lithium bursting into flame on being wet or thrown into water — and ammonia gas dissolves with remarkable rapidity in twice its weight of water, forming a hydrate. The gas may be completely expelled from the water by heat- ing, and is liberated to a considerable degree at ordinary temperatures. The alkalies impart a peculiar soapy taste and feel to water.

The alkaline earth metals barium, strontium, calcium, and magnesium, have many characteristics in common with the alkali metals. The basic compounds of this* group are less soluble, however, and their alkaline reactions are less pronounced.

34. Salts. — A salt is a compound produced by the replacement of part or all of the hydrogen of an acid by a metallic element or an equivalent group of elements. Many metals are directly soluble in acid, the reaction giving a salt of the metal and liberating hydrogen gas, thus:

Bases (oxides and hydrates) react with acids, the metal of the base interchanging with the hydrogen of the acid, form- ing a metallic salt and water, thus:

FeO + "IHCI FeCl, -\-Hfi or iNHfiH + HSO, (AV/J, SO, + "iHfi

The salts of the alkali metals are all soluble, hence they do form precipitates, except in very highly saturated solutions.

18 Blowpiping. § 34

35. The salts of the hydracids are essentially binary, and take the binary termination -ide — chloride, fluoride, sulphide, etc. The salts of the lower or -cms oxacids take the termination thus:

(sulphurous (sodium

acid) sulph/'/r)

The salts of the higher or -ic oxacids take the termination atCy thus:

'IHNO + PbO Pb{NO,), + Hfi

(nitric acid) (lead xiWrate)

Oxidation And Rgouction.

36. Oxidation, strictly speaking, is a reaction by which a substance takes up oxygen, or is actually oxidized the proportion of oxygen to the metallic constituent being increased. In its chemical sense, however, it applies not only to reactions in which there is an actual increase in the proportion of oxygen, but also to all analogous reactions in which there is an increase in the proportion of the non- metallic constituent. Thus, any reaction by which ferrous chloride (FcCt is converted into ferric chloride (PcC/), or ferrous sulphate {FcSC\) is converted into ferric sul- phate [fi\(SO)], is, chemically speaking, just as truly ox- idation as the reaction by which ferrous oxide (FcO) is con- verted into ferric oxide though in the first case there may have been no oxygen in any of the reagents used.

In blowpiping, however, oxidizing reactions are usually attended by actual or an increase in the propor- tion of oxygen,

37. Reduction is the opposite, or inverse, of oxidation; that is, a reducing reaction is one by which the proportion of non-metallic constituent to the metallic constituent is decreased.

38. Oxidation and reduction always occur simultane- ously ; that is, an oxidizing reaction is at the same time

§ 34 Blowpiping. 19

reducing, for what one reagent gains it must take from another, either directly or indirectly, and the second reagent is therefore reduced. The reaction is termed oxidizing or reducing, according as the principal product to obtain which the mixture of the different reagents was made, is the result of oxidation or reduction.

Blowpiping.

39. The purpose of blowpiping is to furnish a rapid method for the determination of the approximate composi- tion of minerals and ores. In general, blowpipe determina- tions are merely qualitative — that is, they indicate the presence different constituents, but not Xh proportions. In the cases of a few of the metallic elements which can be completely reduced from their minerals before the blowpipe, by methods to be described later, a rough idea of the pro- portions may be gained; but these results are not at all accurate, on account of the roughness of the method and the losses through volatilization. To determine with any accuracy the percentage composition of a chemical com- pound, the more elaborate methods of quantitative analysis must be used.

40. A mineral is a free native element or an inorganic compound occurring in nature. In this sense, not only are the solid rocks minerals, but water is also a mineral.

Wet Tests.

41. In ordinary chemical analysis the substance to be tested must first be brought into a liquid form by dissolving in acids, and the different constituents then precipitated by means of proper reagents; but by the use of the blovvpii)c for qualitative analysis, the reactions by which the different constituents are recognized are gotten directly from the substance tested, without previous sohition. There are certain simple wet tests, however, which are universally

20 Blowpiping. § 34

used in conjunction with the blowpipe tests, and have come to be considered a part* of blowpipe practice. These tests are mainly of the solubility of the substances in the common mineral acids — hydrochloric (//C/), nitric and sulphuric (IfSi\) — and the phenomena attending the com- plete or partial solution.

42. For testing with acids, a mineral should first be powdered; a little of it is then placed in the bottom of a test tube, or matrass, and well covered with the acid. The most important points to be observed are, first, its solubility — whether slow or rapid, complete or incomplete, or whether soluble at all, and whether heating is necessary for the solution; and second, the attendant phenomena — whether a gas is evolved, producing bubbling or effervescence, or a solution is formed without effervescence, or whether a precipitate is formed or an insoluble constituent separated.

43. Hydrochloric acid is the acid most frequently used in testing the solubility of a mineral, though in the case of compounds of lead, silver, and mercury, nitric acid is required, as these metals form insoluble chlorides with HCL Sulphuric acid is the acid least used as a solvent. Dilute acids are generally used. Minerals which are insoluble or only partially soluble in either HCl or HNO alone, are usually soluble in aqua regia, which is a mixture of 3 parts of IICl with 1 part of IIXO.

Rkactions Op Diffkrknt Minbrals In Acids.

44. Carbonates. — All carbonates dissolve in acids, liberating 6'(, carbonic acid gas") with lively efferves- cence (see equation III, Art. 19). With many carbonates the solution will take place in cold acid, but with some it is necessary to heat the acid to obtain the reaction, as in the case of magnesite (magnesium carbonate), dolomite, and siderite. Dilute IICl is generally used for the tests. HNO gives the best results with lead, coi)per, and zinc car- bonates.

§ 34 Blowpiping. 21

45. Sulphides. — When metallic sulphides are dissolved in HCl or HSO, the gas HS (sulphureted hydrogen) is liberated. This is a colorless, highly poisonous gas, very readily recognized by its characteristic odor, which is that of rotten eggs.

Many sulphides, when treated with boiling HNO, decom- pose, forming a metallic nitrate or oxide, and liberating sulphur, which separates as a white or yellowish precipitate.

46. Silicates. — Many silicates, when finely powdered and treated with boiling concentrated HCl or are decomposed, the silica separating as a gelatinous precipitate or as a fine powder. Many silicates are unaffected by acids.

47. Oxides. — The majority of the mineral oxides are soluble in acids. HCl alone will dissolve most of them, and there are several more that are soluble in HNO or in aqua regia. There are a number of oxide minerals, however, which refuse to yield to the solvent powers of acids, as the minerals corundum {Alfi, spinel {MgAlO), chromite rutile {TiO)y cassiterite (SfiO), quartz (5/(9,), etc.

48. Besides the insoluble silicates, there are a number of other minerals that are insoluble in acids; mostly, how- ever, of rather unusual occurrence, as titanates, tantalates, columbates, etc. Among the commoner insoluble minerals are barite, celestite, and anglesite — the sulphates of barium, strontium, and lead, respectively — and many phosphates.

Apparatus.

THE BLOl'PIPB.

49* The blowpipe has been employed for a very long time for producing an intensely heated flame, and in later years its use has been extended by such eminent men as Gahn and Berzelius to the determination of minerals and to the preliminary examination of substances before analyzing them quantitatively.

Blowpipixg.

§34

50. There have been numerous modifications of the blowpipe. In its simplest form it is a conical curved tube of brass, terminating in a small orifice about the size of a needle point. This form of blowpipe is not very satisfac- tory, however, as the moisture which con- denses from the breath is, after blowing some time, thrown into the fiame, and becomes very troublesome, and the better forms of blowpipes are all supplied with some sort of enlargement at the turn, to act as a moisture reservoir.

The most improved form of blowpipe is shown in Fig. 1. It consists of four parts: the mouthpiece /, made of hard rubber or bone, which pnssiti agatpisf the lips and is so large as not to tire the operator; the tube J, which fits by a ground joint into the moisture reservoir J; and the tip- holder 4, fitting by a ground joint into the reservoir; on the other end of the tip- holder is soldered a small disk or tip of platinum foil, pierced in the center by a very fine hole. Some varieties of blow- pipes have detachable conical tips of platinum, fitting onto the tip-holder with ground joints; these are considerably more expensive, however, than the form described, and no better; and the tips are small and apt to get lost, and new tips cost ()() cents apiece. A plain brass blowpipe of the form illustrated in Fig. 1 (the Plattner pattern) costs about II.oO. The pipe can he taken to pieces for packing. The trumi)et mouthpiece is especially desirable as it makes the use of the blowpipe much less tiring to the operator than it would be without it.

rn;. I

51. A much cheaper blowpipe (costing about 25 cents) is shown in Fig. 2. It is made of japanned tin, with the parts brazed together. It is just as satisfactory for pro-

Blowpiping.

a good flame as the Plattner p piece has to be inserted between tl fatiguing, and which necessi- tates the large moisture reser- voir, as the saliva passes into the pipe — something; which ran not happen when i mouthpiece is pressed oi against the lips. fcg. a

52. The Blast.— The success of the blowpipe as a means of qualitatively determining the ingredients of a compound depends upon its careful manipulation. As a necessary condition, the operator must frequently main- tain an uninterrupted stream of air for several minutes at a time, and must be able at will to produce an oxi- dizing or a reducing flame, two diametrically opposite chemical effects. Considerable practice is necessary to cultivate a proficiency in this, and no determinations should be undertaken until the operator has become some- what expert.

The blowpipe is held in any convenient and comfortable position, usually between the index finger and the thumb, as a pen is held, with the arms resting against the edge of the table. The operator chooses his own position.

53. The blast is produced by the contraction of the cheek muscles, and is not furnished directly from the lungs. The mouth is filled with air. distending the cheeks, not, however, to an uncomfortable degree; then the throat is closed and the operator continues to breathe naturally through his nose, while the air in the mouth is slowly and gently forced out through the blowpipe by the contraction of the distended cheeks. From time to time, the throat is iipcncd for an instant to renew the air supply in the mouth, and then immediately closed again. It is advisable to practice at first without a flame, until the knack of breath- ing and blowing at the same lime is acquired.

The beginner generally commits thcerrors of blowing too

u

Tpiping.

hard and not shutting off the connection between chest and mouth. In the first case it will be well to remember that very little more force is necessary to produce the blast than naturally results from the contraction of the cheek muscles after 1)eirig distended; and the second method of blowing will prove injurious to the health. Never, under any cir- cumstances, draw air into the mouth through the pipe. If this were done with the pipe in the flame it might result seriously.

Blowpipe I.Amp8 And Fuels.

S4. Bunsen Uurnr. — The most convenient fuel for blowpipe operations is illuminating gas, and the burner best suited for the purpose is the Bunsen burner shown in Fig. 3. There are various forms of these burners, the essential feature being the mixture of air with the gas before combustion, but the one shown is the most commonly used.

The neck a is connected to the gas fixture by rubber tubing. The tube t screws onto the body of the lamp and the gas flows up into it through a small , tube, or tip, /', which is flattened at the top so that the gas issues from a mere Pn, g slit about a quarter of an inch long.

Near the bottom of the lube / are two holes c, and there are corresponding holes in a short sleeve s, around the base of /. A small guard-ring r keeps the sleeve s in position. By turning the sleeve, the quantity of air passing into / and mixing with the gas can be regulated. When the openings in the sleeve are between the openings in the tube, the blank spaces in the sleeve cover the open- ings in the tube and exclude all air, and the gas burns at the top of the tube / with- the ordinary yellow, luminous

; but if theslef

; be tu;

the t

e will be partly uncovered and ;

ed a little, the openings in

1 rush in and

mix with the gas, and the flame will become hotter and less luminous, and by opening the air-holes the proper amount a clear, blue, non-luminous flame is obtained, which is very hot. If there is very little dust in the air, ibis flame can sometimes be gotten so clear as to be invisible against a dark background. If too much air is admitted it is apt to blow the flame out, or off the burner. This colorless gas flame is very convenient for making the flame tests described further on. For blowpiping, however, a yellow flame about inches high is used, the blowpipe furnishing the neces- sary oxygen for perfect combustion.

55. In some forms of burners the regulating sleeve is not provided, and in order to get a yellow flame a second tube, whose outside diameter corresponds to the bore of the tube f, is slipped inside of /, shutting off the air. By flatten- ing this tube at the top into a narrow slit, and cutting il at a slight angle, lengthwise of the slit, instead of hori- zontally, a flat flame like that of an oil lamp is obtained. Flattened tips are also made to set on the top of the ordi- nary Bunsen burners to get a flat flame for blowpiping, and specially designed blowpipe burners with flat-tippecl tubes are also made.

56. Oil and Spirit Lamps, Etc. — The oil and spirit lamps for blowpiping are of various patterns. They are made of both metal and glass, and with single and double wicks. The oils used in blowpipe lamps should be rich in carbon. Kerosene, refined rapeseed oil, olive oils, and mix- tures of alcohol and turpentine, and alcohol and benzine are v;iriously used in lamps, but none of these is as satisfactory as illuminating gas, burned in a Bunsen burner.

Spirit lamps can be used for some blowpipe tests, but alcohol is comparatively poor in carbon and its flame is not very hoi, and it is impossible to obtain a strong reducing flame with it. It is very convenient, however, for flame tests.

Candles are sometimes used for blowpiping when no better flame is obtainable, but they are rather unsatisfactory, as the water in the tallow or wa.t cools the flame and makes it sooty.

28 Blowpiping. §34

combustion of the volatilized tallow at c in the same way as the air through the ports of a Bunsen burner affects that of the gas. The mixture of gas and air burns with a pale-blue, non-luminous flame, to CO, CO, and JIO (water vapor). The outside cone a, in which all the carbon has burned to CO, is unaltered. This flame is called the oxidlzlnsr flame — abbreviated to O. F. in the text — and a substance held at the tip of the outer cone, where the air can get at it, but away from any possible reducing action of the CO in the cone h, will be rapidly oxidized.

60. The oxidizing flame is also used for flame tests, on account of being colorless, and for melting, as it is the hot- test flame obtainable with the blowpipe. The hottest point of the flame is just beyond the tip of the inside cone c.

Note. — To test the oxidizing flame the student can prepare a borax bead and add a little manganese* mineral to the same. As long as the bead is kept in the oxidizing flame it will remain violet when hot and reddish-violet when cold. But the reducing flame will clear the bead and render it colorless both when hot and when cold.

Supports.

61. The materials to be examined before the blowpipe are supported by certain substances which are either infusi- ble or are capable of withs-'tanding a high heat without appreciably changing their form.

62. Charcoal. — For roasting, obtaining coats, redu- cing metals, and making sulphur tests, charcoal is the sup- port used. A wood that gives a dense coal, with very little ash, is used for making the charcoal. Charcoal can be bought in specially prepared blocks or sticks, of convenient size for blowpiping, for fifty cents a dozen, and in this form is much more satisfactory than lump charcoal. Artificial charcoal, made of charcoal dust, compressed into sticks, is also used. If the artificial charcoal gets damp, it is liable to explode with considerable violence on heating, from the impossibility of the steam escaping fast enough ; if such charcoal is slowly dried out for several hours over a stove, it will no longer cause trouble. A small hole is bored with a knife-blade

§ 34 Blowpiping. 29

into the charcoal, for holding the assay, which is moistened if it tends to blow away. Old coats are scraped off with a knife, leaving the coal ready for reuse.

63. Platinum Wire. — For holding the borax beads, platinum wire — No. 27 (or jeweler's hole 12.}) — is used, as platinum withstands the high heat and is unaffected by the reagents or flame. Pieces about 2 or 3 inches long are used, held, preferably, in special wire-holders that are made for the purpose (costing about $1), or else one end is fused into a short piece of glass tubing for a handle, or held in the forceps.

64. Piatinum Foil. — For testing for manganese and chromium, a small piece of platinum foil is employed. Care must be taken not to fuse metals like lead, zinc, tin, nickel, copper, or silver on it, nor should compounds of these metals be treated on platinum foil or wire in the R. F., as the metals reduce and form a fusible alloy the infusible platinum.

65. Forceps. — For testing the fusibility of minerals, the platinum-pointed forceps shown in Fig. 7 are used ;

Fig. 7.

they have a pointed steel forceps at the other end that will be found very convenient. Such forceps cost about <52.25 a pair.

For trimming the flame and for rough work, the fig. 8.

iron forceps shown in Fig. 8 are used. They cost only ten or fifteen cents.

66. Glass Tubes. — Open tubes, of hard glass, free from lead, from inch inside diameter, and from 4 to 6 inches long and open at both ends, are used in the exami- nation of substances to be ignited in a current of air. The tube is sometimes bent slightly an inch or two from one end, to keep the body under examination, which is placed in the bend, from falling out.

30 Blowpiping. § 34

Closed tubes are used for the ignition of bodies in a lim- ited supply of air. They are made of the smaller sizes of tubing, ,V i ivich bore, and closed at one end. They are usually made by heating in the middle a tube of twice the desired length, turning it slowly in the flame so that it will be uniformly heated all the way around, and when it is soft and pasty, pulling it out at both ends, into two closed tubes. The filament of jlass on the bottom of each tube can be melted up into the tube by directing the flame on it for a moment, giving a smooth bottom.

A clean tube should be used at each new operation. Tubes may be cleaned by swabbing with soft paper wrapped around a wire.

67. Matrae8. — Glass matrasses are used for testing for acids by fusion with potassium bisulphate, etc., and are

also frequently used for the same purposes as are closed tubes. They are of the form shown in Fig. 0 — practically only a closed tube with the closed end blown into a bulb. An ordinary, straight, closed tube, about 4 inches long and -inch bore, is a satis- factory substitute for a matrass, or the student can blow a bulb on the end of such a tube and have a '' " matrass or bulb tube which will answer his purpose fully as well as the matrasses he might buy. For holding matrasses, special holders with wooden handles are made, but a strip of paper, folded lengthwise several times and held around the neck of the matrass, with the ends serving as a handle, will answer the purpose.

68. Test TubeH. — Test tubes are used in making wet tests, boiling in acids, effervescence, etc. They are straight glass tubes, closed at one end and with a lip on the open end, and are made of thin, hard glass, that will stand con- siderable heat without cracking. A test-tube rack, in which the tubes can be stood u[)right, is also necessary. A holder, for holding tubes while heating, is convenient, but a slip of paper, used as described in Art. 67, will answer.

Blowpiping.

ACCEHSORV APPARATtlS.

9, Mortars.— A small agate mortar and pestle are used for reducing materials to a very fine powder. The lubstance should be powdered by grinding, and never iwunded in this mortar, as the mortar is liable to be dam- aged,

A diamond mortar and pestle, made of the very best tool siee! and very hard, are used for crushing minerals and for

I Fig. 10, The bot-

flattening beads. One form is shoi torn of the mortar is used as an anvil, while the mortar and pestle are used for crushing hard and brittle minerals, as they pre- vent the loss of pieces by flying out. Such a combined anvil and mortar costs from fi to t,4.

70. Hammer. — For knock- ng chips off of minerals, flattening beads, stamping cupels, :tc.. a small hammer is necessary. Any small, square- headed hammer, with sharp corners and made of good steel, will do.

71. Pllerit.— Cutting pliers are useful in detaching fragments from mineral speci- mens.

72. File.— A small three-edged file is necessary for cutting glass lubes.

73. Cupel Mold and Htand.— For

making the cupellation assay, special iron ..r steel molds [{,t), {a), Fig. 11] are used. After filling these loosely with finely ground bone-ash, moistened with a little water in which a. little carbonate of soda has been dissolved, the die is placed on top, and then given two tir three smart blows with a hammer, producing a nice, smooth cupel. Cupels should be thoroughly dried before using. The mold with its cupel is set on a stand (r) with

34 Blowpiping. § 34

name is usually shortened to soda. The purest must be used, otherwise it will be apt to give a sulphur reaction; and every new lot should be tested before using to insure its freedom from sulphur (in the form of sulphate of soda). On account of its lightness, it is apt to trouble the beginner by blowing off of the charcoal; but if a very gentle flame is blown on it until it is melted, the strong blast can then be used without any trouble. A gas flame should not be used in testing for sulphur, as it always contains enough sulphur to give a reaction.

81. Cobalt Solution. — For certain tests, a dilute solution of nitrate of cobalt is employed. The substance is moistened with the solution (preferably with a dropping tube), strongly heated on charcoal for about 5 minutes, and then allowed to cool, when different colors result. The colors of certain minerals under this test are very charac- teristic.

82. Niter. — For a few special tests, niter (sodium or potassium nitrate) is employed on account of its powerful oxidizing effect. While either potash or soda niter can be employed, the former is better.

83. Copper oxide, in the form of a powder, is used in testing for the haloid (chlorine, bromine, and iodine) salts.

84. Bismutti Flux. — F(;r testing for lead and bismuth, a special flux is made u[) (f one part each of iodide and bisulphate of potash and two parts sulphur, which are ground together. Two to four parts (by volume) of this flux are mixed with ope of the substance, and heated on charcoal, when bismuth gives a brick-red coat, and lead a yellow coat close to the assay, and greenish beyond. The flux itself gives a white coat, but does not interfere with the above.

85. Test Lead. — For the silver-cupellation assay, finely granulated lead, known as test lead, is employed to collect the silver into a button preparatory to cupelling. It usually contains more or less silver, and should be tested by cupella- tion before using.

Blowpiping.

86. Bone-ash is employed for making the cupels; it is made of calcined tiones, hoofs, and horns, ground to a fine powder.

87. Tlo. — For obtaining a strong reducing action, finely ground metallic tin or tin shavings are sometimes used,

88. Blsulpbate of potasb (KHSOJ, in the form of crystals, is used in testing for acids.

89. Acid.~Hydrochloric acid {NC/), sulphuric acid {/iSO,), and nitric acid (HNO,) are necessary in blowpiping. As a rule, the strongest sulphuric acid should be used, while the hydrochloric and nitric acids should be of only medium strength. All these acids should be kept in glass-stoppered bottles, as they corrode and destroy corks,

90. Hydrlodic Add. — For obtaining a very charac- teristic series of bright-colored coats with the volatile metals, hydriodic acid (///) is employed on white tablets of plaster of Paris. The substance is placed on the end of a tablet, moistened well with hydriodic acid (preferably with a drop- ping tube), and then heated with a pure blue flame, as a yellowish flame would smoke the white tablet. The acid itself gives a brownish coat of iodine, but this quickly evap- orates and leaves the bright iodide coats. If the acid can not be made fby passing sulphureted hydrogen through water containing iodine crystals until a clear solution is obtained) or purchased, a substitute that will answer, though not so well, is to dissolve iodine in alcohol, or else fuse equal parts of iodine and sulphur together and grind to a powder; the latter is a solid, and much more convenient in traveling than the liquid acid or spirits of iodine,

91. L.ltmuM paper is necessary to test for alkalies and acids, the blue turning red for acids, and the red turning blue ft'r alkalies. It will be found convenient to use it cut up in the form of strips.

92. Turmeric paper has a fine yellow tint, and is used to detect boron and zirconium, and the alkalies. The

3G Blowpiping. § 34

test for boron is very delicate. If a piece of the paper be moistened with a dilute solution of a boron mineral in HCl and then dried at boiling temperature by wrapping around a test tube of boiling water, it assumes a reddish-brown color, becoming inky-black if moistened with ammonia. Moistened with a solution of anv zirconium mineral in HCl it turns orange-red. Alkalies turn it brownish-red.

93. Hruzil-'ood paper is used to detect fluorine, which gives it a straw-yellow color; also to detect the alka- lies, which color it violet.

The list of reagents could be almost indefinitely extended. The most important and most frequently used have been given above. There are others which are used only in special tests and need not be dwelt on here.

Rcaient Box. — The dry or solid reagents can be con- veniently kept in a block of wood, say 2' X X 8' in size, in which .J -inch holes have been bored. Common corks can be used for stoppers, and the name of the flux written on top of them or on the box. Such a reagent box can be purchased for :.!)out 41, but it is easily made. Small pill- boxes or vials mav be used instead of the block of wood.

Examination Of A Substaxck Before The

Bm)\Vpipe.

94. Piatt ner has recommended the following order of examination :

(r?) Examinution vittiout rcatents :

1. Hcatitii in a sittall matrass or in a closed 1ubt\ to observe whether the substance is hydrous or anhydrous; whether it gives off volatile products; whether it decrepi- tates, or is phosphorescent, or changes color, etc.

2. Catini in an open tubi\ to observe whether any con- stituent is present which oxidizes on ignition in a current of air; and if vapors are given off, attention should be paid to

§ 34 Blowpiping. 37

their odor and to the sublimates they form on the inner surface of the tube, etc.

3. Heating on charcoal to observe the characteristic alterations which substances undergo in both the oxidizing and reducing flames; whether metallic constituents are present which volatilize and form coats on the coal ; and to observe the odor after a short exposure to heat, etc.

4. Heating in platinum forceps to test the fusibility, and to observe the colorations of the flame, etc.

Examination ritti ttie aid of reagents :

1. Treatment with a weak solution of yiitrate of cobalt of infusible or nearly infusible substances of a light color, to observe what color is imparted to them.

2. Fusion ivith borax to observe the colors imparted to the bead, etc.

3. Fusion with salt of phosphorus to observe the colors imparted to the bead, etc.

4. Treatment with carbonate of soda on charcoal, to effect the reduction of any metallic oxides present, which can thus be more easily accomplished than by the use of the reducing flame alone.

In all the above operations the smallest possible amount of the substance to be examined, consistent with the success of the reactions, should be used. The substance should, in most cases, be finely powdered. The blowpipe lamp should be set on a piece of stout wrapping-paper, or glazed paper, if convenient, so that the assay may not be lost if, through carelessness, it is allowed to fall. The operations in blow- piping should be conducted in the daytime and in a good light

95. The closest observation will be found necessary for the detection of the various reactions, and the student is advised to begin with simple substances whose exact com- position is known, so that he may fix in his mind their characteristic behavior when treated with and without reagents.

38 Blowpiping. § 34

I. HBATIKG IN A CLOSEn TUBE.

96. The substance in a finely powdered state is placed in the bottom of a tube sealed at one end, care being taken that none of it adheres to the inner surface of the tube. It may be introduced by placing it first in a paper trough, holding the tube horizontal, then pushing the trough in the tube clear to the bottom, and finally bringing the tube to a vertical position and carefully withdrawing the trough. The tube is now held in a slightly inclined position over the flame and heated, gently at first, and then, if necessary, more intensely, before the blowpipe. The successive phe- nomena are closely observed and noted; thus:

1. The substance decrepitates, as fluorite, barite, etc.

2. The substance is phosphorescent, as fluorite, apatite, etc.

3. The substance changes color, and nothing volatilizes except, perhaps, a little water, as zincite and cerussite, which turn yellow, and malachite and siderite, which turn black.

4. The substance fuses, as stibnite, etc.

5. The substance gives off oxygen, as psilomelane; told by placing a bit of charcoal in the tube, heating it first and then heating the assay, whereupon the charcoal will glow brightly.

G. The substance yields water, which condenses in the upper and cooler portions of the tube, as limonite, etc.

7. The residue is magnetic, as in the case of siderite {FcCO), pyrite (/>5J, etc.

8 The substance gives sublimates which condense on the cold part of the tube.

{a) Sulphur. — A sublimate, dark yellow to reddish- brown while warm, pure sulphur-yellow when cold; this indicates the presence of sulphur either originally free or in combination as a sulphide as in the case of metallic sul- phides, like pyrite {FeS) and chalcopyrite {CuFeS.

{h) Arsenic. — A sublimate, dark brownish-red to almost

8 34 Blowpiping.

black while warm, orange-red or reddish-yellow to red cold; this indicates the presence ol snlphiiif of arseiiH', p the case of realgar {AsS) and orpiment or in c binations of metallic sulphides and arsenides, like ; pyrite {FS,+FfAs,, or /'eAsS). A sublimate of a black, brilliant luster, having a garlic odor; this indicates metallic arsenic, as in the case of native arsenic, arsenous and arsenic oxides, and various arsenides. The lest may be made very delicate by placing a splinter of charcoal in the tube above the assay, and first heating this red-hot and then heating the assay. The volatilized arsenous oxide will be reduced in passing over the glowing carbon, and will deposit a black mirror of metallic arsenic just above the charcoal. This test will distinguish arsenic when combined with antimony, as the latter gives no mirror under these circumstances.

Antimony. — A sublimate when the substance is strongly heated, condensing just above the assay, black when hot, cherry-red to brownish-red when cold; this iiidi- cates the presence of siilpkide of antimony, as in the case of stibnite (5,5,), or of compound siilphidea of antimony and some other metal or metals, like pyrargyrite ruby silver

Mercory.A sublimate, dull black when cold, which becomes red when rubbed with a splinter of wood; this indicates the presence of sulphide of mercury, as in cinnabar (HgS), or where other metallic sulphides are com- bined with sulphide of mercury, as in mercuriferous tetra- hedrite. A sublimate of a lustrous graycolor, consisting of metallic globules (use a lens) which can be rubbed together with a splinter; this indicates metallic mercury, as in case of amalgams.

Selenium. — A sublimate of a dark red to an almost black color, having the odor of decaying horseradish; this indicates the presence of selenium, as in the case of various selenides.

(/) Tellurium. — A sublimate of metallic luster, which condenses in_small drops in the upper end of the tube; this indicates tellurium, as in the case of various telluride.s.

42 BLOWPIPING. g 34

Lead. — Sulphide of lead yields, in addition to sul- phurous acid, a white sublimate of sulphate of lead, which condenses on the bottom of the tube, and when heated strongly, fuses to yellow drops, which are white when cold.

(//) Bismuth. — Most compounds of bismuth yield a sublimate of oxide of bismuth, which condenses near the assay, and is fusible to drops which are brown when hot and dark-yellow when cold.

(/) Molybdenum. — Sulphide of molybdenum yields, in addition to sulphurous acid, a thin, white, crystalline sub- limate, fusible to drops which are yellowish while hot and nearly colorless when cold. When the R. F. is directed upon them, they become blue, or even copper-red, from reduction. High heating is necessary for this reaction.

Iii. Heating On Charcoal.

99. A fragment of the substance is placed in a shallow cavity in the charcoal and the flame directed downwards upon it. Its behavior in both flames is observed. If the mineral decrepitates, it will be found necessary to powder it and make it into a paste with water; this is placed on the charcoal and heated, slightly at first, and then more intensely. If any difficulty is encountered, when infusible and non-volatile substances are treated, in keeping the assay in its place sufficiently long to observe its behavior fully, it will be found advantageous to heat the fragment to redness and then touch it to a grain of borax. The borax attaches itself to the fragment, and both are put on the charcoal and heated. The borax melts and adheres to the charcoal, keep- ing the assay in place.

100. The characteristic phenomena to be observed are the odor after short exposure to the heat, the fusibility of the substance, the character of the residue, and the subli- mates, or coats, formed at a distance from the assay. The color of the coats must be closely observed, both while hot and when cold ; it should be noted at what distance from the assay they condense, whether they disappear when

§34

Blowpiping.

cither (J. F. ur R. F. is directed against them, and how they color the flame.

The following are the most important and characteristic reactions;

(tr) Selenium melts easily; yields brown fumes in both O. F. and R. F., which deposit near the assay as a steel- gray coal with a feeble metallic luster, and at a somewhat greater distance as a dark-gray, dull coal. The coat is volatile in both flames, and when treated with the R. F., it disappears with a fine azure-blue flame. The odor of decay- ing horseradish is strongly perceptible Ihroughoiit the entire operation.

(d) Tellurium melts easily; volatilizes in fumes in both Barnes; and coats the coal at no great distance from the assay. The coat is white, with a red or dark-yellow border, and is volatile in both flames. Under the R. F. the coat disappears with a green flame. In the presence of selenium, the flame is bluish-green.

(r) Arsenic volatilizes without fusing, and coats the coal in both flames. The coat is white, appearing grayish when thin, and it forms at a distance from the assay. It can be easily driven oflf by simply warming with either flame, and if rapidly treated in the R. F., it disappears, coloring the flame a pale blue. During the volatilization of ar.senic in the R. F., a strong alliaceous, or garlic, odor is evolved.

[if) Antimony melts easily, and forms a coat with both flames. The coat is while, bluish when in thin layers, and is not as distant from the assay as the arsenic coat. It is volatile in both flames, and disappears when treated with the R. F.. tingeing the flame pale green.

if) Lead melts easily, coating the coal with oxide in both flames. The coat is dark lemon-yellow while warm. sulphur-yellow when cold, and bluish-white when in thin layers. The coat is volatile in both flames, and disappears in the R. F., coloring the flame azure blue.

(/) BiMmuth melts easily, coating the coal with oxide in both flames. The coat is dark orange-yellow while hot

46 Blowpiping. § 34

coherent plate, which can be held in the forceps and tested in a pure O. F.

The various gradations of fusibility are expressed in deci- mals, thus: B. B. beryl becomes clouded, and fuses at 5.5; which means that in fusibility it is midway between ortho- clase and serpentine.

V. Coloration Of The Fl.Amb.

1 03. Many substances give characteristic colorations to the flame. A pure O. F. which is entirely free from yellow streaks should be used. Either a thin splinter of the mineral is used, as in testing for fusibility, or the fragment is pow- dered, and the loop or flattened end of a platinum wire, moistened by dipping into pure water or HCl is touched to the powder and then introduced into the flame. Often a mere trace of mineral, such as will adhere to a dry wire, will give much better results than a larger fragment, which is difficult to get hot enough to volatilize.

The greatest care should be observed in these tests that no foreign material adheres to the forceps or platinum wire. They should be chemically clean, and when heated alone in the flame should give no coloration to it. This cleaning is efli'ected by dipping while hot into hydrochloric acid, and then rinsing with distilled water. Drawing the wire through the fingers or wetting with saliva is to be avoided, and likewise too much handling of the specimen to be tested, since in so doing it becomes slightly coated with soda, which gives a very characteristic yellow coloration to the flame. If the specimen is to be powdered, the mortar and pestle should both be thoroughly washed before using.

Some substances when heated alone in the flame give only slight colorations, or none at all, in which case they are moistened with sulphuric acid and heated again. By this means the colorations of the flame, as in the case of phosphoric and boric acids, become evident.

Table II gives the various colors and the minerals which impart them.

§34

Blowpiping.

Bxauination With Cobalt Solutiok.

104. The (jobalt test is applicable only to those sub- stances which are of a light color, either before or after ignition, and are infusible, or nearly so.

If the substance will absorb the solution, a splinter or fragment of it is moistened with the solution, and then strongly ignited in the O. F. Friable substances and crys- talline substances which are too dense to absorb the solu- tion, are powdered, made into a paste with water, and spread upon the charcoal. They are then gradually heated until a coherent crust is formed, which is moistened with the solution and ignited in the O. F. The colorations imparted to the assay are then closely observed in a good light. The various coats on charcoal may likewise be tested in this way by moistening with a drop of the solu- tion and gently igniting in the O. F.

The colors thus obtained are :

1. From magnesia, flesh-red.

2. From baryta, brownish-red.

3. From alumina and silica, blue.

4. From the oxides of zinc, green (yellowish-green); from tin (bluish-green); titanic acid (yellowish-green); anti- monic acid (dirty, dark green).

5. From strontia and lime, gray.

Various other elements give more or less peculiar colora- tions with the cobalt solution, but only the colorations for alumina, magnesia, zinc, and tin are to be at all relied upon. This test for alumina and magnesia is infallible when they are in the pure state, and also in many of their combina- tions. Silicates of zinc, on strong heating, give an ultra- marine blue, from the silica, instead of the zinc green. The blue of alumina is not to be confounded with the blue of silica. The blue of the silica almost always appears fuseii on careful examination, while the blue of alumina is dull. The blue of the silica also appears only after intense ignition, and it is therefore well if, after moderate heating, the substance shows no blue, to discontinue the heating before fusion.

48 Blowpiping, § 34

Roastiig.

105* When borax and salt of phosphorus, or microcos- mic salt, as the latter is sometimes called, are fused with certain metallic oxides, they exert a powerful solvent action upon them, and highly colored glasses are formed which are exceedingly characteristic.

106 It is essential, in the bead tests, when the pre- liminary examination of the substance has shown the pres- ence of sulphur or arsenic, that these elements be removed, as they interfere with the reactions. This is effected by roasting, which is conducted in the following manner:

The finely pulverized material is placed in a shallow cav- ity on charcoal and pressed flat with a knife-blade, forming a thin layer. The assay is then treated with a feeble O. F. so that only the tip of the flame touches it. It is thus heated and kept for some time at a low, red heat, during which operation most of the sulphur is volatilized as sulphurous oxide (SO), and the metals are oxidized. This sulphurous oxide has a tendency to change into sulphuric oxide at the expense of the already forming metallic oxides, and these are converted into sulphates, and if arsenic be present, into arsenates. When, therefore, the odor of sulphurous oxide has disappeared, the assay is treated to a feeble R. F., which, for the most part, reduces the sulphates and arsenates thus formed, and the arsenic is more or less completely volatil- ized. When the arsenical odor is no longer apparent, a feeble O. F. is again used, which generally causes a slight odor of sulphurous oxide. The. assay which is thus baked together, fff/t not fuscd is turned with a knife-blade, and the other side treated alternately to the O. F. and R. F. in the same wav. The coherent mass, after this treatment, is removed and powdered in a mortar, and since it is not entirely free from sulphates and arsenates, antl, if it has not been carefully roasted, may even contain slight quantities of sulphides and arsenides, it is replaced on the charcoal, and subjected to still further roasting.

If the assay fuses, it must be removed from the coal.

§ 34 Blowpiping. 49

powdered in a mortar, and then replaced on the coal and roasted.

Substances containing selenium, tellurium, and antimony, if free from sulphur and arsenic, usually need not be roasted, since these elements do not interfere with the reactions.

FUSION lITH BORAX.

107. In tlie O. F. — A clean platinum wire, in one end of which a small loop has been made, is heated to redness and the loop dipped in borax powder, which will adhere to it. The borax is then heated until it fuses to a transparent, colorless bead. This bead, while still hot, is brought in con- tact with a very small quantity of the substance to be tested, and heated before the blowpipe in the O. F.

The phenomena attending the solution of the substance in the borax must be closely observed, whether it dissolves slowly or rapidly, quietly or with effervescence; and when the solution is effected, the color of the bead must be care- fully noted while hot (not red hot, but still soft and pasty), while cooling, and when cold, as well as whether its trans- parency is disturbed upon cooling. The bead is held before the eyes against the light. A lamp light will not do, as the colors are greatly modified, and the experiments must be conducted in the daytime.

The intensity of the colors depends upon the degree of saturation of the bead. It is well at first to use the small- est possible quantities of the substances to be tested, and afterwards increase them by successive additions until a sat- isfectory degree of saturation is obtained. If too much of the substance has been used, and the l)ead is so deeply colored that it is difficult to decide what color it has, it may be flattened, while still hot or pasty, on an anvil with the butt end of the blowpipe; or a portion of the bead may be thrown off the wire by a sudden jerk, and the remaining portion diluted with more borax. If the operator is in doubt

52 Blowpiping. § 34

antimony, tellurium, copper, bismuth, tin, lead, zinc, indium, cadmium, nickel, cobalt, and iron. Arsenic and mercury are also reduced, but are immediately volatilized. They can be obtained in the metallic state by fusing in a matrass.

1 1 3. Neutral oxalate of potassa or cyanide of potassium may be advantageously substituted for soda when treating oxides which are with great difficulty reduced. The cyanide has the disadvantage of spreading over the coal and scatter- ing the metallic particles. These fluxes are both serviceable when the reduction is conducted in a matrass.

114. Many oxides can not be reduced to the metallic state by soda, but form with it more or less fusible com- pounds. Silicic, titanic, tungstic, molybdic acids, etc., form fusible compounds, and so also do baryta and strontia, while most lime salts are decomposed. The compounds formed by baryta and strontia sink into the coal. The lime salts are decomposed, and the soda sinks into the coal, leaving the lime behind.

1 1 5. A few elements which have not been mentioned and which are of decided interest, as they form a very important set of compounds, are the halogens — bromine, chlorine, fluorine, and iodine.

(a) Bromine. — When bromides are added to a salt of phosphorus bead which has previously been saturated with oxide of copper, and the blowing is continued, the bead is surrounded with a beautiful halo of blue flame, inclining to green on the edges, and this continues as long as the bromine remains. As this reaction may be confounded with those given for chlorine, another test is recommended. The sub- stance should be fused with dry bisulphate of potash in a glass matrass. Bromine and sulphurous acid fumes are liberated, and the matrass becomes filled with yellow fumes. The bromine is recognized by the extremely suffocating odor of the bromine fumes, or by exposing moistened starch or starch paper to these vapors, which turn them yellow.

§ 34 Blowpiping. 53

{6) Chlorine. — Chlorides may be detected, like bromine, by adding them to a salt of phosphorus bead previously satu- rated with oxide of copper, and again igniting. The bead is instantly surrounded by an intense purplish-blue flame without any tinge of green.

(c) Fluorine. — Substances containing fluorine, when heated in a glass tube with bisulphate of potash, give off hydrofluoric acid, which etches the tube immediately above the assay, and imparts to a strip of moistened Brazil-wood paper, placed on the end of the tube, a straw-yellow color.

(d) Iodine. — Iodides added to a salt of phosphorus bead, previously saturated with oxide of copper, tinge the outer flame an intense emerald-green.

Like bromides, they also are decomposed by fusion with bisulphate of potash, and free iodine is liberated, which may be distinguished by its violet color and disagreeable odor.

116* Nitrates. — When nitrates are fused in a glass tube with bisulphate of potash, dark reddish-yellow fumes of nitrous oxide are liberated. The color is best observed by looking into the tube.

117. Sulpliuric Acid. — The presence of sulphates may be detected by fusing the substance with chemically pure soda, then placing the fused assay on a silver coin and moistening with pure water. If sulphuric acid had been present originally in the substance, it was converted in the fusion to sulphide of sodium. This sulphide of sodium will leave a dark-brownish or black stain on the bright surface of the silver.

1 1 8. Water. — The presence of hygroscopic moisture may be detected by heating the assay in a matrass or closed tube. Water is immediately given off, and condenses in the cooler portions of the tube.

1 19 Determination of Gold and Silver in Ores. —

Occasionally ores are rich in gold and silver, and their respective minerals can be determined by the blowpipe, but as a rule the ores are of comparatively low grade, and the

54 Blowpiping. § 34

amount which could ordinarily be treated before the blow- pipe would not be sufficient for the isolation of the precious metals. On this account, one of two methods must be fol- lowed. If the ore is free milling it may be amalgamated, while if it is a concentrating ore it may be concentrated in the gold pan.

In either case, the sample (which may weigh several pounds) should be crushed fine in a mortar, so as to set the valuable materials free.

1 20 In the amalgamation test the sample is placed in the gold pan with sufficient water to saturate and cover the ore. After this a small amount of mercury is added, and the material vanned or panned in such a manner as to carry the pulp around and around over the mercury, or in some cases the pulp is worked comparatively stiff and the mercury worked back and forth through the mass, either with a spatula or by hand. After the ore has been thoroughly exposed to the amalgam, the waste material or gangue is washed away and the amalgam collected.

The excess of mercury is squeezed from the amalgam by passing it through buckskin or canvas. The small piece of the amalgam so obtained can be placed on charcoal, heated before the blowpipe, thus volatilizing the mercury and leav- ing a small piece of the precious metals, which can be melted down to a bead or button. In case no buckskin or canvas is at hand, the mercury can all be driven off by means of the blowpipe.

121. In the concentration test, the ore is washed as in ordinary panning, and the rich mineral collected as concen- trates. It is best to employ two pans, and to wash from one to the other, each time obtaining a small amount of con- centrates, which are laid to one side. After the concentra- tion has been carried as far as it is considered necessary, the concentrates may be dried, placed on charcoal, and any arsenic or antimony driven off by roasting them before the blowpipe. The roasted concentrates are mixed with soda and metallic lead. The soda acts as a flux in melting the minerals, and the lead takes up any gold or silver they may

§ 34 Blowpiping. 55

contain. The lead button obtained in this manner must be cupelled in order to separate the lead from the gold or silver. As has already been stated, cupels are made from bone- ash, but in case the prospector has neither bone-ash nor a cupel mold, he may accomplish the desired results by burn- ing a few bones in his camp-fire and then pound them to a fine powder, which can be mixed with water and pressed into a small cupel on a block of dry wood or in a spoon or thimble. When cupelling the lead button, it must be heated with an oxidizing flame, which action results in the forma- tion of lead oxide, part of which is absorbed by the bone- ash and part of which is volatilized. When all the lead has been oxidized, the precious metals will remain as a small bead. Just before the last of the lead is driven out, the bead will appear as though it were spinning rapidly, and be covered with a thin film of oxide. At the moment the last of the oxide disappears, the bead will appear to brighten, and after this will not appear as though spinning.

122. If it is desired to separate the gold and silver in the bead, this may be accomplished by dissolving out the silver with nitric acid (providing there is times as much silver present as there is gold). Strong nitric acid diluted with an equal amount of water answers this purpose very well. The bead is dropped into the acid, and after the first evolution of gas ceases the acid must be boiled. The acid is then poured off and a fresh supply added, and the bead once more boiled. Any gold will remain behind as black specks, or as a black skeleton of the bead. In case there is more gold than the proportion given, it will be necessary to add scme silver to the bead before it can be parted. After the silver has all been dissolved, the gold which remains behind should be washed with clean water (preferably distilled water) and then heated to a red heat, which will restore the ordi- nary yellow color to the metal. If there is enough gold pres- ent, it may be melted down into a bead before the blowpipe. If water or acid give a white precipitate with silver nitrate solution, chlorine is present, and they are not fit for part- ing.

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§34

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After a strong blast.

blue color, the intensity of which is prop- erly apparent only on cool- ing.

With a little of the solution

feeble bluish color, becom- ing black or dark gray with

thinnest edges can be fused to a reddish- blue glass in a very hot flame.

s .

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the coal.

o 1

it

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that is always clear. When much is added the undis- solved part be- comes semi- transparent.

Dissolves in very small quantities to a clear glass. The undis- solved port ion becomes semi- transparent.

Dissolves slow- ly to a clear glass, becoming opaque neither by fla- ming nor satura- tion. When much is added in fine powder, the glass la cli. udy and scarcely fusible, and shows a crys- talline aurface on co<.ling.

Dissolves slow- ly lo a clear, dif- ficultly fusible glass, that can not be made opaque by flaming.

jll

Aluminum. (Alumina.)

g 34 BLOWPIPING. 67

Eg.£f0.aja£ESsSxibi

Blowpiping.

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Blowpiping.

With hydriodic acid the coat becomes white when heated.

In the presence of copper or nickel, the bead must be treated on charcial with tin before the blue color is dis- tinctly observed.

O.F. Insol- uble.

R.F. On coal is immediately reduced and

coating the ctial with red- dish-brown ii> dark-yellow oiide. The

portion of the

tarnish.

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O.F, As with borax.

R. F. The ox- ide dissolved in the bead is slowly and imperfectly reduced on coal, forming :i \ltv sligii (hiik-vct- low coat, show-

cold. Tin accel- erates the reduc-

Oncoal,inR.F.. it shortly disap-

the !:iiriuunding coal mill a red- ,1 brown to dark-yellow coat. The proper color is seen when cold. The coal beyond the coat shows a variegated tar- nish.

O.F. Unchanged.

R. F. Shrinks

somewhat, and is reduced, without fusing, to metal, which is mag-

a metallic luster when rubbed in the mortar.

Cadmium.

Cobalt.

Blowpiping.

S34

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Substances containing Molybdenum, if finely powdered and heated in a porcelain dish with con- centrated //a5(?i,give,upon

the addition of alcohol, a fine azure-blue color, es- pecially on the sides of the dish.

]

P

On coal fuses with effer-

firBt.bm after- wards is ab- sorbed by the coal and the greater part is reduced to metallic .fl/o which can be obtained as a steel-gray powder by washmg away the particles

J It

O.F. Dissolves easily to a clear glass, which is yellowish-green while hot, if a moderate amount is added, but be- eomes nearly colorless on cool- ing.

Oncoalbecomes quite dark, and on cooling is fine green.

R.F. The glass becomes quite dirty green, but purer green on cooling. The

With tin a some- what darker green.

s

as t

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O.F. Dissolves easily and largely to a clear glass, yellow while hot, ancf color- less on cooling. A very large addition

Sroduces a glass, ark-yellow to dark- red while hot, and opaline to bluish- green enamel when cold. R. F. The glass produced in the O. F. becomes brown with a certain de- gree of saturation, and with more, is opaque. In a good flame black flocks of Afo separate and can be seen in the yel- lowish glass when mashed flat.

O.F. Fuses, spreads out. vola- tiliaes.and forms, at a certain dis- tance, a yellow- ish, pulverulent coat, consisting of small crystals

The coat becomes white on cooling, and the crystals colorless. Be- yond this a thin. non- volatile coat of oxide forms, which, on ciml- ing. is dark cop- per-red, and has a metallic luster. R.F. The great- er part sinks into the coal, and can be reduced to metal with a hot flame. It appears as a gray powder.

£

Blowpiping.

Oxides of tin are best reduced on charcoal with soda or cyanide of potassium. If much iron is present, borax is added.

of tin, when treated with nitric acid, sepa- rate oxide of tin as a white precipitate which can be tested in the usual way.

Assumes a bluish-green which must be observed after the assay

i!

as

33

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oil

O, F. Very slowly soluble in small quan- tity to a color- less glass, that remains clear on cooling.

R. F. The

glas.s from the O. F. is unal- tered either on the wire or on charcoal.

O.F. Veryslow- !y soluble in small quantities

bead, which re- mains clear after cooling, and is not made turbid by flaming.

A bead satu- rated with oxide, allowed to be- come perfectly cool, and then heated gently be-

loses its round form and mani-

crystaliization.

O.F. The pro- toxide of tin takes fire and burns like tin- der to a higher oxide, called the binoxide, which glows strongly and is yellowish while hot ; on coolingbecomes dirty yellowish- white.

R.F. By long blowing the ox- ide may be re- duced to metal- lic tin, with for- mation of a slightsublimate of oxide, which coats the char- coal near the assay.

Tin.

Blowpiping.

1'

Substane tellurium

with soda dust, and f tube; then and a lit I dropped The water purple colo solved tellu Teliuriumc edwithconc imp;irt to it

ing or on

precipitate

When sil withlargeq or bismuth, be fused to the additio lead and the resul

cupel.

t

1 1

On charcoal is reduced and volatilized with the for- mation of a coat of tellu- rous acid.

Is immedi- ately reduced ; fuses to me tal- lic globules, white the soda is ab- sorbed by the charcoal.

s

£

'5

O.F. Both the oxide and the metal yield a yel- lowish glass. A

opaline on cool- ing. Its color is yellow by day- light, and red bv candle-light

R. F. As with borax.

O.F. Soluble ton clear.colorlesK glass, which becomes gray from separation of when heated on coal.

R. F. Theclear glass from O. F., heated on coal, be- comes first gray and finally colorless, all the tellurium being reduced and volatil- ized and coating the coal with tellurous acid.

O.F. Is partly dis- solved, and partly reduced to metal. The glass on cooling becomes opaline or milk-white, accord- ing to the degree of

R. F. The glass from the 0. F. be- comes at first Rrav from separation of meta then clear and L-oIorless. al the silver aeparating and fusing to a. globule.

O, F. Fusesand is reduced with effervescence. The reduced metal votaliies

awhitecoa-tingof tellurous acid de- posits on coal. The edges of the sublimate are

dark yellow.

R. F. AsinO. F. The outer flame is tinged bluish-green.

Easily reduced to metallic silver, which fuses to globules.

Tellurium.

(Tellurous

Silver.

Blowpiping.

§34

:"&j:-ti2-ig;j4S

IlisSi

g 34 BLOWPIPING. 8

llllilllllil=-iiHfild.:illil.iii

Mineralogy.

Minerals And Their Properties.

1. A mineral is a natural, inorganic substance, of definite chemical composition. A mineral may be either an element or a compound, so long as it is one of the forms in which theelement or elements constituting it occur in nature. For instance, the most important gold mineral is native, or metallic, gold, while iron very rarely occurs in nature in the metallic form.

2. Mineralogy is the study of minerals, their compo- sition and physical and chemical characteristics.

In a careful preliminary examination of a mineral speci- men, the student will naturally be struck first by those physical characteristics which are at once obvious to the senses; viz., transpanttcy, color, luster, feel, structure, cleav- age, fratliire, hardness, tenacity, and crystalline form, if distinct; and also, if the specimen be of sufficient size, the weight will give some idea of the specific gravity.

The importance of these different physical characteristics varies greatly in different minerals. Thus, the color and luster of some minerals are very characteristic of those minerals and are, consequently, of the utmost importance in their identificatioD, while in other minerals the color and luster are neither characteristic nor important; and the same is true of other properties. Crystalline form and cleavage are usually of less importance to the average pros- pector or miner than the other physical characteristics, but some knowledge of them will frequently stand him well in hand, and for this reason the student should know al least the principal crystalline forms. §35

Mineralogy.

§35

Transparency.

3. Transparency is the property, possessed by most substances to a greater or less degree, of transmitting light. or ailowing light to pass through them. The following terms are used to define the different degrees of trans- parency ;

Transparent, when the substance transmits light per- fectly, so that objects viewed through it appear distinct. For example, glass and crystallized quartz are transparent.

Sublrannpnrent or Hemitransparent, when objects can be seen through the substance, but only indistinctly.

Translucent, when the substance allows light to pass through it, but objects can not be distinguished. Ground glass, loaf sugar, and some marbles are translucent.

Subtranslucent, when there is a slight transmission of light through only the thinnest edges of the substance. When a substance transmits absolutely no light, it is said to be opaque.

COLOR. A, The color of a mineral is usually more or less char- acteristic of the mineral. In the case of some minerals, the finely powdered mineral has a definite color of its own, entirely different from that of the specimen as a whole. The color of the powdered mineral is known as the streak of the mineral — from the fact that it is best observed by making a mark, or streak, with the specimen, on an unglazed porcelain surface — and is frequently of great importance in identifying minerals.

Luster.

S. The luster of minerals depends upon their power of reflecting light, and consequently upon the nature of t surfaces. According to the nature we have seven kinds of luster, familiar substance of which it i as follows :

re of the reflecting surface, i

, each named from some 1 characteristic. They are

Mineralogy.

Metallic, the ordinary luster of metals. An imperfect nietllic luster is described as subtetallic.

Vitreous, the luster of brolcen glass. Imperfect vitreous luster is called subvitreous. This is the characteristic luster [ of quartz.

Resiaous, the luster of fjrdinary rosin. This is the luster which gives the name " Rosin Jack " to some varieties of zinc-blende.

Greasyi looking as if smeared with oil or grease. This luster is occasionally observed in quartz, and in some vari- eties of serpentine and steatite.

Pearl}', like pearl. This lusler is frequently found in

rsuch minerals as mica, talc, and gypsum, which are made

fupof very thin leaves, or layers. Pearly luster combined

irith submetallic luster forms what is known as mctallic-

\feaTly luster.

Silky, like silk. This luster is the result of a fibrous I structure, like that of asbestos, or of fibrous gypsum.

Adamantine, the luster of the diamond. Minerals M having this luster may also be submetaliic; in such cases luster is called mftallk-adamaniine. Cenissite and yrite have such a luster.

Besides the different kinds of lusler, there are differ- mt degrees of intensity of htster, depending upon the ciear- |Dess of the reflection. These are:

Splendent, when the surface is a perfect mirror, reflect- thig light with great brilliancy, and giving well-defined K images.

Shinlnst when an image is produce<l, but not a clearly Idefined image.

GllstenlnK or sheeny, when there is a general reflec- rtion of light from the whole surface, but no image.

GllmmerlaK, when the reflection is very imperfect, and the reflected light comes to the eye not from the entire surface, but from a number of separate points scattered Lover the surface.

Mineralogy.

When there is a total absence of luster the mineral is said to be dull, or earthy. Chalk is a good example of this condition.

7. The feel (or feeling) of a substance is of importance in the case of only a few minerals, such as talc and the tal- cose minerals. The feel of substances will be readily recog- nized from the terms used to define it, as greasy, smooth, harsh, gritty, etc.

Sthuctuhe.

8. Among minerals will be found a variety of structure. Most mineral specimens are aggregations of imperfect crystals. Even those whose structure to the naked eye appears destitute of crystallization are probably composed of impalpable crystalline grains.

The structure of a mineral is said to be:

Columnar, when it is made up of slender columns or fibers.

There are-several varieties "f columnar structure, classi- fied as follows:

Fibrous, when the columns or fibers are parallel, as in asbestos.

Reticulated, when the fibers cross in various directions, and assume a net-like appearance.

Stti/ateii, when the fibers radiate from a center and pro- duce star-like forms.

Radiated, when the fibers radiate from a center without producing stellar forms, as sometimes in stibnite.

l<amellar, when it consists of plates or leaves. These leaves may be curved or straight; in either case the struc- ture is BO described; and they may also be very thin and easily separable — a micaceous structure.

Granular, when it is composed of crystalline grains. If the grains are not to be distinguished by the naked eye, the structure is said to be impalpable.

Ogy.

There are, in addition to these kinds of structure resulting from crystallization, many imitative shapes assumed by dif- ferent minerals and described as follows:

Reniform — kidney-shaped; Botryoidal — like a bunch of grapes; Mammillary — breast-shaped, resembling botryoidal, but composed of larger prominences; Dcndritk — branching, tree-like; Filiform or Capillary — very long and slender crystals, like a thread or hair; Acicular — slender and rigid, like a needle ; Slalaclitic and Stalagmitic — like the stalactites and stalagmites found on the roofs and floors, respectively, of caves.

Cleavage.

9. Most minerals have certain directions in which their cohesive force is weakest and in which they yield most readily to a blow. This tendency to break in the direction of certain planes is called cleavage.

Cleavage differs, first, according to the ease with which it may be effected, and second, according to the direction as crystallographically determined. We will direct our attention, for the time being, only to the first.

The different degrees of cleavage arc classified as follows:

Perfect) or emlaentt when obtained with great ease, affording smooth, lustrous faces, as in calcite, mica, and galena. Eminent is used only in reference to the most per- fect and pronounced cleavage.

Distinct, when obtained with tolerable ease, and with fairly good cleavage faces, hut neither so easy nor so com- plete as pcrfict cleavage.

Indistinct, when obtained with some difficulty, and the cleavage faces and angles are not well defined.

Difficult, when obtained only with considerable difficulty, and barely discernible. Cleavage of this sort is very apt to be only in traces, that is. with a bit of cleavage face show- ing here and there.

Interrupted, when the cleavage face discontinues abruptly, only to be continued in another cleavage plane

Mineralogy.

S35

parallel to the first. This condition may occur iu minerals having perfect cr distinct cleavage.

The inferior degrees of cleavage are of themselves of no value in identifying minerals; but the absence of cleavage, or very poor cleavage, will sometimes serve to distinguish a mineral from minerals similar to it in appearance, but having more pronounced cleavage.

Fracture.

10. The terra fracture is used in mineralogy to define the kind of surface obtained by fracturing a specimen, or breaking it in any direction except along a cleavage plane. The different kinds o£ fracture have been classified as follows:

ConcholdBl, when the mineral breaks in curved, she!!- liko surfaces.

Even, wien the fracture surfaces are approximately reg- ular surfaces, though perhaps somewhat rough.

Uneven, when the fracture surfaces are irregular and rough.

Fracture is characteristic in the case of only a few min- erals, and then, like the inferior degrees of cleavage, is val- uable only as a distinction from minerals having a similar appearance but a different fracture.

Hardness.

11. By hardness is meant the resistance which a min- eral offers to abrasion. Thus, talc can be scratched by the finger rail, while the diamond is the hardest substance known. As minerals differ in this characteristic, and as each has usually a more or less constant hardness of its own, the following scale, known as Moh's scale of hardness, has been arranged to measure the different degrees of resistance to abrasion offered by minerals:

1. Talc — easily scratched by the finger nail.

§ 35 Mineralogy. 7

2. Gypsum — scratched with difficulty by the finger nail; does not scratch a copper coin.

3. Calcitc — scratches pure copper; not scratched by the finger nail.

4. Fluor it e — not scratched by a copper coin ; does not scratch glass.

5. Apatite — scratches glass with difficulty; easily scratched by a knife.

6. Feldspar (prthoclasc etc.) — scratched with difficulty by a knife ; scratches glass easily.

7. Quart:: — not scratched by a knife ; yields with diffi- culty to a file.

8. Topaz — harder than flint ; very few substances are as hard as this.

9. Corundum — hardest substance known except the diamond.

10. Diamond — the hardest substance known.

The hardness of any mineral is determined by ascertain- ing a point in the scale such that the given mineral will scratch any mineral in the scale below that point, and will be scratched by any mineral above the point. It is well to supplement the test by the minerals of the scale with a test by the finger nail, a copper coin, and a knife. If no set of minerals comprising the scale of hardness are available, a mineral may be tested very well by the finger nail, copper coin, and knife.

Tenacity.

12. The tenacity of a substance is the persistency with which its particles cling together. This is different in different substances, but, like hardness, is more or less con- stant for any one substance. The different degrees of tenacity have been classified as follows:

Brittle, when the substance flies to pieces under a sharp blow, and powders under the edge of a knife in the attempt to cut it, like galena.

8 Mineralogy. § 35

Scctlle, when pieces may be cut oif with a knife without falling to powder, but the substance still goes to pieces under the hammer. This is really a condition intermediate between brittle and malleable.

Malleable, when the substance can be beaten out under the hammer without flying to pieces, like gold.

Ductile, when the substance can be extended or drawn out by tension, as in wire drawing. Ductility is only another phase of the same property as malleability, and is possessed to a remarkable degree by gold, silver, iron, and copper, and some of the rarer metals.

Flexible, when the substance can be bent. Substances which are malkabU- and duclUe are usually also flexible.

Elastic, when the substance can be bent or otherwise distorted, but returns to its original form as soon as the distorting force is removed. Steel is remarkably elastic. Highly elastic substances are usually more or less brittle.

Crystalline Form.

13. All minerals, at some time or other, have been in a liquid state, either through solution or fusion (melting), or in the state of gas, or vapor — conditions in most cases the result of very high temperatures. On cooling, molten matter solidifies and gases condense to liquid or solid form; and as water containing mineral matter in solution cools and evaporates, the mineral contents are precipitated. As the minerals solidify they tend to form crytitals, or bodies of definite geometrical form, bounded by plane faces. Each kind of mineral crystallizes separately, in a form or forms more or less peculiar to itself, and crystalline form, therefore, becomes one of the physical characteristics of every crystallized mineral, and is sometimes of considerable service in its identification. The different varieties of crys- talline form are considered farther on under the head of Crystallography,

fiSS MINERALOOy. 9

Spkcific Gravity.

14. The specific gravity of a substance is the ratio of tlie weight of a given volume of that substance to the weight oi an equal volume of another substance, whose specific gravity is assumed to be unity (1). Water is the accepted standard, and its specific gravity is consequently considered as 1 (or unity).

1 5. The specific gravity of a mineral may be determined thus:

1. Find ihe weight of the fragment out of water, just as you would weigh anything else. This weight w.

2. Then suspend the fragment by a fine, silk thread to the balance beam, submerge it in water and weigh again. This weight w,.

Since the /ess of weight of a solid submerged in water is equal to the weight of the volume of water displaced, w — the weight of a volume of water equal to the volume of the mineral, and the specific gravity of the

mineral .

The weights should be accurately taken on a good chem- ical balance, and the water should be distilled; and as the density of water varies with its temperature, in order to obtain uniform results (iO° F. has been adopted as a con- venient temperature.

10. Another method, less accurate, and requiring less elaborate apparatus, will usually give a sulficiently close approximation of the s[)ecific gravity of minerals to serve the student's purpose. The only apparatus necessary is a jiair of scales graduated to about grain or 5 milligrams, and a graduated glass vessel. The graduations on the scales and the vessel should be in the same system, so that the results may be readily figured. Thus, if the scales weigh in grams (metric system), the vessel should be graduated in cubic centimeters and fractions thereof, while if the scales weigh in ounces and grains, the vessel shovild be graduated

10 Mineralogy. § 3S

to correspond, so that the weight "f water in it can be readily calculated.

To obtain the specific gravity of a substance, a piece of it is weighed in air, in the ordinary manner, and then sub- merged in water in the graduated vessel. The height of water in the vessel before putting in the fragment is noted. This is subtracted from the height to which the water rises when the fragment is submerged in it. and the difference is the amount of water displaced. The weight of this volume is readily figured — 1 cubic inch of water weighs 25'2.5-\~ grains, or, in metric measure, 1 cubic centimeter of water weighs 1 gram — and, as before, the weight of the fragment divided by the weight of the water displaced gives the specific gravity of the substance. For this rough work, the change of volume with the temperature need nut be con- sidered.

Examination Of Mineral Specimens.

17. In the preliminary examination of mineral speci- mens, the student must note clearly all striking physical characteristics; the hardness should be determined, and the specific gravity, as nearly as possible with the appliances at hand. These results will of course suggest to the student more or less about the specimen, according to his familiarity with minerals. Finally, the specimen should be thoroughly examined before the blowpipe, in accordance with the method already suggested in the Paper on Blovipiping, and the information hereinafter given will enable him to deter- mine the specimen with reasonable certainty.

In this Paper are described only such minerals as are of commercial importance, and no attention is paid to those of merely scientific interest. The important ores of the ordi- nary metals of economic value will be given, together with

industries.

E extensively used in

§35

Mineralogy.

Crystallography.

18. Crystallography is thai branch fjf mineralogy treating of the crystalline forms assumed by the various

1ft. For convenience in classification, the crystal forms may be divided into six main classes, or systems of crystal- iisaliott, according to their degrees of symmetry.

Aayaimetry plane is a plane which divides a crystal so that the two portions of the crystal bear the same relation to each other as an object bears to its image in a mirror; that is, every point on the surface of the crystal on one side of the dividing plane has a corresponding point directly opposite, and at the same distance from the plane, on the other side. A ttymmetrlcal Iiody is a body that can be divided by a symmetry plane. A symiuetry axis is an imaginary line through the center of a crystal, perpendicular to a symmetry plane and connecting either the centers of opposite crystal faces or the vertices of opposite crystal angles.

In the crystal systems in which the forms are symmetri- cal, the crystal axes are always also symmetry axes; and in determining the crystal system to which a symmetrical crystal belongs, the more prominent group of symmetry axes is selected, and these are considered as the crystal axes of the system. One axis of the group is selected as the fcr- /iea/ crystal axis, and in the examination of the crystal is always considered as being in an upright position; the other axes then become lateral crystal axes.

The six systems of crystallization are the rsiu/ir/rir, tet- ragonal, orthoTliDmhie, monoclink , trirlinic, and liexagonal. The distinguishing characteristics of each system are as follows:

iBonietric has three crystal axes, of equal length and intersecting one another at right angles.

Tetrasonal has three crystal axes, intersecting one another at right angles; two, which are of equal length, are

Mineralogy.

§35

considered as lateral axes; the third is the vertical axis, and is not of the same length as the other two.

Ortborhombic has three crystal axes, intersecting one another at right angles, but no two are of the same length.

Monocllnlc has three crystal axes; the vertical axis and one lateral axis (the one running from front to back) are oblique to each other, but the transverse lateral axis is at right angles to both of the others.

Tricllnlc has three crystal axes, all oblique to one another.

Hexagonal has four crystal axes ; the three lateral axes are at right angles to the vertical axis, and intersect one another at angles of 60°.

Isometric System.

20. The crystal axes of the isometric system being all of the same length, and all at right angles to one another, it is immaterial which one is selected as the vertical axis, as

the shape of the crystal is the same with reference to all of them. In the elementary forms of this system all the faces are exactly alike. In the compound forms, resulting from a combination of two or more elementary forms, this is, of course, not the case, and in nature an almost infinite

Mineralogy.

variety in the shape and number of the faces of crystals is produced by this compounding. The elementary isometric forms — shown in Fig. 1 — and their distinguishing character- istics are as follows:

Cube (rt) has six square faces, meeting at right angles.

Octabedron (/)) has eight faces, each of which is an equilateral (equal-sided) triangle.

Dodecahedron {c) has twelve diamiind-shaped faces.

Trlaoctahcdron (i/) has twenty-fnur triangular faces. It derives its name from its general resemblance to the octa- hedron, and the fact that each face of the octahedron is . replaced in the trisoctahedron by three faces which form a low triangular pyramid,

TrapCKohedron {c) has twunty-four faces, each of which is an irregular four-sided figure known as a trapezium. Like the trisoctahedron, it has the general form of the octahedron, but each face of the latter is replaced in the trapezohedron by a group of three of the trapezoidal faces.

Tetrahexahcdron (/) has twenty-four triangular faces, arranged in groups of four. Each group forms a low, square pyramid, the base of which corresponds to one of the faces of the cube or hexahedron, hence the name.

Bescoctabedroa (g) has forty-eight faces, arranged in eight groups, of six triangular faces each; has the general form of the octahedron, each group of six faces correspond- ing to a face of the octahedron; resembles both the trisocta- hedron and trapezohedron.

Heiuihedkal Forms.

21. Besides these ordinary, whole, or holohedral (all- sided) forms, the elementary hemihcdral forms should be included in a list of elementary forms. Hemltaedral forms are crystal forms in which only every other face is devel- oped, and the intermediate ones are omitted. Thus, if in the octahedron \(b) Pig. I], we consider each alternate face to be omitted and the planes of the remaining faces to be

16 Mineralogy. § 35

axes, as at {a) and (b), Fig. 3; in the indirect forms, the faces cut one lateral axis and are parallel to the other, as at (r) and (d). In all the systems except the isometric, a face parallel to both lateral axes is called a basal plane. Such are the faces closing the top and bottom of an ordinary prism. Cleavage parallel to a basal plane is known as basal cleavage; parallel to the faces of a prism, Vi? prismatic cleav- age; parallel to the faces of an octahedron, as octahedral cleavage, etc., the cleavage in every case taking its name from the face to which it is parallel.

23. Fig. 3 shows the simpler forms of the tetragonal system. With the exception of the four forms already described r, and and the octagonal prism {c) and pyramid (/), the forms are all compound.

Hbmihbdral Forms.

24. The hemihedral forms of the tetragonal system, some of which are shown in Fig. 4, are derived in the same way as those of the isometric system. The tetrahedron (a)

Fig. 4.

is derived from the octahedron; the ditetrahedron (/;) is derived from the dioctahedron, or octagonal pyramid ; and the square prism, which is shown at (r), with its corners cut off by the faces of the ditetrahedron, is derived from the octagonal prism.

25. It is frequently somewhat difficult to distinguish certain tetragonal forms from similar isometric forms. This is particularly true of the octahedrons and their half -forms, the tetrahedrons, in which there is no distinction, except that one axis of the tetragonal forms is longer or shorter

§35

Mineralogy.

ir

than the other two. while all three axes of the isometric forms are of equal length, so that the faces of the isometric crystals are equilateral triangles, while the faces of the tetragonal crystals have only two sides of the triangle equal. Even Ibis distinction is frequently destroyed by a distortion of the isometric crystals, so that the three axes are no longer equal, In such a case we must refer to the crystal angles, or angles formed by the intersection of crystal faces, which remain unchanged, no matter how great the distortion of the crystal. Thus, if the angle at the vertex of an eight- sided crystal is exactly a right angle, we know at once that the form is an isometric octahedron, for the vertex angles of the tetragonal and orlhnrhombic octahedrons are never exactly right angles. In the case of the isometric cube and the tetragonal and orthorhombic prisms, the distinction is much more simple, as, no matter how badly distorted the crystal may be, all the faces of an isometric crystal have exactly the same luster and markings; while the basal plane in the tetragonal and orthorhombic systems has a somewhat different appearance from the prism faces; and in the orthorhombic system the two sets of parallel prism faces differ in appearance from each other, as well as from the basal planes — a characteristic which serves to distinguish orthorhombic prisms from distorted tetragonal prisms. Dis- torted tetragonal pyramids are similarly distinguished from orthorhombic pyramids, the luster of adjacent faces of the latter being different, while that of opposite faces is identical.

Orthorhombic System.

26. The three axes of the orthorhombic system being all of different lengths, but at right angles to one another, any one of them may become the vertical axis, the selection resting with the ojM:rator. and usually depending more or less on the general shape of the crystal. For instance, if the crystal is flat and tabular, the main faces of the tablet are usually considered as basal planes, while if it is long and prismatic, pyramidal, ot barrel-shaped, the longest axis is

ax3 cjzi-T idjtns; J

in diiir=: I:i*:tr the nieascrtn:=i of zh-i j..;!; by the iiiieriec;:':-:: indirect orissi, hjever. : tica! face?, wiich, wse:: b-:;h

I.cr -iie-al

i_j:iin;-i- :;r=5, except

=.-:n -:i:-ii> I=?iead of the Lve ;j rairj -;f jT'ara'IeS, ver- r.iir& ire devel ir.;ersect

to form a vertical, reciar.gtilkr pTi~=i with its faces ;viraliel to the Eateralaxes oi the crystal: the pair OE faces parallel to the longer or m<irr-axis cv>r.~t:t::;e* a <ji-''.yii.v."j, and the pair parallel to the sh-:>rter or .-rj.-ir-aiis is a rraiky- pinacoiJ. And in the same way, instead of the indirect pyramid, we hare two horiiontal prisms, each formed by the four faces parallel to one lateral axis and cutting the other lateral axis and the vertical axis: the faces of the prism parallel to the longer lateral axis (the macro-axis) con- stitute a macrifdome, and those parallel to the brachy-axis constitute a bratkydome. If both domes are developed, the resulting form is a rectangi'lar pyramid, or octahedron.

r1

t

y

27. Fig. 5 shows the principal simple forms of this sys- tem. There is only one purely elementary form — the true

Logy.

octahedron, or pyramid, shown nt (a). The other forms of the system are, necessarily, all compounds of two or more forms, as, excepting the pyramid, none of the forms has more than four faces, and the basal planes and pinacoids have only two, and it requires at least six faces to form a complete holohedral crystal. The heraihedral forms of the system are unimportant — in fact, so far as is known, there are no true hemihedral orthorhombic forms in nature — hence Ihey will not be discussed. The forms shown in Fig. 5 are as follows:

(rt) Octaluiiri'ti uv pyramui.

[b) Prism (1-1) and basal plane (2).

(r) Pinacoidal prism, made up of niacropinacoid (1) and brachypinacoid (2), and basal plant- (3),

id) Tabular prism, made up like (c), but with the long edges beveled by a macrodome (4).

(c) Basal plane (1) anA prism (2-3) with front and back corners truncated by a macrodome (3-3).

(/) Basal plane {I), prism (2-2), macrodome (3-3), and brachydome (4-4).

The tabular orthorhombic forms are very characteristic of the mineral barite.

Monoclinic System.

28. The crystals of the monoclinic system are sym- metrical with reference to only one plane. In examining a crystal of this system, the symmetry plane is always con- sidered as being vertical and running from front to back; the symmetry axis, therefore, coincides with the transverse lateral crystal axis. This axis, being at right angles to the symmetry plane, is, consequently, at right angles to both the other axes, since they both lie in that plane, and for this reason it is called the ortho- (right) axis. The other lateral axis is oblique to the vertical axis, inclining from back to front, and is called the clino- (inclined) axis.

The forms of this system are prisms, pinacoids, pyramids,

Mineralogy

domes, and basal planes, as in the orthorliombic system. Instead of macro- and brachydomes and pinacoids, however, we have the orlhodome and orthopinacoid with their faces parallel to the ortho-axis, and clinodomf sjA. clitiopinacoid with their faces parallel to the clino-axis.

The eiementary forms whose faces intersect both iheclinn- axis and the vertical axis are divided into two classes — posi- five and (-rt/iVr— according to the position of their faces with reference to the central angles of the crystal. Thus, if a plane be assumed through the vertical axis and the ortho-axis, and another through the two lateral axes, these planes will, of course, intersect each other along the ortho- axis, as it is common to both of them, and at their intersec- . tion will form four plane angles, the alternate

angles being equal, but one pair — the tojj-front and lower-back angles — being larger than the other pair, on account of the inclination of the clino-axis; and ail crystal forms whose faces are

in the two sections of the crystal lying within ' the planes of the two larger plane angles are

' known as positive, while those whose faces are in the smaller sections are known as negative. Fig. 6 shows the four faces forming a positive pyramid. The prism, clinodome, and the pyramid are made up of four faces each; the orthodomes, pinacoids, and basal jtJane have only two faces to each form,

29. As the least number of faces a solid, holohedral crystal of any form can have is six. none of these elementary forms occur alone in nature; but all nionoclinic crystals are made up of combinations of two or more of the elementary forms. In Fig. 7, we have shown a few of the simpler and more common forms. To assist the student in identifying them, we have numbered each kind of face as follows:

1. Orthopinacoidal face. -\-l

3. Clinopinacoidal face. —I

3. Prisra face. t

-|-4. Positive pyramidal face.

—4. Negative pyramidal face.

Positive orthodome face. . Negative orthodome face.

Clinodome. Basal plane.

d

Mineralogy.

Zl

The last three forms arc what arc called crystals, twinning; being merely a combination of two (or more) crystals of the same form, but with their axes in different positions. Twinning sometimes produces what are appar- ently entirely new forms, but generally the individual forms

can be readily distinguished. Twinned crystals usually have reentrant, or concave, angles, by which they can be readily distinguished from normal crystals, in which concave angles never occur. They may frequently be recognized also by the tiny ridges or stri;e on the coiiimcm face, meet- ing in a line down the middle of the face, as in the case of gypsum, shown normal at {,i) and twinned at (i). This indicates that the face is really made up of two faces in the same plane, but with their striie in different positions.

Mineralogy.

§35

Trici.Ixic System.

30. As the axes of the triclinic system are all of dif- ferent lengths and all inclined to one another, the system can have no symmetry planes, and there can, under no cir- cumstances, be more than two faces of a kind identical in form, luster, and position with reference to the axes. The simplest crystals thus require at least three different forms to complete the crystal. Thus, the simplest prismatic crystal is made up of two sets of prism faces (two faces to a set) — or the prism may be made up of two sets of pinacoidal faces — and a pair of basal planes; six faces in all, represent- ing three different forms.

The forms of the triclinic system are practically the same as those of the monoclinic prisms, pyramids, domes, pina-

FlG. 8.

coids, and basal planes. Since both lateral axes are inclined to the vertical axis, however, we can not very well specify either as the clino-axis, so we resort again to the terms macro- and hracJiy- to distinguish the long and short

Mineralogy.

lateral axes, respectively, as in the nrthnrhnmbic system, and the domes and pinacoids are distinguished in the same way, macrodomes and macropinacoids having their faces parallel to the longer lateral axis, and the faces of brachy- domes and brachypinacoids being parallel to the shorter lateral axis.

Fig. 8 shows some of the simpler triclinic crystals with the fares of the different forms marked as follows:

1. Macropinacoid. — 4, Negative macrodome.

3. Brachypinacoid. + 5. Positive brachydome.

-|-3. Positive prism. —5. Negative brachydome.

— 3. Negative prism. 0. Pyramid.

-j- 4. Positive macrodome. 7. Basal plane.

31* Occasionally the inclination of the lateral axes to each other is so slight that it becomes very difficult to dis- tinguish the triclinic forms from similar monoclinic forms. In such a case the student should remember that the angle between the pinacoidal crystal (and cleavage) faces of the monoclinic crystals is always exactly a right angle, while in the triclinic system there is never any angle less than three or four degrees away from a right angle.

Hexagonal System.

32. The hexagonal system is very closely allied to the tetragonal system. All the forms of the latter system have exactly corresponding forms in the hexagonal system ; there tieing three equal lateral crystal axes in the hexagonal system, however, all the lateral faces of hexagonal forms occur in multiples of three, while in the tetragonal system they occur in multiples of two, only. The angles between lateral faces also differ correspondingly.

The elementary forms of the system are direct and indirect hexagonal prisms and pyramids (called prisms and pyramids of the onier and second order, respectively), dlhex- agonal prisms and pyramids — corresponding to the octagonal

34 Mineralogy.

prisms and pyramids of the tetragonal system — and basal planes. These forms are shown in Fig. 9 in the order named.

Hemihedral Forms.

mihedral forms of the hexagonal system are

33. The he: nore abundant ant than the holohedral form!

Pyramidal Hemlbedral

insequently, more impor-

rmi4. — There are two dis- tini-t classes of hemlhedral forms in this system. The elementary forms of the first class, which are called pyra- wdt/ff/hemihedral forms, are only two in number, and are derived by developing the faces in the alternate sections of the crystal forms between the six vertical symmetry planes. Thus, if in the dihexagonal prism we develop the alternate prism faces, which are shown shaded in Fig. 9, we get a prism of thf third oriliT ; and by developing the shaded faces of the dihexagonal pyramid, we get a \\e.x- 2.%(ii\-A pyramid of the third order. The prisms and pyra- mids of the third order can be distinguished from those of the first and second orders only through their association with other hemihedral forms.

§35

Mineralogy.

34. Rbomboliedral Hcmihedral Porin The

liemihedral forms of the second class, called rhombohedral hemihedral forms, are derived in the ordinary manner, each alternate crystal face above and below the horizontal sym- metry plane being developed. The class derives its name from the most common and characteristic form — the rhoiit- hohfiiroH — which is the hemihedral form of the hexagonal pyramid. The rhombohedval hemihedral form of the dihex- agonal prism is the scalftlohcdroii, a double-ended he.tagonal prism, each face of which is a scalene triangle (a triangle with no two sides equal).

Calcite always crystallizes in the rhombohedral-hexagonal system, and so also do dolomite and siderite, Calcite crys- tals assume a great variety of forms. Fig. 10 represents

some of the many characteristic forms of calcite. The forms from a to f/ are rhombohedrons; c is a scalenohedron; prisms with rhombohedron and basal plane; g, n rhombo- hedrun with basal plane ; It and r', prism and rhombohedrons ; and_/' shows a rhombohedron, scale nohedron, and basal plane. It is sometimes very difficult todistinguish rhombohedrons from cubes, but the faces of a rhombohedron are never exactly square, or even rectangular, but are always more or less diamond-shaped. The vertical axis in the rhombohedron always connects two opposite solid angles, while in the cube it connects the centers of opposite faces.

Hi MINERALOGY. g 35

Rhombohedral hemihedral furms may be easily distin- guished from any other forms from the fact that the inter- section of the upper and lower pyramidal faces of this class with one another, or with prism faces, forms a broken, jagged line, with angles alternately above and below an intermediate horizontal plane, whereas the basal edges of pyramidal faces in all tilher forms are horizontal.

35. Tetartohedral Forms. — Prisms and pyramids of the third order have still further hemihedral forms, formed in the ordinary manner, and called tetartohedral forms, because they have developed only one-fourth of the faces of the holohedral forms. The principal forms are a rhombohe- dron, identical with the rhombohedron of the rhombohedral section, a trapezohedron, almost identical in form with the rhombohedron, the only difference being that each of the six faces is trapezoidal (has four sides, in two pairs of equal sides, but the sides of one pair are not equal to the sides of the other) instead of rhomboidal (diamond-shaped — four equal sides). These forms sometimes occur in quartz crystals.

Distortion.

36. Natural crystals are usually more or less distorted — in fact, perfect natural crystals are comparatively rare. The crystal axes are extended lineally, destroying their proper proportion to one another, and making faces, which should be identical in shape, very different; or the axes may be bent or twisted — sometimes very much so, twisting com- pletely around — giving curved crystal faces instead of the normal planes. This curvature of the crystal axes appears to be characteristic of a few certain minerals, as dolomite, siderite, quartz, and chlorite, but linear distortion is com- mon in ail minerals.

However badly a crystal may be distorted, it nevertheless always retains certain characteristics of its crystal system, by which it can be identified. Besides the similar luster and markings of corresponding faces, which have already

§35

Mineralogy.

Fkj. 11.

been discussed, we have the fact that the crystal axes, how- ever badly they may be distorted as to relative length, are never distorted as to their relative position to one another; that is, if all or any two of the axes in the normal crys- tal intersect at a given angle, this angle is maintained in the dis- torted crystal, and the corresponding angles between the faces are likewise never distorted. Thus, in Fig. 11, there are shown a normal iso- metric octahedron and three distorted octa- hedrons, and it will be seen that the faces on the distorted forms are in every case exactly parallel to the corre- sponding faces in the normal form. Fig. VZ shows a dodecahedron

way. This same peculiarity runs through all the systems, and forms an infallible guide in identifying them.

IRON (Fe).

37. Iron is the most abundant of the metallic elements, and, from a commercial standpoint, by far the most impor- tant. Native metallic iron is occasionally found in meteor- ites (shooting-stars), but, so far as is known, it does not occur in the native state as a constituent of the earth's crust. The various minerals, however, particularly the oxides, are

Mineralogy.

Color of fractured surface is some shade of brown, commonly dark, and never bright. Specimens sometimes have a nearly black, varnish-like exterior. Theearthy varietiesare brown- ish-yellow to ocher-yellow. The streak is, for all varieties, yellowish-brown.

Composition : A combination of iron sesquioxide and water (2/'V,0, + 3//,(9), iron sesquioxide 83.0, and water 14. 4;. The percentage nf metallic iron is nearly 60. In bog ores and ochers, manganese and phosphorus are com- mon impurities; likewise, clay, sand, etc.

Like hematite, limonite has several different varieties, as follows :

BrotVH Hi-iiiatitf. — This variety includes all the compact forms — botryoidal, stalactitic, etc.

Brown Ocker and Ycllo'ii' Ocher. — Loose, finely powdered, earthy varieties, of brown or yellow color.

Bog Iron Orc.—Kx\ earthy, brownish-black Hmonite, occurring in marshy ground,

Broivn Clay Trans tout: — Similar in composition to hematite clay ironstone, from which it is distinguished by having a brown, instead of red, streak. It occurs as concretions — more or less rounded, ball-like forms or aggregations in clay and sandstone formations. It is frequently of a pisoiitic structure, made up of an aggregation of small concretiims about the size of a pea, or oolitic (looking like the roe of a fish).

B. B. gives the same reactions as hematite. Inclosed tube, gives water. In salt of phosphorus bead, some varieties give a skeleton of silica which exists in the ore as an impurity.

Limonite is distinguished from hematite by its yellowish- brown streak, its giving water, and its inferior hardness. It occurs in secondary and more recent deposits.

41. Maiinetlte. — Magnetite, or magnetic iron ore (also called loiifstone), is remarkable for its strong magnetic prop- erty, being very strongly attracted by a magnet, and some- times being itself a magnet. It usually occurs massive, but

§ 35 Mineralogy. 31

crystals are not uncommon. It crystallizes in the isometric system, usually in octahedrons and dodecahedrons, with an imperfect to distinct octahedral cleavage. The luster ranges from metallic to submetallic on crystal faces. The fracture is subconchoidal, of a shining, slightly greasy luster. The mineral is brittle, and its hardness ranges from 5.5 to 6.5, and its specific gravity from 4.9 to 5.2.

Composition : Combination of iron sesquioxide and iron protoxide (Ft\0 + or F(\0), corresponding to iron 72.485 and oxygen 27.52. Titanium and manganese are common impurities.

B. B. fuses with considerable difficulty. In the O. F., loses its magnetic qualities. In the beads, and on charcoal with soda, reacts like hematite. Soluble in hydrochloric acid.

It is distinguished from hematite and limonite by its black color and streak and by being attracted by the magnet.

Magnetite is most abundant in the older crystalline rocks, such as granite, gneiss, and mica, hornblende, and chlorite schists, and in crystalline limestones. Also common in dis- seminated grains in basalt and other rocks of igneous origin.

42. Siderite. — Siderite, or spathic iron usually occurs massive, with a foliated, or lamellar, structure and slightly curved cleavage faces. It has an eminent rhombohedral cleavage. When crystallized it occurs in simple rhombo- hedrons, with slightly curved faces. It assumes, also, botryoidal and globular forms, having a subfibrous, and occasionally a silky-fibrous, structure.

Perfectly pure sidcrate is nearly white, but it discolors very rapidly on exposure, from the formation of oxides of iron. It is generally fawn color, changing to brown or nearly black. The streak is white. The coarse crystalline varieties have a pearly luster, while the finer-grained varie- ties are duller. The hardness ranges from 3. 5 to 4. 5, and the specific gravity from 3.7 to 3.0. The mineral is brittle and has an uneven fracture.

Composition: Iron carbonate {FcCO) corresponding to

32 Mineralogy. §35

carbon dioxide (CO), 37. and iron protoxide (FiO), 62. 1. Metallic iron 48.2f. In most cases, a part of the iron protoxide is replaced by manganese oxide, lime, or magnesia. Some varieties of siderite contain from 8j to 10 of man-

ganese, which makes the ore more valuable. As the iron diminishes, the calcareous and magnesian siderites pass into varieties known as brown spar and dolomite.

C/ay ironstone or ball ironstone which resembles nodules of hardened clay, is a siderite clay ironstone, similar to those of hematite and limonite, which is found in the shales of the

coal measures.

Clayband ironstone which is of similar composition, is in connected beds rather than in nodules, and blackband iron-

stone contains much carbonaceous matter.

B. B. blackens and fuses at 4.5. In closed tube, decrepi- tates, gives off carbonic oxide and carbonic acid gas, blackens and becomes magnetic. In the beads and with soda on charcoal, reacts for iron, and when heated with soda and

niter on platinum foil, generally reacts for manganese. Only

slowly acted upon by cold hydrochloric acid, but dissolves

t with brisk effervescence in hot hydrodiloric acid.

Siderite may be distinguished from caU ite, the carbonate of lime, and dolomite, the carbonate of lime and magnesium, both of which it much resembles, by its higher gravity, and by becoming magnetic before the blowpipe.

Siderite occurs in many of the rock strata, in gneiss, mica slate, clay slate, and as clay ironstone in the coal measures.

43. The foregoing iron minerals are the ones from which practically all the iron of commerce is obtained. The sul- phides of iron are important, less on account of the iron they contain — though sometimes smelted for iron after roasting to expel the sulphur — than on account of their sulphur con- tents, and because of their frequent association with other metals of great importance, n<nal)ly gold.

44. Pyrlte. — Py rite, or /rr/V-.v, occurs both crys- talline and massive, and also in imitative shapes — globular.

§35 Mineralogy. 33

reniform, and stalactitic. It crystallizes in the isometric system, usually in cubes, with the striic on each face at right angles to those on the adjoining faces — a characteristic of the hemihedral cube. The pentagonal dodecahedron [(i). Fig, 2] is also a very coninion form, and the octahedron somewhat less common. Combinations of two or all of these forms are frequent,

Pyrite has a pale, brass-yellow color, but the streak is greenish or brownish black. Its luster is metallic, and from splendent to glistening. It is quite hard (from to 6. 5) and will strike fire with steel. It is brittle, with a conchoidal and uneven fracture. Specific gravity ranges from 4.8 to 5.2.

Compoiitien : Bisulphide of iron (/c,), corresponding to sulphur 53.3 and iron 46. T;*. It is used largely in the manufacture of sulphuric acid, and frequently contains gold in paying amounts, for which reasons it is of commercial importance. Small amounts of nickel. C(ibah, and copper occur frequently as impurities,

B. B. on charcoal gives off sulphur, burning with a blue flame, and leaving a magnetic residue. In the closed tube, gives a sublimate of sulphur and a magnetic residue. Gives, when pure, reactions for iron in the beads; insoluble in hydrochloric acid, but decomposed by nitric.

Pyrite is distinguished from chalcopyrite by its greater hardness, as it can not be scratched by a knife and strikes fire with steel; and its color is also characteristic. It is dis- tinguished from gold by its brittleness and by giving off sulphur fumes when heated.

Pyrite occurs in rocks of all ages, from the oldest crystal- line rocks to the most recent deposits. It occurs usually in small cubes; also in irregular ball-like nodules, and in veins; in clay slate, clay sandstones, and in the coal measures, where it is commonly known to the miner as "sulphur." In other localities it is called "mundic," "brasses," or " fool's gold."

In many gold regions it is worked for gold with profitable results,

34 Mineralogy. § 35

45. Pyrrhotltc. — Pyrrhotite, or magnetic iron pyrites occurs both crystallized and massive. It crystallizes in the hexagonal system in tabular hexagonal prisms with perfect basal cleavage. It has a granular structure, a metallic luster, and in color is between a bronze-yellow and a copper- red, and tarnishes rapidly. Its streak is dark grayish- black. It is brittle and is slightly susceptible to magnetism, being attracted by the magnet when in a fine powder. It ranges in hardness from 3.5 to 4.5, and in specific gravity from 4.4 to 4.7.

Composition : Variable, but mostly corresponding to sulphur 39.5?, and iron (]().5,'. Sometimes contains from 3j to of nickel, this ore (nickclifcrous pyrites) being one of the most important nickel ores.

B. H. on charcoal in R. F., fuses to a black magnetic mass; in the (). F., is converted into iron sesquioxide (/v\(>,), which, when pure, in the beads and on charcoal with soda, gives only an iron reaction; many varieties give reactions for nickel and cobalt also.

It is unchanged in the closed tube, but gives off sulphur fumes in the open tube. It is decomposed by hydrochloric acid with the evolution of sulphureied hydrogen, which has the odt>r of rotten eggs.

Pyrrhotite is distinguished from pyrile and chalcopyrite by its magnetic character and its bronze color on surface of fresh fracture.

COPPKR (Cu).

4ft* This metal has boon known Irom remote antiquity, and was anciently cmploy<l, all>ycd with tin, as bronze, for making edge tools and other Chopper has a red Color and brilliant liisitM\ and is nialicahU-, ductile, ami tenacious, and wIumi warmed .r ruMxd hales a char- acteristic rdi>r. The copper oi" coinn-jorcc is riot pure, but contains traces .f other metals, sn h as ars(Mn\\ tin, silver etc. Its specihc jiravity varies in ai-iNrlant< :ih the treat- ment it has underginc-, Irom It: to >.ih;. lis hardness

Mineralogy. 35

ranges from 2.5 to 3. When heated to whiteness, copper gives off metallic vapors, which impart a green color to the flame. At ordinary temperatures, exposed to the action of dry air, copper is not oxidized; but if acted on by a damp atmosphere it becomes covered with a green basic carbonate, known as "verdigris." A concentrated solution of hydro- chloric acid attacks finely divided copper with facility, and the more solid masses with greater difficulty. Nitric acid, even when cold and dilute, dissolves it very readily, with a rapid evolution of nitrous oxide, which, coming in contact with the air, produces large quantities of characteristic red fumes of nitric oxide.

Copper Minerals.

47. All the copper minerals are colored, all give colored streaks, are rather soft, and most of them are moderately, heavy. They are very apt to be associated with one another, which is a great help in distinguishing some of the less characteristic ones. All except the sulphides, which need roasting first, give copper beads with borax and salt of phosphorus, and when treated with soda on charcoal, can be reduced to a button of metallic copper. They all dissolve in aqua regia, and most of them dissolve in boiling nitric acid, and if ammonia is added to the solution, it gives first a whitish-blue precipitate; this dissolves, on adding an excess of ammonia, giving an intense blue color. The car- bonates dissolve readily in nitric acid, with effervescence. There are numerous rare copper minerals in addition to the common ones here given. The foregoing list, however, includes all those of commercial importance.

48. Native Copper. Copper frequently occurs in the native state, as the result, perhaps, of electrochemical action, by which sulphate of copper, arising from the oxidation of its various sulphides, is caused to slowly deposit the metal it contains.

Native copper crystallizes in the isometric system, in various forms, usually more or less distorted. It is malleahle

36 Mineralogy. § 35

and ductile ; is red in color ; has a metallic luster and shining streak; has no cleavage; fuses readily before the blowpipe into a metallic globule, which, on cooling, becomes coated with a thin layer of black oxide.

Native copper is met with in irregularly-shaped grains and masses in fissures in rocks containing copper ores, and is most abundant in the vicinity of dikes of igneous rocks. It is frequently found in small amounts at or near the out- crop of copper veins, and in the Lake Superior copper region it forms the entire product of the region, occurring mostly in the shape of fine grains, disseminated through the rock.

49. Chalcopyrlte. — Chalcopyrite, or copper pyrites is distinguished by its strong metallic luster and brass-yellow color. It is very much like iron pyrites, but is deeper in color. It usually occurs in amorphous or uncrystallized masses, with an irregular or slightly conchoidal fracture; it is alsrj found in mammillary, stalactitic, and botryoidal forms, and sometimes occurs crystallized, in tetrahedrons and octahedrons of the (hemihedral) tetragonal system, with indistinct cleaVage.

Chalcopyrite ranges in hardness from 3.5 to 4, and in specific gravity from 4.1 to 4.3. Its brass-yellow color is subject to tarnish, becoming deep yellow, and often irides- cent; streak is greenish-black, and slightly shining.

C. mposition : Approximately CuFeS — sulphur 34. 9j, copper 34.02, and iron 30.5,1. Different specimens give different proportions, chalcopyrite really consisting of indefi- nite mixtures of iron pyrites and copper pyrites.

B. B. on charcoal gives fumes of sulphurous oxide and fuses to a magnetic globule. In the closed tube, decrepi- tates, and gives a sublimate of sulphur; in the open tube, gives sulphurous oxide fumes. The rt)asted ore reacts for copper and iron in the bead; with soda on charcoal, gives a magnetic globule of copper and iron. Dissolves in nitric acid, excepting the sulphur, forming a reen solution, which ammonia in excess changes to a iku'p blue color.

Chalcopyrite is distinguished from pyrite by its deeper

§35

Mineralogy.

color anil by its tarnishing, by being easily scratched with a knife, and by the reactions for copper B. B.

The mineral occurs in veins or in lodes in granite, in clay slate, serpentine, gneiss, and other rocks, and is commonly associated with pyrite, blende, galena, and with the other ores of copper.

Chalcopyrite is one of the largest sources of the copper of commerce, and practically all the sulphuric acid of com- merce is made from chalcopyrite and iron pyrites.

50. BornKe. — Bornite, or variegated copper pyrites — also called peacock copper— a somewhat important posi- tion among copper-producing ores. It has a reddish-brown color and metallic luster; its surface tarnishes rapidly on esposure, and is commonly iridescent with different shades of blue, purple, and red; hence, its common names. Its streak is pale grayish-black, and slightly shining. Its struc- ture is massive, granular, or compact. It is brittle, and its fracture is uneven. When crystallized, it is in isometric octahedrons and dodecahedrons; cleavage in traces. Its hardness is 3; specific gravity 4.4 — 5.5.

Compoiition : For crystallized varieties is approximately FcCu,S„ or sulphur 28.0(!*. iron I(i.33*. copper 55.55:*. The above proportions change for other varieties.

B. B, on charcoal fuses in R. F. to a brittle magnetic globule. In the closed tube, gives sublimate of sulphur; in the open tube, gives sulphurous oxide fumes. When roasted, gives reactions in the beads for iron and copper; soluble in nitric acid with separation of sulphur.

Bornite is distinguished from chalcopyrite by its copper- red, or bronze-red, color on surface of fresh fracture.

51. Chalcoclte. — Chalcocite, sftmetimes called vitreous copper — o and massive. It crystallizes in the frequently in compound, six-sided pr

r copper glance — also curs both crystallized orthorhombic system, sms. It is found more

frequently, however, in compact lamellar masses. The min- eral is of a blackish-lead-gray color, often tarnished blue or green by oxidation, which gives it an iridescent appearance.

38 Mineralogy. § 35

It has a metallic luster, and its streak is the same color as the mineral on surface of fracture. The ore is friable, slightly sectile, and has a conchoidal fracture. It varies in hardness from 2.5 to 3, and in specific gravity from 5.5 to 5.8.

Composition : CuJ (subsulphide of copper) sulphur 20.2;r; copper 70.8. Sirovicycrite is chalcocite with half of its copper sulphide replaced by the corresponding silver sulphide.

B. B. on charcoal alone melts to a globule, which boils with spurting; with soda, is reduced to a globule of metal- lic copper. It yields nothing volatile in the closed tube, but in the open tube gives sulphurous fumes. It is soluble in nitric acid.

Chalcocite is distinguished from the sulphide of silver (argentite), which it greatly resembles, by the copper reac- tions, and by not being sectile.

52. Tetrahedrlte. — Tetrahedrite, ox gray copper usu- ally occurs massive, granular (coarse or fine), or compact. When crystallized, it occurs in isometric tetrahedral crys- tals, from which the mineral derives its name. It ranges in color from steel-gray to iron-black, with the streak the same, or sometimes brown, or cherry-red. It is brittle, and has a conchoidal, uneven fracture. The hardness ranges from 3 to 4.5, and specific gravity from 4.7 to 5. (J (in the mercury- bearing variety).

Composition : It is essentially a mixture of sulphides of copper and antimony, corresponding to the formula 4 O/.S'-f- SbJ>i (or CuSl\S, but the sulphide of antimony may be partially replaced by sulphide of arsenic, or of bismuth, or both, and the subsulphide of copper may be partially replaced by corresponding sulphides of silver, mercury, iron, or zinc. The argentiferous variety constitutes quite an important silver ore, and is steel-gray to dark gray in color. The mer- curiferous variety, which often contains 15 to lS*i of mercury, is dark gray to iron-black.

B. B. the characteristics difi"er in different varieties. In the closed tube, all fuse and give a dark-red sublimate of

§35

Mineralogy

antimonoiis sulphide ; when containing mercury, a faint dark- yray siiblimaic appears a low, red heat; if much arsenic, a siitiliniute of arsenous sulphide first forms. In the open tube, fuses, gives sulphurous fumes and a white sublimate of antimony. If arsenic is present, a crystalline volatile sub- limate condenses with the antimony; if the ore contains mercury it condenses in the tube in metallic globules. B, B, on charcoal, gives a coating of an timonous oxide; sometimes arsenic oxide, zinc oxide, and lead oxide. The arsenic may be detected by the garlic odor exhaled when the coat is treated in the R. F. ; the zinc oxide assumes a green color when heated with the cobalt solution. Roasted, the mineral reacts in the beads for copper. With soda on charcoal, yields a bulti>n of metallic copper; during this test the presence of even a trace of arsenic becomes apparent by the odor. The presence of mercury is best told by fusing the pulverized ore in the closed t'.'be with about three times its weight of dry soda, the metal subliming and condensing in small metallic globules. The silver is determined by cupellation. Nitric acid decomposes the mineral, with a separation of sulphur and antimonous and arsenous acids.

Tetrahedrite is widely distributed, and is valuable, not so much as a copper ore as an ore of silver.

53. Cuprite- — Cuprite, or red cofififr ere, occurs both crystallized and massive and sometimes earthy. It is remark- able for its color, which is deep red, of various shades. The streak is reddish-brown. It crystallizes in isometric octahe- drons and dodecahedrons, and combinations of the two. It has a well-defined cleavage, adamantine to submetallic luster, and an uneven or conchoidal fracture, and is very brittle. Hardness, 3.5 — i; specific gravity, .i.S,') — (1.15. When crys- tals of this mineral are opaque, they have an iron-gray tint on the surface, but their peculiar red color becomes appar- ent when they are reduced to a fine powder.

Coinpositipii : Suboxide of copper {C'lO) oxygen 11.2;*, copper 88. y?:.

B, R. in the forceps, fuses and colors the flame emerald-

40 Mineralogy. § 35

green ; moistened with hydrochloric acid, the flame is momen- tarily colored azure-blue. Unaltered in the closed tube. On charcoal, first blackens, and is then reduced to a globule of metallic copper; in the beads, reacts for copper; soluble in concentrated hydrochloric acid.

It is a very rich and pure ore of copper, but seldom occurs in large quantities, and usually only at or near the outcrop of copper veins.

54. Melaconite. — Melaconite, or black copper orc is another oxide of copper, resembling cuprite in its blowpipe reactions, but differing from it in physical characteristics. It usually occurs as a black powder, or as dull black, friable masses and botryoidal concretions, in veins of other copper ores. These masses are composed usually of melaconite mixed with earthy impurities.

Melaconite frequently contains sulphur and arsenic and often considerable quantities of oxide of iron and manganese. This would indicate that black oxide of copper, which is obtained in many localities in sufficient abundance to render its extraction an important consideration, is the result of the decomposition of other ores, such as copper pyrites. The hardness is about 3; specific gravity, 6.25.

Composition : Copper oxide (CfiO) oxygen 20. Ij; cop- per 79.9.

B. B. in O. F., infusible. Other reactions, as for cuprite.

55. Malachite. — Malachite, or great carbonate of cop- per occurs both crystallized and massive, more usually the latter, with a botryoidal, stalactitic, or divergent structure which is very characteristic. Often it is fibrous and banded in color; frequently granular and earthy. It has a perfect cleavage, and crystals have an adamantine luster, inclining to vitreous. The fibrous varieties have a more or less silky luster. The color is usually bright green, the same speci- men, hcnvever, exhibiting a diversity of shades from bluish- or grass-green to nearly black. The streak is paler green. The fracture is uneven. Hardness, IJ.") — 4; specific gravity, 3. T— 4.

§35 Mineralogy. 41

Composition : May lie represented by the following fiir- raula : CnCO + CuH,0 (or CuCO + ( uO + }lfi)—s. mixture of carbonate and hydrate of copper, containing alAi metallic copper and %.'!% water.

B. B. fuses at 2, coloring the flame emerald-green; on charcoal, with soda, is reduced to metallic copper; in the beads, reacts for copper; in the closed tube, blackens and yields water; effervesces with acids.

Malachite is easily distinguished by its softness and green color and streak from all other minerals except a series of rare copper minerals that are also green and soft {the phosphates, arsenates, and chlorides); and from these it can usually be distinguished by its radiating structure and by its effervescing with acids.

Malachite is a very common mineral at or near the out- crop of most copper veins, and if hard and solid, it is highly prized as a beautiful ornamental stone for inlaid work, vases, etc., as it takes a fine polish.

56. Ajeurltc. — Azurite, or blue copper carbonate, occurs

both in mammillary concretions and in well-defined and brilliant crystals. It also occurs massive and likewise earthy. It has a nearly perfect cleavage and a vitreous, almost adamantine, luster. Its color comprises various shades of azure-blue, passing into Berlin blue. Streak is lighter in color. The mineral is brittle and has a conchoidal or uneven fracture. Hardness, 3.5 — 1.5; specific gravity, 3.5";i.83.

Composition; May be represented by the formula ZCuCO 4" CuHO, corresponding to carbon dioxide So.G<t, copper oxide (i9.2;< (metallic copper 55.4), and water fi.2l<,

B. B. the same reactions are observed as for malachite. It is easily distinguished by its softness, blue color and streak, and by effervescing in acids.

Azurite occurs almost always with malachite (or the green carbonate), and is found usually at or near the outcrop of copper veins. The staining power of both of these carbon- ates in rocks is remarkable, a very small proportion giving

Mineralogy.

the rock a decidedly blue or green color, and a few per cent. I is siifficienl to make the rook appear to be almost solid I malachite or azurite. For this reason, the appearance of copper-stained rocks is apt to be seriously misleading ai their value.

S7. Chrysocolla.— Chrysocolla is nevt-r crystallized." It occurs usually as an incrustation, or in thin seams iftJ crevices, and as copper stains on rocks. It also sometimes. I occurs massive and botryoidal. It is often opal-like or I enamel-like in texture, and is sometimes translucent. Most ' varieties are seotile and have a vitreous or shining luster, or are sometimes earthy. Color is mountain-green or bluish- green, passing into sky-blue and turquoise-blue. Streak, when pure, white. Hardness ranges from 2 to 4; specific gravity from 3 to 3.24.

Coitiposition : Hydrated silicate of copper; compositionJ varies considerably in different varieties, owing to the prea-l cnce of impurities. The formula for the pure mineral ia CuSiO -f %Hfi, corresponding to silica 34.2;*, copper oxiddl 45.3 (copper 3C.2), and water 20.5;*.

B. B. decrepitates, colors the flame emerald-green, and i infusible. On charcoal, with soda, is reduced; in closed] tube, blackens and yields water; decnniposed by the acids 4 without a gelatinization of the silica.

LEAD (Pb).

58. Lead is a soft metal of a bluish-gray color, and whea J recently cut exhibits a surface of strong metallic luster. IJ rapidly tarnishes when exposed to the air. Lead is botl malleable and ductile, but its tenacity is inferior to that cfl nearly all other ductile metals. It is flexible and inelastitf It is only feebly attacked by hydrochloric acid, even wheoi'fl concentrated and boiling. Weak sulphuric acid does nots act on lead when air is excluded, but if heated in a concen-- trated solution, SO is evolved, and lead sulphate is slowl/ 1 formed. The proper solvent for lead is nitric acid. Hard-

5; specific gravity, 11.45.

Mineralogy.

Lead Minerals.

59. The lead minerals are all very heavy, quite s

Dft.

and, if pure, all except the sulphide (galena) have a non- metallic, highly adamantine luster. Galena has an eminent metallic luster. They easily reduce to a soft, malleable button of metallic lead when treated on charcoal with soda, and, excepting the sulphate, all dissolve readily in boiling nitric acid, and from this solution sulphuric acid precipi- tates the lead as a white, insoluble sulphate. The carbon- ate dissolves readily, with effervescence, in nitric acid,

60. Galenlte, or Galena. — This mineral, which is also called lead glance, occurs principally in cubes, which are frequently of considerable size. It also occurs in coarse and fine grained, massive forms. The very fine-grained steel galena, which is quite common in silver regions, cuts under the knife, leaving a smooth, shining, metallic surface. <ialena is remarkable for its perfect cubic cleavage and its eminent metallic luster. It is lead-gray in color and streak, very brittle and fragile, and its fracture is uneven. The surface of the mineral is susceptible lo tarnish. Hardness, 3.5—3.75; specific gravity, 7.25—7.7,

Camposilion : Sulphide of lead {I'dS), corresponding to sulphur 13.4;t. lead SO.Ii;. All galena is more or less argentiferous, but no external characters serve to indicate the amount of silver present.

B. B, fuses, gives off sulphurous fumes, coats the coal with a yellow coat, and yields a metallic button of lead. In the open tube, gives sulphurous fumes; is soluble in nitric acid.

Galena is distinguished quite easily from other soft, metallic, lead-gray minerals by its perfect cubic cleavage, which is rarely absent, and by its high gravity

Galena occurs in granite, limestone, and in sandstone rocks, and is frequently associated with ores of copper and xinc. The matrix in which this ore has been deposited is, in most cases, either quartz, calcite, fluorspar, or "heavy- spar" (barium sulphate) It is the most common and

44 Mineralogy. § 35

important ore of lead, and frequently is also a very valu- able silver ore. All galenas carry more or less silver, usually at least 1 or 2 ounces per ton, and when the amount runs up to 10 ounces or over, it generally pays to extract the silver. These silver-bearing, or argentiferous, galenas are more abundant in disturbed or mountainous regions, where they sometimes carry as much as 200 ounces of silver per ton. Every find of galena should be assayed for silver, as this is the only reliable way of determining whether it is silver-bearing.

61. Ceruite. — Cerussite, or white-lead ore is found both crystallized and massive. The massive forms some- times, though rarely, show a fibrous structure. The crys- tals take the form of modified orthorhombic prisms, and often compound, two or three crossing each other ; frequently they interlace or are in radial masses. The mineral occurs also in concretions and in amorphous, or uncrystallized, friable deposits. The crystal and cleavage faces have an adamantine luster, inclining to vitreous or resinous; some- times pearly. The crystals are usually thin, broad, and brittle. Cleavage is imperfect. The color is generally white and gray, though it sometimes happens that crystal- lized specimens are nearly black, from the decomposition of some associated galena; sometimes tinged yellow or brown from iron, or blue or green from associated copper salts. The streak is uncolored. Hardness, W — 3.5; specific grav- ity, 0.47.

Composition : Lead carbonate (PbCO), corresponding to carbon dioxide l(>.r)V', and lead oxide 8:5.5;, or metallic lead about 77.0';. Hard carbonates are impure cerussite, corre- sponding to the clay ironstones.

B. R. fuses easily, and in R. F. on charcoal, yields a metallic button. In clostl luh(!, decrepitates, loses carbon dioxide, turns yellow at first, and then dark red at a higher temperature, and finally, on cooling, becomes vellow again. EfFerv(S(Hts and dissr)lves in nitii*- .icid.

Cerussite is r<a(lily reeujLni/.rd hy its liili jrravitv, bv its

§35 Mineralogy.

cfEervescing in nitric acid, and by giving a lead button on charcoal.

It IB a very valuable ore of lead, quite common in the lining camps of the West. It runs into galena with depth. Like galena, it always contains some silver, and should always be assayed to determine if the silver occurs in profit- able amounts — over 5 to 10 ounces per ton.

62. AntEleslte. — Anglesite occurs sometimes crystal- lized, especially on galena, but generally is massive, and is found occasionally as a grayish, ash-like, iirmly adhering incrustation on galena. It is brittle, and varies from trans- parent, in the crystallized variety, to opaque in the massive. Cleavage is usually absent. The fracture is conchoidal.

The color of the pure mineral is white, but generally it is stained brown or yellow by iron, or slightly gray or green by undecomposed galena, copper, and other impurities. The streak is colorless. The luster of the crystallized min- eral is adamantine, sometimes inclining to vitreous or resinous; of the massive mineral, dull to earthy. The name "rock ore "is very appropriately applied to some mas- ; varieties having a very stony appearance. Hardness, 2.75 — 3; specific gravity, 6.3.

Composition: Lead sulphate (PbSO corresponding to sulphur trioxide, 2G.4s*, and lead oxide 73.;*, or metallic lead, about 6K.

B. B. alone decrepitates and fuses at 1.5 (in candle flame); on charcoal, in the O, F., fuses to a clear glass, which on cooling becomes milk-white; in the R. F., is reduced with effervescence to a metallic button. With soda on charcoal, the lead is reduced, and the soda sinks into the coal. When the surface of the coal is removed and is placed on silver and moistened, it turns the metal black — the test for sulphur in sulphates. Very slightly soluble in nitric acid.

Anglesite is distinguished from cerussite by its compact, dense structure, and by not effervescing with acids, and from other similar minerals by its high gravity, adamantine luster, and by its blowpipe characteristics.

46 Mineralogy. § 35

It is an important ore of lead, and occurs chiefly in the upper parts of lead-bearing veins which run into galena with depth. It always contains a little silver, and should be assayed for this metal whenever found.

63. Pyromorpliite. — Pyromorphite occurs usually in hexagonal prisms of a bright green, yellow, or brown color, of different shades, sometimes in crystalline crusts, and sometimes globular or reniform, with a radiated structure. The crystals have a lateral cleavage in traces, and are often nearly transparent. The luster is resinous. The streak is white, sometimes yellowish. The crystals are brittle and have an uneven fracture. Hardness, 3.5 — i; specific grav- ity, 0.5.

Cofnpositiofi : A phosphate and chloride of lead jpO,)+ PbCl —dPb.PO + PbCQ, corresponding to phos- phorus pentoxide 15.75fl, lead oxide T-A'p, and lead chloride 10.25.r?. Some varieties have arsensic replacing the phos- phorus, and in some others lime replaces part of the lead.

B. B. in the forceps, fuses at 1.5, and colors the flame bluish-green, showing the combined presence of lead and phosphorus. This reaction is especially apparent after moistening with sulphuric acid. In the closed tube, gives a white sublimate; alone, on charcoal, fuses, without reduc- tion, to a globule which assumes a crystalline form on cool- ing, while the coal is coated at a distance from the assay with a white sublimate of lead chloride, and nearer the assay, yellow from lead oxide; on charcoal, with S(Kla in R. F., is reduced to metallic lead. In a salt of phosphorus bead, previously saturated with cop{)er Oxide, it colors the O. F. blue, thus showing the presence of chlorine. Soluble in nitric acid.

Pyromorphite is distinguished by its hexai;(nal prismatic crystals, which are frequently hollow inside, by its green color and resinous luster, by its high gravity, and by its blowpipe characteristics.

It occurs chieflv in veins, associated with other ores lead.

§ 36 Mineralogy. 47

ZINC (Zn).

64* Zinc has been used from ancient times for the pur- pose of alloying with copper to form brass. It is a bluish- white metal, and upon a surface of fresh fracture presents a brilliant crystalline structure. At ordinary temperatures it is brittle, but between 100'' C. and 15U° C. it is ductile and malleable. At 205® C. it again becomes brittle and may with ease be pulverized in a mortar. At 433° C. it fuses, and upon cooling exhibits a highly crystalline texture. Hardness, 2; specific gravity, 0.8 — 7.2.

Zinc is soluble in hydrochloric and dilute sulphuric acids, with an evolution of hydrogen gas. It is also soluble in boiling solutions of potash or soda, with a similar evolution of hydrogen gas.

The zinc of commerce, known as spelter," is never chemically pure, but is more or less contaminated with such impurities as lead, cadmium, and iron. It is largely used for galvanizing sheet iron, as a constituent of brass, in electrical appliances, for precipitating gold from potassium cyanide solutions in the cyanide process of gold extraction, for separating gold and silver from lead in the refining of base bullion (lead containing gold and silver), etc.

Zixc Minerals.

65. A specimen of native zinc is stated to have been dis- covered at Melbourne, Victoria, in a cavity in basalt; but the occurrence of this metal in tlie native state requires con- firmation. It usually occurs in nature in combination with sulphur, oxygen, and carbonic, silicic, or sulphuric anhy- drides.

B. B. the ores of zinc are almost completely infusible. They all, except franklinite, have a non-metallic luster; they are only moderately heavy, are rather hard, and are apt to be associated with one another. On charcoal, after strongly heating with soda, they all give a white coat, which glows brightly, is non-volatile, yellow while hot, but white

48 Mineralogy. § 35

on cooling, and which, if moistened with cobalt solution, gives a characteristic yellowish-green, infusible mass. They all dissolve in aqua regia, on boiling, while the carbonate dissolves with effervescence in warm nitric, hydrochloric, or sulphuric acid.

66. Sphalerite. — Sphalerite, or zinc-blende varies greatly in color, from white to yellow, red, brown, and black, and the streak is white to reddish-brown. The luster in some of the black varieties is submetallic to adamantine, but is most frequently resinous. It often occurs crystallized, in isometric dodecahedrons, octahedrons, and their modifica- tions, but is more frequently massive, and has a perfect dodecahedral cleavage. It is brittle and usually opaque, though sometimes transparent when crystallized. The fracture is conchoidal.

The variations in color in this mineral are due to the pres- ence of impurities, the dark variety containing sulphide of iron, while the red variety has frequently as much as bi> of cadmium. Hardness, 3.5 — 4; specific gravity, 3.9 — 4.2.

Composition: Zinc sulphide, (ZnS) containing sulphur 33j, zinc (j7. It often has some of the zinc replaced by iron or cadmium.

B. B. difficultly fusible ; alone on charcoal, some varieties give first in the R. F., a reddish-brown coat of cadmium oxide; afterwards a coat of zinc oxide, which is yellow while hot and white when cold. With cobalt solution in the O. F., this coat becomes green. With soda on charcoal in R. F., gives a strong green zinc flame. In the open tube, gives sulphurous fumes, and usually changes color. When roasted and treated in the beads, gives an iron reaction.

Distinguished by its resinous luster, softness, yellow streak, cleavage, and infusibility.

It is the most common and important ore of zinc, and most of the zinc of commerce is derived from this ore. It occurs frequently associated with other sulphide minerals (like galena, pyrite, chalcopyrite, etc.) in fissure veins, and carries more or less silver, and occasionally gold, but usually

Mineralogy.

in insufficient amounts to pay for extraction, as the zinc makes it difficult and expensive to work.

67. SmllhsonJte. — Smithsonite is sometimes found in crystals, but more frequently as incrustations, and in reni- form and stalactitic forms and concretionary masses, and occasionally earthy and friable. When crystallized, it has a perfect cleavage.

Its color, when pure, is yellowish -white, but when con- taminated with iron, it is frequently brown or reddish- brown. The streak is white. The luster is vitreous, inclining to pearly. It is brittle and has an uneven fracture. The massive mineral is frequently called "dry-bone" by American miners, from its very characteristic appearance. Hardness, 5; specific gravity, 4 — 1.5.

Composition: Zinc carbonate {ZnCO, corresponding to carbon dioxide 3S.2, and zinc oxide (J-t.S;, or metallic zinc 52. Part of the zinc is sometimes replaced by iron or manganese, and by traces of calcium, magnesium, or even cadmium.

' B. B. is infusible; moistened with cobalt solution and heated in the O. F., gives a green color on cooling. With soda on charcoal, a coating of zinc oxide is formed, yellow while hot. white when cold, which behaves as above when treated with cobalt solution. Those varieties containing cadmium, when treated with soda on charcoal, give a deep yellow or brown coating before the zinc coat appears. In the beads some varieties give reactions for iron, manganese, copper, etc. In the closed lube, it loses carbon dioxide, and if pure, it is yellow while hot, white when cold. It is soluble with effervescence in warm hydrochloric acid.

Distinguished with some difficulty, owing to the absence of any marked individuality. It is usually grayish-white to green or brown, and massive; is soluble with effervescence in warm hydrochloric acid, and gives characteristic blowpipe reactions.

Smithsonite is one of the most important ores of zinc. It occurs almost invariably associated with the silicates.

60 Mineralogy. § 35

together with which it is extensively employed for the pro- duction of spelter.

68. Calamine. — Calamine was for a long time con- founded with the carbonate of zinc, although they differ materially from one another, in both chemical and physical characteristics. It occurs in botryoidal and fibrous forms; also granular, massive, and crystallized. It has perfect pris- matic cleavage.

Color is usually white; sometimes it has a bluish or green- ish shade ; also yellowish to brown. Streak is white. It is transparent to opaque, is brittle, and has a vitreous luster and uneven fracture. Hardness, 4.5 — 5; specific gravity,

Composition: Hydrous silicate of zinc, ZnJSiO -\-Aq. cor- responding to silica 25,, zinc oxide (37.5;, and water 7.5j; metallic zinc 54.

B. B. is almost infusible 0). Moistened with cobalt solution, gives a deep, ultramarine-blue color when strongly heated, from the formation of a silicate of cobalt. The characteristic green color of the zinc-cobalt test is very difficult to obtain directly, but by fusing with soda on char- coal, a coat is obtained which gives the characteristic green with cobalt solution. On charcoal, it gives the same reac- tions as those already described for smilhsonitc. It gelati- nizes with acids, and is soluble in a strong solution of caustic potash. In the closed tube, decrepitates, whitens, and gives off water.

Calamine is distinguished by gelatinizing with acidf, by its infusibility, and its reactions B. B. for zinc, and by its bladed or radiate structure.

It occurs associated with the other ores of zinc.

69. ZIncite. — Zincite, or red zinc ore, occurs rarely in any well crystallized form, but more frequently in foliated masses or in coarse grains, associated with franklinitc and willemite. It is red to orange-yellow in color, and has an

Note— is the abbreviation for aqua (water), and indicates that the substance contains water.

§ 35 Mineralogy. 51

orange-yellow streak ; it ranges from granular to massive in structure, and has a perfect cleavage. It is brittle and opaque, with a subadamantine luster. Hardness, 4 — 4.5; specific gravity, 5.5.

Composition: Zinc oxide (ZnO), containing zinc and oxygen 19.74. Frequently contains traces of iron and manganese.

B. B. infusible; in the beads, gives a reaction for man- ganese; on charcoal in R. F., gives a coat of zinc oxide, yellow while hot, white when cold, which gives the charac- teristic reaction with cobalt solution. Heated in closed tube, blackens, but resumes its original color upon cooling. Soluble in acids.

Zincite is distinguished from allied minerals without difficulty by its physical characteristics.

70. Franklinlte. — Franklinite, or /?/aci' zinc orCy occurs usually in coarse, octahedral and dodecahedral grains, resembling magnetite, almost universally associated with zincite, willemite, and calcite. Occasionally it is found massive. It has only an indistinct cleavage. The luster is metallic, color iron-black, and streak reddish-brown. It is brittle, has a conchoidal fracture, and is slightly magnetic. Hardness, 5.5 — 0.5; specific gravity, 5.1.

Composition : A variable mixture of iron oxide (magnet- ite), zinc oxide, and oxide of manganese. The average of several samples gave: iron 45. 10, manganese !).I58;*, zinc 20.30, and oxygen 25.10. It is essentially a magnetite, containing zinc and manganese oxides partly replacing both oxides of iron.

B. B. infusible. With borax in O. F., gives a reddish- amethystine bead, showing the presence of manganese, and in the R. F., the bead becomes bottle-green, which indicates the presence of iron. On charcoal, with a mixture of soda and borax, gives a coat of zinc oxide, which may be further identified by the cobalt solution. When fused with sodium carbonate and sodium nitrate on platinum foil, gives an alkaline manganate of a bright green color. Franklinite is

52 Mineralogy. § 35

soluble in hydrochloric acid, with the evolution of a small amount of chlorine gas.

Franklinite is distinguished from magnetite, which it greatly resembles, by its slighter magnetic property, and by its reactions B. B. for zinc.

It is found abundantly at Franklin, New Jersey, asso- ciated with the other zinc minerals, zincite and willemite, hence its name.

71. Willemite. — Willemite occurs in minute crystals; massive; disseminated in grains, and infrequently fibrous. Its color is whitish or greenish yellow, to green, red, or brown when impure; streak, uncolored. Its luster is vitreous-resinous. Transparent to opaque. It is brittle and has a subconchoidal fracture. Hardness, 5.5; specific gravity, 3.H9 — 1.27.

Composition : Anhydrous silicate of zinc {ZnSiO con- taining silica 27.15 and zinc oxide 72. 9j.

B. B. in forceps, glows and fuses with difficulty to a white enamel. With soda on charcoal, gives the characteristic coat of zinc oxide. It is decomposed by hydrochloric acid with separation of gelatinous silica. With cobalt solution it gives the same reaction as calamine.

Many impure varieties give reactions for manganese and iron.

Found almost universally associated with zincite and franklinite. At Franklin, New Jersey, it occurs in such quantities as to constitute an important ore of zinc.

SILVER (Ag).

72. Silver is a white metal, capable of receiving a bril- liant polish. It stands next to gold in point of ductility and malleability. It is harder than gold and softer than copper. Hardness, 2.5—3; specific gravity, 10.5 — 11.1.

Unless in a fine state of division, silver is not acted upon by hydrochloric acid, and even then it must be heated to boiling before decomposition of the acid is effected. It is

Mineralogy.

not acted upon by dilute sulphuric acid, but when heated in concentrated sulphuric acid, the acid is decomposed with the formation of silver sulphate and the evolution of sul- phurous oxide. Nitric acid attacks silver at even ordinary temperatures, with the formation of silver nitrate, and the evolution of nitric oxide. Oxide of silver may be reduced by heat alone.

Sii,Ver Minerals.

The silver minerals are all soft, all are heavy, most of them have a metallic luster, and several are sectile. They are all easily fusible, and can be reduced to a button of metallic silver, on fusing with soda on charcoal, or when cupelled with metallic lead. With the exception of the chloride group, they all dissolve in boiling nitric acid, and hydrochloric acid or common salt added to a silver solution throws down a white, curdy precipitate of chloride of silver, which is soluble in an excess of ammonia.

While there is a large number of silver minerals, many of them are very rare, and only those of common occurrence are here described. The ores of lead, copper, zinc, anti- mony, and arsenic often contain silver in paying quantities, especially in disturbed regions, but in a form that is invisi- ble to the eye, so that it must be cupelled or assayed to determine the presence or quantity of silver.

Dry oris, oT milling ores, are those consisting essentially of quartz and rich silver minerals, suitable for amalgama- tion ; those containing sulphides of lead or copper in quantity are smelting ores.

Free milling ores are dry ores suitable for direct amalga- mation without any previous treatment save crushing.

Refractory ores are those containing antimony, arsenic, sulphur, and zinc-b!ende, making it necessary to roast the ore before amalgamation. These elements render ore refractory for smelting also, zinc-blende being especially undesirable, and reductions are made on the price of ores when the amount of this ingredient exceeds a certain pro- portion, usually 12;<.

54 Mineralogy. § 35

73. Native Silver. — Silver is found in a metallic state accompanying almost all of its ores, particularly the sulphide and chloride. It occurs in distinct crystals, in amorphous masses, in long filamentary strings {hair or wire silver) and in compressed plates.

It has a shining, silver-white color and streak, but is frequently tarnished to a grayish-black color. It has a metallic luster when freshly fractured, has no cleavage, and is extremely ductile and malleable. It consists of nearly pure silver, containing usually small amounts of copper and gold.

Native silver is readily distinguished by its high gravity, pure white color, and malleability. It is easily dissolved by nitric acid.

74. Argentite. — Argentite, or silver glance usually occurs massive ; also in reticulated and filiform shapes and in modified isometric dodecahedrons. Its color and streak are blackish-lead-gray. The streak is shining. It has a metallic luster, conchoidal fracture, and is malleable. Hardness, 2 — 2.5 ; specific gravity, 7.3.

Composition : Silver sulphide {AgS) sulphur 12.95, sil- ver 87. W.

B. B. on charcoal, fuses in the O. F. with intumescence (swelling), emitting sulphurous fumes, and yielding a glob- ule of metallic silver. In the open tul>e, gives off sulphurous oxide. It is fusible even in the flame of a candle.

Argentite is distinguished from other ores of silver by its nialleabilitv.

75. Stcphanlte* — Stephanite, or brittle silver is of an iron-gray color, inv lining to black, with streak of the same color and metallic luster. It has a conchoidal fracture. It iisuallv iHVurs massive, has nv> oleavavre, and is verv brittle. Hardness, "5 : sjHvitic gravity,

or JV.IxX r sulphur liv-i, antinuMn- KV3<, silver

IV Iv v>n V harvvMl, fuses witi\ spurting of small panicles, coals the v\v;il with antimv>nous oxide which, after long

blowing, is colored red from oxidized silver, and a globule of metallic silver is obtained. In the closed tube, decrepi- tates, fuses, and afterwards gives a faint sublimate of anli- raonous sulphide. In the open tube, gives fumes of antimo- nous oxide and sulphurous oxide. It is soluble in heated dilute nitric acid, with a separation of sulphur and antimo- nous o.\ide.

Stephanite is distinguished from other silver-aiilimony minerals by its color and streak, and from argentite by brittleness and antimony reaction.

76. Pyraruyrlte.Pyrargyrite, ovruhy silver, usually occurs massive, though occasionally crystallized. The cleavage is imperfect. The mineral is dark-red to almost black in color ; has a cochineal-red streak, slightly darker than that of proustite. Its luster is from vitreous to ada-

mantine. It i gravity, 5.8.

Composition : antimony 22. 5;, :

B. B, on chai

very brittle. Hardness, ;

specific

I'ii,

soff

AgSbS, (or 3yJiV>Ji*,.S\)-sulphu

r 59.8. lal, fuses with spurting to a globule, ( antimonoHS fumes, and coats the coal white ; with soda on charcoal, in the O. F., or by prolonged heating without fluxes in the R. F., gives a globule of silver. In the closed tube, gives a reddish sublimate of antinionous sulphide; in the open tube, gives sulphurous fumes and a while sublimate of antimonous oxide. In some varieties arsenic is present, in which case it can be recognized by its garlic odor when the pulverized mineral is treated in the R. F. with soda on charcoal.

It is decomposed by nitric acid with a separation of sulphur and antimonous oxide.

Pyrargyrite is distinguished by its dark-red color, its streak, and its high gravity.

77. Proustite. — Proustite, or light ruby silver, is of practically the same composition as pyrargyrite, but with arsenic replacing much or all of the antimony. It is similar, also, in occurrence and physical properties. It occurs both

56 Mineralogy. § 35 !

crystallized and massive. It has a cochineal-red color and ' a cochineal-red streak, inclining to aurora-red. Luster is ' splendent adamantine. It is transparent and very brittle. Hardness, 3.25; specific gravity, 5.5.

Composition : AgAsS, (or 3-,.S+v4f,5,)=sulphur 19.4;<, arsenic 15.1, silver 05. 5;<. I

B. B. un charcoal, fuses and emits odors of sulphur and arsenic; or with soda on charcoal, in the O. F., or by pro- longed heating without fluxes in the R. F., gives a globule I of silver.

In the closed tube, fuses easily, and gives a faint sublimate of arsenous sulphide ; in the open tube, sulphurous fumes ' and a white crystalline sublimate of arsenous oxide. Some i varieties of proustite contain antimony.

Proustite is distinguished from pyrargyrite by its lighter i color and streak and by the reaction B. B. for arsenic.

78. CerarKyrite.—Cerargyrite, or horn silver, is so .1 called from its horn-like color and luster. It usually occurs massive and looking like horn or wax; often in grains and thin seams ; rarely crystallized, and cleavage is absent. It has a grayish color and streak, but becomes tarnished to a brown or violet-brown color on exposure. It has a non- metallic, wax-tike luster. It is very sectile, and can be cut into shavings with a knife. A plate of iron rubbed with it becomes silvered. Hardness, 1 — 1.5; specific gravity, 6.5.

Composition: Silver chloride (j,fC"/) chlorine 24.7 and silver 75. 3;(,

B. B. on charcoal, givesaglobuleofsilver. Added toasalt of phosphorus bead previously saturated with copper oxide, and heated in theO. P., imparts an aitire-blue color to the flame, indicating chlorine. In the closed tube, fuses without decomposition. A fragment placed on a strip of zinc and . moistened with a drop of water swells up, turns black, and is finally reduced to a globule of metallic silver. Insoluble in nitric acid, but soluble in ammonia.

It occurs at or near the surface of most silver-bearing veins, and is distinguished by its sectiKty and waxy appearance.

Mineralogy.

GOLD (Aa).

79. Gold has a characteristic orange-yellow color, and is the most malleable of all metals. Hardness, 2.5 — 3; specific gravity, 19.3.

When precipitated from its solutions, gold has a dark- brown color, but assumes its ordinary color and metallic aspect upon beinj polished or heated.

Gold is not attacked by sulphuric, nitric, ur hydrochloric acids separately. Aqua regia completely dissolves it, form- ing auric chloride. Free chlorine gas attacks gold, and this reaction is the basis of the chlorination process. Dilute solutions of the alkaline cyanides also dissolve it. Pure gold may be indefinitely exposed to the action of air and moisture without becoming tarnished. It is highly esteemed, on this account, for jewelry and coins.

Gold Minerals.

80. Gold occurs metallic in nature, alloyed with more or less silver, and frequently with minute quantities of copper and iron. It is also found in combination with the rare metals palladium, rhodium, and platinum, and likewise with mercury, forming a native amalgam. With tellurium it forms several compounds of some commercial interest.

81 1 Native Gold. — Gold, in the native state, presents a characteristic yellow color, somewhat paler than that of the refined metal, from the presence of some silver. Its natural surfaces are sometimes dull or tarnished, and must be rubbed with some hard substance before they assume the ordinary appearance of gold. When broken by repeated bending, it presents a matted, silky structure, more or less fine in accordance with the purity of the specimen.

It occurs in veins, as grains, scales, wires, leaf-like, and seldom as more or less perfect isometric octahedral and dodecahedral crystals, and very commonly as rounded grains and nuggets in gravel beds and placer deposits. It is very

58 MINERxVLOGY. § 35

malleable, and can be hammered out into thin leaves. Cleav- age is absent.

Gold can always be distinguished from all minerals of similar appearance by its great weight, softness, eminent malleability, characteristic yellow color, and the fact that it is not attacked by any single acid.

It is soluble in aqua regia (three parts of hydrochloric acid to one part of nitric acid), and fuses quite easily in the blowpipe flame.

Native gold is found most commonly as rounded grains and nuggets in stream beds or placer deposits, at the bottom of the gravel bed. It occurs also in association with quartz and pyrite in veins in slate, schists, and the granitic rocks, especially in highly disturbed regions.

It is also found, though invisible to the eye, in many copper ores, iron ores, and arsenic ores. It contains from a trace to 40 of silver, and sometimes small amounts of other metals.

82. Sylvanite. — Sylvanite, or graphic tellurium is, perhaps, the most abundant combination of gold and tel- lurium. It occurs most frequently interspersed in quartz vein-stuff in groups of silvery-white crystals, resembling Hebrew characters. This resemblance to written characters gives it the name of graphic tellurium. Its color and streak are from silver-white to pure steel-gray, and sometimes nearly brass-yellow. It has a metallic luster, rather a dis- tinct cleavage, and an uneven fracture. Hardness, 1.5 — 2; specific gravity, S.2.

Composition is {AgAu)Tc., a telluride of silver and gold; tellurium 55.Tfi, silver 'i.Tfi', and gold 28.(1. Antimony sometimes replaces part of the tellurium, and lead replaces part of other metals.

B. B. on charcoal, fuses to a dark-gray globule, covering the coal with a white coating, which, treated in the R. F., disappears, giving a bluish color to the flame, indicating tellurium; after prolonged heating, a yellow metallic button is obtained.

§35

Mineralogy.

In the open tube, gives a white sublimate, shading into gray near the assay; when further heated, this sublimate fuses to clear, transparent drops. Most varieties also give a faint coating on charcoal of the oxidirs of lead and antimony. Boiled in concentrated sulphuric acid, the tellurium gives a purple color, which disappears on cooling.

Sylvanite is distinguished by its characteristic graphic structure, its high gravity, and its blowpipe characteristics.

83. Nasyaelte, nv foliated lelluriu?n, has a dark, lead- gray color and streak and a foliated structure; generally massive. It is sometimes called black Ifllurium. Its luster is metallic and splendent; it is sectilc, and flexible when in thin laminie. Hardness, 1 — 1,5; specific gravity, 7. 1.

Composition \'i indefinite, approximately /1,//,5i, 7>,.5i, lead 57, gold 7.7, antimony lAi, tellurium I7.fi*, and sulphur 10.7?6; this corresponds closely with the average analysis of the mineral, though all of the constituents vary considerably in different specimens, and several other ele- ments are sometimes found in varying proportions.

B. B. on charcoal, forms two coatings; one white and volatile, consisting of a mixture of antimonate, tellurate. and sulphate of lead, and the other of yellow ONide of lead, less volatile and quite near the assay. If the mineral is treated for some time in the O. F., a malleable globule of gold remains, which, cupelled with a little granulated lead, assumes a pure gold color.

In the open tube it gives, near the assay, a grayish subli- mate of antimonate, tellurate, and a little sulphate of lead; farther up the tube the sublimate consists of antimonous oxide, which volatilizes when treated with the flame, and tellurous oxide, which fuses at a high temperature to clear, colorless drops. In concentrated sulphuric acid it gives the same reaction as sylvanitc and other tellurides. It is decomposed by aqua regia.

It is distinguished by its foliated structure and blowpipe characteristics.

60 Mineralogy. § 35

Coal.

84. The mineral coal is essentially carbon, associated with more or less of various hydrocarbons (chemical com- pounds of hydrogen and carbon, in various proportions). It is the result of the decomposition of vegetable matter in the presence of water and out of contact with the air, as, for instance, the submerged accumulations in swamps. The immense coal-beds of the world were formed at periods when such vegetation was much more luxuriant than at present. The beds of prat resulting from such decomposi tion alone were in time covered by other formations, and were gradually consolidated and metamorphosed, by the weight of the accumulating strata and the heat of the earth, or iHxasionally by the heat due to local faulting or volcanic action, intortei/, the variety depending upon the stage to which the raetamorphi>sis has progressed. Peat grades into roxvH iihi/ or /iMiU: lignite grades through srmi-dituminaus cv>al into one of the varieties of bitmmimoms coal, and bitu- minous ixvil grades through St-mimtkracite into anthracite which is the highest form of coal. Graphite represents a still higher stage in the metamorphosis of vegetable carbon into mineral matter, and the Jiamamd is the ultimate prvnluot — pure crvsitallised carbon.

All Vvirieties ot cv>al have a more or less compact, massive struvimw not crystalline, and without true cleavage, though son\otimes breaking with a degree of regularity, but from a jointvxl rather than a cleavage structure. It is sometimes lanuiuitxU auvl is often faintly and delicately banded, suc- wsNiYv* Uivcrs ditlerin< slivjhtlv in luster.

The varies in different coals from black to grayish- black. brvwiush-black. and sonnet imes dark-brown; occasion- allv JN ii idcsvxtu Its luster varies also from dull to bril- lumi ; NvinvtiriK- either earthy, resinous, or submetallic. KkivUhv u'K'vcn It is brittle: rarely somewhat scctile. H'v uixio vvccic trotn the impurities present. Infusi- bk' iv xtiSfn'-vc, 'n.: vrteJi beo.>ming a soft, pliant, or Mxiv Ukc luao whci*. heated. On distillatioz most kinds

g 35 MINERALOGY.

yield more or less of tarry or oily substances, which are mixtures of various hydrocarbons,

85. The different varieties of coal are classified princi- pally according to the proportion of volatile matter they contain and the character of this volatile matter. The volatile matter is made up of more or less water, some sul- phur, and the balance, the various hydrocarbon oils and gases. The diilerent varieties of coal also differ from one another, and more or less among themselves, in structure, luster, and other physical characteristics. The hardness varies in the different varieties from 0.5 to 2.5, and the specific gravity from 1 to 1.8. The principal varieties of coal are atithracitf, bituminous coal, cannel coal, and brown coal or lignite.

86. Anthracite. — Anthracite hasabright luster, often submetallic. Color, iron-black, frequently iridescent. Frac- ture, conchoidal. Volatile matter after drying (volatile hydrocarbons) from to ii% (with a trace of sulphur). Burns with a feeble blue flame. Contains from 80 to 9oi( of carbon and 4;< to 12* of earthy impurities (ash). Anthracite graduates into bituminous coal, becoming less hard and containing more volatile matter; an intermediate variety is cMed /rc-c-buriiijig anthracite, or siini-an/Aracite.

87. Bituminous Coal. — The term bituminous coal includes several varieties of coal differing widely in constitu- tion and in their action when heated. They have the common characteristic of burning with a smoky, yellow flame, and giving off hydrocarbon oils and tar on distilla- tion. The proportion of these volatile hydrocarbons in the ordinary varieties varies from 20*to45#, and some varieties contain over 60j(. The proportion of ash varies from l.fijt to 1.% — considerably less than that of anthracite. The explanation of this lies in the fact that anthracite was orig- inally bituminous coal, and as its volume was reduced by the expulsion of volatile matter, the proportion of ash to combustible matter naturally became greater. The sulphur

Mineralogy.

in bituminous coals ranges from a fraction of I3!, in the coals, to 2; and 2.5* in poorer varieties.

88. Bituminous coals may be divided into caking (or coking) and non-caking ciir]s.

Caklns coals soften when heated, and become pasty, or semi-viscid, and the pieces gum together. If the heating is conducted in retorts or in heaps, with a limited supply of air, so that the volatile matter is distilled off without burning the carbon, the latter will remain, after the distillation is com- plete, as the familiar iron-gray mass known as coiv. Non- caklnie coal is apparently in no wise different from caking coal, but will burn freely without any indication of softening or fusing together. Thus far there has been 110 plausible explanation advanced why one coal should cake and another apparently exactly like it should not, but the fact remains. The only way to recognize a caking coal is to cake it,

80. Cannel Coal.— Cannel coal is frequently con- sidered a variety of bituminous coal and is often coking, but it differs considerably from the ordinary bituminous coals in texture and to some extent in composition, as shown by its products on distillation, and is therefore given a separate place in this classification. It is compact, with little or no luster, and has a staty appearance, but without any suggestion of a banded structure. It breaks with a conchoidal fracture and smooth surfaces. Its color is dull black or grayish-black. On distillation it affords, after dry- ing, from 40 to 60 of volatile matter, which includes a large proportion of burning and lubricating oils, much larger than the above kinds of bituminous coal.

Alhertlte, or asphaltic tool, is a mineral intermediate between cannel coal and asphalt. It resembles coal in hard- ness, but is like asphalt in color and luster, is slightly soluble inelher, and about one-third of it is soluble in tur- pentine, and it softens slightly in boiling water.

90. BrownCoal.or Llffnlte. — Brown coal, orlijite,

is sometimes pitch-black, but ofiener rather dull and brown- ish-black. The structure is usually like that of bituminous

g35

Mineralogy.

coal, but it is occasionally somewhat lamellar. The term lignite should properly be restricted to those varieties of brown coal which retain the structure of the original wood. These coals usually contain la;* or 20 of moisture.

Brown coals are non-coking;, but afford a large proportion of volatile matter. Jet is a black variety of brown coal, compact in texture, and takes a good polish.

The varieties of coal known as semi-bitiiminaiis and sriiii- anthracite coals merge into one or the other Sf the above, and can not be said to be distinct varieties.

Metallic Ores Of Secondary Importance.

91. The ores of the six most important commercial- metals, iron, copper, lead, zinc, gold, and silver, and the differ- ent varieties of coal, have been described at some length. In Table I we have presented the metallic ores of secondary importance ; viz,, the ores of manganese, tin, mercury, nickel, cobalt, and antimony.

Minerals Of Secondary Importance.

92. MaatcaneHs. — All the manganese minerals are colored ; most of them give colored streaks ; they are only moderately heavy, and most of them are not hard. They all give amethyst-colored beads with borax in the oxidizing flame, and a very characteristic bluish-green mass when fused with nitrate and carbonate of soda on platinum foil. They all dissolve in boiling HCl (hydrochloric acid), and the oxides give off free chlorine, while the carbonate effer- vesces freely with warm HCl.

93. Tin. — There are only two tin minerals — the oxide, caiMtlterlt, and the sulphide, tin pyrites or tttannlte. The latter is so rare as to be of no commercial importance. The oxide is insoluble in acids, is infu.sible, but gives a while coat on coal when strongly heated with soda in the R. F.

Mineralogy.

: 1

Radiated struc- ture; softness; black color and streak, and blow- pipe reactions.

Bolryoidal struc-

Hardness, color, and streak, and blowpipe reac-

Usually massive

structure.

Color, streak, hardness, and

tiona.

s

If.

m

8S

mi m

s

le

s

tills!

'M

t5 S J

Is

If

Is

Mineralogy.

gravity, , infusi- nd blow.

ure gran- ten rem- otryoidal oncentric ure; also

Usuall ive.

Coloi 1 cleavage

pipe reac

1 l:f.

if-llf i

B. B. Chang decrepitates s

infusible; m: reaction in be solves with

"i-l 6 S 6 S

.s

?

1!

lAl

i- in

U -JlJ

y 'ji-i

u m J

Sis

nS

e

It

s s.

1 i '

1 Is

pI

11

r

a""

Mineralogy.

§36

Si

i ,1

Never crys t a 1 - liied: occurs in crusts. Resembles chrysocolla. Falls

Color and blow- pipe reactions.

B. B. gives arsenical fumes and fuses to a globule, which treated with borai affords re- actions for nickel, cobalt, and iron, which exist as impurities. In the closed and ODen lubes, characteristic re- actions for arsenic, the astMy becoming yellow- ish-green. Soluble in aqua regla.

B. B. infusible. In closed lube, blackens andgivesoff water. In the eada, reacts for nickel. Decom posed bjr //a without gelati- nizing.

!

m

Doubtful: A hydrated

silicateof nickel and magnesium,

composition.

Is

If

o

Garnierite (silicate)

i

§35

Mineralogy.

1'"

Sj Is

gssas

Co U I U

u Ul .J

Mineralogy.

§36

Mi

Perfect cleavage and often needle- lilteor bladed crystals of a steel- gray color.

Extreme fusibil-

reactions.

k

!

B. B. 00 charcoal. fuaca at 1. spreads out and gives sulphurous and antimonoua fumes, coating tbe coal while; this coating, treated in the R. F., tinges the flame greenish-blue. In open tube, gives sul- phurous and an ti mo- nous fumes, the latter condensing in a non- volatile white subli- mate. When pure, perfectly soluble in

B. B. acts like limon- ite. Bauxite is really a limonite in which most or all of the iron has been replaced by aluminum. Gives char- acteristic reactions for

and water.

!

ti

Color: Lead- pray to black -

Streak: Same as color.

Luster: Metal- lic, shining.

Color: White to brown.

Streak: Same as color.

Luster: Sub- earthy.

lis IF

If

B

1 36 Mineralogy.

J. M;2 .

B. B. in the open tube, heated so that the flame enters the tube, gives

off hydrofluoric acid, which etches the glass; the water which con-

denscs in the upper part of the tube reacts for fluorine withBrazil- woikI paper. Fuses in the fiame of a candle. Reacts for sodium in a colorless flame. On tharcuiL fusestuaclear bead which on cooling becomes i>paque; after long blowing the assay spreadsout, the sodium fluoride is absorbed bv the coal, a suffocating ixlorof fluorine is given off. and a crust of alu- mina remains which reacts for alumina with cobalt solution. Solu- ble in sulphuric acid, with evolution of hy- drofluoric acid fumes.

s

Color: White to brownish- red.

Streak: White.

Luster; Vit- reous and greasy.

Cryolite (fluoride)

Mineralogy.

Hardness— it scratches quart e and topaz; its infusibility anJ high gravity; tht- peculiar barrel shape of well-de- veloped crystals. The varieties of

named according to their color; sap- phire (blue); ori- ental ruby (red); oriental topaa (yellow); oriental emerald (green): oriental amethyst (purple); emery (Slack).

£

S

B. B, unaltered; dis- solves slowly in borax and salt of phosphorus to a clear glass, which is colorless when free from iron. Not acted upon by soda. The finely pulverized min- eral when heated with cobalt solution gives a beautiful blue color. Friction excites elec- tricity, and in polished specimens the electrical attraction continues for a considerable length

S

5

as

S

'

Color: Red, blue, green, yellow; color- less when

Str"ea1i; White or colorless.

Luster: Ada- mantine to

vitreous.

E

a-

Mineralogy.

This coat is yellow while hot, but white on cooling, is not volaiiie, and gives a bluish-green color when heaieii with cobalt solution, which is a very characteristic test (but must not be confused with the yellowish-green color that zinc gives when similarly treated).

94. Mercury. — The only mercury mineral of any importance cinnabar.

95. Nickel and Cobalt. — All the nickel minerals are colored and give colored streaks, and most of them arequite hard and very heavy. They are all soluble in aqua regia, giving green-colored solutions, and on treatment with soda on charcoal in the reducing flame, can be reduced to a magnetic mass. They give, after roasting, a brownish-red bead with borax, and a yellow bead with salt of phosphorus in the oxidizing flame, the latter being especially characteristic. The corresponding cobalt minerals are usually associated with the nickel minerals, and when present impart the characteristic cobalt-blue color to the beads.

96. Antimony. — The antimony minerals are soft, are not very heavy, and some have a metallic luster and colored streak, while others have an earthy luster and colorless streak. Most of them are very rare, the only one of com- mercial importance being the sulphide. They all give a volatile pure white coat on charcoal that turns to a dirty yellowish-green when moistened with cobalt solution and heated. When treated on charcoal with soda, they reduce easily to metallic antimony, but this volatilizes at once, forming a white coat; the volatilized antimony has no odor, which distinguishes it from arsenic, which also gives a pure white coat ; but arsenic is more volatile and condenses farther out beyond the assay than antimony, and has a peculiar odor like garlic.

97. Aluminum. All the aluminum minerals are light, they all give colorless streaks, and most frequently they are while, but are liable lo be of any color from the presence of impurities. They differ so from one another as to require special tests for their determination.

Mineralogy.

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Mineralogy.

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(See Calcite.) Like cal- cite. Attacked but little by cold acids. Powder dissolves with efferves- cence in warm acids.

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Mineralogy.

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Mineralogy.

Precious Stones.

98. There are several minerals which, from their trans- parent brilliancy, theii beauty of color, and their hardness, ' coupled with the comparative rarity of their occurrence, are highly esteemed as gems. These are the diamond, sapphire (corundum), ruby (spinel), topaz, emerald (beryl), zircon, garnet, turquoise, and opal, and several others holding a doubtful place in the list of precious stones.

The diamond is the most highly valued. This mineral, which is pure crystallized carbon, is the hardest of all known substances. The peculiar value of the diamond lies in its singular brilliancy of luster and in its remarkable hardness. It is usually colorless, but has not infrequently a slight tinge of color, of which yellow is the most common and the least esteemed. A diamond of the first water is per- fectly transparent and colorless, and free from spots or flaws. The clear green and rose tints are also highly prized. The great diamond-producing regions of the world are South Africa, Brazil, and the southern part of Hindustan.

Corundum ranks next to the diamond in hardness. It is pure crystallized alumina (A/O,), and, when occurring in transparent crystals of pure colors, it yields gems ranking ne.xt to the diamond in value. They receive different names, according to their color ; the blue variety is called sapphire ; the red, oriental ruby; ihegrtcn, or ieti/a/ emerald; the violet, oriental amethyst ; and the yellow, oriental topaz. The finest stones are obtained mostly from the East Indies. Gems of this species are also occasionally found in North Carolina, Colorado, New Mexico, and Arizona,

Spinel is a mineral composed of alumina and magnesia, with usually a little iron. It ranks in hardness next to corundum, and when used as a gem is of a fine red color, though green and violet and other tints also occur. This gem, which is called by jewelers spinel ruby, is obtained chiefly from Siam and Ceylon. It is also found in the United States in Sussex County, New Jersey, and Orange

Viineralogy.

County, New York, sometimes in crystals of large size, but rarely fit for jewelry.

Topax is a silicate of aluminum containing a consider- able amount of fluorine. It has a hardness equal to that of spinel, and its color is most commonly yellow, though some- times green, blue, and white. Those used in jewelry are mostly brought from Siberia, Kamchatka, and Brazil; topaz is also found in Arizona and New Mexico, and on Pike's Peak.

Beryl is a silicate of aluminum and beryllium, which occurs in hexagonal prisms, sometimes of great size. When transparent and of fine colors it affords the valuable green gem, emerald, the sea-green or bluish-green aqua- marine, and the yellow or light green beryl. Its hardness is somewhat less than that of spinel and topaz. Crystals fit for jewelry are sometimes found in the New England States, and in Alexander County, North Carolina, but the emerald and aquamarine are obtained chiefly from the United States of Colombia, Brazil, Hindustan, and Siberia.

Zircon is a silicate of zirconium. The transparent red crystals constitute the gem called hyacinth, and the colorless or smoky crystals, the jargon. The hardness of zircon is about the same as that of beryl and exceeds that of quartz. The valuable gems come mostly from Ceylon, Siberia, and Greenland, the United States having as yet afforded but few.

Garnet is a silicate of very variable composition, and Is of about the same hardness as quartz. Although of quite com- mon occurrence in mica schist and hornblende schist, and some other crystalline rocks, clear, red crystals, of propersize, are held in some estimation as gems. Stones of the finest quality are found in Colorado, New Mexico, and Arizona.

TurquolM; is a hydrous phosphate of alumina. It is opaque, of a delicate blue or bluish-green color, due to copper, which exists as an impurity. Its hardness is inferior to that of quartz. Despite its inferior hardness and opacity, it is estimated as a gem because of its pleasing color and the bcantiful combinations it makes when cut with a smooth, rounded surface and set with diamonds or pearls.

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Mineralogy.

The most valuable specimens come from Khorassan, a prov-l ince of Persia, and from New Mexico. It is also found inj Nevada and Arizona.

Opal is a peculiar, massive, uncrystalline variety ofl quartz, containing variable amounts of water. It is som&rfl what softer than crystalline quartz and has a lower specificfl gravity. The variety used as a gem presents a vivid irides-l cent play of colors. The opal fit for jewelry has not been>l found in the United States, but is obtained from Hungary, Honduras, and Mexico.

Table III gives the more important physical and chemical"! characteristics of each of these gem

Gangue Minerals.

99. The following are a few of the minerals which occur J most commonly in the gangue or vein material of metal* liferous veins, and are associated with most ores:

100. Quartz. — Quartz is a pure oxide of silica. Its formula and chemrcal composition are given in Table II. Quartz in veins may occur either crystalline or massive, in which case it is usually banded and has a structure similar to that of agate. It may be transparent, or it may be . colored by iron or other coloring matter, so as to render it J pink, gray, or almost any color to black.

101. Calclte. — Calcite, or calcspar, is composed i calcium carbonate, and its composition and characteristics] are also given in Table II. It is mainly detected by the easaJ with which it effervesces with acids. Calcite as it occurs itim vein material is usually crystalline, though it may be present,! practically as a crystalline limestone.

102. DolomltcDolomite is a carbonate of lime and magnesia, being merely a limestone with part of the lime replaced by magnesia. The only difference that this substance makes in the appearance of the crystals is that they are less transparent and that the crystals and cleav- age faces become slightly curved, whereas calcite cleaves

J

§ 35 Mineralogy. 89

along the plane faces parallel to its crystal faces. Dolomite is slightly harder than calcite, and is distinguished from the former by the fact that it effervesces in hot acids only, while calcite will effervesce with cold acids. Dolomite frequently occurs massive in vein formations.

103* Barite, or Heavy-Spar. — This is composed of barium sulphate and is described in Table II. Barite is of value as a pigment-forming mineral, and, when it can be obtained pure, may find a ready market. Barite usually occurs crystalline in gangue material, but is sometimes found massive, and in certain deposits or veins from which it is obtained as a pigment material it occurs massive.

104. Fluorite, or Fluorspar. — This is calcium fluo- ride, and usually occurs crystalline in metalliferous veins, but may be massive ; it varies in color from colorless to dark brown or black, according to the impurities it contains, and is often colored a beautiful blue or purple. Fluorite is of commercial importance, being employed for the manufac- ture of hydrofluoric acid, which is used for the etching of glass and for similar purposes ; it is also used as a fluy in smelting works.

Assaying.

Methods Of Analyses.

1. The quantity of any given element or elements in a

substance is determined by quantltat 2. Assaying, generally speaking,

e analysis.

: the quantitative analysis of ores and metallurgical products.

3. There are two general ways of making analyses — the wet way and the liry ',<.-ay. When the term "assay " is used without any qualification, it is commonly understood to mean the dry, or fire, assay. Wet assays are generally spoken of as amilyses. In distinguish them from dry, or fire, assays, although the term is, strictly speaking, equally applicable to both.

4. Wet Assay. — In the wet assay or analysis, the sub- stance tinder examination is first taken into solution by liquid chemicals, usually acids. The amount of any given element in the solution is then determined in one of the two following ways:

1, Reagents are added which precipitate the element in the form of an insoluble compound of known composition. This precipitate is then separated from the solution by filter- ing, and is washed, dried, and weighed. The composition and weight of the precipitate being known, the weight of the element in question may then be readily figured. This method is known as tcravlmetrlc analysis (analysis by weighing).

2. Reagents are added which combine with the elements in question, forming new compounds, either soluble or insoluble. The strength of the reagent sfilution is known; that is, we know the weight of the element in question

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Assaying.

assay to the determination of gold and silver and a very few other metals, which can be more quickly and conve- niently determined in this way, with results sufficiently accu- rate for practical purposes, and which are, therefore, custom- arily bought and sold on Che results of the fire assay. For instance, in America, lead in ores is almost universally determined by the fire assay, as the wet assay for lead, although more accurate than the fire assay, is quite difficult and complicated, and requires considerable time, while the fire assay is very simple ; and by the observation of ordinary precautions, the error in the fire assay may be restricted to a few per cent, of the total lead contents; in the case of a metal as cheap as lead, this error may be disregarded. Moreover, the conditions of the fire assay are practically identical with those of actual smelting, and the results and losses in the fire assay correspond very closely with those in the smelting by which the lead is extracted from its ores on a large scale. Fur exact chemical analyses, however, the wet assay would have to be employed.

Copper and tin in ores were formerly determined by the fire assay; but the results were very inaccurate, and the practice is now practically abandoned, as the wet analyses have been greatly simplifiedparticularly in the case of copper — and are vastly more accurate.

The determination of copper by electrolysis is also used to considerable extent in some of the larger smelters, on account of its simplicity, accuracy, freedom from intricate calculation, and the ease with which it can be acquired. The electrolytic method consists of dissolving the copper out of its ores by means of acids, and then, by passing an electric current through the solution, depositing the copper, in the metallic state, upon a platinum cathode, from which it is washed, and, after drying, weighed.

7. This Paper deals with the assays for the precious metals, gold and silver, and the more important of the base metals and gangue materials, commonly associated with them, which have to be assayed at mines or smelters.

4 Assaying. § 36

H. The value of an ore depends almost as much upon its general composition as upon its metallic contents, as the. expense of treating an ore is directly dependent upon its composition. Thus, some ores flux or smelt much more readily than others, according to the proportions of certain minerals in their gangues. For example, either iron oxide or (]uartz (silica) alone is infusible, but mixed together in cMjual parts (by weight), they readily fuse to a silicate of iron. Lime acts with silica in much the same manner, and with iron oxide and silica forms a double silicate of lime and iron, which is readily fusible ; this is the s/tif of lead and cop- ier smelters. The charge of smelters for treating ores is based on the proportions of these minerals they contain. A fixed charge is made for neutral ores, or ores in which the percentage of silica (StO) is equal to the percentage of iron oxide (FcO) or of iron oxide and lime {CaO). A premium is allowed by the smelter for each unit or per cent, of iron oxide or lime in excess over the silica, and a bonus is charged for each unit of silica in excess over the iron oxide and lime.

9. Gold-silver smelters also make an extra charge for every unit of zinc in ores above a certain amount — usually I'l per cent. ; sometimes less — as zinc renders the ore refrac- torv. On the other hand, smelters alwavs pav for the lead and copper in ores it' they are present in any c<Misiderable amounts, as thev are saved bv smelt ini:: and not onlv do thev have an intrinsic value of their own, but tne or the other is indispensable to the operation (f smeltino;. It is the lead or copper in furnace chari4:es that makes it pt)ssible to extract from their ores the almost infinitesimal amounts of gold and silver — amounts often only a fraction of an ounce to the ton. The lead copper in the charge is reduced to a metal, and sinkiiu. gradually ihroiivrh the melting mass, cillects the gold and silver and carrie- them down with it into the well of the furnaie v.\ r-Tin bullion. This bullion corres{H>nds tiie !e.u: 'iiit'Mi obtained in assaying. In tact. /rVtc/jr.w;; ;.v' v ; .:v- or less than smelting en a small Sk\u\. Tl;e precious

J Assaying. 5

metals may be separated from the base metals of the bullion in various ways — cupelling, dissolving in acid, etr, — which will not be discussed here.

From the foregoing explanation, ihe student will readily understand the importance of knowing something more about an ore than merely how much gold and silver it

Fire Assaying.

described as nearly : operations.

d apparatu; possible ii

the (

of the

sctual

The outfit of an assay office depending not only upon the work to be doni of the assayer.

naturally vary somewhat,

Dunt and character of the

but also upon the individual preferences

We give here only the most essential appa-

ratus of the fire-assay office. There are many articles listed by dealers in assay supplies which, though convenient in special cases, are of little or no use in the ordinary run of fire assaying. There are also many little labor-saving devices, however, which the assayer will find very conve- nient as the work grows heavier. Such articles and their uses wc will at least menti'>n.

preparik: thi; sample.

11. Samples for assaying must be very finely pulver- ized, in order to obtain uniform results. It is customary to pas.s the entire final assaysample through an 80 or 100 mesh screen (80 or 100 openings to the linear inch, or 0,400 to 10,000 openings to the square inch, respectively). In the assay of some very refractory ores, a 120-mesh screen is used, as the finer the ore, the more rapid and complete the fusion.

Apparatus.

12. Crushers. — Lump samples are first broken up quite fine by means of a small laboratory jaw crusher, which may be driven cither by hand or by a small electric motor.

6 ASSAYING. g 36

In the absence of a jaw crusher, a heavy iron mortar and pestle may be used foe crushing. If neither is obtainable, the lumps may be broken up with a hammer, but this method is very slow and unsatisfactory.

13. Bucking Board.— The final pulverization of the sample is usually done on a "bucking board" or rubbing plate. This is a smooth cast-iron plate, usually 18' x 24' in area and 1 inch thick, with raised sides, as shown in Fig. 1, The ore is ground on this plate by means of the cast-iron "nniUer" or rubber a, which has a curved face and is fitted with a handle, as shown in the illustration.

The crushed ore is placed in the middle of the plate, and the muller is passed back and forth (ver it. The operator I'l ns down on the mul- with one hand, while with the other he grasps the handle and guides the muller, giving it a slow rocking motion, as

he draws it back and forth, by lowering his hand on the forward stroke and raising it on the back stroke, so that the entire face of the muller comes into use during each stroke. Samples are sometimes pulverized in an iron mortar, but the bucking board is much quicker and more convenient.

For reducing samples which are already comparatively 6ne. some assayers prefer circular bucking boards or rub- bing plates. These are usually about feet in diameter, J are placed upon a table so situated that the operator n walk around the table as he draws the muller back and rth. They have the advantage that the rubbing lakes B in different directions across the plate, so that there is f to wear crevices or scores in the face of the

14. Sampler. — A tin sampler, or "riffle," is conve- nient for cutting down or reducing the size of samples. It is merely a number of troughs, side by side, with open spaces between. The width and number of the open spaces and troughs can be made surh that the riffle wiil take out any desired portion of a crushed sample spread evenly over it. The riffles are commonly made to cut the sample into two equal parts, half remaining in the troughs and half fall- ing through.

Samplers, while convenient, are not absolutely necessary, as samples may be cut down by " quartering," as described in Art. l(i — a very simple and convenient method.

15. Spatulas. — The steel spatula is a form of knife used in the laboratory for mixing or sampling pulverized ore or for handling other materials about the laboratory. Fig. 2 shows a com- mon form of spatula. The blade should have some spring and

at the same time should be stiff enough so that it will not be broken If used for digging material out of a bottle or for similar purposes. The laboratory should usually be provided with several sizes of spatulas, from those having a 3 or i inch blade for use at the balances, etc.. to those having 10 or 12 inch blades for use in mixing several pounds of material and for sampling large pulps, etc.

Horn spatulas are frequently employed for removing precipitates from beakers and for similar purposes where steel spatulas would be attacked by the acids in the solution.

16. Quartering. — This method of reducing samples takes its name from the peculiar manner in which it is per- formed. Suppose an assay sample is to be taken from a 100-pound sample of ore, made up of coarse and fine lumps, and representing, perhaps, a carload of ore. The sampling floor is first swept thoroughly, to prevent any rich dust from former samplings becoming mixed with the sample in hand. Then the entire sample is run through a crusher.

which rediiLCs the liiiii|is tn

lay,

I inch. If the ore Is high grade or contains rich lumps i a comi>aralively barren gangiie, the first crushing should be considerably liner, in order to make the even distribution of the values more certain. Two or three 1-inch lumps more of rich ore in one-half of a sample than in the other, when the main mass of the sample is barren gangue material, would cause qniie a serious error; but if the ore is crushed to inch as the maximum diameter, a lump more or less of rich ore on either side would cause an error only one-eighth :is great as that from a 1-inch , us the volume is pro- portionate to the cube of the diameter, and the chances of the ore lcing evenly mixed will also be much greater.

The crushed ore is now thoroughly mixed on the floor and heaped up into a conical pile, each shovelful being thrown upon the apex of the eone, so as to run down all around. Now walk round and round the heap, continually I raking down a little ore from

the pile with the shovel, until the ore is in a flat, circular pile, aliout 4 inches thick. With a stick mark the pile off into ipiadrants, as shown in Fig. 3, by two diametrical lines at ji right angles to each other. ' Shovel two alternate (|uarlera carefully away. Thus, consid- ering the ipMilrants as numbered consecutively from I to 4, Nos.. / and S vcould be disca.rded, and Nos. J am) i saved, or rirc rrrsa. This leaves but half the sample to \te t<)>crated on; and this, if the work has l*ecn carefully done, should be J of the same value as the di-icarded portion. This is "quar- 1 tering." The two quarters which were savetl are again 1 crushed — this time to a maximum diameter of perhaps inch — and the entire i>}>eration is rejwate*!. This will leave a sample iMiIy one-fourth as large as the original Baunplc. but of the same average vUie. This is further ]

Assaying.

crushed to inch and again quartered; and so un until only about 3 pounds remain, the largest pieces of which are not more than J inch in diameter. This sample is further reduced by quartering, or by using the tin sampler, to about pound; and this is pulverized and screened.

17. For mixing small samples, say 10 pounds and leas, heaping up and shoveling will be found rather a tedious and clumsy process. After the sample is down to that size, and for small assay samples, the following method is gener- ally adopted:

The crushed sample is placed on a sheet of oilcloth or rubber cloth, which is placed on the floor or table; the alter- nate corners of the cloth are then drawn over, one at a time, towards the corners diag- onally opposite, rolling and mixing the sample within. When thoroughly mixed, the sample is heaped up into a conical pile by drawing the corners of the cloth upwards. The pile is then flattened as fol- lows: A thin sheet of iron, held as shown in Fig, 4, is pressed down slightly into the ape-t of the cone; then, i the axis of the cone as the axis of revolution of the plate, Fio

twist it gently around. As the plate revolves, it flattens and spreads out the ore, the process being continued until the pile is reduced to the desired thickness. The pile is then marked out into quadrants with a spatula, and quar- tered as previously described. Quartering has been found by experiment to give accurate average samples, if the work is carefully done.

18. !:teren

pulverized ore, a

and Screen! ntc. — For ;

ivered tin or wooden Ijo.'c

[ng the is used,

10 Assaying. §36

Tlir fonnrr is preferable, as it is much stronger and more durable. The screen cloth is made of brass wire. Very fine sieve cloth is made of hair, but it does not wear very well. Screens should be KO 100 mesh (see Art. 11). Tht sieve is circular, about 8 inches in diameter, and fits into a pan which catches the screened material and prevents loss fnuu dust blowiufj away. Any ore which fails to pass the screen is returned to the bucking board and further pidverized until it will all go through. The sifted ore is called the *'pulp."

1H If any metallic scales are loft on the screen after the ore has passed through, they should be tested with a magnet; if they are attracted, they are iron from the crush- ing apparatus, and niay be thn>wn away; but if not, they are saved and assayed, and their value per ton of ore is cal- culated ai\d added to that of the pulp, as described in Arts, I 22 to 127.

If the scales are principally silver, and quite fine and small in quantity, instead of going to the trouble of a sepa- rate assay and tlie ctuisequenl calculations, they may be gro\n>tl down until tlu\v will pass through the sieve, and mixed with the pulp. To do this, place the scales on the bucking Kurd, and cover them with a liiilc vt the pulp which has already pasNcd through the >icvc: then grind heavily lor a few minulcs. NLst vi" il\c >v\r.cs will now pass through the , paiticuUulv it tlu* x:,i:x:i:c is b..irvi and manr.cv, anvl vM\ until all aic tlv.\;-.g!v

8 Assaying.

the assayer's work will be thrown away, as the amounts to be weighed are so small that a very slight error will multi- ply itself enormously when the results are reduced to the basis of ounces of metal in a ton of ore.

The extreme accuracy required of assay balances may be better realized if the student will consider that the usual charge of ore used in assaying is only a trifle over half an ounce, or, in the scorification assay, only a little more than one-tenth of an ounce (avoirdupois), the charge in each case representing a ton of 2,000 pounds avoirdupois; and from the weight of the gold and silver obtained from the assay of this charge the assayer is required to estimate, within a few cents, the value of the guld and silver in a ton of the ore. Ores containing less than %'i in gold per ton are, in some instances, profitably worked, and much smaller pro- portions of gold than this can be recovered by the fire assay, even from a -jV-assay-ton charge {see Art. 30), and the buttons accurately weighed. Compare the weight of a gold-piece with a ton of ore ; then note the size of a [J-assay- ton charge, and the extreme delicacy, both of the assay balances and of the fire assay as a method of quantitative analysis, becomes apparent.

Balances.

2t. Two balances are necessary for gold-silver assay- ing—one for weighing the charges of ore and the other for weighing the gold and silver buttons resulting from the assays. For general analytical work, a third balance is required having a capacity between the two mentioned. These balances constitute the most important, delicate, and expensive part of the assayer's outfit.

22< Pulp Balance. — The pulp balance for weighing the ore or pulp should have a capacity of at least 300 grams in each pan, and should be readily sensitive to a difference of 6 mg. (milligrams) in the weights in the two pans. A convenient pulp balance is shown in Fig. 5. Such a bal- ance, in a glass case — as shown-costs about t'25. Pulp

Assaying.

balances are frequently used reduces the cost somewhat.

cases, and this balanced

watch-glasses make the best possible removable scale-pans, though metal pans are frequently used. The watch-glasses are made with a glass lip. or handle for convenience in

23. Button Balance. — The balance for weighing tlw gold and silver bnttons ;hniild have a capacity of ] or 'i

Assaying.

in each pan, anel should ije readily sensible to -J mg. or less. Balances .ire made which indicate a variation of yIb i"B- Such extreme accuracy as this is, however, unnecessary in ordinary work, and such balances are very expensive, rang- ing in price from #125 to (i350. Balances sensible to ,'„- mg. can be bought for from *05 to *B0, and for $W or *95 a balance may be obtained sensible to j-Jtj mg.

24. Fig. G shows a button balance with rider attach- ment, with which device all the more delicate and higher priced balances are equipped. The "rider" is a small loop of platinum or aluminum wire, of the shape shown in Fig. 7, and of definite weight (usually 1 mg. for button bal- ances and Itl mg. and 13 rag. for less delicate analytical balances). This rider is set astride the beam of the balance, which is graduated like the beam of a steelyard. The two pans are_ brought nearly to a balance by the use of ordinary weights, and the rider along the beam until the balance b sides is perfect. Each division t the balance is equivalent to a i (usually -jJo, ,'b, or a) of a milligrs each division is of the length of the beam from ''' the middle bearing to the end, or pan bearing, and a 1-mg. rider is used, each division that the rider is distant from the middle bearing is equivalent to a weight of mg. in the pan on the same side; that is, it will balance that weight in the pan on the other side. If a 10-mg. rider is used, each division represents JJ, or -J, mg. The weight thus indicated by the rider should be added to the sum of the weights in the pan on the same side, to obtain the weight of the charge in the opposite pan. If the rider is used on the opposite side from the weights, the amount indicated by the rider must be subtracted from the sum of the weights, in order to get ihe correct weight of the charge.

The rider is moved back and forth along the beam by a hook on the end of a sliding md extending through the side of the case of the balance. This enables the assaj-er to do

14 Assaying. § 36

the final balancinj with the case closed, so that the balance can not be disturbed by drafts. The rider is extremely con- venient, as it does away with the use of very small weights and renders the accurate adjustment of the balance much more rapid and easy.

26 Analytical Balance. — For weighing material used in gravimetric analysis and for weighing precipitates, platinum or porcelain crucibles, and similar objects, which recjuire the handling of material too heavy for the button balances, an analytical balance is necessary. This is con- structed ('(>nsiderai)ly like the balance illustrated in Fig. 5, but is provided with a rider and should have a capacity of from loo to 200 g. in each pan and be sensitive to a weight of from one-fifth to one-lenth of a mg. Such balances can be obtained for from $50 to $75 each.

26. Directions for setting up are furnished with each, set of balances, and these should be carefully observed, as balances are very delicate instruments and are easily injured. The button balance in particular should be set in a dry place, away from the furnace, so that it will not be affected by the heat. Any sudden change of temperature is bad; and even the shifting of the sunlight, if it strikes the balance, is sulVicicnt to throw it out of adjustment. No jar or disturbance of any kind should he permitted, as it not only interferes with the weighing, but injures the balance. In ordinary buildings it is ililVicult to secure a solid sup- port, for if the table on which the balance is set rests directly on the floor, the vibrations from persons walking around the room will be a serious annoyance. In such a case, it is a good plan to set the sup[)ort for the balances on wooden posts or brick piers, set in the ground under- neath the office and projecting u[)wartls through the floor without touching it. The balances should always be tested before using, to see that they are in perfect adjustment.

27. The beam of a balance, while weighing, is sup- ported on steel or agate knife edges, and the pans are also hung from knife edges, thus making the balance almost

§36 Assaying. 15

frictionless. When not in use or while charging, the beam is raised from the knife edges by turning a knob projecting through the front of the case, and the weight of the pans is supported from beneath by rests or stops, which are worked either by a separate knob or, in most button balances, by the same knob that releases the beam. These rests should always be raised while putting on or taking off weight from either pan, as the knife edges will be dulled if the weight is allowed to fall on them while charging.

28. To protect balances from moisture, a small beaker, partly filled with strong sulphuric acid, may be placed in the case. The acid will absorb the moisture from the air in the case, and thus prevent rusting of the balance. A small quantity of calcium chloride (CaC/,) in a glass vessel, placed inside the balance case, will answer the same purpose as the sulphuric acid, and will not cause so much trouble if accidentally spilled.

29, While any accurate weights may be used for assay- ing, the metric system has been generally adopted by assayers and chemists, as it greatly simplifies the calcula- tions, all the weights being divided decimally. The assayer should have two sets of weights — one set of metric weights, from 20 or 50 g. to 1 mg., and one set of A.-T. (assay-ton) weights, from 4 A. T. to A. T. An accurate set of metric weights as described above costs from t9 to $14. The set usually includes three riders. A set of assay-ton weights as described costs about tO.

30. The assay-ton system is a system of weights devised to simpHfy the calculation of the results of gold and silver assays. With the exception of fine-bullion assays, which are always reported in parts per I.OIW, the returns of gold and silver assays are always reported in troy ounces per ton of 2,000 pounds avoirdupois. Consequently, if the ore charge were weighed in grams or ounces and the button in milligrams or grains, considerable figuring would be

Tng

ncccaaary to convert the result into troy ounces per ton. The use of assay-ion weights in weighing the ore charge disi>enfies with all this figufing; for the assay ton weighs 0,1 (!*J mg. (2ft. Ifili g.). or just as many milligrams as ikere arc froy ouiicis in an at'oiriln/'ois Ion; hence, if an ore charge of 1 A. T. tic taken, each milligram that the result- ing button weighs represents 1 ounce (troy) of the metals com[H)Bing the button in a ton of ore. The proportion is obtained as follows:

An avoirdupois pound contains 7,000 grains, and a ton of 2,000 pounds will therefore contain U,O0O,0f)Ograins. Now, since there arc 480 grains in a troy ounce, by dividing 14,0110,IHKI by 4K0 wc obtain 20,l(iC-i-, or the number of troy ounces in a ton avoirdupois. Then, if we consider 1 mg. as representing 1 ounce troy, we obtain the following propor- tion:

a.OOO lb. (avoir (28,106 oz. troy)

. (troy) I A. T. : 1 mg. (29,16<i mg.)

If more or less than 1 A. T. of ore is used, the contents of the ore in ounces per ton may be found by dividing the weight of the button, in milligrams, by the weight of ore taken, in assay tons. For example, if 3 A. T. of ore are taken, the resulting button would be twice as heavy as the button from a l-A.-T. charge; and its weight would, there- fore, have to be divided by i to obtain the weight of the button from 1 A. T., in which each milligram represents 1 troy ounce per ton. With a ,',|-A.-T, charge of ore, the button is only one-tenth as large as the button from 1 A. T. ; consequently, each milligram represents 10 times as much as the same weight in the button from a full A.-T. charge; or. in other words, the weight of the button from t, A. T. of ore divided by (or multiplied by 111) the weight of the button fmm 1 A. T. The following general rule, there- fore, may l>c adopted for the calculation of the results from the HKsay of any weight "f ore:

The tvtight I'f buttmt in milligrams .Hvuli-d by the weight of ore takt-n in assay tons gi'i'iw tin- of ouncfS per ion.

§3

31. The weights sliould always be handled with the pin- cers suppHed for this purpose, as the moisture of the hands corrodes them, and may also appreciably alter the weight of smaller weights. They should always be returned to the box as soon as the weigher is through with them, both to prevent their loss and to save time and prevent errors from the overlooking of small weights which have been left in the pan from a previous weighing.

Method Of Weighing.

32. Before starting to weigh, it should always be seen that the balances are in perfect adjustment. They must, first of all, be perfectly level. Leveling screws and bubble tubes are provided for this adjustment. The scales are then brought to a perfect balance by means of the adjust- ing appliance on the beam or by the use of the rider. They are now ready for weighing.

When weighing with delicate balances, or with practically any balance for analytical work, it is as a rule best to weigh on the "swing," as it is expressed, rather than to try and bring the scale to perfect rest. For instance, if the weights have been placed in one pan and the load in the other, the supports are carefully removed and the pans allowed to swing slightly. The long pointer will travel backwards and forwards across the graduated scaie between the pans. ,If after the first two or three swings the pointer were to travel seven divisions to the left, sis and one-half divisions to the right, six divisions to the left, five and one-half divisions to the right, etc., thus dropping off a half division (or other equal fraction of a division) each time, but swinging approx- imately equal, the pans would be equally balanced and the weight would be read without spending the time necessary to bring the beam to rest. The adjustment of the scales should made in the same way, i. e., they should be made to swing to equal distances on both sides of the center, either when the pans are empty or when they contain equal weights. Usually in a good balance, pans will not come In rest as

Ih ASSAYING. § 36

rapidly as a half division for each swing, and hence it might require a few minutes to bring them to rest with the pointer in the center. This method of weighing by means of the deflection of the needle to the right and left is b'>th much more rapid and accurate than the system of trying to bring the pans to rest, but at the same time the swing should not exceed a deflection of more than four or five divisions each wav.

33 Charie. — The weight of the charge is usually fixed, and so the desired weight is put into one pan. The pulp from which the charge is to be taken is poured upon a sheet of glazed paper or a mixing cloth (a sheet of rubber cloth or oilcloth, about 10' X 15') in front of the scales, thoroughly mixed by rolling, as described in Art. 1 7, and then with a large spatula spread out into a thin pile. Take out the empty scale-pan and place the pulp charge in it. The charge is taken from all over the surface of the pile of pulp, a dip here and a dip there, to further insure an aver- age sample. When approximately the right amount is in the pan, it is replaced on the scales. Then pulp can be added or removed as required with a small spatula until the correct weight is obtained. The beam is held off the knife edge during charging, being let down unly to <.bserve th*: balance, until very nearly the correct weight is struck. It may then be let down; but the pan rests are still kept up, the pans being released only for observing the balance, and then immediately stopped again. As soon as the correct w<:ijht is obtained, the beam is raised from the knife edge aain, and the pan removed and its tents brushed into the rrnrihle or other receiving vessel, using a soft cameTs- hair bruh for this pur|JOse. If duplicate charges are being u>ed, the rharges may be weighed separately, all in (jne pan, or tlie weights may be removed before emptying the loaded pan, and a charjjje fnit into the pan which c)ntained the W'ihts, to l)alan<e th<; weighed charge. The pulj should be rolI(l and mi.xed anew ea( b. charge. The pans must always hr brushed [>erfectly clean after each weighing, and sh<>ulrl he handled as lightly as possible.

Assaying.

One great objection to weighing balanced charges, that is, placing the weights in one pan and a charge in the other and then removing the weights and balancing the charge already weighed out with another supply of ore, is that there is danger of getting the pans of the balance interchanged, and, as a rule, the pans are not exactly of the same weight, and hence should be kept in their respective places. Most chemists make it a rule to do all their weighing in one pan and to always use the weights in the other. One great advantage of this system is that the small weights are never in danger of becoming mixed in with the ore, or there is no danger of ore or pulp becoming attached to the pan in which the weights are used. When the weights are always used in one pan, a right-handed man will usually find it most con- venient to keep the weights in the right-hand pan.

34. Buttons. — The buttons are weighed in practically the same manner as the pulp, except that the unknown weight (button) is put in one pan and then balanced by weights in the other pan. The final balance is usually obtained by the use of the rider. If duplicate buttons are being weighed, the weight of one may he obtained as described, and then the second button substituted for the weights in the weight pan, and the difference in the weights of the buttons, if there is any, balanced by the use of the rider (and the small weights, if necessary, although a differ- ence great enough to require as much as a milligram to measure it is altogether too large to overlook, except in extremely high-grade gold ores or rich silver ores). The front of the scale case should be closed as soon as the dif- ference in weight comes within the limit of the rider, and the final balance obtained without any interfering air-cur- rents. The work can be done about as quickly by leaving the weights in the pan and substituting one button for the other and noting the difference with the rider.

The assayer should have a weight book in which to record

all weighings of buttons or other materials obtained in

assaying or analytical work, and in reading any given weight

.t'

L .

r.-

I- ' I'

I '

r

. . I

Mil I In III /m. . I Miiif f liif kn'--.s of tlir walls (.. Ihj. II Hill, h -m I' 111*1,1.; Thr walls ar(; bound

Assaying.

together by angle-irons and tie-rods, or, in some 'cases, by a complete casing of sheet iron. The latter strengthens the furnace, but radiates more heat than the bricks. The fire- chamber is ordinarily 12 inches square, but may be made of any size desired. The grate- bars are separate and re- movable, their ends resting on narrow iron ledges built into the furnace walls.

The draft is regulated by the iron door of the ash-pit. The top of the furnace may be either flat or inclined as shown, with a ledge in front on which to set crucibles and molds. It is made of a cast- iron plate, with the opening usually flush with the sides of the firebox. This open- ing is covered while working with a cast-iron plate or lid. In large furnaces this plate is sometimes lined with fire- brick, and slides back and forth on rollers. The flue connects with the firebox at the back, near the top, and i. usually from Ifi to 20 square inches in area (4' X 4', 3' X '"'c. a.

fi', or4' X 5*) for a 12' x 12' furnace. The stack should be 5' X 6' or 6' X 15' in the clear, and should be at least 30 feet high — the higher the better.

For crucible furnaces intended for melting quite large charges, the covers are frequently provided with iron rings and are hoisted off and removed by means of a small tackle hanging from a trolley which runs on a rail supported over the furnace. The same trolley may be employed for hoist- ing Ihe pots from the furnace.

Assaying.

Small portable crucible furnaces for assaying are made of fireclay tile, buund together by a sheet-iron casing or by wrought-iron bands.

When gasoline or gas is used to fire assay furnaces, a special style of furnace is sometimes employed in which 4 to 8 crucibles are placed in a small chamber which is covered with a firebrick lid. The fire enters at the back, passes around the crucibles and out through a small flue. The crucibles are removed by lifting off the cover and handling them with tongs. This style of furnace is more economical than a muffle would be for heating crucibles where a limited amount of work is done, using gasoline as a fuel, and a smaller muffle may be employed for the cupellation of the buttons obtained.

37. MufHe Furnace. — Muffle furnaces are built to receive fireclay muffles similar to the one shown in Fig. 9;

these muffles are heated from the outside, hke an oven, and the crucibles, scorifiers, or cupels are placed inside. The front of the muffle opens into the air, and a small hole or slit in the rear permits

a. constant current of fresh air lo How through the muffle while working. The heat of the muffle and the draft through it may be regulated by the door in front. Assay muffles are made in various sizes, from 7 inches long by inches wide to 18 inches long by 14 inches wide. The 12' x C and 14' X 8' sizes are the most commonly used, as they are plenty large enough to receive a double row of 10-g. cruci- bles—the size most commonly used in assaying. Muffles usually last only a few weeks, but are easily replaced when they break.

38. Fig. lU shows the construction of a brick muffle furnace built for three muffles antl to burn bituminous coal. The construction of muffle furnaces varies somewhat with the nature of the fuel used. Furnaces for burning long-flaming, bituminuus coal have the muffle 13 to 18 inches

J

above the grate-bars, and u

upnn the flami; to heat the r is on the level nf the pfrate. In furn; charcoal, or anthracite, on the o

ompaiali vely thin bed of fuelfl

i for burning cokeu r hand, the muffle is s

within

the grate, and the fuel is packed in around the muffle. These fuels arc all very short flaming, and their heat, though intense, is only foca and will scarcely rai a glow in a muffle plac a few inches above t fire bed, hence I necessity of surround- ing the muffle by I The fire-door in fuiJ naces of this type I Fi". n- placed some distancel

above the muffle, and a narrow horizontal slit is made in thi furnace on the level of the grate-bars for stirr and cleaning the grate. Stationary muffle ( usually built of red brick, lined with one course of firebrick.,| The walls are firmly braced with buckstays and tie-rc The sheet-iron pipe shown in Fig. 10 is to draw c fumes that tend to escape from the front of the muffle and, conduct them to the chimney.

Portable muffle furnaces are made in all sizes, designed;! for burning coke, charcoal, or anthracite. They are built off fireclay tile, bound together by wrought-iron ,as shown 1 in Fijj. 1 1, or completely encased in sheet i

39. There are a luimlier of g;is and gasoline furnacet!,| made. They are very convenient, particularly when thj amount of work is limited and the furnace is used onljq interniittiuUly. The muffle need be kept lu>l only while inj actual use; llie gas may be shut off as soon as the assayerfa

§36

Assaying.

through with it, thus economizing greatly in fuel, prolong- ing the life of the muffle, and adding greatly tu the comfort (if the office during hot weather. Their neatness is also a great recommendation, as they dispense entirely with coal dust and ashes. Gas is n.sed entirely in the U. S. mints for both melting and muffle furnaces.

Furnace Tools.

40. Firing TooIh. — Firing tools — poker, shovel, and scraper — are, of course, necessary in connection with assay furnaces using solid fuel.

41. Crucible Tomes- When a crucible furnace is used, a pair of crucible longs is necessary for lifting the

crucibles. These are of various designs. Fig. 12 (if) shows the double-bent and the single-bent crucible tongs which are commonly used for handling medium-sized melting crucibles. They arc made of wrought iron and are from 30 to 30 inches long.

A pair of small crucible tongs, the kind used for hand- ling small porcelain crucibles, is convenient for removing nails from assay iTucibles and for handling annealing cups.

42. Scoriner Timss. — Fig. 13 shows the scorifier tongs used fur hanrlling the scorifiers and small crucibles

32 Assaying. § 36

cup — merely a small crucible — with a series of slits in the bottom to allow free circulation of the acid and permit it to drain off readily on removing the tray from the bowl. The gold-silver cornets," made by rolling the buttons out into thin strips, annealing them by heating to redness in the muffle, and then twisting them into a spiral coil, are put in the tray, one in each cup, and the tray is then hung in a platinum bowl about 3 inches in diameter and 2 inches deep, filled to within about inch of the top with dilute nitric acid of 1.28 Sp. Gr. (50 per cent, concentrated acid), and heated nearly to boiling. They are boiled 10 minutes in this acid; then this is poured off and the dish refilled with fresh acid of the same strength (or sometimes the second acid is used stronger), and they are boiled 10 minutes longer. The crate is then lifted out and the cornets washed in the crate with pure distilled water. They are then dried out over a Bunsen burner or an alcohol lamp, and the crate and its contents are then put into the muffle and allowed to come to a red heat to anneal the cornets. After cooling, the cornets are weighed.

Fluxes.

GO. The majority of ores are by themselves infusible, or nearly so, at the temperatures obtainable in an assay fur- nace; but if the pulverized ore be well mixed with the cor- rect j)roportions of certain solid chemical reagents, the mixture will readily fuse at a moderate heat to a fluid mass, called siai; from which sucli heavy metals as lead, gold, and silver, which reduce to their metallic state during the fusion, settle out on account of their greater specific gravity. The reagents used for this purpose are called fluxes, from their property of making the mixture fluid.

61. Fluxes may be, like the ore itself, infusible alone, although fusible when mixed in the j)roper proportions. For example, iron oxide, caU ium oxide (lime), and silica (the most common gangue material of ores) are eac h, sepa- rately, extremely infusible, but when properly mixed thev

Assaying.

Fig, 15 shows ii 12-hole mold for ordinary work with scorifiers and 10-g. crucibles. For larger crucibles, a mold with deeper holes must be used. Fig. I'i shows one form of crucible mold.

45. Cupel Board. — An almost indispensable part of the assayer's outfit is the cupel board, or hot board, on which hot cupels are set as they are withdrawn from the furnace. It is merely a bit of 1-inch board, about 10 inches wide, with a handle at one end, as shown in Fig. 17, and with a rectangular piece of |-inch sheet iron, about 10' x 13', screwed to the upper side. It is a good plan to cut a number of small, radiating grooves in the board under the plate, to allow the escape of the gas which forms at first, before fig, ir.

the wood has become charred, when the iron piaie becomes heated from the red-hot cupels. The gas will usually escape without this precaution, but occasionally it accumulates between the board and the plate and e.\plodes. The explo- sion is not violent enough to injure the board, but it will upset and mix the cupels, making it necessary to repeat s number o£ assays.

46. Hammer. — A hammer is necessary for beating lead buttons, to free them from slag and get them into con- venient shape for cupellation. A a-pound machinist's ham mer with a square face is of a very convenient size and shape for this purpose.

47. Button Tonfffi. — A pair of spring button tongs, similar to the iron forceps described in Art. 65. Blowpiping, is necessary for handling the button while beating it out,

48. Mlacellaneouti Tools. — Besides the preceding tools, there are many others that are handy around a fur- nace, such as cupel shovels, cupel rakes, etc. ; but these are not neces.sary, and their work can be conveniently done by the tools at hand. The assayer should, however, be

supplied with a scraper for cleaning up spilled slag and lei from the muffle in case of any accident, such as the boilinj

over <jf 3. crucible or the rracking <ir spilling i>f a cupel.

Crucibles, Scohifiehs, Etc.

49. The crucibles and scorifiers used in assaying musl be able to withstand very high heats and sudden changes temperature without fusing cr cracking, and to resist tht corrosive action of the charges.

50. Crucibles. — There are various makes and style of crucibles. In America, fireclay crucibles, Colorado or Uad-assay pattern, are used almost exclusively for muffle work. This crucible is iJlustrated in Fig.

The size known as A, or lQ-gra\ (made for running a charge of 10 of lead ore), will serve for a gold-silver assay; or for a 1-A. assay, a 20-g., or B, crucible le crucibles are low, and broad at I the base; this shape is much safer and more convenient for muffle work than that of the regular Baftirsca gold-assay crucibles. The latter are '''""' narrower in proportion to their

height, and are made with a Up for pouring. They are made, like the lead-assay crucibles, of the best quality of fireclay. Fireclay crucibles are very strong and durable and are smooth and pour cleanly.

51. Sand, or Hessian, crucibles are very little used in this country. They are rather bulky and are not well adapted to muffle work, as their comparatively small base renders them liable to upset. They serve well for melting, but their roughness unfits them for pouring.

S2> Graphite, or plumbago, crucibles are largely melting bullion. Large Battersea clay crucibles 3 used for this purpose.

used foi

J

§36

Assaying.

2!

5S. Scorlflerst. — Scorifiers are made of fireclay. Fig. lH shows the usual form. They are made in sizes from 1 to 5 inches in diameter. The sizes most commonly used are the aj-inch and 2i-irich, which will receive a iV- A,-T, charge of ore.

54. RuastliiE Dishes.

— Roasting dishes are wide,

shallow, saucer- shaped

dishes of fireclay, used for roasting sulphide ores, drying

and calcining ores, etc. While not indispensable, they

are very convenient. They range from 2 to 7 inches in

55. Cupels— Fig.

30 shows the most of the bone-ash t separating the goltl the lead buttons. may be purchased i

L-ommon form [pels used in nd silver from These cupels ady made, but most assayers prefer to buy the hone-ash in bulk and make their own cupels. The home, made cupels are much cheaper, and if well s the purchased articles. trc a brass or iron mold Fig. 21) and a wooden

made are fully as good All the tools required and pestle (shown in mallet.

A pound or so of bone-ash is thoroughly mixed with just enough water to dampen it, so that when squeezed in the hand it will stick together and show distinctly the impression of the fingers. It must not, however, contain enough water to feel wet and dampen the fin- gers; the proper consistency is difficult to de- scribe, but is soon learned. The cupels will be stronger and less liable to crack in drying if a

sc

Assaying.

68. Sodium Chloride. — Sodium chloride (en salt) is also quite commonly used as a cover for crucible charges. Covers are not absolutely necessary, but arq universally used.

69. Litharge. — Litharge (yellow oxide of lead) acts as a basic flujt and an oxidizing and desulphurizing agent, and by reduction to a metal supplies the necessary lead for the colleclion of the values in gold-silver crucible assays. Lith- arge is never entirely free from silver, and each new b should be assayed, in order that the weight of the silvCi contained in the litharge of a crucible charge may be deducted from the weight of the resulting button, and the silver not credited to the ore. The crucible method of assay— Che same as for oxidized gold and silver ores — is used for determining the silver in the litharge, and the chi taken is usually 1 or 't A. T. ; but theassayer will save time trouble, and the possibility of arithmetical error if he uses for the assay charge the same amount uf litharge as he uses in the flux for his gold-silver assay charges. A good charge for the litharge assay is: litharge, 3 A, T, ; sodium bicarbonate, 1 A, T. ; argol, 1 g. Cover with borax, and fuse as in regular assay for gold and silver ores. Charcoal or flour may be used instead of argol (see Art. 76)- If he mixes his litharge with his stock flux, he need only duplicate assays of the flux alone, using the same amount for the charge as he mixes with his ore assays. A little silica (sand or powdered glass) added to the litharge-assa] charges wil! save the crucibles, which will otherwise bit corroded to furnish the necessary silica for the sla

70. Silica. — It is sometimes necessary to add silica, in the form of sand or powdered glass (ordinary window or bottle glass; lead glass is to be avoided), to the flux of extremely basic ores, in order to save the crucibles.

71. Niter. — Niter (sodium or potassium nitrate) is a basic flux and a very powerful oxidizing and desulphurizing agent. Its use is, however, objectionable for various rea- sons. In the fir-it place, its oxidizing power must be

§36

Assaying.

determined, as Ihe amuunt used must be only just sufficient to acciimplish the purpose for which it is added, any excess tending to prevent the reduction of the litharge. This determination involves two sets of assays. The reducing power of the stock flux must first be tested by running duplicate charges and weighing the resulting lead buttons. The amounts of flux and iitharge in these charges should be the same as are used in a regular assay charge, the litharge being somewhat in excess of the amount the flux will reduce to metai. Next run two similar charges, with the addition of 1 g. of niier to each. The buttons from this assay will be smaller than those from the previous one, and the differ- ence between the average weight of the lead buttons from the two assays — without and with niter— represents the oxidizing power of niler per gram. If more than 1 g. of niter is used, the difference in weight of the buttons will have to be divided by the number of grams of niter used, to obtain the oxidizing power per gram. After the oxidizing power of the niter has been determined, before it can be used in an assay charge it is further necessary to determine the reducing power of the ore with which it is to be used, in order to know just how much niter to add, and avoid excess. To do this, make up the following charge: ore. A. T. ; litharge, 15 g. ; sodium bicarbonate (or mixed soda and potassium bicarbonate), 10 g. Run this charge like the previous charges, and weigh the resulting button. The button reduced hy J A. T. of ore would be five times as heavy; and in an ordinary assay this weight would be added to that of the button reduced by the flux charge. The amount of niter added should be just sufficient to reduce the button to the desired weight.

72. Besides necessitating all the extra work, niter in the flux is troublesome in itself. Its oxygen is given off so rapidly as to cause deflagration and spitting of the charges before they commence to melt, and unless very large cru- cibles are used, charges containing niter are almost certain to boil over if left unwatched, as the niter causes violent

Assaying.

boiling and effervescence. Taking all these things inttf consideration, most assayers prefer to use iron wire or nails rather than niter to prevent the reduction of sulphur and arsenic into the buttons from sulphides and arsenides — the principal purpose for which niter is used.

73. Cyanide and Ferrocyanlde of Potassium.-

Potassium cyanide is a very powerful desulphurizing and reducing flux. In lead flux, it is apt to reduce some of the more readily oxidizable metals — such as bismuth, tin, imd antimony — along with the lead, causing a brittle, heavy button. It is intensely poisonous, and should be handled with the greatest care, never touching it with cracked or sore hands, and grinding it in the open air, with a towel over the top of the mortar. For this reason, it is little used in assaying. The commercial cyanide is used for assaying. The ferrocyanide acts in a similar manner in the flux, though much less powerfully, and is much safer to handle, although care should be exercised in its case also. Like niter, both cyanide and ferrocyanide are apt to cause boiling over, and their place as desulphurizers is usually filled by J iron wire or nails.

74. Iron. — Metallic iron is a powerful basic flux. Its principal use, however, is in the crucible assay of sulphides and arsenide ores, to form a matte with the sulphur and arsenic, and thus keep them out of the lead button. It is usually used in the shape of nails or wire coils; the former are more convenient. From two to four nails, according to the amount of sulphur in the charge, are stuck point downwards into the crucible before putting it into the fire. As the charge melts, the sulphur rapidly eats away the iron, forming a matte of iron sulphide. If there is much of this matte, it forms a distinct layer between the button and the slag, both before and after pouring. The matte can be readily distinguished from both slag and button by its crys- talline structure and metallic luster. If any of the nails remain undissolved in the crucible, they should be removed, before pouring, by means of the small crucible tongs

ightly against the edge of the crucible, as they I'D, to shake off any adhering globules of lead.

§ 36 Assaying.

ping them are withdra

75. Lead. — Metallic lead actii as a basic flux and also as a collector of the precious metals in gold and silver assays. Test lead (pure, granulated lead) is the principal flux used in the scorihcation assay. Sbeet lead or lead foil is used in assaying bullion (see Art. 141 ). Test lead, like litharge, almost invariably contains more or less silver, and should be assayed for that metal and the proper deduction made from the results of all silver assays in which it is used. The assay is run exactly like an ordinary scorification assay, adding silica to the charge.

76. Reducers. — The principal reducing reagents used in fire assaying are charcoal, flour, argol, cream of tartar, sugar, cyanide and ferrocyanide of potassium, or any car- bonaceous substance. The first three — charcoal, flour, and argol — are the most commonly used. The carbon in these carbonaceous reagents burns to CO, deriving the necessary oxygen from the reducible metallic oxides in the ore and the litharge in the flux, and reducing them to their respect- ive metals. Sulphur, arsenic, and antimony in ores have a similar reducing effect and assist the reducer in the flux. This fact should be borne in mind in making up the flux for any particular ore. Powdered sulphur is sometimes, though seldom, used as a reducing reagent in flux.

MIXED Pl.l'XES.

77. The following are the formulas for stock crucible fluxes recommended by different authorities. These fluxes have all been thoroughly tested, and while no one of them is suited to rt// ores, any of them will flux the majority of ores met with in custom assay practice. Special fluxes, adapted to particular types of ores, are given in Table I. An assayer whose work is mainly confined to ores of any particular type or district should experiment with various fluxes until he finds the one best suited to those ores and should then stick to that as his stocic flux.

40 Assaying. § 36

78. Lead Fluxes. — The following fluxes are primarily calculated for the fire assay of lead ores. They are all good general fluxes, however, and any one may be used as the basis of a gold-silver crucible flux, merely adding litharge :

No. 1, Sodium bicarbonate 4 parts.*

Potassium carbonate 4 parts.

B<jrax glass 2 parts.

Flour 1 part.

No. 2. Sodium bicarbonate 13 parts.

Potassium carbonate 10 parts.

Borax 5 parts.

Flour to 4 parts.

If the ore contains sulphur, the proportion of flour may be reduced, or for heavy sulphides the flour may be omitted entirely. From 1 to 4 tenpenny nails should be added to the charge for a sulphide before the salt or borax cover.

79* C;old and Silver Crucible Fluxes. — Most of the gold-silver crucible fluxes are merely lead fluxes to which litharge has been added. The amount of litharge added should be sufficient to give a lead button weighing about 15 g. from a i-A.-T. assay. As a general rule, from 20 g. to 1 A. T. of litharge are added to a -A.-T. assay charge. Any uiircdu(*ed litharge goes into slag, and is a splendid flux. If a large amount of litharge is used, the reducing [)ower of the charge must be kept down, so that too large a lead button will not be reduced. A good charge to use is 20 g. of litharge, as there is only a slight excess of litharge over the amount necessary to produce a lo-g. button, and unless the ore contains lead, the button can not run much too heavy. A charge of IT g. of litharge gives a button weighing slightly over lo g. — the usual charge of lead flux (without litharge) for a A-A.-T. assay is about 'M) g. ; there- fore, if the litharge is to be mixed with the flux in bulk, the

*In all the fluxes given in this Paper, the proportions of tlie constit- uents are given in parts by weight.

§36

priiport

of litharge

, made

ds uf litharge in 25 pounds uf mixed flux. If a Id-g. crucible be filled about two-thirds full of this mixed flux — which is about the amount com- monly used in J-A.-T. crucible assays — and run, the result- ing button of lead will weigh approximately 15 g. — the desired weight. The following flux is practically lead flux No. with litharge added in the above proportion:

No. ;i. Sodium bicarbonate 5 parts.

Potassium carbonate 4 parts.

Borax 'i parts.

Flour 1 part.

Litharge IH parts.

SO. Flux No. 3 is a typical general flux for oxidized ores. For sulphides, the flour may be omitted and from 1 to 4 nails added, according to the amount and nature of the sulphides. In this flux and similar fluxes, the amount of litharge is kept as low as is consistent with the formation of a lead button of convenient size for cupellalion.

Another class of fluxes less used employs a large excess of litharge, using it largely as a flux as well as an agent for collecting the precious metals in the charge. These fluxes belong to what Brown, in his " Manual of Assaying," calls the "litharge process." Fluxes Nos. 4 and ,") are types of this class.

No. 4. Sodium bicarbonate I part.

Borax glass 1 part.

Litharge 5 parts.

Ore I part.

To this charge sufficient reducer {or niter, if the ore is itself strongly reducing) is added to bring down a button of convenient size for cupellation, and a cover of salt is put on, (For reducing power of the various reducers, see Table II.) The oxidizing or reducing power of the ore should be determined by a preliminary assay, adding a measured quantity of reducer (i g. of charcoal or 1 g, flour,

J"

If cover of salt is used instead of borax, add 3 to 5 g. borax glass.

Special metliod. If oxide of iron is present, add soda in proportion.

If gangue is oxide or carbonate of iron, add 2 or 8 g. argoi.

Borax glass may be substituted for part of the silica.

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for example) if the ore is known to be oxidizing, or even if there is any probability of its being oxidizing. The differ- ence between the weight of the button and the weight of lead that would be reduced by the reducer alone represents the oxidizing power of the ore, if the button is lighter than the reducer button; if it is heavier, the difference repre- sents the reducing power of the ore. For this assay, the may be run down with or 2 A. T. of flux No. 4, covering the charge thickly with salt.

The great excess of litharge in this flux renders it highly corrosive in its effect on the crucibles, unless a large quan- tity of silica is added. Another flux of the same class, more commonly used, approaches more nearly the proportions used in fluxes of the first class and largely overcomes this objection. It is made up as follows:

No. 5. Sodium bicarbonate 3 parts.

Litharge 5 parts.

Borax 2 parts.

Reducer or oxidizer, as in No. 4. Salt cover.

81. The accompanying table (Table I) of crucible charges for gold and silver ores, covering both general and special cases, is taken, with a few unimportant changes, from Furman's Manual of Practical Assaying." The figures in column 4 (grams of lead flux) refer more particu- larly to lead flux No. 1, but will answer just as well for No. 2 (;r any similar lead flux. It will be observed that the lead flux forms the base of nearly all the charges. A large excess of litharge is necessary with tcllurides in order to oxidize the tellurium, which will otherwise be reduced and make the button brittle.

82. Table II gives the approximate reducing power of such reducing reagents as are commonly used in assaying, in terms of the number of parts of lead reduced from litharge by 1 part of the reducer. These figures are, how- ever, only approximate, and should not be used in the deter- mination of the oxidizing or reducing power of an cne or a

§3r,

Assaying.

reagent. For this purpose a test assay of the reducer should always be run, following the method given for determining the reducing power of ores (Art. 71) and using from i g. to 3 g. of the reducer in place of the ore charge. For the calculation of general charges, however, they are sufficiently close.

Tabl-E Ii.

Approximate RenucrKG Power jf Rswcma Agents (in Terms or

Parts of Metallic Lead Reduced prom Litharge

Bv 1 PAkT oe THK Reducer).

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83 parts of lead.

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1 part of erudt argol

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1 part of cream of tarti

r will reduce to

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Gold And Silver Assay.

83. There are two general methods in use for the fire assay of gold and silver ores: scorificalion and the crucible, or fusion, assay. With most ores, either method will give accurate results; but certain classes of ore may work better by one method than by the other, either in point of accu- racy or of convenience, or both. For example, sulphides, tcllurides, and ores carrying much arsenic and antimony can he worked much more conveniently, and frequently somewhat more accurately, by scorification than by the crucible process, for the reason that sulphur, tellurium, arsenic, and' antimony, in the crucible assay, unless spe- cially provided for, are apt to be reduced along with the lead and make the button brittle. The difficulties attendant on the oxidation of sulphur, etc., by means of niter have been mentioned in the discussion of fluxes. If they are brought into a matte by the use of iron (nails), the matte

Assaying.

and button have to be scorified tiigether to get rid of the! undesirable elements. The matte is brittle, and a little of J it is almost certain to fly off and get lost when separating' I it from the slag, and if the ore is rich this will cause more f or less loss. In the scorification assay, on the other hand, J the entire operation is one of oxidation, and sulphur, arsenic, etc., are volatilized and pass off in fumes. The I scorification assay also gives slightly higher results than J the crucible assay on most silver ores.

84. For assaying low-grade gold ores (for assaying pur- poses, ores carrying over 45 in gold per ton may be con- sidered as high grade and those less than $5 as low grade), the crucible process is generally used, as the button from a J scorifier charge A. T.) is so small as to be difficult to J handle and weigh, and any error in its weight represents J five times as much in the final calculations as the same error j in the weight of the button from a -A.-T. crucible charge. This difficulty may be avoided by running a number of scorifier charges and combining the gold buttons, but thisJ involves considerable extra work and expense.

In using nails to decompose sulphide ores, the button can I often be rendered soft and the matte gotten rid of by f removing the nails about ten minutes before the crucible9->| are taken from the furnace, and then raising the heat so a to render the slag thoroughly fusible and to as far as possi ble decompose the matte at the expense of the oxides in ] the slag. If but a small amount of matte were formed, this method will usually decompose it and carry the gold and .1 silver all into the lead. In some cases, it is necessary to add j some excess of litharge to the flux. The litharge will first 1 pass into the slag, and later during the decomposition of the J matte the lead will pass into the button and the matte i become oxidized and its iron and copper constituents pasa I into slag. If care is taken in proportioning the charge and f too great an amount of reducer is not added, it is usually ' possible to obtain a lead button of about the desired weight; for the sulphur will first pass into the matte and i

subsequently act as a reducer on a portion of the litharge in the charge, thus bringing the button to about the right size.

SCOBiriCATION ASSAV.

85. The ordinary ore charge for the scorification assay is -["j A. T. in or SJ inch scorifiers. Occasionally A. T. is used. The principal fluxes are test lead and borax glass. Litharge, and occasionally soda and niter, are used in special cases as covers. Silica added to the charge for a basic ore will save the scorifier. Table III is a table of scorifier charges for various ores, recommended by Fur- man. The charges are figured on a basis of a -A.-T. ore charge.

86. About half of the test lead is put in the scorifier. (The lead need not be weighed, but may be measured with sufficient accuracy by a shot measure or small crucible, the capacity of which is known.) The ore charge is then weighed out and brushed in on top of this, and they are thoroughly mixed with a small spatula. The remainder of the lead is now put on as a cover, and the borax glass on top of this. The borax may be added by measure or by pinches, a little practice enabling the assayer to guess suffi- ciently close to the correct weight. Duplicate charges are always run, to prevent the possibility of errors from care- lessness or accident going undetected. If the two buttons do not check very closely, the assay should be repeated.

87. The scorifiers are now charged into the hot muffle, and the door is closed and kept closed until the charge melts down and active scorification commences, when it is opened to admit a plentiful supply of air. The surface of the charge now displays a clean, mirror-like surface of glowing, molten lead, with a narrow ring of slag around the sides of the scorifier. This slag is formed by the fusion of thegangue of the ore with the borax and the litharge formed by the oxidation of the melted lead in the current of air flowing through the muffle.

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After ihe door is opened, oxidation goes on more rapidly than before. Sulphur, arsenic, etc., are oxidized l)y the action of the litharge and of the air-current, and the fumes pass off through the opening in the rear of the muffle. Any metallic gold or silver in the ore is immediately dissolved by the lead as it sinks through the charge. Compounds of gold or silver with other elements — sulphides, tellurides, etc. — are broken up by the action of the litharge, the gold or silver and the lead being reduced to metals and sinking together into the button, while the oxygen of the litharge converts the sulphur, etc., into gaseous oxides, which pass off through the back of the muffle.

88. As the oxidation progresses, the slag ring gradu- ally spreads inwards towards the center, until it finally closes over the top of the lead button, preventing further oxida- tion. This marks the end of the scoTtficatiiin. The door is now closed for a few minutes and the heat raised, to make the slag thoroughly liquid; the scorifier is then removed, tapped lightly on the ledge of the furnace, to settle any suspended shots of lead, and the contents poured into a moid. The mold should be warmed beforehand, or the sud- den chilling may cause the slag to break up before the lead has solidified and thus spatter the button; some of the lead, too, is apt to chill in small shots instead of going into the button. The slag should be clean, liquid, and glassy, and the lead should all be collected in one button at the bottom and not scattered in shots through the slag. This button should be soft and malleable. .

60. As soon as the assay is cool, the button may be separated from the slag by a few blows with a hammer and then beaten into the form of a cube, to make it easy to handle with the cupel tongs when placing it into the cupel. Brown recommends flattening the sharp corners of the cube by light blows of the hammer, to prevent their injuring the cupel when dropped into it. The buttons are now ready for cupellation, provided Ihey are not too large. The cubes should be about inch on a side — this size button will

Assaying.

weigh about 15 grams. If much larger than this, or brittle, they should be rescorified with borax glass and a little more lead, if necessary, and this should be repeated until they are of the proper size and purity. The loss of precious metals is less by this method than if a large button is cupelled directly, as the only loss in scorification worth mentioning is through volatilization, and is very small, while in cupella- tion the principal loss is through silver being carried into the cupel by the litharge, in addition to which we have a loss from volatilization nearly or quite as large as that in scorification.

90. CupelUnjt. — For cupellation, the muffle should be heated to a good rtd heat. The empty cupels are then set in the mufHe, arranged in the proper order for receiving tl buttons, and allowed to come to the heat of the mu; When the cupels have all reached the proper temperature the buttons are gently placed in their proper cupels, and the door is then closed for a few minutes to melt the but- tons down rapidly and "open" the cupels. The butti mell almost immediately and sink down into the bowls of the cupels. The surface of the melted lead is at first cov- ered with a film of dirt, slag, and oxide; but if the heat is correct and the button is comparatively free from serious impurities, this will soon break up and disappear, and when the muffle door is again opened, the surface of the lead in the cupels will be glowing brightly and giving ofi fumes of lead oxide. If the buttons refuse to open, place a little coke, charcoal, or a small piece of wood in the front of the muffle and close the door. The gases from the coke or charcoal will usually decompose the film, and as soon as the buttons are open, the door may be opened and the coke or charcoal drawn, and cupellation will usually proceed all right. A small fragment of charcoal placed in the cupel will accomplish the same result, but it is apt to cause a slight loss from "spitting."

91. The heat of the muffle during ihit cupellation of the

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tion is greatly increased by cupelling at a high heat. With gold ores, the heat is less important, as the loss of gold from volatilization is practically nothing. As a general rule, however, do not carry the temperature of the tiiuffle beyond a good. Strong, red heat wliile cupe/ling, and for ores rich in silver keep the heat down as low as possible ivithont risk of 'freezing" the buttons. With the proper heat, the cupel is red, and the lead inside is distinct and glows strongly, the fumes rise plentifully, and towards the end of the operation, "feathers" or crystals of litharge gather around the sides of the cupel.

92. If the heat Is too high, the cupel appears white hot and glowing and the lead button is scarcely visible, while the fumes are very thin and rise rapidly to the top of the muffle, and the lead may even boil. On the other hand, if the heat is too low, the fumes will be dense and heavy and sink to the bottom of the muffii.-; the litharge will form on the surface of the lead, too thick to absorb properly and not hot enough to volatilize, and with a tendency to crystal- lize or freeze over the surface of the lead.

93. In case the buttons do freeze, they may be reopened by employing the schemes given in Art. 90 for opening the cupels at first and raising the heat. The results from a button that has been frozen and then reopened are never thoroughly trustworthy, however, as the reopening usually volatilizes considerable silver. Care should therefore be taken to prevent freezing, and if the button-s show the least sign of it, the door should be closed and the heat raised until they are out of danger.

94< As the cupellation progresses, the litharge formed by the action of the air on the lead is partly absorbed by the cupel, and the remainder is volatilized and passes off in fumes. The button gradually dwindles down until the last of the lead is finally driven off. leaving the puri? gold and silver behind in a small bead. Just before the last of the lead is expelled, if the button is watched, rainbow colors will

fiS

Assaying.

be observed to play over the surface, arising from a film of melted litharge over the gold and silver bead, and the but- ton appears to spin rapidly around. As the last of the lead leaves, the bead will brighten and glow brilliantly for an instant; then a film closes over it, and the cupellation is completed. This brightening of the button at the end of the cupellation is known as " brightening," "blinking." or "flashing." Just before the button brightens, the tempera- ture should be raised somewhat, to make sure of expelling the last traces of lead. This is usually accomplished by pushing the cupel back into the hotter part of the muffle and leaving it there for two or three minutes after "blink- ing." If this precaution is not taken, a little lead is apt to remain in the button and be credited as silver.

95. The cupel may now be removed from the furnace and the button cooled and weighed. Buttons of nearly pure silver, especially when quite large, are apt to "spit" or "sprout " if cooled suddenly by drawing directly from the hot muffle into the open air. The liquid silver on the inside of the button bursts through the thin shell of solidified metal around it, sometimes forming very beautiful effervescences, and frequently throwing fine particles of sdver some dis- tance from the button. To prevent this, cover the cupel in the furnace with a hot, empty cupel and withdraw gradually from the hot part of the muffle to the front, and after it has cooled down to the temperature of the front of the muffle, take it out, still with the covering cupel on, and allow it to cool for some time before removing the cover. The results from a sprouted button should never be accepted, as there is almost certain to have been some loss in sprout-

96. A good cupel will efficiently ab.sorb just about its own weight of litharge. As a considerable part of the lith- arge from the oxidation of the lead buttons passes off in fumes, a cupel may be safely used for a button somewhat heavier than itself. It is much better, however, to have the cupel about a quarter or a half heavier than the button, as

J

Assaying. 63

a cuptl nearly saturated with litharge absorbs any additional litharge nmre and more slowly, and absorption may even cease entirely — even with some untouched bone-ash at the bottom nf the cupel — just at tjie time when absorption should, if anything, be most, rapid. The bowl of the cupel will usually hold more lead than the cupel will efficiently absorb. If a large button is being cupelled, and it is seen that the cupel will have difficulty in absorbing all the lith- arge, a second hot cupel may be inverted, and the cupel containing the button set upon this; cupellation will then proceed, though somewhat slowly, the excess of litharge passing into the lower cupel. It is much better, however, to reduce lead buttons to the proper size by scorilication and not take any risks.

97. WeiifhlnK th: Buttons.- As soon as the cupels

are cool, the buttons may be removed and weighed. For handling the small gold and silver buttons, a small pair of pincers are neces- sary, the sharp-nosed style shown in Fig. 23 being preferable. The button is fio.*:.

grasped firmly with these and pulled loose from the cupel. Any litharge-soaked bone-ash adhering to the bottom of the button is brushed off with a stifl tooth-brush or with a small, cylindrical, double-ended button brush made espe- cially for this purpose, but which is hardly as handy as the tooth-brush.

08. Before starting to weigh, the button balance must be carefully leveled up and adjusted. The scale-pans are first removed (use the weight forceps for this purpose; the pans of the button balance must never be handled with the fingers), turned upside down, and shaken by tapping the back of the forceps, tii shake out any dust or traces of gold left from previous weighings, and then replaced in their hangers. Then, having adjusted the balance, place the but- ton to be weighed in one pan; sufficient weights are placed

ASSAYING. g 36

ill the othor pan to balance the button within the limit of tlie sniaMest weight of the set, and the balancing is finally eoinpleted with the rider (or if the button weighs less than Xhc smallest weijrht of the, set, the balancing is done entirely with the rider).

99. Having found the weight of one button, mark it down, and leaving the weights in the pan, remove the but- ton wliich has been weighed, clean the duplicate button, and place it ill I lie pan which formerly contained the one already weigiied. If the buttons are of eipial weight, the second one will exactly balance the weights already in the pan; if not, tlu difTerencc can be made up by shifting the rider or with the use of small weights, but, as a rule, a difference of as much as 1 mg. is altogether too much imless the ore is extremely high grade in silver or gold. For example, sup- post' an assayer wish<*s to weigh two duplicate buttons. The balance is in accurate adjustment, the beam on each side is divided into fiftieths, and he is using a 1-mg. rider. The first button is placed in iht left-hand pan, and he finds that by j>lacing his lo-mg., ."i-mg., and two '-mg. weights in the other i)an, he slightly '>)alances the button, while if he replaces oiu' nf ilu* *i-ing. w<'iglUs by his 1-mg. weight, the button side is heavier. Hence the weight of the button must li<; between IS and PJ mg. Leaving the 18 mg. in th(* pan and using the rider on the right-hand side, he finds that he must inve it out divisions to exactlv balance the weight of the l)nlt)n; hence he must add ;i; mg. or.64nig. to the sum of the weights in the right-hand pan to obtain the weight the button; consec[uently button No. 1 weighs IS. r>4 mg. The same result would be obtained by leaving tlie P. mg. weiglits in the right-hand pan and moving out tile left-hand rider till the beam balanced, which it would do in this case with the rider at IS divisions, and subtracting from P. mg. the amount indicated by the rider, thus

m — .:;i; is.o-l-mg.

As a rule, it is best to have all the weights com- as addi- tions; that is, if the button is in the left-hand pan, it should

i-M

Assaying.

5S

not be (jiiite balanced by means of the weights, so that the weight indicated by the rider will always be added, as this may avoid mistalies. Having obtained and recorded the weight of the first button, both by reading the weights in the pan and that indicated by the rider and the weight indi- cated by the empty spaces in the weight box and the rider, the operator next removes the button and cleans its dupli- cate and places it in tlie left-hand pan, and finds upon test- ing the balances that No. 2 is somewhat heavier than No. 1. In other words, it overbalances the weight, and hence to balance it he moves the right-hand rider out slightly. He finds that by moving it out 7 divisions from the point it for- merly occiipied, the weight is exactly balanced; hence the weight of the second button is 18 + |S, or 18.78 mg. Both buttons are then dumped into their parting capsules, the rider is returned to its place and the weights to the weight box, and the assayer is ready to weigh the next set of buttons. Some operators prefer to balance the buttons against each other, and finding the difference by means of the rider, add or subtract it from the weight of the first button to obtain the weight of the second button; but both this system and the use of the rider on the opposite side of the scale-beam from that on which the weights are placed are more or less confusing where rapid work is required. As it is no uncom- mon thing for the gold-silver assayer in a large works to be required to run from 30 to 40 samples a day, accurately determining both the gold and silver contents of each, it is evident that he must so systematize his work that every- thing will be read as directly and systematically as possible. In other words, if the weights are all additions there is never any danger of making mistakes, while if some of the weights are obtained by addition and some by subtraction, there is always a possibility of error.

lOO* Parting. — The buttons from the cupellation con- ' tain l>oth the gold and the silver in the ore. To determine the exact amount of each, the buttons must be treated with dilute nitric acid, which dissolves the silver and leaves the

56 Assaying. § 36

gold behind as a black spongy mass or powder, which assumes its characteristic yellow color on heating. This operation is called parting.** The gold thus obtained is weighed up, and its weight, subtracted from the weight of the gold-silver buttons, gives the weight of silver in the ore. Duplicate buttons, unless very large and containing a con- siderable proportion of gold, may be parted together, in order to get a larger amount of gold to weigh and thus reduce the liability of error.

lOl. The operation of parting, in detail, is as follows: The buttons, if of any size, and particularly when contain- ing much gold, are first flattened in a diamond mortar or by a blow of the hammer on an anvil, in order to expose as much surface as possible to the action of the acid. They are then replaced in a capsule, which is next filled about half full with dilute nitric acid of about 1.2 Sp. Gr. (made by mixing equal parts of strong chemically pure nitric acid and distilled water), and placed on an iron plate or piece of asbestos, or in a platinum triangle, over a Bunsen burner or alcohol flame. If there is enough silver in the button, it will at once commence to dissolve; if not, the acid will not attack it, and it will require to be first " inquarted " (see Art. 105). , Assuming that there is a sufficient proportion of silver, the button will rapidly dissolve, the heat not being allowed to reach the boiling-point until all action has ceased and the solution has become colorless. If there is no gold in the buttons, they will not blacken on adding the acid, and will dissolve completely, leaving no residue, and the parting may be stopped at this point and the ore reported as containing no gold.

If, however, the button blackens on adding the acid, and a black, spongy residue, or even a small black speck is left on the bottom of the capsule or floating around in the solution after action has ceased, the solution is brought to a boil for a minute; the capsule is then removed from the heat, and the gold, if it has broken up, should l)c collert(Hl by gently tapping the side of the capsule and giving it :i

Assaying.

rotary motion. Very .smali panicles of gold may become enveloped in a film of air, and thu.s buoyed will float around on tliu surface of ihe acid solution, and refuse to be sunk by tapping the crucible. In such a case, "churn" or stir the contents of the capsule vigorou.siy with a glass rod; this will collect the floating particles, and they may then be sunk by tapping. All black particles in the capsule must be assumed to be gold until proved other- wise, and if any black specks show, the parting shotdd be continued through to the end, even if there is good reason to suspect that the specks are dirt. A little extra work is many times preferable to false assay returns.

102. Having gotten all the gold together at the bottom of the capsule, pour off the acid very carefully (preferably into another porcelain crucible, so that any gold which might escape through accident may be seen and recovered), using a glass rod to guide the streams and keep it from run- ning hack down the outside of the capsule. Then add fresh acid,* and boil for about three minutes. This removes prac- tically the last traces of silver. The gold is collected as l>efore, the acid poured off, and the gold washed three times with hot water. The washing is dune by filling the capsules with water, allowing the gold to settle, and then pouring the water off very carefully. Remove the last drops of water with a strip of blotting-paper, being very careful not to take up anyof the gold. Then heat for a moment overa Buiisen burner, to drive otf the last of the water, and finally place in the muffle or over the blast-lamp and bring to a good red heat. The gold will have assumed its natural yel- low color, organic matter will have been burned off, and by the aid of a magnifying-gtass any impurities can be readily distinguished. This heating is called "annealing."

The annealed gold sticks together and can be transferred

The praclice in the Western mining Slates is tu have the second acid of the same strength as the first. Many assayers prefer to use twu slretiglhs of acid for parting— a solution i>f about 1.1 Sp, Gr. (10 parts of strong acid ti) lit of water) for the first healing, and another of 1.28 Sp, Gr. (Ill parts acid tu 10 of water) for the second.

60 Assaying. § 36

106. The weight of the gold subtracted from the original weight of the buttons leaves the weight of the silver in the buttons. Thus, returning to the example given in Art. 99, suppose the buttons used in this case be parted and found to contain together 2.4(5 mg. of gold; subtract- ing this from the combined weight of the two buttons (37.42 mg.) the result is 34.90 mg., the weight of silver in the two buttons. The average weight of the silver in the

34. fK) buttons is, therefore, --7—, or 17.48 mg., and the average

2 4G weight of the gold is or 1.23 mg. Then, if ore charges

of -jV A. T. were used, each milligram weight in the button represents 10 ounces per ton, and the ore assays 174.8 ounces of silver and 12.3 ounces of gold per ton.

Cruciblb Aay.

107. The charge of ore used in the crucible assay varies from A. T. to 4 A. T. In the Western mining vStates the common practice is to use an ore charge of A. T. in a 10-g. Colorado crucible and fuse in the muffle furnace, dis- pensing entirely with the wind furnace. The muffle fur- nace is absolutely necessary, in any event, for scorification and cupellation; hence its use for crucible fusions is clear gain for crucible work. It is much neater and handier than the wind furnace, the heat can be better regulated, and a larger number of crucibles can be run at once than with the ordinary crucible furnace, thus offsetting the advantage of being able to use larger charges.

If the muffle is large enough, low-grade gold ores may be run in l-A.-T. charges, using 2()-g. crucihlcs; ])ut for gen- eral assaying it is more economical to use smaller muffles, as they are cheaper and nearly or cjuite as dural)le as the larger sizes; then, if sam[)les are occasionally received so low grade that the ordinary double .\-A.-T. assay will not give sufficient gold to weigh atHUirately, run a number of J-A.-T. charges, cupel, combine the buttons for gold, and average the results.

§ 36 ASSAYING. Rl

108. Charges larger ihaii 1 A. T. can nut be safely run in crucibles small enough to enter any of the muffles ordi- narily used ; and therefore unless the charge is divided, wind furnaces must be used. Very large crucible charges, on account of the amount of ore used, are not usually run in duplicate. The amounts of fluxes in larger crucible charges are in the same proportion to the ore as in the A.-T. charge, and the reactions in the crucible are the same in both furnaces. No further description of fusions in the wind furnace will therefore be necessary, as the student can readily figure it out for himself from the following description of the crucible assay in the mufie:

108. Charjte. — As previously stated under "Fluxes," the crucible charge is to a considerable extent dependent on the general composition of the ore. If the sample is in lump form, this can usually be determined by a simple inspection, with a few blowpipe tests if necessary. If the sample is pulverized, the minerals composing it may be determined by washing and vanning (shaking gently from side to side and rotating) a little of the pulp with water in a watch-glass, and examining the separated minerals with a magnifying-glass. Then refer to Table I and choose the flux best suited to the ore. If the general character of the ore can not be ascertained by examination, try one of the stock fluxes alone. These will generally flux the ore satis- factorily; and if they do not, they will at least give an index as to where the difficulty iies so that it can be cor- rected.

IIO. The flux and litharge can be put in the crucible, and then the ore weighed out and placed on top of it, the ore and flux being mixed thoroughly with a small spatula, the nails inserted point downwards, if the ore is a sulphide. and then the cover of salt tf borax glass added. The entire charge should till the crucible from S to J full — never more than three-quarters, or the charge is apt to boil over in the muffle. The crucible is now ready for the furnace.

:.-."r :? t-ui ihe flux :md

. . :T -wriirhrv: charge at ore

T-Xri :v lifting first one

- ..- - - :ir harire over and

1 -:'.:.- r ::h:y mixed the

.:."r: v-i rar.dnailsadded.

- . rd i:\ the niuflle rake from hall" -. '.::'.:. r verv hot. ..':-.. .:-.:r:r.i: ihe first : .. vc-r. If the - "r : : :he cruci- : r.v.::r o."-!ed d'lwn. - V ur.::l :::e danijer ;.- >J: v.'.d never be ;.-rr:cvt!y quiet - -. '- ;.-m:'leted.

: -.v ar.d

.\r .xs :hey

. "' . !" . t lie -..:':v in

I ,

4 t .V V

Assaying.

from samples or results becoming cunfiised, and the assayer will never be ahsoliitely sure of his work.

113. Marklnfc iiamples. — The pulverized samples shoidd be put in envelopes, bottles, or boxes, marked with the assayer's number of the sample or lot, the name of the sender or mine, the metals to be assayed for, and any addi- tional remarks that may be considered necessary. It is a good practice to also put the date of receiving the sample on the envelope or bottle. Envelopes are much more con- venient for samples than bottles or boxes, and are cheaper and less bulky. Special sample envelopes are made for assay samples, which close tightly, without sealing, in such a man- ner that none of the pulp can leak out nor any dirt find its way in, and at the same time they can be opened very readily and without damaging the envelope. Large assay offices usually have their name and the blank form for mark- ing the samples printed on their sample envelopes.

Many assayers, instead of marking samples as above, put only the name and lot number on the envelope, and then under the lot number in a note-book enter a more detailed description of the sample, its character, etc.

114. Numberlng.Assayers usually employ running numbers for their samples; that is. the samples are num- bered consecutively, and the numbers are never repeated. This avoids confusing different samples from the same per-

115. Weighing and Furnace Work. — When weigh- ing samples, a record should be kept in a note-book of the order in which the samples are weighed and the amount taken. Number earh day's work consecutively, from 1 upwards. The same order should then be preserved all through fusion, cupellation, and parting, to the final weigh- ing of the gold. This will avoid any confusion from the assayer losing track of which buttons came from which ore, etc. If a single one uf a batch of assays goes astray, the entire lot might as well be tlirown nut, as the assayer can never be positively sure just which assays are out of place,

Assaying.

and u result to which the least doubt attaches is worse than useless. In addition to keeping his assays in a fixed order and to help him in sit doing, it is well for the beginner to mark his crncibles and scorifiers plainly, in several places, with the numbers of the assays they contain, using reddle (red ocher), in the form of either chalk or paint, as it is not affected by the heat of the furnace. The numbers of the buttons can also be scratched on the sides of the cupels as a further precaution. This marking may be abandoned as soon as the assayer has his system thoroughly worked down.

116. The accompanying sketches (Fig. i'-i) illustrate a convenient system of handling the assays from the weigh- ing of the charge to the weighing of the gold and silver but- tons, in order to avoid confusion. The scheme is here wiirkcd

It

(0

0©

nut for six du]>lioaie assays and a the same principles are applicable in any furnace.

The charges as they are weighe respective crucibles or scorifiers 1

§ -Mi ASSAYING. 65

No. 1 at the right-hand back corner, and the rest succes- sively, as shown at {a). With this arrangement, the assayer never has to reach over already charged crucibles or scorifi- ers to set assays in their proper places, and thus run the risk of lipping over a crucible or brushing some of the ore off a scorifier charge with his sleeve.

The assays are carried from the weighing room to the furnace on the cupel l>oar(l. The board is set sidewise on the bench, with Nos. 3 and (5 to the front, as shown al (a). and the assays are put into the muffles in the natural order of their positions — those at the front side of the board going to the back of the muffles, and I't'ce versa, as shown at {b). When the fusion is finished, Nos. 1 and 4, which are in front in Ihe respective muffles, are naturally withdrawn first, and are poured into the back holes of the mold, as at (c), bring- ing the assays once more inln the original order. In the cupels in the furnace, the buttons are again in reversed order, as at ((/), and the cupels are drawn in their proper sequence, as at (c), and carried to the weighing room.

117. To Heat the Muffle.— To raise the heat of the

muffle rapidly, build a good fire under it, heaping the coal well up and allowing it to burn down to glowing coals; then, as soon as the muffle commences to show a dull red heat, throw a little charcoal or coal into the muffle and shut the door. The coal in the muffle will take fire from the heat of the muffle, and its heat added to Chat of the fire below will quickly bring the muffle to a good fusing heat, when the coals inside may be withdrawn and the crucibles or scorifiers inserted. A shovelful of burning coals from the grate will accomplish the same purpose in even less time. The same scheme may be employed in case the heat should be allowed to fall low while using the furnace, placing the coal or charcoal at the front. In cupelling, this also assists in opening frozen cupels (see Art. 90).

The use of coal in the muffle should be avoided, as the ash is liable to form a sticky slag that is troublesome. The use of wood or charcoal is not so objectionable.

06 Assaying. § 86

118. To Cool the Muffle.— While cupelling, if the muffle gets too hot at the rear, it can be cooled down locally, without touching the fire, by merely putting in one or more cold crucibles or scorifiers. If any particular cupels get too hot, they can be cooled down without seriously affecting the rest of the cupels in the muffle by putting cold scorifiers on them, each scorifier resting on the edges of two cupels.

11 9. Accidents. — In spite of the greatest care, an occasional accident is unavoidable in an assay office. Cruci- bles, scorifiers, or cupels may be spilled, crucibles may boil over, a defective scorifier may be corroded through, or cupels may crack and let the molten button through on. to the floor of the muffle. Litharge and oxidizing lead corrode the muffle very rapidly ; if the lead is left on the floor of the muffle, it will soon eat its way through, and, once started, the muffle soon goes to pieces. Most slags are not very actively corrosive, but slag is a great nuisance on the floor of the muffle, even in very small quantities, as it causes the vessels to stick, and if they are not released very cautiously a spill is apt to result.

The standard remedy for all such troubles in the muffle is bone-ash. If a vessel boils over or spills, remove it at once and throw in a handful of bone-ash. This will mix with the slag and form a thick paste, which can be readily removed with a scraper. If any lead is left on the floor of the muffle, throw in some more bone-ash on top of it. The bone-ash will absorb the litharge as it forms, and save the muffle to a con- siderable extent. It is advisable to keep the floor of the muffle always thinly covered with bone-ash; this will afford considerable immediate protection in case of spills, etc., and wmII also prevent vessels sticking to old slag spots on the bottom.

Calcltlatioxs.

1 20. The calculation of the results of gold and silver assavs is a matter of simple arithmetic. It has already been touched upon incidentally under tiie description of the assav- ton system (Art. 3C)) and in Arts. 99 and 106, but will

§ 86 Assaying. C7

be taken up separately and explained in detail, with exam- ples.

The rule for the calculation of the number of ounces of precious metals per ton of ore (Art. 30) must be kept in mind; the rest of the calculation is mere multiplication. This rule we will here repeat in the shape of a formula:

weight of button in mcf. , .

— r-TT — ? i : — a rj numbcr of ounces per ton.

weight or ore taken m A. T. '

For example, if the button from an A. T. of ore weighs 213 mg. before parting and the gold from parting weighs 13 mg., the contents of the ore in gold and silver are figured as follows: 213 mg. (gold and silver) — 13 mg. (gold) 200 mg., the weight of silver in the button.*

Then, since we have 200 mg. of silver from a l-A.-T. charge of ore, if we set these values in the formula, we have

ip 200 ounces silver per ton,

and for the gold (13 mg.),

13 ounces gold per ton.

If only i A. T. of this ore be taken, the buttons will, of course, weigh only half as much as the buttons from 1 A. T. ; but as the ore charge also is only half as large as in the l-A.-T. assay, the weight of the buttons divided by the weight of ore used gives the same result as in the l-A.-T. calculations; thus,

-— 100 X 2 200 ounces silver per ton,

and — 0.5 X 2 13 ounces gold per ton.

If only A. T. of the ore were taken, the silver and gold would weigh 20 mg. and 1.3 mg., respectively, and the figures would read

— 20 X Wi) ounces silver per ton,

Tw

and =1.3x10=13 ounces gold per ton.

For' the purix)se of calculatiiig. the joUl and silver are considered separately, as if they were in separate buttons, one pure gold and the other pure silver.

08 Assaying. § 36

121. The value of gold is definitely fixed at $20.67 per troy ounce, and this value is the same in all civilized coun- tries. Most custom assayers, however, figure gold at $20 per ounce, as this value is much more convenient for calcu- lations, and is, moreover, the value adopted by smelters in purchasing ores.

The value of silver fluctuates considerably, and the silver values in an ore are figured at the prevailing market price of silver. In all the calculations in this Paper, gold is fig- ured at $20.07 per ounce and silver at 60 cents per ounce. At these prices, the value of the ore in the preceding exam- ples would be.

Gold : 13 ounces @ $20.07 per ounce $268.71 Silver: 200 ounces @ $ .00 per ounce 120.00

Total value of ore in gold and silver, $388.71 per ton.

Orbs With Metallic Scalks.

1 22. When an ore contains particles of metallic gold and silver too coarse to pass through the screen with the pulp, these scales must be assayed separately, the amount of gold and silver they contain determined and added to the total gold and silver in the pulp, and the sum divided by the number of assay tons in the entire sample — pulp and scales — to obtain the tt)tal gold and silver in each assay ton of the sample.

If the sample is known to contain metallic scales, it may be weighed before crushing. After the sam[)le is pulverized, the pulp and scales are weighed separately. Their combined weight should be only a trifle less than that of the original sample, if the work has been carefully done. If the scales do not show in the lump sample, it would naturally be crushed without weighing, and the combined weight of the pulp and scales would then have to be taken as the weight of the original sample; hence, care should be taken, in l>ucking samples, to lose as little of the sample as possible. If the bucking is carefully done, the loss o( ore in an ordinary

§ 36 Assaying. Go

sized sample will be so small that the error in the calcula- tions from this cause will not be appreciable.

123* If there is any considerable quantity of scales, they should be scorified down in the usual manner and the lead button cupelled. If there is only a small quantity, they may be wrapped in lead foil and cupelled directly. The gold-silver button is weighed and parted as usual and the gold weighed. The weight of the gold subtracted from the weight of the button will give the weight of silver in the scales from the entire original sample.

124. The pulp is assayed in the usual manner by either scorification or crucible process, using the regular charge — or 1 A. T. The results may then be calculated as follows :

Let A weight of the pulp in grams; B weight of the scales in grams; C assay value of pulp in ounces of gold or silver

per ton (or mg. per A. T.); D weight of the gold or silver in the scales, in

milligrams.

A Now, ;y-Ar . . weight of the pulp in assay tons, and

A + B , . , , , . A C

- , total weight of sample assay tons. —

number of milligrams of gold or silver in the pulp; and if the weight of gold or silver in the scales be added to this, we have

A C I /) j total number of milligrams of 20.100 / gold or silver in entire sample.

To obtain the weight of gold or silver in 1 A. T., we must divide the total weight of gold or silver in the sample by the weight of the sample in assay tons; thus,

20.nw> ./ r-t-20. 10(; /; milligrams of gold or silver

A + /)' A -f- /) " / per A. T. (or oz. per ton).

20"; 100

Assaying.

§36

does the ore contain per ton ? (d) What is the value of the ore

per ton ?

'' '/ Silver, 12.5 oz. per ton.

Ans. -:

r Gold, 101.28 per ton. J Silver, 7.5<l per ton.

I Total, $H>s.78 per ton.

( Gold, 1.29 per ton. J Silver, 2.90 per ton.

2. Crucible Assay. Ore charges, A. T. Weight of gold-silver

buttons, 2.96 and 2. 90 mg., respectively. Weight of gold, 1.03 mg.

{a) How many ounces of gold and silver does the ore contain

ton ? {b) What is the value of the ore per ton ?

r M Gold. 1.03 oz. ton. Silver. 4.83 oz. per ton.

Ans.

(h

I Total, .19 per ton.

3. Crucible Assay. Ore charges, 1 A. T. Weight of gold-silver

buttons, 0.78 and 0.81 mg., respectively. Weight of gold. 1.34 mg.

(Buttons would have to Ije inquarted.) {a) How many ounces of gold

and silver does the ore contain per ton ? {b) What is the value of

the ore per ton ?

, j Gold, 0.670 oz. per ton. ''' '/ Silver, 0. 125 oz. per ton.

j (;oKl. §13.85 per ton. I Silver, 0.07 per ton.

Total. $13.92 i)er ton.

Ans.

XoTE. — When the quantity of silver contained in an ore is as small as this, it is usually ignored entirely when cakulatinji the value of the ore and rcjMirtrd as a "trace." Such small (|uantitiesot silver are never onsidered in buyinj and sellinj ores, and in such a case as the above, only th<t gold would he paid for. In assaying gol<i ores known to (ontain so little silver that it may be safely neglected, it is a com- mon prac ti< e to add enough silver to the assay charges — in the shajK' of silvr foil or a small crystal of nitrate of silver — to inijuart the gold buttons. This silver will go into the lead buttons along with the gold and silver in the ore, aini when they are cupelled the assxiyer has his buttons all ready to part, and does not have to take the risk of losing them in iiHjuariing with the blowpipe, to say nothing of the work saved. only the gold is determined, it is not necessiiry to weigh the init<ns ixfori; parting, except as a check on the assaying.

1. (h-,- (On/ti/ii/fiL: Metallic Scalt"i. Weight of ])ulp. i:{H.r>7 g. Wrirlit nt scales, l.*J*i g. Scales contain 832.4 mg. silver and mg. gold. The j)uip is assiiye<l by the crucible process, using i-A.-T. charges ot orr . the gold-silver buttons obtained weigh 107.54 and 107.28 mg.. resp. ( lively, and the gold from parting weighs 2.2<) mg. How

§ ae ASSAYING. 73

many ounces of gold and silver the ore contain per ton ?

What is the \'alue of the ore per ton ?

Gold, 4.03 oz. per ton. V Silver. 3K4. 20 02. per ton-

Ans. G.jid. $ H3.30 per ton.

,t Silver, 23iJ.52 per ton.

Total. $:}i:i*2 per ton.

Coxtkol Assays.

128* The price paid by mills, smelters, or sampling works for ores is fixed or controlled bv the result of assays run independently, by different assayers. duplicate sam- ples from each lot of ore. Such assays are aptly named control assays or, briefly, C'jntroh. The only way in which they differ essentially from ordinary assays is in the extreme care taken in sampling and assaying, in to insure f>er- fect justice to both the shipper and the works. The follow- ing are the details of the method commonly adopted in the Western mining States.

129* Samplinsr. — When the ore comes into the mill or smelter, the entire lot is crushed, if necessary, and a .sample of from 5 to 10 tons, according to the size of the lot, is cut out, usually by an automatic sampler, or by quartering, or by the use of the split shovel. (Small lots of ore are not cut down, but the entire lot is treated in the .same way as the sample from a larger lot.) This sample is further cut down in the same manner to 2'A or 3<Xi {y>unds.

This last sample is crushed quite fine by fine-crushing rolls or by a sample grinder, and is then cut down to alx/ut 2 or 3 pounds by quartering or by the us/ of a tin sampler, or riffle. This is the final sample. The whole of this sam- ple is ground down to mesh and screened.

The pulp is very thoroughly mixed by rolling on a rubl>er mixing cloth, as desf:ribed in Art, ] 7, and the ftample then divided into four equal parts by quartering or by th riffle. These are the control samples, and should weigh from 8 to 12 ounces each. They are put into nrparate ftam- ple envelopes, of which each mill has its own printed form.

74 Assaying. §36

Each envelope is sealed with the seal of the works, and is marked with the mine number, the name of the mine, and the mill or lot number. The shipper is then given his i pick of the samples, generally taking two, another is kept by the mill for assay, and the remaining sample is stamped ' or marked with the word "Umpire "and retained by the mill, to be assayed by a third party in case the assays of the shipper and the mill fail to agree within reasonable limits. The shipper sometimes also writes or stamps his name on the envelope containing the umpire sample. Some works divide their final sample into five parts, so that both the shipper and the works can have two sampies, in addition to the umpire sample.

130. AsHBylnfE for Settlement.— The shipper takes one of his samples to the mine assayer, if the mine employs . one, or, if not, to any reliable custom assay office, and has it assayed, while the mill assayer assays the sample kept by the mill. They then compare results, and if they check reasonably close — say within 3 or 4 points (a "'point" is jj-j ounce, or 20 cents per ton, in gold) on an ore carrying ; $20 or more per ton in gold — they "split," or average, the results, and the ore is paid for on this basis. For example,

if the mine assay shows the ore to contain 3.06 ounces of , gold and the mill assay gives 5J.02 ounces of gold per ton, the shipper is paid for the average, or 2.0-1 ounces of gold per ton.

131. If, however, the two assays do not check within these limits, both assayers repeat their work. If, after repeating, they still disagree, and Jarticularly if the mine assay is high, the umpire sample is sent to some disinterested and reliable assayer agreed upon by both parties concerned, and his result is usually taken as final. If he does not check with either of the other a.ssayers, however, the shipper may demand that the lot be resampled or may send his ore else- where, as it is always he!d until the assays are satisfactorily completed and the shipper has been paid for it, before treating.

Assaying. 75

llt2. tisneral Metbod tif AwtaylnE. — The assays

may be run by either the scorifier nr crucible assay, using I'o, i, or 1 A,-T. charges, according to the grade and char- acter of the ore. The assaying is dune hi the usual manner, but with great care. Many assayers prefer to use 20-g. crucibles for J-A.-T. charges, or to take double the number of A.-T. charges in lO-g. crucibles, in order to have room for a considerable excess of flux. Each assayer has his own way of checking his work, A good scheme is to run three charges and part two buttons together and the third sepa- rately as a check. If the work has been well done, the gold from the two buttons should weigh almost exactly twice as much as that from the single biittron. If it does not, there is something wrong and the assay should be repeated. In parting, it is best lo use the first acid quite weak — about 1 in 0 — and the last acid strong.

The results of control assays are calculated as in ordinary assays, with gold at t20 an ounce and silver at the market price.

Bullion A8Sav8.

133> In smelting gold and silver ores by the ordinary lead-bullion process, the gold and silver are carried down by lead, exactly as in the -crucible assay. This enriched lead is known as "base bullion," or lead bullion. As it is taken from the lead well of the furnace it is cast into bars or pigs. These are afterwards refined, the greater portion of the base metals being removed, leaving nearly pure gold and silver. The refined bullion is known as "line bullion," or sometimes as gold bullion or silver bullion, when composed almost entirely of gold or silver, respectively. Fine silver bullion containing considerable gold is known as "dore silver "or "dor6 bullion." It is, of course, necessary to assay both base and fine bullion in order to determine their respective values.

134. BaHC-BulIion Astiay. — The samples are taken from the bars of bullion by means of a steel punch similar to a harness-maker's punch, but larger and heavier. This

Assayixg.

punch is driven about half way through the bars, taking out cores about inch in diameter. Two sets of samples are taken from each bar, one from the top and one from the bottom, towards opposite sides and ends. When sampHng a lot of bulUon, the bars are usually sampled in bunches of five, as follows:

The five bars are laid side by side on the sampling plat- form, as shown in Fig. 24, and one sample is taken from each bar, starting at the outside upper or lower corner and working diag- onally across, the samples being taken out at the points indicated by the solid circles. Then the bars are turned over, and a Pic- 2*. second set of samples

taken out in the same order, but starting from the opposite end of the first bar and working along the other diagonal. In the figure, the positions of the punch holes in the lower sides of the bars are indicated by dotted circles.

135. The samples from the entire lot are melted up together in a clay or graphite crucible, care being taken that the heat does nut rise to a point where the lead begins to cupel or scorify (volatilize), as any reduction in the propor- tion of lead in the bulliim is equivalent to an increased pro- portion of precious metals, and the results would therefore be too high. As soon as the sample is perfectly fluid, it is

thoroughly

stirred w

th a dean in

1 rod, an

then p.

ured

into

mold

and cast

nto a thin, fl:

t 1 ,r-

bar, ;j inc

JO to imple

18 inches long, aboi e, and A or J inch thick f<jr assay are taken froi

this

)ar eit

icr by ])

nching out p

em from

the ends

and

sides

as sh

nvn in F

ig. 25, or by

ont pieee

s at

inter

agonal ly

across the ba

, tir cutting slrijis

ik'I't

across the!)

ir. These samples sli')U

.1 caoh be

ipiir.ixim

.tcly

of ilii; weight required fur ilie assay, usually i A, T. samples are usually taken from each bar.

136. One-half A. T. is accurately weighed out from I each sample. Each -A.-T. sample is then cupelled sepa- rately, the cupellation being conducted exactly as in ordi- nary ore assays, with as low a heat as is practicable. The cupels should always show '"feathers." If the bullion is impure — if it contains considerable quantities of other base metals besides lead, such as copper, arsenic, and antimony.

with a little borax, , before cupelling, e hotter part of the uld then be with-

A sprouted button

or sulphur — it should be scorified doi and if very impure, a little test le The cupels should be moved back into mufiRe just before " blinking," and ) drawn gradually, to prevent sprouting should always be rejected.

As soon as the cupels are cool, the buttons are removed, brushed, and weighed. The weights should agree very closely — say within half an imnce on bullion running 2O0 ounces of silver to the ton.

After weighing, the buttons are flattened out in the dia- mond mortar or on the anvil, and are then ready for parting,

137> The parting may be performed in small porcelain capsules, as in the ore assay, but with such large buttons it is better to use parting flasks or matrasses, or test tubes. Place two buttons in each flask, add 20 to 30 c. c. of c. p. nitric acid of about I.IC Sp. Gr, (about 30 percent, strong acid) and heat slowly till the silver is all dissolved. Then boil until all red fumes have disappeared. A bit of char- coal or a couple of charred pepper beans in the acid will prevent it from bumping and spurting while boiling. About ten minutes is usually sufficient for the first heating. Shake the matrass gently to collect the gold, and then decant (pour) the acid off very carefully and replace it with fresh acid, somewhat stronger (about 50 per cent, strong acid). Boil for about three minutes; then again collect the gold by tihaking and pour off the acid. The gold is next washed three times, by decantation, with distilled water, and is

78 Assaying. § 86

finally transferred to a porcelain capsule or an annealing cup, in the manner described in Art. lOS, dried, annealed, and weighed. The weights of gold from the two sets of buttons should check very closely, and if they do not, two more samples should be assayed. Their results will usually check one or the other of the first two pairs. If they do not, the assay should be again repeated, and so on until good checks are obtained.

1 38. Base-bullion assays are always reported, like ordi- nary gold and silver assays, ounces per ton. Fine-bullion assays are reported in parts per 1,000, or as so many thou- sandths fine."

139. Fine-Bullion Ansay. — Gold in fine bullion is always determined by fire assay. Silver maybe determined either by fire assay or by volumetric wet assay. The wet assay is adopted in the mints and in most large metallurgical works, as it is slightly more accurate and less troublesome than the fire assay. It involves considerable knowledge of chemistry and very delicate manipulation, and hence will not be given here. The fire assay, if carefully run and the proof assays are properly made up, will give very closely approximate results and is the method commonly used by custom assay offices and sniall works.

140. The sample is obtained from the bar by chipping off the diagonally opposite upper and lower corners with a cold-chisel or by boring to the center of the bar from the top and bottom, near the diagonally op[)osite corners, with a drill-press or ratchet-drill. The latter practice is the bet- ter, except in the case of bullion known to be very fine and uniform, and will detect any attempt at fraud, such as fill- ing the center of the bar with lead or copper — a trick that is frequently tried. The very first borings should he rejected, as they are apt to be dirty and give low result. Borings are ready for immediate weighing. Chips have to be flattened out on the anvii or in a small set of rolls made especially for the purpose, until they are thin enough to be cut up ly the shears. The samples, borings, or rolled chips are placed in

g 36 ASSAYING.

envelopes properly marked with the number stamped on the bar from whieh they are taken.

141. The approximate composition of the bullion is first determined by a preliminary assay. Half a gram of bullion is weighed out accurately on the button balance; this is wrapped in from 5 to 10 g. of pure lead foil and cupelled in a small cupel (weighing about 10orl2g,). The cupellation is conducted as in the base-bullion assay, with the same precautions, the cupels showing "feathers" just before finishing. The button should then be weighed and parted as usual.

The results indicated by the preliminary assay are used in making up the proof or correction assay, which should be as nearly as possible identical, in every particular, with regular assay charges. The amount of pure silver put into the proof charge is from 5 to 10 mg. greater than the amount indicated by the results of the preliminary assay, as it is roughly estimated that this amount is lost in the cupellation. If the bullion contains very much copper, the amount should be determined as described in Art. 236, and a correspond- ing amount added to the proof. Small amounts of copper, however, may be disregarded.

142. If the preliminary assay shows the bullion to con- tain too much gold to part without inquarting, sufficient pure silver is added to bring the proportions up to parts of silver to 1 of gold. If the gold is not up to this pro- portion, some assayers add enough pure gold to make it so. This is not the general practice, however. The only advan- tage it gives is that the gold stays together in a cornet, and is consequently easier to handle, with less danger of loss during washing.

143. Table IV is used in making up the proof. The method of making up the proof and the use of the table are best illustrated by an example. Suppose a preliminary assay of 500 mg. of bullion gave us 350 mg. of silver and an analysis showed 30 per cent, of copper. The table shows us

80 Assaying. § 36

that we will have to weigh out 355 to 3G0 mg. of pure silver and that 12 g. c. p. lead foil will be required f or cupellation. Now, as the bullion contains 20 per cent, copper, we must add 100 mg. of c. p. copper foil and 50 mg. of c. p. test lead. [The weight of test lead necessary in the proof is obtained by subtracting from the weight of bullion used the sum of the weights of silver and copper contained in the 500 mg. of bullion, viz., 500 — (.350 + 100) 50 mg. of test lead.] The whole is wrapped in the 12 g. of c. p. lead foil, when it is ready for cupellation with the regular assay. The proof is

Table Iv.

si "f w

u

a

Si:

—

if c

r

5 £ c

tc

it

i

?

Mm

u

X

4N>

i

S ac

5.

d.

Js

I5.n

:Is0-:K%

eivo

liNi.O

1

i:

I75.n

.wo

i:

21Kvo

:s>

4Vm

rM

e.'

lMilh.M\ viuMMi; uiv'latNv. v;o:vy.v:> ;i: r. :ho amounts of

Assaying.

placed lietween the two regular assays and run along with them. The resulting buttons are weighed, rolled out into ribbons, annealed, rolled into cornets, and parted in parting flasks or in a platinum parting tray (described in Art. 59)- The gold-silver buttons should check within 1 milligram, and the gold almost exactly. The loss of silver in the proof assay should not be more than 5 mg., if the cupellation has been run properly; the gold loss, unless the bullion runs quite high in gold, will be hardly noticeable. The amount of the loss of the proof assay is carefully determined and a corresponding amount added to the results of the bullion assay, to make up for the loss during cupellation. The but- tons should be bright and clean.

first button contains -

r 843 parts of fine

144. The result of the assay is reported in parts fine per

thousand — that is, the bullion is reported to contain so many

parts pure silver and so many parts gold, and the remainder

is base metal, usually lead and copper, the whole summing

up to 1,(KX) parts. For example, if the gold-silver buttons

from two 5(H)-mg. (J-g.) charges weigh il7 and 418 mg.,

respectively, and the proof assay shows a loss of 4.3 mg., the

1,000' '

silver and gold, and j'sVu. or 157 parts of base metals; and

, , . 418 + 4.5 845

the second button contams — — ,— rrr, or 845 parts 600 1,1100

fine silver and gold and 155 parts base metals; or, the

average total fineness (silver and gold) of the bullion is 844.

If the weight of the gold from the two buttons is a4 mg.,

this weight divided by the weight of the bullion from which

the gold was derived, 1,OUO mg. (two J-g. charges), gives

the contents of the bullion in gold. The bullion therefore

contains jjijo. '"" parts fine, of gold. This amount

deducted from the total fineness of the bullion (844) gives

the fineness in silver, which is thus found to be 820. The

silver contents may also be found in the same way as

the gold, by dividing the weight of silver in the buttons by

the weight of bullion taken; thus,

4'21..5 — '4-2-2.5= >i4 mg., corrected weight of gold-silver

844 mg. — *24 mg. 8'20 mg., weight of silver in 1,000 mg. (tw.' -g. charges) of bullion.

y*,."- .S20, or S'2n parts silver in bullion.

The results uf the preceding assay would be reported:

Silver 820 /wr.

Gold 24 /r.

This would Iht stamped on the bar with steel dies as a decimal: that is.

Silver 820

Gold 024

Using two 4-g. charges for assaying greatly facilitates the calculations, as the weights of the two charges sum up to l.iMMi mg.. and by adding the results from the two buttons t<ii:cther, each milligram is ipVif 1 part, so that no divi- sion is necessary, the fineness in silver or gold being the same as the weight of silver or gold in milligrams.

Kkai> Assay.

145. The tirt assav f'r k-ad is verv similar to thecruci- Mr assay tir okl aiul silver: in fact, the fluxes and the reac- tions in iho turnaci* are [radically identical. The lith- ari;r is, it course, emitted, as the object of the assay is lt> (Icicrmint* mm h lead there is /';/ ore\ and if lith- arge wtre ustd, its lead also would go into the button and make it far t(M) heavy. The lead fnm the ore is reduced in the same way as the lead from the litharge in the gold-silver assay.

Tile fluxes are made up, as in the gold-silver assay, in accordance witii the character and composition of the ore. Either of the sl<.ck tlu.xes given in Art. 78 will successfully flux most lead oivs, however, without any changes or addi- tions.

14H. Hither o or v::. charies of ore may be used. The general prarti( e in the Western mining States is to use

Assaying.

5g. of ore and run duplicates. The method is as follows: Two 5-g. charges of ore are mixed in 10-g. clay crucibles with from 15 to 20 g. of lead flu.x apiece (for 10 g. of ore use 30 g. flux) ; the assay is then covered with borax and the fusion is made in the muffle furnace. Put the crucibles into the muffle when it is at a low red heat, and then gradually raise the heat to a full red at the finish. This will avoid danger of boiling over and will give higher results than if the assay is run very hot, as there will be less loss from volatilization. In about 20 to 30 minutes all "cooking " will cease and the charges subside to a quiet, liquid fusion. The heat is then raised-or the crucibles are set back into the hotter part of the mufHe, and they are left in for a few minutes longer, in order that the slag may become thin and fluid. They are then removed, tapped gently on the edge of the furnace to collect the lead, and poured. As soon as the charges in the mold are cool, they are removed, the slag is broken away from the buttons, and the buttonsare hammered out flat, or if large may be hammered into cubes. The hammering will free them of slag. They should be soft and malleable. If they are brittle, they contain sulphur, arsenic, antimony. bismuth, or some similar element ; copper or iron makes the buttons hard; any impurity makes the buttons heavier than they should be. The slag .should be clean and brittle and should contain no shots of lead.

The buttons are brushed and weighed. They should agree within about per cent. (25 mg. on 5-g. charges). The weighing is done on the pulp balance, or, better, on the analytical balance, as no such great delicacy is required as to necessitate the use of the button balance. The assay is reported in per cent. — that is, the ore contains so many per cent., of lead. The figuring is very simple, particu- larly if 5-g. charges are used. The weight of the buttons is added and the sum divided by the total weight of ore taken, giving the percentage of lead in the ore. For example, if the buttons from two 6-g. charges of ore weigh 3.73 g. and 3.75 g., respectively, the lead contents of the ore are:

Assaying.

3-73 + a. 75

to

.748, or the iire c

74.8 of lead,,]

If the ore runs very high in silver — several hundred ounc< per ton— the buttons should be cupelled and the amount ofM silver determined and deducted from the weight of the lead. T Small amounts of silver may be nejjlected.

147. To assay lead by the fire assay and get good

results retjuires very careful work and considerable prac'i tice. There is invariably more or less lead lost through -1 volatilization, and the results of the assay are, consequently, 4 always somewhat lower than the actual contents of the ore, unless the button contains impurities. How to keep the. I loss as small as possible is the problem confronting th.l assayer. If the heat is too high, considerable lead is vola-J tilized; if it is too low, on the other hand, the assay i be kept in the furnace longer, and as slow volatilization isl constantly going on, the ultiitiate result is apt to be the I same as though the heat were too high. The proper heat I and time must be determined by experiment, A number J of assays of the same ore with the same charge should I run under different conditions, at various temperatures, and J for different lengths of time at the same temperature. The 1 highest result is in all probability the most nearly correct, I provided the button i.s jiure and malleable: and the condi-. tions under which it was obtained should be adopted for 1 general W')rk.

148. Sulphides.— The charge given in Art. 146 is for oxidized ores — carbonates, oxides, sulphates, etc. If the lead is in the form of a sulphide (galena) or is associated with other sulphides, iron nails or wire should be added to. the charge, as in the crucible assay of sulphide ores for gold 1 and silver, to take up the sulphur. Two ten|)enny nails are usually sufficient. Potassium cyanide may be used as a ' desulphurizer instead of iron, but it is very dangerous to handle and is apt to reduce other metals than lead, so that most assayers prefer to use nails.

[6 Assaying.

I49> Lead assays may be run in the wind furnace if desired, although the mufSe furnace is much more conve- nient. If run in the wind furnace, the crucibles are placed in the furnace while the fire is low, in order to get a gradual heat, and fresh fuel is piled around them. The fusion takes from 15 to 35 minutes. As soon as they are quiet they may be removed and poured, and the buttons cooled, beaten out, and weighed as before. The heat in the wind furnace is not so readily controlled as in the muffle furnace, and the results of lead assays run in this way arc consequently less uniform and reliable than those run in a muffle furnace.

Examples Fob Practice.

1. Ore charges, 5 g. each. Weights of buttons, 3.47 and 2.5 g., respectively. What is the jier cent, of lead in the ore ?

Ans. 4B.7*.

2. Ore charges, 10 g. each. Weights of buttons, 6.98 and 6.89 g., respectively. What is the per cent, of lead in the ore ?

Ans. 69Ai.

Wet Assays.

1 50. Assayers are frequently called upon to make deter- minations of other elements than gold, silver, and lead — elements which can not be accurately determined by the fire assay, and for the determination of which some knowledge of chemical analysis in the wet way is necessary. For example, the price paid for ores by smelters depends upon the amount of iron oxide, lime, and silica they contain, as explained in Art. 8. Manganese oxide acts, up to a certain point, like iron oxide, and the same premium is paid for both, and copper in ores is also paid fiT if present in any considerable quantity ; hence, the assayer will find it greatly to his advantage to be able lo perform the analyses for these substances. The wet determination of lead is also becoming quite common in smelters and lead works. Zinc is quite an important, though undesirable, constituent of many silver

86 Assaying. § 36

and gold ores, and its presence and amount are apt to affect the value of the ore considerably; the method commonly used for its determination is therefore given here.

151. Volumetric analyses are usually considerably quicker and less troublesome than gravimetric, and are therefore used wherever possible in smelters where speed is more essential than absolute accuracy. It must not be inferred from this that volumetric determinations are not accurate. Any of the schemes given here are accurate to a small fraction of 1 per cent., and the volumetric assay for some elements is more accurate than the gravimetric. There is rather more room for error in volumetric work, as a slight variation in the end point of the titration or a change in the strength of the standard solution may make a slight difference in the results; but such errors, if the chemist is careful and standardizes his solutions frequently, are so very small that they may be safely neglected. If duplicate determinations are run, any considerable error could not very well escape notice. The average result of the duplicate determination is always taken. Duplicates are seldom run in gravimetric work, on arcount of the extra work involved and the small j)rol)al)ility of error. The final result in gravimetric analysis is obtained by actually "a'cigJiing the preci[Mtate containinic the clement sought, and consequently, if the analysis has been prr)perly conducted and no error has been made in the weijjhing and calculations, the result is practically absolute. A good (diemist can make volu- metric determinations check verv closely on ifravimetric work, however, and for smelter work extreme accuracy is unnecessary, as the determinations are made ])rineipally for the calculation of the furnace charge, the results of whi(di are only ai)proximate at best.

In all analyses, in (.)rder that ores may be in the best con- dition to be acted upon by acids, they must be pulverized as finely as possible. This is accomplished by grindini: or rubbing in an agate mortar, treating C)nly a few grams of ore at one time. The pulverization should be carrictl on

until the ore is in the form of an impalpable powder, that i, until no gritty feeling can be noticed when a small pnrtifin is rubbed between the thumb and fingers.

Apparatus.

1 52. The list of apparatus given here includes only such articles as are absolutely necessary to properly perform the analyses following. The chemicals necessary will not be described sepa- rately, but will be mentioned in their ' proper places in the descriptions of the methods of analysis, and a table of proportions for the mixing fif reagents is given in Art. 2S2.

153. Beakers. — Glass beakers are necessary for holding solutions. They are made of thin, tough glass which will stand considerable heat, so

that solutions can be boiled in them. They come in "nests" of si.T, as shown in Fig. 2(i. The smallest, or No. 1, beaker will hold about 100 c. c, while the largest, or No. 6, has a capacity of 1 liter (1,000 c. c). The form with the lip for

pouring, as shown in general work, but are form without a lip. 15-1. Cai!M:ruleH.

used for dissolving o

the

figure, is most what more

pen:

for than the

crack as :

Casseroles

n casseroles. Fig. 27, are Is. They are particularly useful when the solution must be evaporated down to dryness, as with care they will stand this opera- tion without any danger of cracking, whereas beak- ers would be very liable to in them are boiled dry. The 2, 3, or 4 ounce sizes

precipitate forr

are most convenient for ordinary work, as the ore can he well covered without using an excess of acid.

Flasks.— Flasks of the shape of the wash-botlle I Fig, 3i, made of the same kind of glass as the beakers, are useful for various purposes — dissolving ores, receiving solutions, etc. The 4, 8, and 16 ounce sizes are most con- venient.

Fig. 28 illustrates an Erlenmeyer flask which is very handy for precipitating solu- tions in and for general analytical work, on account of the large flat bottom which is exposed to the action of the hot plate or sand-bath and owing to the fact that any ning in the solution in the flask has a tend- ency to fall away from the sides and c the bottom of the flask.

Small flasks of this shape are sometimes used in the copper determination.

156. Funnels. — Glass funnels are necessary for making filtrations. The angle between the sides should be 60",

and the stem should be ground off at an

angle, as shown in Fig. 29, to draw the

stream off to one side, lessening thecapil-

lary attraction between the tube and the

solution, and consequently hastening the

H flltration.

Watcli-G lasses. — Watch-glasses, Fig. 30, are handy for covering beakers, cas-

seroles, and funnels, and for re- ceiving weighed charges of ore or chemicals, precipitates, etc. Like assorted sizes.

s beakers, they come

ISS. Burettes —

fitted with glass stop-c

ttes arc graduated glass tubes as shown in Fig. :u at (a), or

H with rubber hose connections and pinch-cocks, as shown at (4),

from which standard soUitions arc run into solutiims to W tit-

rated or tested vohi- .

H metrically for certain

J

H elements. They

H come in 25. 50, and

100 c. c. sizes gradu-

H aled to tV c. c. The

1

50-c. C. size is must

J

convenient.

H 1 59. S p o t -

m

H Plate.— The spot-

r

plate is an oblong

plate of white porce-

lain, with a number

receiving the indi-

3 f

cator solutions used

in some titrations.

Vf

A few drops of the

indicatorsolution are

/I

put into each depres- Sm f 1 JL 1

the solution undei

examination, the lat-

— ' 1

ter is tested from no. .,i-

time to time for excess of the standard solution, by taking

a drop out on the end of a stirring rod and adding it to the

indicator solution in one of the depressions. As soon as the

standard solution is in the slightest excess over the amount

necessary to convert the element sought in the solution

under examination, a drop of the latter solution will cause a

characteristic reaction when added to the indicator solution.

Assaying.

§36

160. Crucibles. — Porcelain and platinum crucibles are necessary for making fusions and igniting (heating at a high heat) precipitates.

161. GraduateH. — Glass graduates are necessary for measuring acids, etc. They may be had in various

shapes and sizes. A graduate with straight sides, as shown in Fig. 32, is most conve- nient. They may be had in sizes varying from 50 to 500 c. c.

162. Titrating Dlh. — A flat, shallow, white porcelain dish, of about 1 quart capac- ity— an ordinary ironstone porcelain vegetable dish answers very well — is very convenient for making titrations, as the end point shows sharply against the white porcelain. A sheet of white paper behind a beaker will serve the same purpose.

1 63. Filter and Burette Stands. — Wooden or iron stands are necessary for holding funnels and burettes while filtering and titrating. A wooden burette stand is shown in Fig. 'M. The filter stand is somewhat similar, but has conical holes cut in the cross-bar for the funnels. Some- times racks are used that will hold several funnels.

164. Filter Paper. — Filter paper is tough, porous paper, used for filtering solutions. It may be obtained in circular sheets of various sizes, in packages of 1(>(). The sheets are folded to fit into the funnel. The folding is done as follows:

Fig. 83.

ri... :r..

Fold t>ver along the diameter, as at d. Fig. X): ajain, corner to corner, as at then open out into form i7 again,

g3fl

Assaying.

fuld one corner and outside edge in to the center line, and turn the paper over and fuld the other corner in the same way on the other side, as at c. The filter will then open out into the form d. which fits exactly into the funnel. After placing it in the funnel and moistening with water to make it stick t'l the sides of the funnel, it is ready for filtering.

165. For use in quantitive work where the filter paper has to be burned nr ignited with the precipitate, it is neces- sary that the weight of the ash of the filter should be known. There are two methods of accomplishing this. One is to employ what are known as ashless or acid-washed fillers. These are filter papers which have been washed with hydro- chloric and hydrofluoric acids, thus removing the solid por- tion of the ash and leaving practically nothing but carbon in the filler paper, so that it will burn without leaving any ash. The other method is to determine accurately the weight of the ash of the filter paper, and then to subtract this weight from the amount obtained after igniting each precipitate upon its filter paper. Such filter papers can be bought in packages of 100. with the weight of the ash that each sheet will produce stamped on the back of the package. Where very accurate work is desired, the chemist can deter- mine the weight of his own filter papers by burning three or four down to a white ash in an accurately weighed porcelain or platinum crucible. The crucible containing the ash is then weighed, and the increase in weight over the weight of the crucible alone is the weight of the ash. This amount divided by the number of filter papers used gives the weight of the ash from each filter. Ashless or acid-washed filters can be tested in the same way, and three or four of them should give such a small amount of ash that it would not give any perceptible increase in the weight of the crucible.

166. Wash-Bottle.— The chemist has constant use

for distilled water. The water for immediate use is kept in a large flask or "wash-bottle," of 16 to 3'3 ounces capacity, with two lubes passing through the cork and arranged so that on blowing in one the air-pressure forces the water up

Assaying.

§36

and out through the other, which is drawn out to a fine jet at the tip. Fig. 34 shows the wash-bottle and the arrange- ment of the tubes. The air-tube need only extend through

the cork. The long water-tube should extend nearly to the bottom of the flask, so that it will remain under water even when the water in the flask gets very low. A good plan is to stop the glass tube an inch or two from the bottom, and then put on a short piece of rubber tubing, as shown in the figure, extending to the bottom, or barely clearing it. This avoids the risk of pushing the tube through the bottom of the Fig. 34. flask when putting in the cork. A flexible

joint of rubber tubing at the jet, as shown, is also convenient for directing the stream. Ordinary flasks may be used for wash-bottles, but specially made flasks, with a heavy ring around the mouth to bear tight corking, are stronger and better. The neck may be wrapped with twine for handling when the water is hot. When boiling water in a wash-bottle, the cork should always be loosened and set up on the edge of the mouth, or the pressure of the steam will force the water out through the jet, little by little, the air-tube being so small that the steam does not escape fast enough to keep the pressure in the flask down to atmospheric pressure.

167. Stirring Rods. — Glass stirring rods, of assorted lengths and sizes — say from 3 to 8 inches long and from (i to inch in diameter — are essential in the laboratory. A short piece of rubber hose on the end of the rod will prevent it from Ix'ing pushed through the bottom of the beaker. The rods may be bouglit of the proper size, or the chemist may buy llu! jlass in 3 or (J foot lengths and make his own rods. To break the glass rod, make a scratch with a file at the point where it is desired to break it, grasp the rod with both hands, one hand on caeh side of the file mark, and close the thumbs togetlier, on the side of the rod opposite the mark, and break by pressing up with the thumbs. The broken ends

S 36 Assaying.

may be made round and smooth by heating with the blow- pipe or in the blue flame of a Bunsen burner. Stirring rods may also be made from glass tubing by closing the ends of the tubing in the Bunsen flame or with the blowpipe flame. A glass rod with a piece of rubber on the end is sometimes called a "policeman," and may be used for removing precipitates from beakers or other dishes.

168. Bufisen Burners, Tripods, Rtc- — Bunsen burners and tripods with wire gauze and asbestos cloth are essential fur heating water and solutions. Every laboratory, moreover, should be supplied with an exhaust hood, under which all boiling with acids should be done. The hood is simply a small chamber connected by a flue with the outside air, to draw off disagreeable and poisonous fumes and pre- vent their spreading through the laboratory. An iron heat- ing table or "hot plate " and a large gas-burner are neces- sary under the hiMid if much work is to he done, and are very convenient under any circumstances.

169. Sink and Slop-Jar. — Every laboratory should have a sink and faucet in connection with or convenient to the working desk. A five-gallon earthenware jar should be set under or alongside the desk, to receive washings, spent solutions, etc.

Iron Determination.

1 70. The two methods most commonly used in smelters and metallurgical works for the determination of iron are both volumetric— one by titration with a standard solution of potassium pirmangauate {KMiiO,), and the other by titration with a standard solution of potassium bichromate {/CCrO,). They are about equally used, hence both are given here. The two methods are very similar in their reactions, both depending upon the fact that the reagent used for titrating is an oxidizer, and when added to a solu- tion of a ferrous salt converts it into a ferric salt. Thus, in the permanganate method, ferrous sulphate {FeSOJ is converted or o.\idized by the permanganate to ferric

94 Assaying. § 36

sulphate and in the bichromate method ferrous chloride {FeCl) is converted by the bichromate to ferric

Preparing Thb Standard Solutions.

171. A normal solution of potassium permanganate or of potassium bichromate is a solution each cubic centimeter of which contains just enough of the reagent to oxidize 10 mg. of iron from the ferrous to the ferric state. With ore charges of 1 g. (1,000 mg.), then, each c. c. of a normal solution of permanganate or bichromate will oxidize 1 per cent, of iron. Standard solutions are usually of approx- imately this strength.

172. Pcrmangaiiate Solution. — To prepare an approximately normal solution of potassium permanganate, dissolve 5.G g of pure crystallized permanganate in 1 liter (1,000 c. c.) of distilled water. Place the solution in a glass- stoppered bottle and shake from time to time until ready for use. The solution should be made up at least 48 hours before standardizing.

1 73. BIcliroiiiate Solution. — The standard bichro- mate solution is usually made approximately a half-normal solution — liiat is, 1 c. c. of the solution will oxidize about 5 nii. iiiMi. The end point in this method is very sharp, and there is less danger of runninn: bevond it with a weak sohiliiMi than witii a stroni which each drop contains twt> or three times as nuu h biehrtMnate as a drop of the weak st>lutii>n. Some eheniists reeommend using a strong sohition (normal or even somewhat stronter) until nearly to the end point, and then linishini;- liie titration with a deci- nt>rnK\l ( ,\,-nonnal) solution (1 e. o. ii solution 1 mg. of ironV The half-normal sojulion is dilute enouii'h, however, and its U'e obviates the neeessiiy oi niakinj up two solu- tiiM\N and yi taking* two separate readi-.vs oi the burette for eaeh ti'ratiMi auvl tiviurinj; up :b.e amount of iron o\idi.-ed I'v eaeh sohnion. Tlu iMlf-Tiormal solution is pre- parevl by vlissolviuvi (m-, loujiiriy. I. O v:. M pure potas-

Assaying.

siiim bichromate in 1 liter nf distilled water. Like the permanganate solution, the solution should be allowed to stand for a day or two before standardizing.

STANDABniZINfi THE SOLUTIONS.

1 74. To Bta:idardize the solutions, a solution containing a known weight of iron is titrated with the standard solution whose strength is to be determined. The weight of iron in the solution divided by the number of cubic centimeters of the standard solution used, up to the end point, gives the weight of iron which each c. c. of the solution will oxidize. The iron used is in the form of piano wire, which contains !)!).? per cent, of pure inm. The wire should be well rubbed with fine sandpaper or emery-paper before weighing out, to remove dirt and the shellac with which it is sometimes covered to prevent rusting. The pieces for weighing are cut off and coiled around a lead-pencil to get them into con- venient shape for weighing, which is very carefully done on the button balance.

Two separate iron Sfjlutions are always run for standard- izing, and the average result of the two (if they check within reasonable limits) is accepted as the standard of the solution. (If they do not check properly, the work must be repeated.) The charges of wire are intentionally made to differ by from 20 to 50 mg. in weight; this makes accurate work necessary in order to get good checks, whereas, if the two charges were of very nearly the same weight, there might be a perfectly unintentional and unconscious "jug- gling" of results, to make them agree whether they will or not.

The methods of standardizing both solutions are as follows :

175. Permanganate Sol uC ion.— Weigh up accu- rately two portions of piano wire of about 2fiO and 250 mg., respectively. Place each in a 250-c. c. fla.sk or beaker and add 10 c. c. of liiluli- sulphuric acid — concentrated

90 Assaying. § 36

will not dissolve iron — and 10 drops of hydrochloric acid.* Heat gently until the iron is completely dissolved, adding more HSO and another drop of HCl if necessary. The solution will take onlv a few minutes. As soon as the iron is all dissolved, dilute the contents of the flask up to about 200 c. c. with distilled water.

1 76. More or less of the iron will be oxidized to ferric sulphate during the solution, and this must be reduced to ferrous sulphate before titrating. To reduce the solution, add 2 or 3 g. of pure granulated zinc, and let the solution stand for a short time. The hydrogen liberated by the action of the acid on the zinc reduces the ferric sulphate to ferrous sulphate. The solution, which is at first tinged yellowish by the ferric sulphate, soon becomes perfectly colorless. Very small amounts of ferric salts do not color the solutions perceptibly; hence, to be absolutely certain that all the iron is reduced, the solution should be tested with a weak solution of potassium sulphocyanate {KCNS) or of the corresponding sodium or ammonium salt. A few drops of sulphocyanate solution are put into the depressions of the spot-plate, and a drop of the iron solution is taken out on the end of a stirring rod and added to the sulphocy- anate on the spot-plate. Ferrous salts do not affect the color of the sulphocyanates, so that if the iron is completely reduced there will be no reaction; if there is the least traee of ferric salt present in the solution, however, a drop of the iron solution added to the sulphocyanate on the spot-plate causes a strong and characteristic red coloration. If, then, the test gives a red coloration, the reduction is incomplete, and nuist be continued initil the sulphocyanate no longer gives any reaction on the addition of the iron solution.

//( 7 is added merely in order to have the conditions in the stand. u di/atit>i\ as nearly as ])ossihle the same as the conditions in H'i'.mI.u 'rnunalii>ns. in which il is necessary to use some //CV in dis- iniN iiu', th' kaw //( 7 has a tendency, if there is much of it present in MlMlion anl particularly if the solutit>n is warm — to decompose Ww |ui m.uu'anatr and raue a iiiiih nsult. Hy usinjr, however, as httle rxM-.'. nl //( .' in ilisolvinvj the ore. and then diluting the 'icijil iMij n|) l.n Iv. vuidnii- a Miidcral>le excess t)f J/SOa and titrating Ihr 'sMhihnn ohl, tiuM'iU'v I i>t the //t 7 can be completely counteracted.

§ 36 Assaying. 9?

177. As soon as the reduction is complete and the excess of zinc has entirely dissolved, the titration should be proceeded with immediately; if allowed to stand very long exposed to the air, some of the iron will reoxidize. Transfer the contents of the flasks to No. 5 beakers, rinsing out the dasks well with distilled water, and add 20 c. c. of dilute //,S0, or a correspondingly smaller quantity of concen- trated HSO,, pouring in slowly and stirring constantly to prevent spurting. Concentrated acid has the disadvantage that it heats the solution considerably. (The excess of JfSO is necessary in the solution, both to promote the desired reactions and to counteract the //CI.) Next dilute the solution up to about 700 c. c. in bulk with distilled water. It is now ready for titration.

178. Fill your burette exactly to the zero-point with the standard solution. The burette should always be rinsed out with distilled water before using, and then a few c. c. of the standard solution should be run through it and thrown away before filling it with the solution. When everything is ready, pour off a little of the iron solution into a small beaker, to hold in reserve, and titrate the main portion, either in the beaker or in a titrating dish. At first several C. C. of the standard solution may be run in at a lime, stir- ring briskly all the while. As the end point approaches, proceed more cautiously, adding a few drops at a time. As the permanganate strikes the iron solution it becomes first brown and then colorless. The action becomes slower and the brown less intense towards the end point, and as soon as the end point is passed, the permanganate no longer breaks up and decolorizes on entering the iron solution, but retains its purple color, lingeing the iron solution a faint pink. The end point may be safely passed in the first titration, as there is more than enough solution in reserve to bring it back. This reserve is now added, rinsing the beaker out thoroughly with distilled water, and the titration is finished very care- fully, drop by drop. The end point is reached when a sin- gle drop of the standard solution added to the iron solution

98 Assaying. § 36

causes a faint, permanent, pink tinge (a pink tinge lasting 1 minute may be considered as permanent" for purposes of comparison). Every chemist has his own particular end point, but whatever tinge is adopted for the end point when standardizing, the same tinge must be used as the end point of all titrations with that solution. The paler the tinge accepted as the end point, the more nearly exact will be the result of the analysis, as the actual end point is not the point at which the color shows, but is one drop or a portion of a drop short of that point, when all the iron is oxidized, but there is no free permanganate in the solution.

179. The other solution is titrated in the same way, and the results of the two titrations are calculated and aver- aged to obtain the standard of the permanganate solution. The following examples will illustrate the method of calcu- lation better than a long verbal explanation : Suppose the two charges of iron wire weighed 0.2054 g. and 0.2396 g., respectively, and the titrations consume 19.9 c. c. and 23.3 c. c. of permanganate solution, respectively. Then we have (see Art. 174)

0.2054: X (>.91T (K204T8 g. of i)ure iron in first solution, and

0.2:>ih; V (I. .2:>SSS ij. pure inn in second solution.

In ihc litiation the first solutiiMi, therefore, c. c. of permanianatt solution oxidize 0. 2'U7> jr. of iron, or each

(I "204 *'8

cuibioeontinu'icr kx ncrnianiianatc solution oxidizes — —

In ilie liiratiiMi t" liu- second svOution, o. e. pcrman- t:[anate solution oxiiii.:e ,%i" ir,n, or each cubic cen-

Tile avera;e vf liioe two resnlts is ::ie taAiarii of the solu- tion. 1 :vvis. lMl''*>?:. - a:r..ii:i: of iron

eacli c;:':ic ceni::v.c:er vf liic >-;.i:wiavc. >l;;:io:i wi!! oxidize,

§ 36 Assaying. 99

the name or formula {KMnfi) of the solution and the standard, thus:

Pot ass in in Per manganate. 1 c. c. 0.010t>7 g. Fi.

180 The solution should be kept in a cool, dark place when not in use, as it slowly decomposes and loses strength if exposed to the light. (A closet under the table or sink is very convenient for standard solutions and other chemicals which are sensitive to the light.) It should be restandard- ized every few weeks, as the strength changes slightly with time. If it is restandardized two or three weeks after the first standardization, the results will show how fast it is changing strength, and from this the chemist will know about how often it will be necessary to restandardize the solution.

181. Bichromate Solution. — For titration with potassium bichromate, the iron may be in solution as either ferrous sulphate or ferrous chloride. Two charges of piano wire, of between 100 and 200 mg. each, are weighed up care- fully, placed in 250 c. c. flasks or beakers, and dissolved by boiling in either dilute sulphuric acid, as in the permanga- nate method, or dilute hydrochloric acid (5 c. c. concentrated y/C/and 20 c. c. distilled water). The solutions are diluted up to about 200 c. c. each, the iron reduced by one of the methods mentioned below, and then the solution transferred to large beakers, diluted up lo about oOO c. c. each, and titrated. The method of titration is the same whether hydrochloric or sulphuric acid is used in the solution. If the iron is in the form of sulphate, however, it must be reduced either by means of zinc, as in the permanganate method, or by intro- ducing several grams of granulated lead into the .solution and boiling until the reduction is complete; while ferric chloride in solution may be reduced by either of these methods, or much more quickly by means of a moderately strong solution of stannous chloride {SnCi bichloride of tin).

100 Assaying. § 36

182* The reduction with granulated lead is accom- plished as follows: The solution is first heated nearly to boiling over a Bunsen burner, and then about 5 g. of test lead are added. The solution is then boiled for some time. The yellow tinge gradually fades and the solution finally becomes perfectly clear. At this point add 5 g. more of test lead. Then test the solution from time to time with sulphocyanate, as in the reduction by zinc. As soon as the solution is completely reduced and no longer gives a ferric reaction with the sulphocyanate, it is poured off from the lead into a large beaker. The lead is washed several times and the washings are added to the main solution. The solution is then diluted and titrated.

183* The reduction by means of stannous chloride is very quick and simple. The solution is warmed and then a dilute solution of stannous chloride is added, drop by drop, stirring after each drop, until the iron solution becomes , colorless. A few drops are usually sufficient. After the solution has become perfectly clear and colorless, add one more drop of stannous chloride, to make complete reduction certain (or test the solution with sulphocyanate to see that iron is all reduced). The slight excess of stannous chloride must then be oxidized by the addition of a large excess of mercuric chloride. About 20 c. c. of a saturated solution of meriuiric chloride are added, all at once — and immediately after the final drop of stannous chloride — to the iron solution, which should be stirred rapidly to distribute the mercuric chloride (juickly throughout the entire solution. The mer- curic chloride instantly oxidizes the stannous chloride to stannic chloride, and is itself reduced, forming a dense, curdy, while precipitate (f mercurous chloride. This pre- cipitate does not interfere in any way with the subsequent reactions. The mercuric chl(M*ide itiust however, be added suddenly and in great excess; if it is not in considerable excess or is added slowly — which, as the reaction between the stannous chloride and the mercuric chloride is almost instantaneous, has the same effect as adding it in small

§ 36 Assaying. 101

quantity — the stannous chloride will reduce part or all of it to gray, metallic mercury, and not only is it then impossible to tell with absolute certainty whether the stannous chloride is completely oxidized, but the mercury renders the result of the titration unreliable. If the precipitate is perfectly white, the chemist is absolutely certain that the oxidation of the stannous chloride is complete, and that his results, if the rest of the work has been done carefully, are correct; but if there is even the faintest tinge of gray, there is room for doubt both as to the completeness of the oxidation and as to the accuracy of the work.

184. As soon as the reduction is complete, the solution is diluted up to about 500 c. c. with distilled water, and about 5 c. c. of strong //r/are added. A reserve portion is poured off and the main solution is then titrated. The bichromate solution is run in from the burette, rapidly at first, and stirring meanwhile. The solution, which was colorless at first — or white if it was reduced by stannous chloride — soon acquires a pale-green tint, which becomes darker as more bichromate is added. Should it turn brown, more //"C/ should be added. After the color becomes dark green, the bichromate should be added more carefully, and the iron solution should be tested after each addition by adding a drop of it to an indicator solution of potassium ferricyanide on the spot-plate. (The ferricyanide solution should not be too strong and should be free from ferro- cyanidi.) Ferricyanide gives a blue precipitate with solu- tions of ferrous salts, even in the most minute quantities, but is not affected by ferric salts; consequently, the indi- cator solution will turn deep blue with the first additions of the iron solution, but the blue coloration will become paler and paler as the titration proceeds and the bichromate solution oxidizes more and more of the iron, and when the last trace of the ferrous iron is oxidized to the ferric state, it will cease entirely. The point at which the blue colora- tion ceases, therefore, marks the end of the titration. The end point may be passed in titrating the main solution, as

102 Assaying. § 36

in the permanganate method; then add the reserve solu- tion, rinsing the beaker out carefully with distilled water and adding the rinsings to the main solution, and titrate very carefully, drop by drop, to the final end point. Titrate the second solution in the same way. The solutions may be titrated either warm or cold; they should both be titrated at about the same temperature, however, and the tempera- ture adopted in the standardization of a solution should be retained in all subsequent determinations with that solution.

185* The results are calculated exactly as in the per- manganate standardization: the weight of iron in the solu- tion divided by the number of cubic centimeters of standard solution used equals the strength, or standard, of each c. c. of the standard solution. As before, the average of the two determinations is taken as the standard of the solution.

Trbatmbnt Of Iron Orbs.

186* Most iron ores will yield all their iron contents into solution by simple boiling with acids. For oxidized ore, hydrochloric acid alone is usually sufficient. If, as occasionally happens, an ore will not yield all its iron to the action of hydrochloric acid alone, it will usually do so if treated with a mixture of nitric, hydrochloric, and sulphuric acids, as described in the treatment of sulphide ores. (Art. 194.)

1H7. Occasionally, however, an ore is encountered that will not yield all its iron, even to the combined action of all three acids; such refractory ores must be treated as described in Arts. 196 and 196*

188. Oxidized OrcH. — Duplicate charges of ore, of I g. each — or A g. if the ore runs very high in iron — are treated in small casser<Wes or beakers with 5 c. c. of con- cent rated //( 7. (Tlie use small vessels in dissolving ores is always tlesirable, as it avi>ids a large excess of acid.) The iMsseroles or beakers sh>iiKl be covered with watch-glasses, concave side up, and should be healed slowly, preferably on a

Assaying.

saiid-bath — a shallow pan of sand set over a burner — to avoid spurting and bumping. The solution usually requires about ao minutes; when it is complete the insoluble residue — consisting usually mostly of silica — is colorless and free from black specks of undecomposed ore. Somewhat refrac- tory ores may sometimes be gotten completely into solution by boiling down to dryness and then adding about 3 c. c. more acid and heating again; or if the iron is to be subse- quently reduced by stannous chloride, a few drops of stan- nous chloride or 3 are sufficient) added to the acid used in dissolving the ore will aid greatly in getting the ore into solution.

18B> When the ore is completely decomposed, dilute with distilled water, and stir and rub the insoluble residue with a rubber-tipped glass stirring rod policeman), to break up any clots which may have formed. Small specks of solution that have dried on the sides of the vessels and on the watch-glasses may be dissolved by rubbing them with a stirring rod moistened with the dilute acid solution from the casserole or beaker and then washing them off into the main solution with distilled water from the wash-bottle.

190. Heat the solution nearly to boiling and filter into the flask for reducing. The heating is not absolutely nec- essary, but it takes very little time, as the vessel may be heated with only a screen between it and the flame, and hot solutions filter much more rapidly and cleaner than cold. The vessel and the insoluble residue are washed three or four times with distilled water and the washings run through the filter into the main solution. (In washing the insoluble residue, the solution should be decanted off very carefully on to the filter, leaving as much of the residue in the casserole or beaker as possible until the final washing, [ as it can be washed much more rapidly and to better advan- t'tage in the vessel than in the filter.) The filter paper itself I J8 finally washed by the jet from the wash-bottle and the wasfaingB are allowed to run through. Always use a fresh Iter paper for each solution.

104 Assaying. § 36

191 The solution is now diluted with distilled water to about 200 c. c. ; 5 c. c. of concentrated or HCl — according to the method of reduction and titration to be pursued — are added (20 c. c. of dilute may be used instead of the 5 c. c. of concentrated acid) ; and the solution is then reduced by zinc, lead, or stannous chloride in the same way as the solution was reduced for standardizing.

192* As soon as the iron is completely reduced, dilute each solution to about 700 c. c. if the permanganate method is to be employed for the titration, or to 500 c. c. if the bichromate method is to be used; add a further excess of 5 c. c. of acid for safety, and then proceed with the titration. The titration is conducted exactly as in the standardization, with the same precautions, the same end point, and, as nearly as possible, the same conditions.

193* The amount of iron in the solution is determined by multiplying the number of cubic centimeters of standard solution used by the standard of the solution. If 1-g. charges of ore are used, this gives the percentage of iron directly; if -g. charges are taken, the result must be mul- tiplied by 2 to obtain the percentage of iron in the ore. The average result of the duplicate titrations — which should agree within 0.1 to 0.2 per cent. — is taken.

Examples For Practice.

1. Duplicalo 1-. ore charges are run. The titration of one solution ii>nsumes liT.U o. c. of the standard sohition ; of the other, 37.4 c. c. The standard of the solution is 0.(H)97 (1 c. c. O.CH)97 g. iron). How nuieh iron does the ore eiMitain ? Ans. 0.8623, or 36.

2. Ore charges A g. (.VH) mg.U'ach. Standard solution used in titra- tion. 27. and 27.5 c. c, resjHVtively. Strength of standard solution, I c. c. - - 0.0109 g. iron. How much iron dv>es the ore contain ?

Ans. 0.6006, or 60.06'?.

I Sulplikic Ores. — Di.solve duplicate charges of li. — or I i*. if iho on runs low in iron — in small casse- rolos or tl.iks. witl\ 2 c. c. sin>ng IlCi, 5 c. c. strong liXO, and S o. c, ililutt //„Si\, added in the order named.

(The sulphuric acid should be ab.iut (JO per c traied H,SO and 40 per cent, water. In diluting I always pour the acid into the -ii'atcr—nol ihe water into llic acid — gradually, stirring the water constantly,) If the ore is dissolved in flasks, the subsequent reduction may be made in the same flasks. Heat on a sand-bath or a hot pialc until dense, white fumes of sulphurous oxide, which arc recognized by their color and suffocating sulphurous odor, are evolved. The purpose of the sulphuric acid is merely make sure that the last trace of nitric acid is expelled. The nitric acid is necessary to break up the sulphides; but if the least trace of it remained in the solution, it would ruin the titration. The boiling-point of //,5(7, is so much higher than that of HNO, and HCl that these last-named acids arc completely evaporated from the solution by the time the H,SO begins to boil and break \ip, liberating sulphurous fumes; hence, the liberation of copious sulphurous fumes is a pretty certain indication that the nitric acid is all expelled from the solution. Continue the heating for a few minutes longer, to make sure that the last trace of HNO, is removed. Then cool the solution and dilute very carefully with dis- tilled water. Do not attempt to add water to the solution while it is hot — the reaction between the water and the hot — which has been concentrated by evaporation — might cause a serious accident. Filter, wash the residue on the filter, add the washings to the filtrate, and proceed with the reduction and titration as in the case of oxidized ores. The stannous chloride reduction can not be used, on account of the iron being in the form of a sulphate; the reduction with zinc will be found the most satisfactory. This method is applicable to all sulphides — lead, copper, zinc, or iron — in whir'i the percentage of iron is to be determined. Arsenic or antimony in the solution will cause a high result in the permanganate titration and should be precipitated by H,S and filteied off before titrating.

:

195. Hefractory Ores.— If an ore will not completely decompose in acids, filter off the insoluble residue, ignite

106 Assaying. § 36

and burn the filter paper to a white ash in a porcelain cru- cible, and then add 5 g. of potassium bisulphate (KHSO and fuse over a Bunsen burner until the fusion becomes quiet. The crucible should be large enough so that the residue and the flux will not fill it more than one-third full, as the bisulphate boils up very quickly and rapidly and is apt to overflow if more than this is used. The heat should l>e slow at first, to avoid boiling over, and should be increased to a dull red at the finish. The fusion will usually require about 15 minutes. The crucible is then removed from the heat and allowed to cofA. When it is sufficientlv cool, the fused mass is dissolved out of the crucible with boiling water, the solution and undissolved mass transferred to a beaker, the crucible rinsed into the beaker with distilled water, and the contents of the beaker boiled for a few minutes, to thoroughly disintegrate the fused mass. The solution is then run through a filter into the original filtrate from the insoluble residue, and the whole is reduced by zinc and titrated in the usual manner.

196. The same result may be obtained by fusing the insoluble rcsiriue with bicarbonate oi soda in a platinum rru'ibi Tilt* insoluble residue is tillered out and ignited as but in a platinum crucible, and then 5 g. of sodium bi':ari;nate are added and fused over a blast-lamp (a gas- h is ja:iven an artificial blast by means of a blower ',v f'v-t-Seii'nvs) until the fusion is quiet. The crucible is th' :. ' '/'.'.'-d and the mass dissolved out with verv dilute HCl 'fV If b'-iled and filtered, and the filtrate added to that fr'-rri :::♦; 'riL:i:ia! in><:nMe residue as before. Redtice and titrate a- u<ual.

li)7. Special Method for Workiiijjr Iron Ores. —

tho fact that b*>tii of tiie methods uiven for work- iiiir an if' ore require at least one riltraiiMi and that thevare ('inparative'.y si- '\v, tiie ciie mists J.ealini wiili the iron (res of the Lake Su:eriv.:- rciivMi have workevl a method for determinirijj: which much vjiiickv r ar.c. ea>ier than either of the o'.vl metlunls, while with careful Wiuk the results

Assaying.

obtained are fully as accurate. The method contains a num- ber of interesting chemical reactions. The ore is dissolved in concentrated hydrochloric add {ffCl), but if free HCl were present in the solution at the lime of titration it would be impossible to use the potassium permanganate solution, hence the work is L-arried on as f<)llows: Take 0.5 of a gram of ore and add 5 c. c. of stannous chloride (SriCl and ~*i.c. c. of concentrated HCl. Cover the beaker with a watch- glaS"TMi..tioil until the residue is white and flocculent. In this method the iron is reduced by means of stannous chlo- ride, and it will be found that a small amount of stannous chloride in the solution will greatly assist in dissolving the ore; hence a portion of it is added at the time mentioned. Some chemists use more hydrochloric acid than the amount given, but as a rule 5 c. c. is enough, and an excess is to be avoided. While the solution in the heaker is still hot, add more stannous chloride from the burette until the solution is light yellow, then boil and add stannous chloride slowly, shaking and stirring the solution until it is colorless, and add about 5 drops in excess. Wash the watch-glass and sides of the beaker with distilled water and add 15 c. c. of mercuric chloride. The mercuric chloride should be added as quickly as possible and stirred into the solution rapidly, for the reason stated in Art. 183. After the solu- tion of mercuric chloride is added and stirred in, there should be a white, silky-looking precipitate formed, but this will not interfere with the titration. Next add 50 c. c. of the ntan- ganous sulphate solution and add 300 c. c. of water. Then titrate with a standard permanganate solution, as in the cases already given. The titration should be done in a large beaker placed on or before a white plate or paper, or, better still, in a white bowl. The titration should be rapid, and as the end reaction approaches a slight darkening of the solu- tion will be noted. The end reaction is a feeble pink, is of short duration, and hence must be ascertained without delay

198. The preparation of the solutions and their u may be described as follows:

108 Assaying. § 36

The tttannous chloride solution can be made as fol- lows: Take 85 grams of stannous chloride {SnCl and add 50 c. c. of concentrated HCl and 50 c. c. of water. Boil until the solution is clear and then dilute up to 1 liter. Keep metallic tin in solution to prevent the formation of oxides.

An excess of the stannous chloride solution in the iron solution is always to be avoided, and in cases where the ore is low in iron it is sometimes necessary to add less than 5 c. c. of this solution while reducing the ore, or else to use 1 gram of ore, add 5 c. c. of stannous chloride and 10 c. c. of concentrated hydrochloric acid. An ore very low in iron may require only a few drops of the SnCl solution to per- form the reduction.

199* The mercuric cblorlde solution {HgCl) is made by taking 52 grams of mercuric chloride and dissolving in 1 liter of boiling water. This makes a saturated solution.

200* The manfanous sulpbate solution {MnSO is made up as follows: Take ir> grams of J/fiSO, dissolve in water, and dilute to 175 c. c. Add 33 c. c. of phos- phoric acid (Sp. Gr. 1.7) and 32 c. c. of (Sp. Gr. 1.84). The sulphuric acid shcnild he added slowly while the solution is being stirred, to avoid undue heating.

When this solution is added to the hydrochloric acid solu- tion of iron, the manganese sulphate is C(nverted into man- ganous chloride, thus avoiding the possible decomposition of the permanganate s<>lution by hydrochloric acid, while the phsphoric acid unites with the ferric iron produced, thereby rendering the soluiivMi white and making the end reaction plainer see.

201. The permanfanatc solution give:! in Art. 172 may be empl-.n-ed, or one may bo nuulo i:: esivciallv t'.> work with -grani weights vt vre v;i>Sv\v:::o 2-V --rams of pure crystallized permargatiate i:: I :i:or of distilled water. In mak:::g up the standard s i:tio:i, it :s wo:: to

5 36 Assaying. 109

have two bottles or carboys in which the solution is kept, and to be using from one while the other is being gotten into shape for use. If a fairly accurate solution is desired, it should be made up and the bottle shaken every day for a week, and then kept in the dark for at least another week before using.

202. Ores Containing OrKanlc Matter.—Certaiii

ores contain organic matter, and if this is left unchanged in the solution to be titrated, the organic matter might be acted upon by the standard permanganate solution. Such ores may be treated as follows: Dissolve the ore in as little concentrated hydrochloric acid as possible, and when the solution is complete add a few crystals of potassium chlo- rate. Evaporate until the chlorine is expelled, when a very small quantity of acid will still remain. From this point the operations can proceed as before, by adding a small quantity of acid and stannous chloride to reduce the iron. If the organic matter is not destroyed, it renders the slight excess of stannous chloride difficult to adjust, because it imparts to the solution a yellow color resembling ferric chloride.

203. Standard Iron Ores. — As a rule, chemists employed in the determination of iron ores do not standard- ize their solutions against pure metallic iron, but employ an iron ore of known character. Such standard iron ores, the percentage of iron, phosphorus, silica, and alumina in which is given, can be obtained from chemical-supply houses, and any chemist can easily make up a standard of his own and determine its value by means of the standard received from some supply house. It is a good practice to have a bottle of standard ore at hand near the balances and to weigh out one sample of it each day and run it through with the regu- lar samples to be tested. If the standard sample runs high or low, it shows that the permanganate solution has changed, and hence a slight change will have to be made in the results obtained from all the other samples run in that batch. The

110 Assaying. §36

running of the sample along with the batch of ores will not require more than from eight to ten minutes per day where large numbers of samples are being run, and hencQ it is not much of a tax on the men doing the work, while the fact that the standard is run with each set of samples serves as a check on all the work.

204. Adjusting ttie Weight of Ore to the Solu- tion.—In laboratories where a great number of iron deter- minations are made each day, the chemists rarely attempt to make the permanganate solution read directly into per cent., but adjust the weight of the ore taken so that the solution at hand will read into the per cent, desired. As an example, suppose that the laboratory is using a standard iron ore known to contain 57ji iron, and that this standard is titrated with the permanganate solution made up so that it is supposed to read of iron for each cubic centimeter of solution used when gram of iron is taken. Now, if this solution were employed and it were found that only 56. 5 cubic centimeters of solution were required,it is evident that the solution is stronger than the half normal solution, and luMire the weight of ore which must be taken in order that 1 cubic ccntinicter of sohition would equal of iron can he found by the following ccjuation :

.T) : :)(;..5 x : 57,

.r) X 57

A — (>..')044.

So, in weighing up tlio samples for analysis, the assayer woiiKl first sol his balanros lo weigh 0. r>(-4-4 (the tenths of a milligram wouKl |ri>hably bo i>biainoil by moans of the rider), and afliT iho \\oiv;hls had biHMi ad justed work would proceed as usual, weiiihiiig tuil samples which would just balance this weiiihl. It" the >taiulard whivii was run out with the ordinary work tor any viiven ilay div! lut show the per cent. itoa ii sliouUl. ii would iudieaio that the strength of llu liiraliux; soluthMi had ohar.ced, and henee the weight of

|3C

Assaying.

ore taken for the next work would have to be adjusted to the present new strength of the solution.

An experienced operator can usually make from 90 to 100 iron determinations per day by the method given above.

MANGAIVESE DETERMINATION. 205. Manganese may be determined volumetrically by titration with potassium permanganate, using the same solu- tion as is used for iron. The standard of the solution for iron multiplied by 0.iJ94fi gives the standard for manganese. Thus, if 1 c. c. of the permanganate solution will oxidize 0.01 g. of iron, it will oxidize 0.002040 g. of manganese.

206. Treatment of Mansanese Ores. — Two slightly different methods in nianipiiUition may be followed in man- ganese determination. In the first one described, the entire operation is carried on in the vessel in which the first solu- tioa is made. Dissolve 1 gram of the ore to be tested in from 30 to 40 c. c. of HCl and add a few drops of HNO to oxidize any ferrous iron present. The solution should be effected in a beaker at least 5 inches high by 3i inches in diameter at the top and having no Up. When practically all the acid has been expelled, allow it to cool somewhat, add 50 c. c. of water, and Ijoil to make sure that all the salts are in solution. Then remove from the hot plate and fill with boiling water to within 1 inch of the top of the beaker. Next, add dry zinc oxide (ZnO) in excess, which will pre- cipitate the iron as ferric hydrate, leaving the solution above colorless. The solution will contain the manganese as a chloride. Zinc oxide should be added slowly until all the iron has been precipitated and the acid all neutralized. (Test with litmus paper.) The solution should be stirred thoroughly with a glass rod while the zinc oxide is being added and 1 or 2 grams in excess should be employed. The solution is then ready for titration with potassium perman- ganate, and it should be vigorously stirred after each addi- tion of permanganate. The oxidation is complete when the

112 Assaying.

solution, after settliQg, shows a faint pink color. The ] heavy precipitate of iron hydrate and zinc oxide has the I advantage that it carries ihe precipitated oxide of manga- nese to the bottom very quickly, thus enabh'ng the operator ] to easily determine the end reaction. The titration should be done rapidly while the solution is hot. If the value of the normal permanganate solution is known in terms of iron I the resulting number of c. c. should be multiplied by the ] factor 0.3941), which will give the percentage of manganese. This method has the advantage that the entire operation is I carried on in one vessel and that the ordinary permanganate solution for iron is employed.

207. When gram of ore is used in the iron determi- nation, a one-half normal potassium permanganate solution I is usually employed, and if this same solution is used for the I determination of manganese, it will be necessary to take one-- half of the number of c. c. of permanganate solution used and multiply it by the factor given. If the solut:ion iaJ neither exactly a normal nor a half normal solution, it will be J necessary to multiply by a factor which will render it normal i before employing the manganese factor as given above.

208. Some operators prefer to remove the heavy pre- I

cipitate of iron hydrate and the zinc oxide so that the titra- I tion can be done in a clear solution. This may be accom- plished by taking grams of the ore and treating as above I stated, but removing from the hot plate and transferring to J a graduate before adding the zinc oxide. After the zinc I oxide has been added, the solution should be made up t9 300 c. c. Then filter through a dry filter and take 200 c. c. - of the filtrate, which will correspond to 1 gram of ore. The 1 rest of the filtrate containing the zinc oxide and the precipi-' tated hydrate of iron is thrown away. The filtrate is thent'l brought to a boil and the titration carried on as before, f The fact that the precipitate has a slightly greater specificfl gravity than the solution will have practically no effect! upon the accuracy of the results. As this operation require!

the treating of larger amounts of ore and the use of several vessels for the determination, it is not as rapid as the one first described.

Determination Op Phosphorus.

209. For the determination of phosphorus there are several methods in use. For individual determinations, the old gravimetric method is probably the most accurate, and hence will be described first.

210. Gravimetric Method. — Dissolve from -J tu 10 grams of the ore to be tested in HCl. When only 3 grams are employed, 20 c. c. of HCl will be sufficient. It is best to keep the solution on sand-hath or hot plate almost at the boiling-point until it is reduced to a syrup; then add 20 C. c. of concentrated HNO. Boil down to about 10 c. c, or until no more fumes of HCl are given off.

211. In case organic matter is present, it will be neces- sary to destroy it by carrying the evaporation with HNO to dryness and then baking the residue until no more acid fumes are given off. When the material becomes cool, dis- solve in HCl. Evaporate down to a syrup as before, add HNO, and evaporate until no more HCl fumes are given off,

212. Wash down the sides of the beaker and dilute to about 30 c. c. Filter through a rapid filter to get rid of the insoluble residue, and if there is much of this it should be ignited with sodium carbonate, the fused mass dissolved in dilute //,.SC>, and added to the //A'(?, solution. The solu- tion should contain as little free acid as possible.

Now add 35 c. c. of concentrated NHfiH, which will precipitate any iron and aluminum present and render the solution alkaline. Then add about 37 c. c. of concentrated HNO. This is to dissolve the precipitate and clarify the solution, thus rendering it slightly acid. If it does not, add a trifle more of the acid. The reaction between the ammonia and the nitric acid will usually heat the solution to about SS" C. Introduce a thermometer, and if the tem- perature is not 85" C. , either cool or heat the solution to this

114 Assaying. §36

temperature and take it off the sand-bath. While still hot add 75 c. c. of molybdate solution. This may be added while the material is in a large beaker or in an Erlenmeyer flask. The thermometer which was used in ascertaining the temperature of the solution should be washed off by means of molybdate solution as it is added.

213. If arsenic is known to be present, the temperature of the solution should be reduced to 25° C. before the molyb- date solution is added and the material allowed to stand at least four hours with occasional agitation, when the phos- phorus will be precipitated and the arsenic will remain in solution.

214. Where arsenic is not present, the molybdate solu- tion is added while the ore solution is hot, as before stated, and the precipitation is assisted by shaking or agitating the solution. If the solution is in a flask or glass-stoppered bottle, it may be shaken mechanically, or if in a beaker or flask, it may be given a rotative motion by whirling or rota- ting the flask in the hand. If the laboratory is provided with compressed air, the shaking may 'oe accomplished by carrying a current of air into the solution through a glass tube and allowing it to ascend to the surface as bubbles.

After the phosphorus has been thoroughly precipitated, it should be filtered off. Care must be exercised in the filter- ing and in the subsequent washing so as not to allow the yellow precii)itate to crawl over the upper edges of the filter. While the precipitate is on the filter, it should be washed with a nitric acid solutiin filling at least six times to its edges. This is to remove all iron.

The yellow precipitate can now be dissolved in ammonia, and if any of the precipitate shouKl adhere to the flask or beaker in which the precipitating was accomplished, this may be dissi>lved in a p(rtion of the ammonia employed for bringing the material on the filter into sihition. The solu- tion should now be made aciil with dilute sulphuric acid and then alkaline with ammonia in excess. to at least *25 C, and when void aild 50 c. c. Ki macfnesia mixture.

Assaying.

All(iw the flask or beaker tu stand in a cool place for at least four hours, with frequent agitations, and finally filter on to 2 filter the weight of the ash of which is known. Wash with water, ignite, and weigh the resulting magnesium pro- phosphate and ash. Subtract the known weight of the ash of the filter from the weight obtained and multiply the result by ().2792H. which will give the weight of phosphorus in the amount of the substance taken, and from this the percentage can be easily figured. It is usually best to test the solution before filtering by adding a few drops of mag- nesia mixture and allowing the solution to stand for a few minutes in order to see if all the phosphorus has been pre- cipitated. If a precipitate results from the addition of more magnesia mixture, it is evident that all the phosphorus has not been thrown down, and the solution must be allowed to stand longer.

215. The Magnesia Mixture. — This may be made

by dissolving I gram of magnesium sulphate (MgSO and 1 gram of ammonium chloride (NHCl) in 4 c. c. of ammo- nia [t\H,OH) and 8 c. c. of water. One c. c. of this solu- tion will precipitate 0.04 gram of phosphoric acid (P,0). The magnesium siilphati- and the ammonia chloride should be in the form of sail.

216. Molybdate Solution. — This may be made up in the following proportions: Dissolve 1 gram of molybdic acid {MoO,) in 4 c c. of ammonia and then pour the solu- tion into 15 c. c. of nitric acid (Sp. Gr. 1.2). One c. c. of this solution will precipitate 0.0013 gram of phosphorus.

2t7. In making either of the above solutions, the pro- portions will be increased so as to make a sufficient volume of the material required. Either one of the solutions should be allowed to stand for a day or two before it is used and then the clear solution siphoned off In making up the molybdate solution, it will be necessary to keep the flask immersed in cold water, in order to keep the temperature down while adding the ammonia solution to the nitric acid.

lie

Assaying.

8 3rt

218. Voluroetrlc Oetermlaatlon of Phosphorual

— From 2 to 10 grams of the ore may be employed fori this determination, and the process is as follows whe 2 grams are taken: Add 20 c. c. of HCl and put on a hogfl plate or sand-bath, and keep almost at a boiling tempera- ff ture until it is reduced to a syrup; then add 20 c. c. i centrated HNO, and boil to about 10 c. c, or until all thej HCl fumes are driven off. Wash down the sides of thfe beaker and dilute to about 30 c. c. Filter through a rapid filter to yet rid of the silica and wash with as little water a possible. If there is much of the insoluble residue, it may b necessary to fuse the same with sodium carbonate and dis solve and add to the filtrate as in the gravimetric method.

Heat or cool the solution to 85° C. and add 75 c. c, molybdate solution. Shake for ten minutes as in the gravid metric method, and then filter off the yellow precipitate on to a 9 c. m. No. 1 F. filter and wash with a potasiiuiii nitrate solution made by dissolving 1 gram of KNO 100 c. c. of water. Be careful not to allow the phosphi}4 molybdate to crawl over the edges of the filter, and see thaq the fiiter is filled with the wash to its edge at least six time& so as to be sure to remove all the iron or acid. Transf the filter with yellow precipitate to a No. 1 beaker and ada 20 c. c, of sodium hydrate {UaOIf) solution. Unfold filter with a glass rod, dissolve the precipitate, and beat ihi filter paper up to a pulp. Dilute with warm water to abou 50 c. c. Add 0.5 c. c. of phenol-phthalein solution; titrate with either JICl or //NO, solution, adding drop drop at the end reaction. The end reaction is indicated bf the solution becoming colorless, and the difference bctweei the number of c, c. of NaO// and the number of c. c. of aci used gives the phosphorus direct. In case the insolubl residue has not been fused, this method does not taJc into account the phosphorus contained in the siliciou*-' matter.

219. The Sodium Hydrate Solution {IaOH).- Take 15.1 grams of sodium hydrate and dissolve in 100 c,

§3

Assaying.

of water, add a salurated solution of bariiim hydrate, and stir in until there is no more precipitate. The barium hydrate is added to free the sodium hydrate from sodium carbonate, which is converted to barium carbonate. The solution should then be filtered and made up to 2 liters by the addition of water.

220. Tbe Standard Acid Solution.— This may be

either //A't?, or HCl. In case the nitric acid is employed, take 200 c. c. of HNO (Sp. Gr. 1.42) and dilute up to 2 liters. 200 c. c. of this stock solution can be diluted lo a liters, and this will form an approximate standard. Run the standard acid solution against the alkali, and so ascertain their relative strength. The stronger can be reduced by the addition of water, and so the two can be brought to an equal value.

After the two solutions have been brought to an equal strength, 0.1 g. of pure ammonium phospho-molybUate may be dissolved in 20 c. c. of alkali solution. This amount of yellow precipitate contains 0.00163 g. of phosphorus, and if the sodium hydrate solution were normal, it should require 16.3 c. c. to neutralize the MoO in the yellow precipitate; hence 3.7 c. c. of acid would be required to neutralize the excess of alkali and change the color of the indicator. In case more or less of the acid is required, the solution can be brought to the right strength by adding water or by adding more of the alkali until the proper strength is obtained. The acid sohilion can then be brought to the same strength that the alkali has, and the solution will be correct for work- ing with 3 g. of ore ; that is. 1 c. c. will be equal to 0.O002 g. of phosphorus or per cent, phosphorus when 3 g. of ore are taken for analysis.

221. Phenol-Phthaleln Indicator.

a gram of phenol-phthalein are dissolved ir

alcohol; from 3 drops to half ; each titration.

tenths of

I in 200 c. c. of %h$

II be sufficient for

118 Assaying. § 36

Determination.

222. Lime, or calcium oxide (CaO), may be determined either gravimetrically or volumetrically by means of a standard solution of potassium permanganate. The latter method is much the quicker, and if pro{>er care is taken, is fully as accurate as the gravimetric determination. It has the additional advantage that the same standard solution may be used for both iron and lime determination. The standard of the solution for lime is just halfoi the standard for iron. Thus, if 1 c. c. of the permanganate solution equals 0.010 g. of iron, it will equal 0.005 g. of lime.

Trbatmbnt Of Limb8Tonb And Orbs.

223. Limestone and ores containing lime are treated in the same manner. 1 g. of ore is treated in a small casse- role or beaker with 20 c. c. of distilled water and 5 c. c. of concentrated HCl. Boil until the soluble portion of the ore is all in solution; then dilute, and filter off the insoluble residue, washing it thoroughly with distilled water and add- ing the washings to the filtrate. If the ore contains any lead, it should be removed by passing sulphureted hydro- gen gas (//.V) through the solution; the lead will precipi- tate as lead suli)hide, which should be filtered off, and the preiipilate well washed. The filtrate should then be heated to boiling and the e.xiess of IIS oxidized by a few drops of bromine water or a little potassium chlorate. The oxidizer should be added, a little at a time, until the solu- tion is ])erferily clear.

Ammonia in slight excess is then added to the filtrate frt>m the sulphide, or, if the ore is free from lead, to the lilt rate from the insoluble matter. (The excess may be recognized b\' llie smell or by testing with red litmus paper, which sln>nKi turn blue if the ammonia is in excess.) The ammonia will prevMj>ilale iron and aluminum as hydrates. The solution is then boiled until all the excess of ammonia is expellevl Thi is necess.nv, Nince aluminum hydrate is sliiihlly soluble in aw excels ,f ammonia. To test the

Assaying.

solution to see if all the ammonia iii expelled, moisten the tip of a glass rod with HCl and hold it over the solution. If there is any ammonia left in the solution, it will form while fumes with the HCl.

Filter off the iron and aluminum hydrates. This is a very tedious job, as the precipitate is flocculent and jelly- like; it may be shortened by filtering hot, using funnels with long stems — the longer the stem the greater the suc- tion— and running two or three funnels at once. Wash the precipitate well with hot water and add the washings to the filtrate. If much iron and alumina are present, the pre- cipitate should be redissolved in a little HCl reprecipitated with ammonia, filtered, and the filtrate added to the first filtrate. This is advisable, as a very dense iron-aluminum precipitate is apt to carry down a little calcium hydrate with it.

To the filtrate from the hydrates add 1 c.c. of ammonia and bring the solution to a boil. If any iron or aluminum hydrate forms, it should be filtered off. IE white magnesium hydrate forms, it should be redissolved by adding a slight excess of HCl, and then again make the solution slightly alkaline with ammonia.

The lime is then precipitated as calcium oxalate by adding a solution of ammonium oxalate or oxalic acid. (If oxalic acid is used, the least possible excess should be added, and the solution should contain a considerable excess of ammonia, so that the solution will be alkaline after adding the oxalic acid.) If the ore contains magnesium, a considerable excess of ammonium oxalate should be added, in order to get all the magnesium into the form of magnesium oxalate, which is soluble. Heat nearly to boiling for a few minutes and then filter off the calcium oxalate. Wash the precipitate with boiling water until the last trace of oxalic acid JS removed. This can be tested by means of a very dilute solution of potassium permanganate, pink or pale purple in color, and made acid with H,SO,\ the least trace of oxalic acid in the washings will decolorize the permanganate solution.

120 Assaying. § 36

If the ore contains much magnesium and very accurate work is desired, the calcium oxalate precipitate should be dissolved in HCl and the lime reprecipitated as oxalate and again filtered; otherwise a little magnesium oxalate is apt to be retained in the precipitate and will cause a high result. The error from this source, however, is usually so small that for ordinary work it may be disregarded.

Remove the filter and its contents from the funnel and wash the precipitate off the paper into a beaker with a jet of hot water from a wash-bottle. After all the precipitate that can be removed in this way is gotten off the filter, wash the filter with dilute HSO and add the washings to the con- tents of the beaker. (Sometimes it is difficult to remove the last trace of calcium oxalate from the filter by dilute HSO ; in such a case a few drops of HCl may be added to the paper. ) Dilute the contents of the beaker up to about 100 c.c.,add 15 c.c. of sulphuric acid, heat the solution up to 70° C. (158° F.), and titrate with potassium permanganate. The titration is performed in the same way as the iron titration with permanganate, and the method of calculating the results is the same, except that the standard of the solution for lime is only half of the iron standard, as before men- tioned. The permanganate solution is reduced by the ox- alic acid liberated by the action of the HSO on the calcium oxalate.

224. The result of the titration gives the contents of the ore in lime [CaO). Lime contains 71.43 per cent, of calcium and 2S.57 per cent, of oxygen, so that the amount of calcium in an ore may be determined, if desired, by mul- tiplying the percentage of lime by 0.7113.

Ixsoi.Uble Matter Am> Silica.

226. Insoluble Matter. — Tiie insoluble residue left after treating an ore with acids usually consists principally of silica, together with other substances that are insoluble in the acids used. This residue is spoken of as insoluble fuattcr.

S3C

Assaying.

To determine the proportion of insoluble matter in an ore, treat 1 g. of the ore with acid, as in the iron and lime deter- minations, and as soon as all of the soluble portion of the ore is in solution, dilute with water, and filter off the insolu- ble residue on a special filter paper, the weight of the ash from which is known, Wash the residue thoroughly on the filter with hot distilled water, then place the filter and its contents in a weighed porcelain or platinum crucible, heat over the Bunsen burner until the moisture has all evapo- rated, and then ignite in the muffie or in the flame of a blast- lamp, and run down to ash. Cool the crucible and contents and then weigh. The gain in weight of the crucible minus the weight of the filter ash is the weight of the insoluble matter.

226. Silica. — The insoluble portion of an ore does not always consist entirely of silica; indeed, it may sometimes contain no silica at all. There are various other substances which are insoluble in the ordinary acids — such as, for exam- ple, ihe sulphates of lead and barium, oxides of tin, chro- mium, titanium, and alumiuum — and these when present in the ore all go to make up the insoluble residue.

All the above insoluble substances, however, except silica, may be rendered soluble by fusion with sodium bicar- bonate. The fusion breaks up the insoluble metallic salts and converts the metals into soluble double salts, only the silica remaining unaffected. This fact forms the basis of the separation of silica from other insoluble matter when it is desired to determine the exact amount of silica in an ore.

227> Lead sulphate, if fused with sodium bicarbonate, would be apt to be reduced to metallic lead. Consequently, if any lead sulphate is present in the insoluble residue, it must be removed before performing the fusion. Lead sul- phate {and all other lead salts) are readily soluble in a hot solution of ammonium acetate. The solution is best made by adding strong acetic acid to strong ammonia water until the solution is just acid (indicated by the reddening of a

122 Assaying. § 36

piece of litmus paper placed in the solution) and then add- ing a few drops of ammonia — just enough to neutralize the excess of acid and make the solution again slightly alkaline (turn the litmus paper blue). Heat this solution nearly to boiling, and then with it wash the residue on the filter sev- eral times. The hot ammonium acetate will dissolve out the lead sulphate. Then wash the residue on the filter several times with hot distilled water, transfer to a platinum cruci- ble, and run down to ash as before.

After the filter paper is completely burned, add 2 or 3 g. of bicarbonate of soda (some chemists prefer to use a mix- ture of equal parts of sodium and potassium bicarbonates or carbonates), and fuse over the blast-lamp or in the muffle until all action has ceased and the fusion becomes perfectly liquid and quiet. The fusion will generally require from 10 to 20 minutes. The heat should be raised as high as pos- sible during the last few minutes.

When the fusion is complete, remove the crucible and dip its bottom into cold water to chill the contents quickly. It is a good plan to place in the crucible before chilling a piece of heavy platinum wire, bent into a hook at the lower end; the fused material will solidify around this hook, and the wire can then be used as a handle with which to remove the fusion from the crucible after it has become loosened. Add boilinj water from a wash-bottle to loosen the fusion so tliat it may be removed. Slightly bending the crucible a few times with the fingers will assist in loosening the fusion, and will not injure the crucible. A little dilute HCl may be used to remove thclast traces of the fused masssticking to the inside of the crucible. Wash out the crucible thoroughly, transfer the fused mass and washings to a casserole, add considerable water, and then acid IICI — drop by drop, to avoid running over, as the carbonate effervesces violently with the acid. Continue the addition of the acid until the carbonate is all dissolved and the acid is in slight excess. Then cover the casserole with a watch-glass and evaporate the solution down to dryness. The evaporation should be completed at a temperature not much above the boiling-

)6 Assaying. 123

point of water; otherwise the solution is apt to spit when it becomes thick, and thus lose some of the silica. After the mass is dry, raise the heat somewhat, to drive off the last trace of HCl. Then add more water and a few drops of HCl and again boil. Filter, wash the residue several times hot water, and then dry and ignite as in the case of the insoluble matter. The residue now consists entirely of silica, the weight of which is determined exactly as in the case of the insoluble matter.

For ordinary work, in which extreme accuracy is not sought, it will not be necessary to evaporate the solution down to dryness and again take up with water. The resi- due from the solution of the fused mass may be filtered off directly, after boiling the solution, and then washed, ignited, and weighed as silica.

228. De term Illation of Silica Aloii. — When silica alone is wanted, the following rapid method can be followed: Dissolve I gram of the ore with HCl; evaporate to dryness and redissolve in dilute HCl. Filter on to an ashless filter, wash, dry, ignite, and weigh the insoluble silicious residue. The material should be ignited in a platinum crucible, then add a few drops of hydrofluoric acid {ffl") and a few drops of concentrated HSO. Evaporate to dryness and the sihca will pass off as silicon fluoride. (The work should be done under a hood.) Ignite the crucible and weigh. The difference between the two weights will be the weight of the silica direct as SiO.

If the insoluble silicious matter contains calcium, magne- sium, potassium, or sodium, the loss in weight due to driving off the silica will not be entirely apparent, on account of the fact that some of the sulphuric acid will combine with the above named elements to form sulphates, and hence the amount of sulphuric acid so combined must be determined and added to the amount already found. This may be accom- plished as follows; Fuse the residue with sodium carbonate and dissolve in water acidulated with a little HCl. Heat to boiling and add a hot solution of barium chloride {BaCl).

124 Assaying.

Filter off, ignite and weigh the precipitated barium siilphattta {BaSO). The amount of 5(7, in the barium sulphate cadi be calculated by multiplying the weight obtained byO.SlSS.iT This should be added to the amount of HiO already obtained.J Wheo the ore contains appreciable amounts of barium sul-l phaie, this method is not admissible, on account of the fact J that the SO, contained in the mineral barium sulphate would; appear as SiO,.

COPPER DETERMINATION. 229. Copper is determined volumetrically by means t a standard solution of cyanide of potassium. It may a determined gravimetrically by precipitating the metallic copper eleclrolytically (by a galvanic current) on platinum, washing and drying it, and weighing it as metallic copper (see Arts. 6 and 237-240). The operation is longer than the vi)lumetric determination, however, and the plati- ' num apparatus is expensive; the electrolytic method consequently, employed only in large laboratories and wher very accurate results are desired, the volumetric methoi being used for most determinations of ores.

Standard H01.Uti0N.

230. The cyanide solution should be approximately half] normal (1 c. c. 5 mg. copper). A solution of about th strength may be made by dissolving froi commercial potassium cyanide (c. p. cyanide is unnecessary ]fl in 1 liter of distilled water. The solution should be kept iitfl a tightly stoppered, colored-glass bottle (dark-green glass M best) in a cool, dark place; or if a dark place is not availJ able, the bottle should be covered with black paper, as thaj cyanide decomposes quite rapidly under the influence i light. Some chemists also pour in a little coal oil above tta cyanide solution in the bottle to further protect it froa decomposition. The solution should be restandardized frej quently. Great care should be exercised in handling it, t it is extremely poisoi

Assaying.

12S

In case of accidents, it is well to remember tiial peroxide o£ hydrogen {/f,0) is a powerful antidote for cyanide poi- soning. It has been applied successfully in a to 3 per cent, solution as hypodermic injections, which were applied every four minutes at different parts of the body. At the same time the stomach was washed out with a 2-per-cent. //,(?, solution. Peroxide of hydrogen {//O,) forms with hydro- cyanic acid {HCN) "oxamide " {CONH,), which is a harm- less compound, thus: %HCN N,0, 'ICONH.

231. Stand ardlxliiK- — The cyanide solution is stand- ardized by titrating solutions containing known weights of copper. Weigh up two charges of c. p. copper foil, of between 2()0 and 300 mg. each {the weights of the two charges should vary considerably, as in the case of the iron wire for standardizing the permanganate solution), place in an Erlenraeyer or flat-bottomed glass flask of about 250 c. c. capacity, and add 5 c. c. of concentrated NNO,. The cop- per will immediately dissolve and the flasks will be filled with dense red fumes of nitric oxide. Place the flasks on the hot plate and heat until the red fumes are completely expelled. Then remove, dilute the contents of each flask to about 100 c, c. with distilled water, and add 10 c, c. of strong ammonia water. Copper hydrate is formed and immediately dissolves in the excess of ammonia, giving a deep-blue solution. The solution is now ready for titration.

Run in the cyanide solution from a burette (the burette should he rinsed with water and finally with a little of the cyanide solution before starling the titration) until the color begins to fade. Then allow the solution to stand for about 10 minutes; then dilute with distilled water to about 200 c. c, and finish the titration very carefully, shaking the flask after each addition of cyanide. It is advisable to hold a little of the copper solution in reserve in case the end point is accidentally passed. The end point most commonly used is the point at which only the faintest tinge of pink shows at the upper edges of the solution when the flask is held against a white background in a gixid light. Many

126 Assaying.

chemists stop somewhat short uf this, while the o:itire soluJ tion retains a pink tinge; and some go beyond, titrating ttU all the color has disappeared. The latter practice attended with considerable risk of running high, howevei with the former it is rather difficult to always strike th&j same tint, and even if there is no error made in this way,! unless the amount of copper in the ore solutions is.approxi-j mately the same as that in the copper solutions used fo) standardizing, there will still be a slight discrepancy, as tb< exact amount of unconverted copper hydrate necessary impart the pink tint of the end point is not known. Th nearer to colorless the titration is carried, the s be the error due to unconverted copper hydrate.

The results are figured exactly as in the permanganate standardization (the weight of copper in grams divided by the number of c. c. of cyanide solution used — the standard of the solution). The average of the two determinations-— J if they check satisfactorily — is taken as the standard of thi solution.

Treatment Of Corpbr Oreh.

232. Treat duplicate charges of ore, of 1 g. each (oi g. if the ore is very rich in copper), in Erlenmeyei flasks or casseroles, with 7 c. c. of concentrated //A'O, ; 5 c. c. of concentrated HSO, {commercial acids will answd all purposes). Boil until the nitric acid is all expelled and the sulphuric acid is boiling freely and giving off dense, white, sulphurous fumes. Any sulphur in the ore will be partially, or sometimes wholly, volatilized, part of it n densing in the neck of the flask. Any sulphur remaining tail the bottom of the flask should by this treatment be fuf into globules which are yellow when cold and are free froi copper. Remove, cool, and dilute very carefully with wat to about 50 c. c. Now add 5 or 6 g. of commercial she* zinc, cut into strips weighing 2 or 3 g. each. Shake ita flask, in order to break up any cake which may have formet in the bottom, and then set aside and allow to stand foi about 10 minutes. By that time all the copper will ham

Assaying.

been precipitated. Then add 50 c. c. of water and SO c. c. concentrated //SO, to rapidly dissolve the excess of zinc. As soon as the zinc is all dissolved, fill the flask up to the neck with water tap " water will answer for this purpose); allow the copper to settle out, and then pour the water ott very carefully, leaving the copper behind. Repeat this twice more, to thoroughly wash out the zinc sulphate. Pnur off the last water, add 5 c. c. of concentrated HNO, (use c. p. acid for this), and dissolve the copper in the same way as the foil for standardizing w.

the operations — dilute, add k to filter the i

or when all L neutralized.

ictlythe same a

lived. From here on the standardization is usually advisable ther before titrating

:opper hydrate solution,

lut about 3 or 3 per cent, of the copper has been The object of this filtration is to remove the gangue, lead, ferric hydrate, etc., which may be present, and afford a clear solution with which to complete the titration.

233. If the ore contains silver, a drop of NCI should be added to the HNO solution before adding the ammonia; if there is very much silver, 3 drups may be necessary; any unnecessary excess should be avoided. The precipitated chloride of silver is then filtered off, the ammonia added, and the solution titrated as usual.

:

234. Strips of aluminum may be used instead of zinc for precipitating the copper. The precipitated copper may be dissolved from off the aluminum with nitric acid and the strips washed and used over and over again until they get too thin to handle.

235. If an ore refuses to go into solution with HNO, and H,SO, a few drops of /C/ added will usually suffice to decompose it. Both the //f/and the NXO must be thor- oughly expelled {see Art. 14) before precipitating the copper, otherwise they will hold a little copper tn solution and cause a low result.

Assaying.

nii:TRRMINATION OF COPPRR IN SILVBR BULLION.

230. If line bullion contains much copper and is to be assayed by the (ire assay, it is necessary to know the portion of copper present in order to make up the proof*] assay properly.

To determine the amount of copper, dissolve J g. of buU lion in dilute nitric acid (the bullion should be beaten orl rolled out so that it will dissolve rapidly) and add HCl inj" very slight excess. Test for an excess of HCl from time] to time by adding a drop of the solution to a drop of silver J nitrate solution. As soon as a white cloudiness results, the J HCl is in excess. Then filter off the precipitate of silver i chloride, make the filtrate alkaline with an excess of ] ammonia, and titrate for the copper as usual.

Blectrolvtic Detbhiuikikg Of Copper.

237. This is also sometimes called the battery assay. 1 There are several slightly different methods of conducting* the electrical determination of copper, but the following is a good general method, especially where zinc and antimony are not present in large quantities: The sample should be passed through an 80-mesh sieve. When determining the contents of copper mattes, gram is sufficient, while in the J case of ores the amount taken may vary from 1 to 2 grams, depending upon the richness of the ore, and in the case o£. slags 3 grams may be taken. After weighing the samples, j they are placed in beakers and slightly moistened with cold.'l distilled water, Then add 25 c. c. of strong nitric acid anda lOto ISdropsof strongsulphuricacid. The beakers should b covered with watch-glasses and set on a sand-bath, where'l they are heated until the nitrous acid fumes have all passel off and the copper is in solution. Wafh the watch-gla: down into the beaker and evaporate the solution until cboj king white fumes of sulphuric acid appear. Set the beakeni to one side to cool, and then moisten the mass with dilute nitric acid (Sp. Gr. 1.20), using about li or 7 c. c. Also adi 4 or 5 drops of sulphuric acid and iU c. c. of water. Heat]

Assaying.

on the sand-bath until the mass is in solution, and then filter off the insoluble residue. The residue should be examined to see that there are no copper minerals left undissolved. The filtrate is saved in the beaker ready for precipitating by means of electricity.

The electrical energy necessary to electrolyze the copper solution may be furnished by one of the various forms of batteries or from a dynamo. The gravity cell is probably the most common form of battery employed for this purpose, but a Grove cell will usually give better results, even though it requires more care in its manipulation. It is best to have a surplus of electrical energy, but too strong a current must be guarded against. Ordinarily three Grove cells, freshly made up, will furnish a current sufficient to deposit the copper from six to eight solutions, none of which contains more than .5 of a gram of copper in 1 gram of sample.

23S. The copper is deposited on a platinum plate called

a cathode, and another platinu as the other pole for the elec tricily, and this is called ai anode. Fig. 35 illustrates ; nient form o

iirface is provided to act

cathode, which is composed a plain platinum cylinder about 2i inches long and 1 inch in diameter. The mil that supports it is 44 inches fic. w fig. m. Fir., S7,

long and usually a little less than inch in diameter. Such a cathode would weigh from Ki to 18 grams. It is well to have the cathodes as large as this, on account of the fact that they afford ample surface for the precipitation of the copper without its accumulating into a spongy mass, which would cause loss while weighing. The anode may be made from platinum wire, as shown in Fig. 36. The wire is a little less than inch in diameter and the straight part is about 7 inches in length. The lower end of the wire is twisted into a spiral, which is situated below the cathode in

Assaying.

the solution to be treated. The diameter of the spiral c is about 1 inch. One advantage of this form of anode i that it affords a uniform evolutiun of gas throughout ch solution, and hence tends to precipitate copper on both tht inside and outside of the cathode in an even manner.

239. The solution to be treated is placed on a dee beaker similar to that, shown in Fig. 37. The cathode i connected with the positive pole of the battery and thS anode with the negative or zinc pole of the battery. ThM cathode should not be completely immersed in the solutidilj to be treated, and when it is supposed that all the copp< has been deposited, the cathode can be immersed deeper ii the solution and the current allowed to run for half an hou longer. If any copper deposits on the clean surface, show at once that all the metal has not been removed fronj the solution. Aft-r all the copper has been deposited, tin anode is loosened and the beaker and anode removed, leav-J ing the cathode with the deposit of copper hangmg to th wire connected with the battery. The cathode washed with distilled water and ther immers What alcohol adheres to it is burned off so as dry the cathode. The copper should appear pinkish color. After the cathode has cooled to ture of the room, it is weighed, and the differ* between the bare cathode and this second weighing is talcei as the amount of copper in the sample treated.

240. Too strong a current will cause too strong s evolution of gas and the copper will deposit dark colorec while if zinc is present it may deposit on the copper, being careful with the work and determining the conditioiH best suited to the products being handled, it is possible to d extremely accurate work by means of the battery assajr! Copper may be completely deposited and removed from solii tions containing iron, aluminimi, manganese, zinc, mckeli. cobalt, chromium, cadmium, lime, barium, strontium, and magnesium. The solution may subsequently be employed for the determination of other elements which it eontains,,.

§ 36 Assaying. 131

The cathode may be cleaned by simply dissolving: the deposited copper in nitric acid. After all the copper is dis* solved, the cathode should be carefully washed to remove any acid or copper salts before it is again employed for a determination.

Lead Determixatiox.

241* Lead mav be determined verv accuratelv and comparatively quickly by titration with a standard solution of potassium ferrocyanide.

Standard Solution.

242. The ferrocyanide solution should be of such a strength that 1 c. c. will precipitate approximately 10 mg. of lead as ferrocyanide of lead. Such a solution is made by dissolving 14 g. of c. p. potassium ferrocyanide (free from ferricyanide) in 1 liter of distilled water. Keep solu- tion in a tightly stoppered, green-glass bottle, and allow to stand at least one day before standardizing.

243. StandardizinK* — The solution is standardized by titrating check solutions containing known quantities of lead. Dissolve two portions of pure lead sulphate, weigh- ing between HoO and 'MM) mg. each, in hot ammonium acetate, made as described in Art. 227. Dilute each solution to about ISO c. c. in a 'iyO-c. c. beaker, heat nearly to boiling, and then titrate. The titration is conducted in the same manner as the bichromate titration for iron (see Art. 184). A moderately strong solution of uranium acetate — made hy dissolving the c. p. salt in water and adding a few drops of acetic acid to clarify the solution — is used as an indicator. This solution should be kept tightly stoppered, in a dark place, as it de(omposes rapidly when exposed to light and air. As long as there is not an excess of ferrocyanide in the lead solution, the indicator solution on the spol-plale will not be afYecte(l by the addition of a drop of the lead solution; as soon as there is the least excess of ferrocyanide,

I3S

Assaying.

however, it will turn the indicator solution brown, the shade becoming darker as the excess of ferrocyanide increases. 1 The first tinge of brown in the uranium-acetate solulioai marks the end of the titration.

TREATMIiNT OP LEAD ORES.

244. Treat duplicate 1-g. charges of ore (or -g. charges I if the ore is rich in lead) in casseroles, with 15 c. c. of con- centrated HNO, and 10 c. c. of concentrated HSO. Boil 1 until the nitric acid is completely expelled and the sulphuric. J acid is giving off dense, white, sulphurous fumes. Theilg remove and cool. Dilute very carefully with cold distillec water, stir thoroughly to break up clots, and then boil untilfl all soluble sulphates are in solution. Filter, leaving as much as possible of the residue in the casserole, and then wash this residue twice with hot dilute sulphuric acid (very dilute — 1 per cent, concentrated acid) and once with cold J water, pouring the washings upon the filter. Wash the'j| precipitate on the filter back into the casserole, using little water as possible, and then add 'i c. c. of a saturated "1 solution of ammonium carbonate. (A solution of any salt 1 is saturated when it will dissolve no more of the salt.) ' Heat quickly to boiling, with only a screen between the flame and the casserole, and boil for a minute, in order to decompose any calcium sulphate that may have formed along with the lead sulphate; otherwise the calcium will react on the lead and cause a low result. Filter, and wash j the precipitate thoroughly with hot water containing a little j ammonium carbonate. Dissolve the washed carbonate of J lead with strong c. p. acetic acid; dilute to 180 c. c. i titrate. The results are figured as usual in volumetric work. The average result of the two titrations is taken.

Zinc Detehmination.

245. Zinc is commonly determined volumetrically bjrJ

means of a standard solution of potassium ferrocyanide,.!

which precipitates the zinc as ferrocyanide of zinc.

Standard Solution.

246. The ferrocyanide solution should be of such a strength that 1 c. c. will precipitate, approximately, 10 mg, of zinc from solution. Such a solution is made by dissolv- ing 45 g. of c. p. potassium ferrocyanide in 1 liter of distilled water. The solution should be kept in a colored bottle, and should be allowed to stand at least one day before stand- ardizing.

247. StandarcHzing. — Weigh out two charges of between 200 and 350 mg. eaDh of c. p. zinc oxide which has been previously heated in a porcelain crucible, to drive off moisture and convert any carbonate of zinc into oxide. The oxide will turn yellow on heating, but will resume its white color when cold.

Transfer the two accurately weighed charges to beakers of about 300 c. c. capacity and disstlve the oxide by adding 5 c. c. of concentrated HCl. Dilute with about 50 c. c. of distilled water. Add ammonia in slight excess, and then neutralize with }iCl, using litmus paper as an indicator. iThe addition of ammonia and its neutralization with HCl are not necessary, but are done simply to have the condi- tions of the standardization as nearly as possible the same as the conditions of an actual analysis,) To the neutral solution add an excess of 10 c. c. of concentrated HCl\ then dilute the solution to aSO c, c. with cold distilled water and titrate. The titration is conducted like the titration for lead, using an indicator solution of uranium acetate.

In all subsequent titrations be careful to have the condi- tions as nearly as possible the same as in the standardiza- tion; the bulk of the solutions should always be the same; the zinc solution should be warm (but not too hot to handle) and should contain the same excess of HCl in all cases, and the temperature of the standard solution should not vary much, if good results are desired. The precipitate of ferrocyanide of zinc should come down pure white, and the solution should be colorless or nearly so.

Assaying.

Xhkatmext Ok Zikc Ores.

248. Treat duplicate l-g. charges of ore in casserole* J with 15 c. c. of aqua regia (2 parts /fC/ and 1 part f/.VO),M evaporating nearly to dryness. When the contents of th&'V casserole iire nearly dry, add 25 c. c. of a solution of potas- T slum chlorate in nitric acid, made by shaking an excess of I crystals of c. p. potassium chlorate with concentrated /iJVO, in a flask. (This solution must be handled with care and [ kept in an open flask, as it is a violent explosive.) Add the J solution very gradually and warm the casserole gently, j without covering, until violent action ceases and no more greenish fumes are given off. Then cover with a watch- glass and run down to dryness. As soon as the mass is dry, and the last drop of acid condensed on the watch-glass has ] evaporated, remove the casserole from the hot plate; i heating or baking the residue will cause more or less e Cool the casserole, and then add 7 g. of c. p. ammonium i chloride, 15 c. c. of strong ammonia, and 25 c. c. of hot dis- I tilled water. Boil for one minute, stirring meanwhile with a rubber-tipped glass rod, to break up any clots ; rub off any 1 splashes that may have dried on the sides, and cover. Then ( filter into a 250-c. c. flask and wash the residue several j times with a hot solution of ammonium chloride, made by dissolving 10 g. of c. p. ammonium chloride in 1 liter of ' distilled water and adding a few drops of ammonia to make the solution alkaline. Any iron and aluminum in the solu- tion will be precipitated as hydrates by the ammonia. If'j the precipitate is heavy, it is apt to carry down some zinc I hydrate with it, and should be filtered out, washed well, transferred to a casserole (using as little water as possible), evaporated down to dryness, and then treated with the J solution of potassium chlorate in nitric acid in the ! manner as the ore was first treated. Run down to dryness, i and again treat with ammonium chloride and ammonia, as J in the case of the ore; filter off the precipitated iron and i aluminum hydrates again, washing with the hot ammonium* f chloride solution, and add the filtrate and washings to first filtrate. If the first precipitate of hydrates is smal

§ 36 Assaying. 135

however, the little zinc it carries down may be neglected. Filter the precipitate out, wash as before described, and proceed. If the filtrate is blue, it contains copper, which must be removed before titrating. Add HCl till the solution is neutral {indicated by the disappearance of the blue color if copper is present, or by blue litmus paper turning red if the solution contains no copper) and then add 10 c. c. esce.ss of concentrated HCl. Then, if the solu- tion contains copper, add 20 to 40 g. of test lead and boil the solution until all the copper is precipitated. Then decant the solution from the lead into a beaker, wash the lead and precipitated copper thoroughly, add the washings to the main solution, and then titrate as in the standard- ization.

249. If, as may sometimes happen, the ore will not decompose completely by treatment with aqua regia, evapo- rate the solution to dryness, dissolve out the soluble salts with water, and filter off the insoluble residue, Fuse the insoluble residue in a porcelain crucible with carbonate and nitrate of soda, dissolve the fused mass with water and nitric acid, filter off the silica, and add the filtrate to the 6rst filtrate. Evaporate nearly to dryness and proceed as before.

Silpiiuh Dbtekmination.

250. The following method will be found useful for the determination of sulphur in practically any compound; Fuse 1 gram of the substance with from one to two slicks of potassium hydrate — KOI! — (the c. p. caustic potassium by alcohol should be used, a.s any other generally contains sulphur, and even this should be tested to be sure that no sulphur is present) in a silver crucible (a crucible lined with gold is to be preferred, as the alkali generally attacks the silver crucible to a slight extent) over a spirit-lamp. The best method of making the fusion is to place the KOH in the crucible and heat over the spiril-lamp until the fused mass is quiet. Remove the lamp from under the crucible,

136 Assaying.

bnish the substance into it, and heat for from five to ihirtjj minutes, or until the substance is thoroughly decomposed; (A spirit-lamp is used on account of the fact that gas alwaysl contains more or less sulphur, and were the gas flame I employed, sulphur would be inlroduced into the material in the crucible.) After the material in the crucible is thoroughly fused, it should be removed from the flame and allowed to cool. As soon as cold, dissolve out the mass into a beaker with warm water, and when it is all transferred tol the beaker boil and filter. Wash the filter with boiling I water until the washings come through free from sulphides! or sulphates. Add to the filtrate from 20 to 40 c. c. oil bromine water, heat to about 'JO C, and then acidify witlur net. If the substance contains silica, it will now be in'J solution and must be removed by evaporating to dryness, I heating the dry materia! to render the silica insoluble, and 4 then taking up the remainder of the material with water and HCl, after which the silica, which has been rendered insoluble, may be filtered off. Boil the filtrate from the silica and add a boiling solution of barium chloride (BaC/,) until all the sulphur is precipitated as barium sulphate {BaSO). By heating the barium-chloride solution before adding it to the solution, the barium sulphate will be pre- cipitated almost immediately, while if the solution were cold it would take some time, After the addition of barium chloride, the solution is brought to a boil and then removed to a warm place and allowed to settle. When the precipi- tate has settled to the bottom, filter and wash the precipitate thoroughly with boiling water; then drop a few drops of dilute //C7 around the edge of the filter paper and wash twice more with hot water. The last washing should be tested with silver nitrate to be sure that all the NC/ has been removed. The object of the last washing with HCl to insure the removal of all the calcium salts.

The precipitate should now be dried by removing the funnel and filter paper to a ring stand or some suitable sup- port and warming until the precipitate is dry.' It may then be removed from the filter paper by placing a platinum

§ 36 Assaying. 137

crucible on a sheet of glazed paper or a clean watcli-glass and gently rolling the filter paper between the fingers over it in such a manner as to rub off the precipitate. After all the precipitate that it is possible to remove has been trans- ferred to the crucible, the filter paper should be rolled up, placed on the lid of the platinum crucible, and burned by holding the platinum over the flame of a burner or spirit- lamp. The ash of the filter paper is then added to the con- tents of the crucible and the whole ignited in a muffle or over a blast-lamp. The crucible is then cooled, when its contents should be perfectly white. The precipitate may be weighed either by transferring from the crucible to the watch-glass of a balance or by weighing with the crucible. The weight of the barium sulphate, less the known weight of the ash of the filter paper, multiplied by 0.13734, will be the weight of the sulphur present in the amount of the substance taken.

251. When silica is not present, the evaporation of the filtrate from the solution of the fusion can be omitted, which will greatly shorten the method. When evaporating to dryness, care must be taken on account of the fact that if it is done too rapidly some of the material is liable to be lost by spurting.

Phkpahation Of Keagents.

252. The following table of proportions for the prep- aration of reagents may be found useful. The concentrated acids have not been included in the table on account of the fact that they are used as received from the supply houses.

Dilute hydrochloric I One porlion of HCl to 3 portions of acid {HCl). water by volume.

Dilute nitric acid ) One portion o( concentrated HNO, to {NfiO,). I 8 portions of water by volume.

One volume of concentrated nitric acid

. , I, . .J added to 8 volumes of hydrochloric acid

Nitro-hydrochloriciidid , ,.,.,. ,j ,

, . , forms aqua reeia. which shou d be pre-

(aqua regia). . , ... . .

pared only as required. It may be used

either concentrated or dilute.

Assaying.

§36

Dilute sulphuric acid

One portion of concentrated HtSO to 4 portions of water by volume.

Note. — Always pour the concentrated acid into the water, and never water into the concentrated acid. The union of sul- phuric acid and water produces heat, and if water were poured into the acid an explo- sion might result.

Note. — Some chemists use 1 portion of concentrated acid to 4 portions of water for all the dilute reagents.

Dilute acetic

acid

One portion of 33j acid to 1 portion of water by volume, or 1 portion of glacial to 4 of water.

Oxalic acid (H%C%

o,). I

One gram of the crystals to 10 c. c. of water, which makes a practically saturated solution.

Tartaric acid

One gram of crystals to 3 c. c. of water.

Hydric-sulphide or sul- phureted hydrogen

This is formed by treating iron sulphide {FeS ) with sulphuric acid. If iron sulphide can not be obtained, it may be prepared by fusing iron nails with sulphur, in the pn portion of about 1 part by weight of iron to 2 parts by weight of sulphur. If.iS gas may be led into water until the water is saturated and the saturated water used as a reagent. The water should be kept in colored-glass bottles, as it is quickly decom- posed when exposed to the light. When it is desired to precipitate any substance from the solution by means of IliS, it will be better to conduct the gas itself into the solution than to employ water charged with the gas, on account of the fact that in order to add a sufficient amount of gas, it would be necessary to add a very large amount of water, thus unnecessarily increasing the bulk of the solution.

§36

Assaying.

Chlorine or water {CI),

chlorine

Chlorine may be generated by treating bleaching powder (chloride of lime, CaOCi) with sulphuric acid, and the gas may be absorbed in water, but chlorine water must be kept in a colored-glass bottle or in the dark, for in the light the chlorine will decompose water and form hydrochloric acid {HCl).

Note. — Chlorine gas may also be pre- pared by mixing 50 grams of coarse salt and 40 grams of powdered black oxide of manganese, and adding to it when cold a mixture of 125 grams of concentrated sulphuric acid and 60 grams of water; shake well together and warm, gently col- lecting the gas as it comes over in water contained in a black-glass bottle.

Ammonium chloride (NH.Cl).

One gram of the crystallized salt to 8 c. c. of water.

Ammonium carbonate

The ordinary commercial carbonate (known as sesqui-carbonate) produces in solution a mixture of the neutral and acid carbonates. This is objectionable when the neutral carbonate is to be used, and hence the reagent should be made up as follows: Dissolve the crystallized sesqui-carbonate in the proportion of 1 gram of the sesqui- carbonate to 4 c. c. of water and then add 1 c. c. of concentrated ammonium hydrate {XlhOH).

Ammonium oxalate j One gram of the crystallized salt to {Nll.hCO,. i 20 c. c. of water.

Plumbic or lead ace-

Potassium chromate

(A CrO,). I

One gram of salt to 10 c. c. of water.

Potassium

cyanide

One gram of salt to 4 c. c. of water.

Note — (ireat care should be taken in handhng potassium cyanide, as it is extremely poisonous.

Assaying.

§36

Potassium hydrate

One gram of salt to 10 c. c. of water.

Potassium iodide (AV). One gram of the salt to 25 c. c. of water.

Potassium ferric y a- j

Potassium sulphocya- j

Potassium ferrocya nide KFe{CN)t.

One gram of the salt to 10 c. c. of water.

Dissolve 1 gram of the salt to 10 c. c. of water.

One gram of the salt to 10 c. c. of water.

Sodium carbonate

Sodium hydrate (NaOH).

Ammonium sulphide (A7A),5.

Yellow ammonium sul- phide {X//,\S.i.

When dry sodium carbonate is employed, 1 gram of the material to 5 c. c. of water makes a practically concentrated solution, while if the crystals are employed it would require 2.7 grams to 5 c. c. of water. This is on account of the fact that the crystals contain water of crystallization.

One gram of salt to 10 c. c. of water.

Conduct hydrogen sulphide gas (//a5) into a bottle two-thirds full of concentrated ammonia hydrate (AVAc)//) until it is saturated, which is indicated by the bubbles coming from the liquid undiminished in size. Fill the bottle with concentrated ammonia and mix it thoroujjhly. This stock solution should be kept in full tightly stoppered bottles, and the bottles should be colored, as light decomposes the ammonia sulphide. Before using, the stock solution should be diluted with twice its volume of water, and this diluted solution should be kept in the ordinary colored-glass reagent bottle.

This is made by adding a small quantity of flower of sulphur to common ammonia sulphide and shaking until the sulphur is dissolved. Enough sulphur should be added to give the solution an amber color.

H a r i u m chloride One gram of the crystallized salt to {lutC/i). i 10 c. c. of water.

gae

Assaying. 141

Barium carbonate may be prepared by

precipitating a pure barium chloride solu-

tion with ammonium carbonate; then wash 1

Barium carbonate

{BaCO,).

have been removed. The wet precipitate M

should be stirred into the water so as to

form a thin cream or emulsion. It should

be thoroughly mixed before using.

Barium hydrate may be prepared by dis-

solving salt in the proportion of 1 gram of

Barium hydrate

salt to 10 c. c. of water. This should be

BaiOH),.

digested or heated for several hours and

then the pure liquid filtered off and kept 1

in a well -stoppered bottle. 1

Bromine water may be formed by making

a saturated solution oE bromine in distilled

water. It should be kept in a tightly stop-

pered colored-glass bottle and in a cool

Bromine water

place. When opening the bromine water

{Br+lf.O).

in warm weather, care should be taken.

for there is liable to be a sudden rush of

vapor upon withdrawing the stopper, and

this vapor is not only disagreeable, but

somewhat poisonous.

This may be prepared by slacking fresh

quicklime and adding a large quantity o(

water placed in a large glass bottle, and

Calcium hydrate or

shake well several times; then allow to

limewater C.i(0//),.

settle. The clear s<ilution can be decanted

oR and used as a reagent. It contains

I part of lime and several hundred parts

[o,w.,„. H

Sodium acetate

(NnC,//,0,).

One gram of salt to 10 c. c. of water.

Argenic or silver ni- trate lAxO,).

One gram of salt to 25 c. c. of water.

One gram of the salt to 3 c. c. of //C/

and 8 c. c. of water. Metallic tin should

Stannous chloride

be kept in solution and should be kept

from the air to prevent the formation of

oxides.

Assaying.

§36

Weights And Measures.

English And Metric Systems.

Avoirdupois Iveight.

16 drams (dr.) 1 ounce 02,

16 ounces 1 pound lb.

100 pounds 1 hundredweight. . .cwt.

20cwt., or 2,000 1b.

1 ton

T.

28.3495 g. 453.5920 g.

45.359 Kg. 907.184 Kg.

Troy Weight.

24 grains (r.) 1 pennyweight. . . ./w/.

20 p>enny weights 1 ounce 02.

12 ounces 1 pound /d.

1.5552 g.

31.1035 g.

373.2419 g.

MEASURES OF LENGTH Metric).

The meter is the unit of lengthy and is 39.37 inches, nearly.

equal to

10 millimeters {mm.). . .

. . 1 centimeter . . . .

,

— 0.3937 in.

10 centimeters

. . 1 decimeter

m.

. . . Dm. ...Hm. . . . Km. . . . Mm.

3.037 in.

10 decimeters

, . — 1 meter

— 3.2 ft.

10 meters

. . 1 dekameter . . . .

- 32.8 ft.

10 dekameters

. . 1 hektometer . . .

— 328.09 ft.

10 hektometers

. . 1 kilometer

— 0.02137 mi

10 kilometers

. . 1 myriameter. .

— C.2137 mi.

MEASURES OF WEIGHT {Metric).

The %r&.v[i is the unit of weighty and is equal to 15.432 grains, or the weight of a cube of pure distilled water at 4° C, the edge of which is one one-hundredth

10 milligrams {mg.)

10 centigrams

10 decigrams

10 grams

10 dekagrams

1 centigram ci;

— I decigram di

I gram g

— 1 dekagram Dg

1 hektogram Ng

, , (1 kilogram f ,. ,

10 hektograms -j ,° ( Ag. or A

10 kilograms

i or kilo 1 myriagram Jfg

0. 1 5 gr. 1.54 gr. ir).482 gr. 154.32 gr.

3.r)3 oz., avoir.

2.20 lb., av(.ir.

22.05 lb., avoir.

§ 36 Assaying. 143

CUBIC MEASURE {Metric).

1,000 cubic centimeters (c. c. or rw.') 1 cubic decimeter, or liter (/.). 1 liter of water at 4" C. weighs 2.2 lb., avoirdupois. 1.000 cubic decimeters 1 cubic meter {cu. ///.). or kiloliter (AV.). 1 kiloliter of water at C. weighs 22.04 cwt.

Assay-Ton Weights.

( 4 assay tons 116.66666 grams.

Unit The assay ton iA. T.) is equal to 29.16666 grams.

See Art. 30.

Subdivisions.

assay ton 9.7222 grams. J assay ton 4.8611 grams. 1*5 assay ton 2.9166 grams. assay ton 1.4583 grams.

Geology.

Introductory.

1. The surface of the earth, as now seen, is composed of land and water, and both the land and the bed of the ocean are composed of soil and rock. Geology is the study of the rocks, not only as to their value as ores or for building stone, coal, etc.. but to learn the history of the earth and to determine the agencies or means which have been instru- mental in forming the various rock formations and deposits; or, as slated in other words, geology is a history of the earth as recorded in the rocks and formations as now seen. This history is plainly written in the rocks about us. It has taken men a great many years to learn to read the story, but at present the alphabet at least has been deciphered, and much of the interesting contents of this great book of nature can be understood,

2. The subject seems naturally to divide itself into Dynamical Geology, in which the forces acting to produce the various formations and deposits and to effect the changes which have given the earth its present form are studied ; Structural and Historical Geology, which is a study of the general form of the earth, structure of its rocks, etc., and the history of life upon the earth; and Economic GeolOKy, under which may be considered the various deposits of valuable material, the conditions under which they are most liable to occur, and the character of the formations in which they should be searched for,

3. It will be best to take up the study of Dynamical Geology first and learn something of the forces which have been acting, and are still acting, to change the form of the

§37

2 Geology. § 8?

world we live on. The agencies or means which re and have been acting upon the earth may be divided into attnos- pheric agencies or the effect of the air in changing the earth; aqueous agencies or the results produced by water; igneous ageneies or the part that fire plays or has played in the formation of the earth ; organic agencies or the effect of vegetable and animal life.

Dynamical Geology.

Atmospheric Agencies.

4. Composition of the Atmosptiere. — The air or

atmosphere which we breathe is composed in the most part of nitrogen and oxygen gases, but it also contains watery vapor, carbonic acid gas, and occasionally other gases or vapors. The inactive gas in the air is practically all nitrogen, but a new element or gas called argon was discov- ered a few years ago and it was found in the atmosphere with nitrogen. The nitrogen and the argon are inactive gases, and hence produce practically no changes in the formation of the earth. The oxygen, watery vapor, and carbonic acid gas are active in producing chemical changes in the rock. They are also active in producing vegetable and animal growth, and the vegetable and animal material in turn decomposes and forms ammonia and organic gases and acids, which assist the elements in the air in the work of decomposing the rocks and changing the surface of the earth.

5. Chemical Anencies and the Formation of Soil. — The chemical action of the elements in the air grades so gradually into those caused by the water that all the chem- ical agencies may be considered under atmospheric agencies, and the effects of water may be confined to its ability to erode or wear awav the strata and carry it to other locations.

B. All ex])ose(l rocks or stones gradually become rounded and more or less worn away, and if we make a careful

§37

Geology.

examination of the rocks, we will find that practically all of them are more or less cut up by cracks or seams, or that they contain small pores or openings which allow the air or water to circulate through them. this way the oxygen of the air may change the chemical composition of certain ingredients of the rock, the carbonic acid or the organic acids may dissolve certain portions of the rock, ammonia or other compounds may affect them so that the rock gradually becomes rotten and disintegrates. This disintegration of the rock forms soil, which may be formed from rock in place or it may be formed from rock which has been broken up and brought to its present location by the force of water and has been subsequently disintegrated into soil by atmos- pheric agencies.

7. Proceiis of Disintegration In Rocks The

process of rock disintegration may be stated in general as follows: Almost all rocks contain soluble matter, which is dissolved by the moisture in the air, together with the aid of acids and other compounds that it contains, thus leaving the insoluble or less soluble portion as soil. Also, certain compounds are changed by the action of the oxygen in the air, aided by the moisture; as, for instance, the sulphides of the various metals are converted into oxides or carbonates of the same metals, while the sulphur set free is reduced to sulphuric acid, which combines with other elements, thus dissolving certain portions of the rock, forming soluble materials, which finally find their way to the sea; or the sul- phuric acid may combine with certain elements to form insoluble sulphates. This action explains the change which has taken place in the outcrop of most mineral veins, and accounts for the absence of the sulphide ores at or near the surface of the rock.

8. Such rocks as granite, gneiss, eruptive rocks, etc., are acted upon by the atmosphere somewhat as follows : Granite and gneiss are composed mainly of quartz, feldspar, and mica. Quartz is practically unaffected by the action of the atmospheric agencies, and mica is only slightly attacked and

J

Geology.

changes very slowly. Feldspar is itself composed of a solu ble and insoluble portion. The insoluble portion is silicate " of alumina, which is combined with other silicates {usually of potash or soda). These other silicates are slowly dis- solved, leaving the silicate of alumina in the form of kaolin or clay. As the granite and gneiss are practically bound together by the feldspar, it follows that this reducing action will result in the formation of clay containing grains of quartz and mica, saturated with water which carries potash or soda sails. The eruptive rocks are decomposed in prac- tically the same manner, resulting in clay soils, which are sometimes deeply colored with iron.

9. Limestone can be considered as a mass of grains of calcium carbonate cemented together by means of the same material, and when the cementing muterial is dissolved out this would result in the lime soil. If the original limestone contained sand or clay, the result would be a marly soil.

10. Sandstone consists practically of grains of sand cemented together by calcium carbonate or by protoxide of iron. The sandstones in which the cement material is cal- cium carbonate are more or less affected by the weather, and will be in time decomposed into a mass of sand containing lime-water (hard water). The protoxide of iron is very little affected by atmospheric agencies, and it is on this account that most of the red sandstones make such extremely good building materia!.

11. The slate rocks and shales decompose into a clay soil when their cementing material is dissolved, this cementing material being, as a rule, composed of calcium carbonate.

I 2. The results thus far described are those which would occur while the material was being transformed into soil in the place the rock had occupied, but most of the soils are composed of material which has been carried by water or other agencies and then broken up by the air. acids, etc., thus resulting in a soil of somewhat more varied composition

Geology.

than that which would have been derived from the decom- position of any one kind of rock.

13. Boulders of Disintegration. — Where the soil is formed by disintegration of rock in place, any hard masses

: material are slower to disintegrate, and hence may form boulders of disintegration, as shown in Fig. 1, in which case the soft rock b at the upper part of the hill has been gradu- ally decomposed and washed away, exposing the harder formation a, and this in turn has been undermined by the

decomposition of the formation c. Pieces of the rock a have broken off and fallen down, forming boulders, as e, e. In time the corners have become rounded until the rocks assume the usual appearance of boulders. The debris

Geology.

and disintegrated material from the softer portions of the hill have formed soil, as at (/, while on the top of the hill the rock # has decomposed and formed soil in place, as at /. The fa

of the hill above

rock a being steep for soil to re- main where formed, this portion I naturally washed off and serves to increase the depth of the soil in the valley. Sometimes the softer portions of the rock are protected to a certain extent by the harder overlying formations, and this results in the formation of. rocking stones or pillars. Fig, 2 illustrates one of th rocking stones formed by disintegration, and Fig. 3 the roi ner in which pillars are sometimes formed.

-In cold climates, moisture findfcj the rock, and becoming frozen,

14. Effect of Frost.

its way into the cracks in splits up the material, often throwing down great mass- es of rock from cliffs, thus resultingin piles of boulders and broken material at the foot of the cliff, as illus- trated at rt. Fig. 4. This pile of broken material is spoken of as talus, or slide rock. The frost is not only masses from the cliff, but pio.

it continues its action in the breaking up of small stones and in the pulverizing of the grains of rock in the soil.

15. The Effects of Wind.— Wind often drives sand before it, and in some locations this action has done a great deal to change the face of the country, as, for instance, in Egypt, where whole districts of once fertile country, together

Geology.

with the villages and temples which once covered them, were buried under the drifting sand from the desert. In a num- ber of places in North America, as, for instance, at Cape Cod. on the shores of the Great Lakes, and on the Pacific Coast, this constant drifting of sand is going on. On the dry plains in some parts of the world, such as those in the Rocky Mountains, the wind drives the sand with such force that it cuts or wears away any rock faces against which it strikes.

16, As wil! be seen from the foregoing, practically all the effects produced by the atmospheric agencies are destruc- tive or have a tendency to disintegrate the material and tear down the rocks.

Aqueous Agencies.

17. General Classification. — The effects produced

by aqueous agencies may be divided into two general classes:

Mechanical s.nd Chemical.

The mechanical effects are erosion, transportation, and deposit of material, and may be effected ) by water flowing in rivers or streams; (2) by currents and waves in bodies of water, as large lakes or the ocean; (3) by ice in the form of glaciers or icebergs.

The disintegrating chemical effects of water carrying gases in solution have been considered in connection with atmospheric agencies, on account of the fact that the gases are largely derived from the atmosphere, and hence the chemical effects to be considered in connection with aqueous agencies will be the formation of deposits either in bodies of water or by springs.

Mecrakical Effects.

18. nraterFlowlnffln Rivers or Streams. — Under

this head may be considered the effects produced by the water during its entire cycle. First, the water descends in the form

8 Geology. § 37

of rain, snow, fog, or dew, and reaches the sea by one of three methods: (1) As floods or by flowing at once to the sea, and this is the portion which effects the erosion. (2) By soaking into the earth and finally reappearing as springs, and this is the portion which effects the disintegration of the soiL (3) By soaking in and reaching the sea through underground passages. This last-named portion may aid in the disintegration of the rocks and assist in forming the soil, but can have no effect in the erosion, while the second portion may assist in erosion after it reaches the rivers. The proportion between the first and second portions depends largely upon the amount of vegetation upon the country over which the rain falls, and hence countries hav- ing comparatively little vegetation are much more sharply eroded than those which are well covered by forests or by vegetable growth. The first portion flows off at once, and is most effective in the work of erosion. Every little rill has a tendency to excavate a channel for itself, and these rills by uniting into streamlets excavate gullies. The streamlets in turn unite with each other and with the water from sfirins to form streams, or, in a mountainous coun- try, torrents, which excavate' ravines, gorges, cafions, or coulees. The streams unite to form rivers, which flow forth upon the phiins and to the sea.

19. Th<; rivers deposit some of the material eroded or exravated from the mountains on the plains over which tli<y j>ass, but a reat part of the eroded material is always carried to the sea to be deposited at or near the mouth of the river.

2(>. The erosive power of water varies as the square of tJM* v(lo<ity of the current, hence the steeper the course of tin- stream and the yreater the volume of the water, the inorr raj)id will be the erosion of the country passed

through.

2 1 . CauHC WaterfallH. — The most common cause of waterfalls is i)lainly illustrated in Figs. 5 and G. In I'i. 5 the str(?am or river illustrated has fallen over the

hard rock formation, as shown at n. This rock formation is, in turn, underlaid by a soft formation, as of shale or soft

sandstone, shown by i. The water falling over the edge of the hard rock cuts away the soft material asshawn at c. This finally undermines the hard rock and causes it to break off and fall down. This action is as- sisted by the fact that all rock contains joint

planes or cracks. In this way a caflon rf is formed, in the bottom of which the river flows. Fig. 6 is a cross-sec- tion at A Bin Fig. 5 and shows the soft surface rock e through which the river flowed above the falls, and the hard rock a which was undercut and broken down by the river excava- ting away the soft material i, thus forming the cafSon. This is practically the way in which Niagara Falls, the Falls of St. Anthony and of Minnehaha, and most uf the large water- falls of the world have been formed. There are occasional falls which have not been in action through a long period of time, and in which case the rock is very hard, that form exceptions to this general rule. Among the latter class may be mentioned some of the falls in the Yosemite Valley -of California, the streams of which occupy beds which they did not themselves excavate, but which have recently been left vacant by the melting away of the glaciers.

22. Cause uf Rapids. — If the upper strata over which a stream flows were softer than the underlying mate- rial, or if the material were of uniform composition and the fall were considerable, the river would erode a channel

Geology.

baring a quick descent, and thus form a rapids. If doring the time this cutting actiuTi vas going on the land were to rise, the result would be a narrow gorge or cafion, as is rommon in many monatatnons regions, bat especially in the western portion of North America,

23. Relation Between Carrrlne and Eroding Power of n'atcr. — The eroding pf.wt-r ol water, as has been stated, varies as the square of the velocity of the stream, and ihis can be proved as follows: The eroding power, or the power of overcoming the cohesion of the mate- rial to be carried away, must \-ary with the forces which the water can exert upon any given area of material being eroded. If the surface of the obstacle were constant, the force of the running water would varj- with the square of thfrJ velocity; for instance, if a pier were standing in ruimii i water and the velocity of the current were doubled, si the momentum or force is equal to the quantity of matter 1 multiplied by the velocity (.1/= Q'x I'), the force o£ the ' current against the obstacle (in our case the pier) would be quadrupled, for there wnuld be double the quantity of water striking against the pier in a given time with double the veloc- ity, hence (J/' 3 (? x 2 / ") or(J/' iQl'). In like manner, if the velocity of the current were tripled, there would be 3 times the quantity of water striking with 3 times the veloc- ity, and the force would be increased 9 times, while if the velocity were quadru- pled, the force would in'd like manner be increased! If! times. This shows that J the force a current exert against a fixed object varies with the square of 1 the velocity. By means of -I mathematics it can iirrent to carry objects varies velocity. As an example to 1

provt'il iluil the p with the sixth pm

Geology.

illustrate this fact, Fig. " is given. If there were a cube of rock as at a. Fig. 7, which a given velocity of current would just move, the statement is that double the current velocity would move a mass of rock 04 times as great, as at 6, Fig. 7. It is evident from the figure that the increased current has an area lli times as large to act upon, and as doubling the velocity of the current would increase the force as the square, it is evident that this new current could move the body 4 times as deep, hence the new current would have force enough to move the body Fig. 7, just 6i times as large as the body a. This statement can be borne out by experiment. It is found by experiment that a cur- rent moving 6 inches per second will move fine sand; a current moving 8 inches per second will move coarse sand ; moving 13 inches per second will move gravel ; moving 2i inches per second will move pebbles; moving 3 feet per second would move angular stones the size of a hen's egg. It will be seen from this that the carrying power increases much more rapidly than the velocity; for instance, the current moving 1 foot per second carries gravel, while the current moving 3 feet per second, only 3 times the velocity, carries stones many times a.s large as the grains of gravel. It was the dis- covery of these facts that led to the investigation which shows that the carrying power of the water varies as the sixth power of the velocity. This transporting power, or carrying power, of the water must not be confounded with its erosive power. The resistance to be overcome in one case is weight and in the other is cohesion; the latter varies as the square, and the former as the sixth power, of the velocity,

24. From the above it is evident that if a current of water carrying sediment in suspension be checked, it will be forced to deposit a portion of the sediment, and also that the coarse material wilt be deposited first.

25. Prom the experimental work, it was found that a current running at the rate of 3 feet per second, or about 3 miles per hour, would move fragments of stone the size of a hen's egg, or about 3 ounces in weight. It follows from the

Geology.

preceding law that a current of If) miles per hour will carrf iragmenis of tons weight and a current of 20 miles per hour will carry fragments of 100 tons weight. From thesQ considerations, one can easily sec why it is that the water rushing through the mountain gorges has such tremendous carrying power, and why it is that the mountains them- selves are eroded so rapidly and the great canons and val- leys formed. One would think that streams would be able to carry practically any size stone through some of the mountain gorges, but the fact that the water passes on its course through a series of cascades and falls and that the bed of the stream is extremely rough may very much reduce the actual speed of the flow and hence the carrying power of the water. It is this carrying power of the water that taken advantage of in hydraulic and placer mining, as will be described later in connection with those subjects.

26. Sortlnic Power of Water. — Another important fact in connection with the action of the water in efl'eating geological changes is the sorting power of the water. If a mass of stones, earth, and clay be thrown into still water, the coarse stones will fall to the bottom first, and each sue-' ceeding layer will be composed of finer material, the fine; clay settling last. Now, if the operation were to be repeated and a second lot thrown into the same water, it would bft sorted in the same manner, the coarse material settling first, and the fine last. This would result in strata or lamina of material, and if this process were repeated a stratified deposit- would be formed. In the case of running water carrying; material in suspension, if the current were slightly reduced the coarse material would be dropped first, and if it were still further reduced, finer material would be deposited on top of the coarse material, the coarse material being depos- ited farther up stream. From this it will be seen that every change in the velocity of a current of water-carrying material in suspension will result in layers of different: classes of material at the same point, and hence stratified' deposits will be formed. These deposits resulting from thw

g87

Is

settling of material . from water are called sedimentary deposits, and as all moving water is constantly changing its velocity, it is evident that sedimentary deposits will always be stratified. Conversely, it may be taken as a rule that all stratified masses in which the stratification is the result of sorted materia! are of sedimentary origin. These facts are of great aid in studying the various rock formations, as they furnish the data by means of which the origin of any particular formation can, to a large extent, be determined.

27, Cause of n'lndioK Course of Rivers. — Practi- cally all rivers have a winding course, and the cause fur this is perfectly plain. By referring to Fig. 8, the various causes acting to produce this winding course can be seen. If the river originally flowed from y to in a practically straight line, as iiidicated by the dotted lines, and if the current were of a constant velocity and the bed smooth, the straight course might be maintained for some time, but ultimately some little resistance, such as a log or stone, would turn the stream slightly against one bank, and it would begin to cut or erode this bank, thus forming a curve in the stream, and as the curve became greater the velocity of the current at the outside would become greater and the velocity of the inside less, and hence the course would become more and more irregular by cutting material from the outside and depositing it on the inside of the curve. Finally, a loop, such as that shown al a c i, would be formed, and then during some freshet or high-water period the water would cut across as from n to the result

Geology.

being that the portion £ would be left as a curved lake or lagoon, similar to that sfaowa at These curred lakes or loons are very common in the beds of large rivers floviog through comparatively flat plains.

26. Flood-Plain of a River. — All the lower portion of the river which is overflowed during the high water, and on which more or less material is deposited each year, is called the Sood-plain of the river, and this deposit is called the flood-plain deposit. The flood-plain may be divided into two parts, the river swamp and the delta. The riz'fr swai is all the portion of the river-bed from the point where it originally emptied into the sea or lake up to the point where the flood-plain deposit ceases. The delta is the portion of the floftd-plain deposit which has been farmed by tin material being carried down by the river, having fonnec land beyond what was once the shore of the sea or lake.

29. River Swamp. — The river swamp often covers a great area of land. In the case of the Mississippi, tbi extends from about 50 miles above the mouth of the Ohio River to the head of the delta in Louisiana, or for 700 miles, and it contains some 10,0(10 square miles of territory. It is - ' bounded on both sides j F[o. B. by high bluffs, which j

belong to the previous geological period. Fig. 0 illustrates an ideal section of a river swamp or flood-plain, a is thef original surface of the ground, b being the original i bed; t/ is a deposit composed of successive layers of material' J which have been deposited during the different periods o£j high water; e is the level of the river at low water, and at the level at high water. The flood-plains naturally slop) from each side of the river-bank back to the adjacent bluffs thus forming slight natural levees at the points f,/- Thit| is on account of the fact that the water rushing down thti main stream carries a greater amount of material in suspen*B , and upon breaking over the bank at any point andl

8 8r

Geology.

Ib

having its velocity reduced, it naturally makes the heaviest deposit at the points/,/. Owing to this action, the river at low water sometimes flows slightly above some of the adjacent country, and in times of high water the bed of the stream may change its course by breaking through these natural levees and silting up or filling up its own bed, thus leaving lagoons, as shown at d in Fig. 8.

30. Deltas. — When a river empties into a tideless lake or ocean, the velocity of the current being reduced by meet-

ing a great body of water outside, naturally drops its sedi- ment and forms a deposit at the river mouth. These deposits continue until what is called the delta is formed. In Fig. 10 a stream is represented as flowing into a lake at a. It has gradually formed a deposit, through which it finds its way to the waters of the lake by a number of mouths. This deposit is known as the delta, and, as a rule, all the

matter brought down the river in suspension is left in the lake, the overflow from b being clear water. Fig, 11 is a cross-section of such a delta and shows the successive layers or strata as they would appear where comparatively coarse material was brought down by a rushing stream. In the case of large rivers emptying into a comparatively tideless sea, as, for instance, lli': Mississippi into theOulf of Mexico.

la

the greater part of llie maleria! carried in suspension is fine, and hence the deposit would not end as abruptly as that shown in Fig. 11. The delta of the Mississippi is very irregular, but its area is estimated at over 12,000 square miles. The name delta comes from the triangular form oC such deposits and is derived from the Greek letter delt Deltas are farmed only where rivers empty into tidelea bodies of water.

31. Estuary. — Where rivers empty into tidal seas oceans, there is a widc-raouthed bay, or, as it is called, estuary, formed by the scouring or eroding action of tide, which rushes in and out again, carrying much of thl debris which the river brings and that which the tideerodefti from the land out into the sea,

32. Deposits are formed at estuaries in two locations: J (I) Where the force of the water rushing out with the tide

m.

is arrested by the water of the ocean, and at this point bar8>fl of sand or other material will be deposited, as shown at . Fig. 12. (2) At the head of the estuary where the tide o comes the current of the river, thus causing still water at-] high tide, there will be a swamp with its flood-plain as rep-;,! resented in the portion from a to d. Fig. 13. If there ar.J any other coves or indentations in the sides of the estuary which are not subject to scouring action, they may be fille* with debris, as shown at c, and ultimately form swamps o marshes. The deposits at the head of the estuary are

g 37 GEOLOGY.

form the salt marshes so common near the sea. The bars at the mouth of the estuary form an obstruction to naviga- tion, and if they are removed by mechanical means they will be formed once more in the same place by the same agencies. To overcome this difficulty, it is necessary to confine the flow, and thus cause the water to scour away the bar, but this will only result in its being formed farther out. Hence man can never prevent the formation of bars at the mouth of an estuary.

33. Effects Produced by Currentt* and Waves In Larfie Bodies "f Water. — Waves produce no currents,

but have great erosive power and may cut away the coast very rapidly and especially where there are currents which win carry away the material as fast as the waves erode it. During a heavy storm, the great waves attain such velocity that they may move rocks of many tons weight and hurl them against the cliffs or against each other, thus rapidly breaking them up into sand or gravel. The ocean currents correspond to a certain extent to the currents in the atmos- phere, and are caused by differences in temperature and by the revolution of the earth. These currents take up and carry the material eroded by the waves or brought to the ocean by rivers, and in turn deposit it in banks or beds in the ocean. The ocean currents differ from rivers on account of the fact that their beds and sides are composed of water, and hence they arc not disturbed by an irregular course, which tends to mix all the water in the stream and its accompanying sediment, as is the case with rivers. Ocean currents are undoubtedly frequently formed 1,000 feet deep, and while their surfaces may be practically clear, the lower portions of the current will be carrying a considerable amount of sediment. It is undoubtedly true that such cur- rents as the Gulf Stream, sweeping out of the Gulf of Mexico, carry a great deal of sediment, and as they come in contact with large bodies of water, such as the Atlantic, their speed is reduced and much of the material deposited. This is probably the cause that has been active in the

Geology

and they have also had a great efEect in the forming of ( tain parts of the continent of North America.

37. Glaciers and streams cut and erode the rock forma- tions and carry the material to the sea. The sea also cuts or erodes the coast in many places by means of waves. The. currents in the sea carry the material eroded by the riven and by the waves and deposit it in beds or stratified deposits Stratified deposits are also formed to some extent in riven and lakes.

38. OrlEin of Sprlnes iind Wells. — As has alread] been statt-d, water which falls upon the surface of the earta either flows off or soaks into the ground, and that whicM soaks into the rocks and aids in their decomposition by dis solving the softer portions may reappear as springs or may find its way to the ocean by underground passages. Fig. 13

illustrates a simple meth- od m which a spring may be formed. The water fall- mt, on top of the hil! a settles through the por- us formation until it 1 1 II I caches the impervious

bed 1, which may he composed of clay, shale, or an imper- vious rock. The water flows along this surface and appears as a spring at c, where the impervious strata outcrop.

39. Erodlnic Action of SprtOKH' — Springs may, under

certain circumstances, perform quite a large amount of work in the changing of the surface of any given region; as, for instance, if water falls upon an elevated table-land, as illus- trated in Fig. 14, and settles through the soil c and the layer of sandstone a until it reaches an impervious shale strata d, the water will be forced to follow these strata and appear as a spring at d. During this course the water will dissolve more or less of the cementing material of the shale, and especially at the point where the water emerges from over the under- hanging sandst'jne. This action finally undermines the sandstone, and great masses break otf and fall down, form-

r

S37

Geology.

of the glacier is not smooth like that of a river, but is always covered with broken and jagged pieces of ice, and often there are deep fissures or crevices formed in the ice. Stone and earth fall from the sides of the valley and are carried on the surface of the ice-river, while the under surface of the ice picks up stones and by their means scours or scores the bed over which it passes, thus eroding a large amount of mate- rial, much of which becomes frozen into the ice and is carried under the mass of ice. This material is deposited at the end of the glacier in a more or less crescent-shaped mass. This mass of stone, gravel, and clay is called the " terminal moraine" of the glacier, and is really the delta of the ice- river. Any rows of boulders on top of the glacier are called "lateral moraines," and under some circumstances, when the glacier melts, this becomes deposited as rows of boulders. Often the glacier scours out basins where the rock in its way is softer than the adjoining material, and after the ice has melted away these become small lakes. This is a very common occurrence, especially in mountain regions, and these small glacial lakes frequently become filled with debris washed into them, and thus form meadows or marshes. Glaciers can carry very large masses of rock with them, and their enormous eroding power enables them to cut through almost any obstacle. On this account, they have been very active in effecting geological changes, especially in the Northern Hemisphere, as, for instance, in North America, Europe, and Asia,

36. IceberKs. — When glaciers run into the sea, great masses of ice break off and float away, carrying their burden of stone and gravel. Icebergs are often of enor- mous size, and may carry many tons of material. Bergs have actually been found grounded in nearly 2.000 feet of water, and at other times they form great ice-floes, which work along through the shallow water, scouring and scratching the bottom and depositing their burden as they gradually melted. Much of the material on the banks of Newfoundland was undoubtedly brought in this manner,

n GEOLOGY.

as at £, the water will rise from the strata 6 and form an artesian well. In this illustration is an impervtoas under- lying strata ; the water-bearing strata, and c the imper- vious stratum which keeps the water down. / is the soil and a the portion of the outcrop where the water finds itq way into the stone to supply the artesian well.

CHEMICAl. EJ'FECTS.

41 . Cave*. — Under the heading of " Atmosphei Agencies," it was shown that water carrying carbonic arid gas or other gases would dissolve certain rocks, and this dis- solving action may result in forming large caves or under- ground passages, as illustrated in Fig. Iti. If at some sit

sequent time the caves become emptied of the original fl of water, but a certain amount of hard water (water con-' taining lime) is still dripping into them, the water will gradually evaporate and deposit the lime it is carrying. This will result in stalactites, as at i, b, which are masses of stone hanging down like icicles on the roof. At the point where the water drips onto the floor an inverted mass will be built up to meet the stalactite; this mass (r) is called stalagmite; and if ultimately a stalactite and stalagmite unite, they will form a pillar, as at (/. Such caverns as this are very common in limestone regions, and the stalactites

and stalagmites frequently form very beautiful effects. In the cave illustrated, a stream flows out through the mouth of the cave at a.

42. Deposits from Springs. — If the deposits of lime- stone or calcareous matter were formed only by the evapo- ration of the water, their growth would be very slow, but at many springs very large de- posits are built up, and hence we must look for some other explanation of the fact. Calcium carbonate is practically insoluble in pure water, but if the water contains carbonic acid gas {CO it becomes soluble, and the amount that can be dissolved in a given I amount of water in- creases with the per- centage of the carbonic acid gasinthe water, but this in turn increases with the pressure. Some carbonic acid gas comes from the atmosphere, but much of it may be derived from underground sources, and this is especially true in volcanic regions or in regions where sulphides are decomposed, form- ing acids which can attack carbonaceous matter and liberate the carbonic acid. This gas is absorbed by the water under pressure, and as a consequence it can dissolve greater amounts of calcium carbonate. When the waters escape at a spring or other ipening, the pressure is relieved, and much of the carbonic acid gas escapes, hence the calcium carbonate is deposited. This explains the rapid growth of

u

Geology.

sa

Stalagmites in some caves and the large deposits of calci reous matter at some springs, and especially at hot springy in regions which have been affected by volcanic action, as, for instance, Yellowstone Park in Wyoming. Fig. 17 is a view of some of the deposits at the hoi springs of the Yellow- stone National Park. It has already been slated that car- bonate of lime is sometimes deposited at springs. Under certain conditions, water charged with carbonic acid gas may dissolve iron, and as the water comes to the surface this will be redeposited as an oxide, the carbonic acid gas escaping. In volcanic regions hot alkaline springs often carry silicious matter in solution, and as the water cools this is deposited in a soft gelatinous condition, but ultimately hardens into a hard silicious rock. Springs which contain hydrogen sul- phide gas {//gS) are usually called sulphur springs, and under certain conditions they may deposit sulphur, or where the gas is also associated with lime salts they may deposit gypsum.

43. Cbemlcal DepottltH In l..akea.Salt lakes may be formed in two ways; Either portions of the sea may be cut off, or rivers may empty into a basin which has no out- let, the waters evaporating, and the small amount of sail contained in them gradually accumulating until the lake becomes salt or brackish. In case the water in the salt lake had the composition of sea-water, materials would be deposited in practically the following order: PMrst gypsum, then salt, and lastly chloride of magnesium. Lakes which are fed by rivers and the waters of which are gradually evaporated sometimes deposit other substances, as carbonate of lime, sulphide of lime, carbonate of soda, and, under certain conditions, iron may he deposited, but this usually requires the presence of organic matter.

4-i, Chemical Deposlltt In the Sea. — Comparatively little is known in regard to the chemical deposits formed in the sea. Many of the rivers flowing into the sea carry a much larger percentage of carbonate of lime than is found

in sea-water, but much of this undoubtedly is taken up by

J

S37

Geology.

%S

the shells and coral, though in some locations the material of deltas is cemented together by carbonate of lime, and in other places, especially in the tropics, where evaporation is rapid, the sand or gravel of sea beaches are becoming cemented into conglomerates by means of the carbonate of lime from the sea-water which is thrown upon them by the waves.

Igneous Agencies.

45. Effects. — All the aqueous agencies and the atmos- pheric agencies have a tendency to tear down or destroy the earth and to bring the surface of the land to the level of the surrounding ocean, or to such a point that the ocean would cover the entire earth. This is prevented by the igneous agencies, which tend to lift the land and to depress the sea bottoms, thus increasing the differences in ele- vation on the earth, and hence increasing the land area. All the different forms of the igneous agencies are con- nected with the internal heat of the earth, hence this must be considered first.

'16. Increase of Temperature With I>epth. — The mean surface temperature of the earth varies from 80" F. at the equator to f)° at the poles, but the rate of decrease in passing from the equator to the poles is not the same in all longitudes. The lines of equal heat, or the isotherms, form quite irregular lines. Below the surface of the earth a point is soon reached where the daily differences in temperature cease to affect the rocks, and a little deeper another point where the annual difference in temperature fails to affect the earth. At the equator this latter point is only a few feet from the surface, while near the poles it may be over 100 feet from the surface. The depth depends largely upon the amount of annual variation in temperatures. The tem- perature of the earth increases as we descend, and a great many experiments have been attempted to determine the rate of this increase. At first it was supposed to be 1 degree for every 53 feet, but other observations have varied from this,

Geology.

and it is probable that wilh the exception of a few volcanic regions, tlie temperature increases at a very much slowed rate, and in some locations it is known to be considerabin less than 1 degree for every 325 feet. Owing to the facttbaa different rocks have different degrees of ability for conduct ing heat, the lines of equal temperature will be at differei depths in different portions of the earth.

47. Condition of the Interior of tbe Earth.-

condition of the interior of the earth is a point upon whicl there has been much speculation. At first geologists sup-'l posed that the earth had simply a thin shell of solid material and that the interior was a mass of melted rock or lava, which burst through the surface of the earth in places, forminj volcanoes, but astronomy has shown that the earth behaveSa as a solid sphere, and that the density of the earth is verf much greater than that of the rocks at the surface. If thi temperature increased equally from the surface downwards a point would soon be reached where all the rocks i be fused if they were under the pressures existing at surface, but the increased pressure increases the fusinj point, and it is probable that the greater part of the earths in a soiid state. Another fact that enters into this case that the increased pressure upon the rocks would increat their density and hence their ability to conduct beat,.! Owing to the fact that there have been such great outflow of lava from the earth at different times, many scientist still believe that the interior of the earth contains greaf chambers or reservoirs of molten or liquid material, and ife( is from these that the volcanoes are fed.

48. Volcanoes. — All bodies shrink as they become cooler, and the surface of the earth is no exception to rule. The shrinking which has gone on in this case haM caused the surface of the earth to fold or rise in places These folds or ridges have resulted in continents or moun tain ranges, and during this action great fissures or faul have become opened, which in some cases have penetratw to such depths that molten matter flowed forth, causii

M7

Geology.

volcanic overflows, which in many cases have covered great areas with lava. The volcanic overflows have usually left comparatively small openings, which in time were surrounded by erupted material so as to form volcanic mountains. The openings which are now active are called volcanoes, and they seem to act as vents for the portions of the earth in which they exist. The eruptions which occur from volcanoes and the action which caused different portions of the land to rise or fall are usually accompanied by severe earthquake shocks. The eruptions from existing volcanoes are of two kinds. In one class of volcanoes the material is a thoroughly melted or fluid lava, which gradually rises until it Alls and

the crater overflows, the bottom of the crater being melted as the material rises. The other class of volcanoes does not give out such fluid lava, and the eruption usually commences by the blowing out of the bed or bottom of the crater with a terrific explosion. These explosions are accompanied by great rushes of steam under high pressure, and the steam in the lava blows it into fine dust, which settles over the coun- try as volcanic ashes, or if, as is often the case, accompanied by heavy rains, it forms volcanic mud, and this material may subsequently flow down the side of the mountain. The volcanoes in the Hawaiian Islands are of the first class, and give forth verv fluid lava, which, when it first comes from

Geology.

the mountain, flows with great rapidity. Most of the volsJ canoes in the Mediterranean and Indian Oceana are of thi explosive class. In Fig. 18 is an ideal section of a volcanic cone or mountain, a is the original crater through whicl the material has flowed out and been deposited in successiv layers so as to form the mountain. Now, when the mounJ tain has attained some considerable height, the great prea-1 sure necessary to raise the lava to the top of the crater oftenJ cracks or rends the side of the mountain, thus giving risetpB secondary craters or sec- ondary cones on the sides of the original mountain,.] as at b. These secondary! cones are called monticules, T

-lU. Laccolltea and ' U 1 k e H . — Sometim _jg_ eruption of lava (especially

when it is of a semi-fluid character) does not have sufficient force to break through and overflow the original strata, but may simply form great mass between the layers of rock, thus for- cing the strata up into a great mound or mountain, as shown in Fig. 10. Such a formation is called a laccolite. When the ac- tion simply causes a crack which is filled with vol- canic material, the sheet of material thus formed is called a dike, as shown in Fig. 20, Sometimes where these dikes are com- posed of harder material

uii '(U"iii ,

EZCxii:

than the surroundi

"g

rock, they Bland out as bold walls, as shown in Fig. 21.

§37

Geology.

50. Chanijes of Elevation. — The various move- ments of the earth's surface are not always accompanied by sudden eruptions or earthquake shocks, but may be simply slow changes in elevation. Many parts of the earth's surface are known to be slowly rising or settling. Part of the New Jersey coast is settling at a very slow rate, while Northern Norway and Sweden are rising at the rate of several feet a century. The deltas of the Mississippi and of several other large rivers seem to be slowly settling, though not as fast as the river deposits build them up. The entire lower end of South America is gradually rising.

but this motion has occurred in a rather irregular and jerky manner, the principal changes being noticed at the time of heavy earthquakes. These changes are usually ascribed to the same general sources that produce volcanoes and similar phenomena.

Geology.

5 1 . Subordinate PhrnoMrna of lcoous Orlffln

— Some of the subordimte phenofocna ronnetrted vitb vol- canic action are hot sprues, vltich nuj be charged with carbonates or carboDic acid gas. and which occur quite abundantly in various parts of the earth. Solfataras, which are springs carry'ing salpburoos acid or sulphureted hydro- gen derived from their passage throogb the still hot volcanic rocks; fumaroles, which are hot springs accompanied with more or less steam and vap'>r: mud volcanoes, which are hot springs carrying mud with them; geysers, which are intermittent hot springs in which the water is thrown forth in a solid column — all these phenomena are found in regions] which still contain active volcanoes or in which the vol*', canic action has not been long absent. The most noted! hot springs and geysers are in Iceland, in the Yellowstone l National Park in the United States, and in New Zealand, f All these hot springs are more or less active in the produc-| tion of mineral veins and mineral deposits, as will be seen I later

Ohuanic Ackscies.

52. Peat UoKii and the Furmatlon of Coal.-

ccrtain locations, especially in swamps, vegetable matter J accumulates in thick beds called peat bogs or peat swamps. : The water prevents the decayof the vegetable material, and'l it gradually accumulates until it attains a great depth. This I material may be gradually compacted, and if it is subse- j qucnlly covered with other strata, may ultimately become I lignite or coal. These peat bogs are very common in s localities And furnish a large proportion of the fuel to the inhabitants of some countries, as, for instance, Ireland, ' France, Scotland, etc. Some deposits may also be formed where there is an accumulation of drift logs and timber at or J near the mouths of large rivers, which ultimately becomeiu covered with soil and pressed into a solid mass of carbon*- ce<tus matter.

A3. KfYiet of dtrtMnacttouH Matter on Iron Ottir Mtiinls. — Bog irv>n ore is often found at the bottom t

Geology. 31

of the peat bog in the shape of a hard pan of from 1 to 2 feet in thickness, and the manner in which it is deposited is of considerable interest. Practically all the red coloring matter in the rocks is peroxide of iron (/'',f ,), and in this condition the iron is insoluble in water. The decomposi- tion of organic matter is an oxidizing process, and if this occurs in contact with peroxide of iron the organic matter reduces the peroxide (ferric-oxide) to protoxide (FeO) (ferrous-oxide). The decomposition of vegetable matter always forms >rganic acids, mainly carbonic acid, which unite to form a carbonate of iron {FeCO, which is soluble in the presence of an excess of carbonic acid. This action decolorizes the soil or rocks in which it takes place. As soon as the water containing the solution is exposed to a lower pressure, a portion of the carbonic acid gas escapes, and the iron is deposited either as a protoxide, or, in the presence of an excess of ca.-bonaceous matter, as a ferrous carbonate. Clay containing both iron and organic matter is not red, but blue or slate color, but it will make red brick, on account of the fact that during the burning of the brick the carbonaceous matter is driven out and the iron reduced to a protoxide state.

54. Organic material may assist in other chemical reductions and in the depositing of metals, as, for instance, silver, which sometimeri replaces carbonaceous fossils, such as leaves, stems, etc,

55. Limestones. — Limestones are derived for the most part from shells or from coral. The shells may be of fresh-water or salt-water origin, but are usually of the tatter. The coral is produced by what is called the coral polyp, which builds the coral reefs and coral islands by gradually forming the coral which is broken up by the waves and piled into coral islands. The amount of mate- rial in the stratified rocks which has been produced from shells and coral is simply amazing, and in many cases amounts to thousands of feet of strata.

Structural Geology.

56. Crust of the Earth. — Structural Geology treati of the general form of the earth, structure of the rocks, etc The portion of the earth on which we live and which comei under the observation of man is commonly called the cru8| of the earth. This does not necessarily signify that it i simply a thin layer of solid rock underlaid by a molten ( liquid interior, but the term is undoubtedly a good one, account of the fact that the surface of the earth is practi cally all oxidized material, and it is not unlikely that tiim central part of the earth consists largely of metals in i unoxidized form.

57. Expusurex Available for Observation, — The" means for observing the various geological formations can be divided into three general classes; Artificial Exposures,

Natural Exposures, and Foldings. Under artificial expo< sures can be classified mines, artesian wells, and all excava-J tions made by man. These very rarely exceed 3,000 feet io-l depth, and are only available over a comparatively limiteX portion of the earth. The natural exposures consist of T cliffs, ravines, cafions, etc., and in some cases furnish j exposures of from 5,000 to fi,000 feet in depth. Foldings.! give, by all means, the best opportunity for studying the j various geological formations. They consist in the bending 1 or contorting of the strata of which the earth is composed,,* and then the subsequent erosion or removal of the elevatec portions in such a manner as to expose a great thickness of strata. Fig. 22 illustrates such an exposure. In pas5ingf# from the point ii to d, the observer would pass over theout-

§37

Geology.

crop of several deposits or beds which had been exposed by folding and subsequent erosion, and then, in passing from b to f, he would pass over the same beds in the opposite order. This means has given the geologist an opportunity of studying the formation and determining something of the nature of the rocks to a great depth.

Some knowledge of the underlying material can alio be obtained from the masses of rock occasionally thrown up in connection with volcanic eitiptions.

5S. Orlffln of Continents. — The general out- line of the surface of the earth, as to continents, ocean beds, etc. , was undoubtedly originally the result of irregular cool- ing and bending of the various portions, so that after the earth became sufficiently cool for the water to condense on its surface, the oceans were gathered together in certain places, thus leaving the land exposed. This explains the existence of continents. The mountains are undoubtedly the result of subsequent foldings or of subsequent eruptions, or both.

59. Meaning; of the Term Rock. — The term " rock," as used in geology, applies to any combination of mineral material deposited in place by natural agents, and it may be hard or soft, for the same bed may be in some portions composed of hard sandstone and in others of sand so soft that it can be easily shoveled from its original bed. This same fact is true of limestone, which may vary in the same bed from marble to soft chalk. Rocks may be divided into two general classes: (1) stratified; (2) unstratified. The stratified rocks are of sedimentary origin and are more or less earthy in their nature. The unstratified rocks are composed of material which has been to a greater or less ex- tent fused, and the masses of which are often crystalline. In general, unstratified rocks are largely of igneous origin.

STRATIFIED ROCKS. 60. General DIvIhIoiih an to Structure. — In

Speaking of stratified rocks, three general terms are em- ployed; Large sheets or masses are called strata. These

Geology.

are in turn divided into beds or layers, and the are usually divided into thinner leaves or laminx. laminx are composed of material whirb has been deposited at the same time, and usually consists of thin sheets. The layers or beds consist of successive laminx which have h deposited under similar conditions and the general chan ter of which is practically the same throughout, large sheets or masses called strata may consist of varying slightly, but in any one strata they will 11 ha somewhat similar composition; as, for instance, in the of a strata of shale which may be composed of beds slightly ditferent colors or composition, which in turn ; composed of thin laroinie, each one of which was depositc under similar conditions, hut probably at slightly differeM times, and the entire mass or strata will represent a set o conditions which do not differ greatly. The next strati might be composed of sandstone, which would in turn 1 composed of beds, which could be divided into laminiE i thin sheets. Frequently the lamtns in sandstones are slightly different color, or they may show ripple i which would indicate that they had been dejjosited in shi low water. The consolidation of stratified rocks may 1 due to the presence of cementing material in the percolit< ting waters, as, for instance, carbonate of lime, silica, fl oxide of iron, or it may be due to long-continued pressurl accomjianied by a greater or less degree of elevation i temperature. Stratified rocks . first deposited ain

nearly always horizontal; hence, when the strata are founi highly inclined or contorted, this state of affairs must li ascribed to subsequent action. Stratified rocks are always laid down in parallel beds of even thickness i extending over great areas, but are composed of compara

Geology.

tively flat cakes which are usually thickest in the center and taper out to the edges, Fig. 23 illustrates the manner in which a scries of beds of sandstone or conglomerate may interlap with a series of beds of limestone. Such a set of conditions would occur on a seacoast in which the sandstone or conglomerate was formed by the erosion of an adjoining continent and the limestone by marine deposits from the sea. If during certain times the erosion were more rapid, the sandstone or conglomerate deposits would extend out over the limestone, as shown, while at other times the lime- stone would extend over the sandstone or conglomerate.

61. Inclined Laminae. — One point that the student of geology wants to observe carefully is that the laminic are not always parallel to the strata. This is illustrated -T~-\- r-—- in Fig. 24, in which the .T., two beds of sandstone have lamina at an angle to their strata. This may z — have been caused I'y the rj " i

waves on the shore of a - '

sea or lake, or by a swift

current of water, either in '''"

a river or large body of water, which deposited the material

in the position shown. These inclined lamina are frequently

mistaken fur inclined strata, and on this account close

observation is necessary before deciding as to whether the

strata arc inclined or horizontal.

62. General Classes of Stratified Hocka as to Material. — Sedimentary rocks are divided into three general classes: arenaceous or sand rocks, which include sand, gravel, shingle, rubble, etc., of the drift material, and the sandstone, grit-stones, conglomerates, and breccias of the rock formations. (The conglomerates are composed of rounded stones and breccias of sharp angular stones cemented together with some other materia!.) Ar- (ClllaceouH nr clay rocks, which include the muds and

Geology.

Si

clays of the drift formation and the shales and slates of ttf rocks. CalcareuuH or lime necks, which include chal]|| limestone, and marble, and rarely have any re present a tiod among the drift material, for few of the time formatioi are much if any softer than chalk.

63. General DefioUloai* of Terms Used In ology. — Some of the commun terms used in geology an

The ifi'/i of the rock is the angle which it makes with the horizontal plane, and it is measured by means of a clinome- ter, or pitch rule, as illustrated in Fig. 25. The strike of the strata is the line of intersection with a horizontal plane, and is always measured at right angles to the dip. For instance, if in Fig. 35 the strata dip to the south, the strike would be east and west. The outcrop of a deposit is its exposure on the surface, and may be very irregu- lar on account of the fact that it depends not only on the dip of the formation, but upon the character of the surface over which the formation outcrops. Care must be taken not to confuse the terms strike and outcrop, for the strike is always measured on the horizontal plane, while the out- crop conforms to the surface, and hence may or may not agree with the strike. This point must be taken into con-

J

§37

Geology.

sideration when determining the dip of any formation. When strata are bent or contorted into successive waves, as shown in Fig. 20, the saddles, as at b, are called anticlines, and the troughs, as at i, are called synclincs, while the trend or direction of the ridge is called the anticlinal axis, and the direction of the valley ihe synclical axis. Subsequent erosion

may entirely remove the original hills and valleys and pro- duce a comparatively level surface, as iUustrated in Fig. 2U. The dotted lines show the manner in which the strata were originally bent. When the straiahave been eroded in such a manner that the anticlines and synclines are no longer hills and ridges, the anticline may be known by the fact that the

same strata are repeated on each side of the axi.s and that they dipped away from the a.iis, as shown at l>; while a syiicline may be known the fact that the same strata are repeated on each side of the axis and dip towards the axis, as shown at n. The action which forced or crushed the material together frequently opens fissures along the

38 GEOLOGY. g 37

anticlines, thus increasing the tendency to erosion along the ridges, and this tendency may cause the ultimate removal of the ridge and the formation of a valley along the anticline, thus resulting in syncline mountains or hiUs, as shown in Fig. 27. Strata are said to be conformable when they are parallel or continuous, and were formed under the same con- ditions, and they are said to be unconformable when they are not continuous, being interrupted by an old land surface which has been eroded. Ptg. 28 illustrates unconformable

FlO, E8.

Strata. The strata shown at a were deposited, contorted, and tilted, and subsequently eroded to the form shown in the illustration. After this they were Once more submerged and the strata shown at d deposited in such a manner as to be unconfurmable with the original strata, and after the strata had been deposited the entire mass was once more elevated and tilted slightly, so that the strata d were no longer horizontal. There are cases in which unconform- able strata are practically parallel, as, for instance, when a land surface has been eroded and then submerged without tilting or contortion and the subsequent strata deposited parallel, or practically parallel, to the original strata, but such cases can always be recognized by the fact that the eroded land surface has intervened between the depositing of the formations.

04. CleavatcB Structure. — As has already been stated in the case of stratified rocks where the material has ben

Geology.

laid by the sorting power of water, the separate layers can frequently be very easily traced. These strata are often so plainly marked that rocks may be cleaved or split along their bedding planes, and it is in tiiis manner that much of the rock used for flagstones is obtained. This cleavage may be called flagstone cleavage, and is always parallel to the strata. Another form of cleavage is that which occurs in crystals or is caused by crystallization, and as an extreme case of this, the cleavage of mica may be mentioned. The slates which are used for roofing material and for writing- slates are cleaved along very distinct planes, and these planes may intersect the bedding at any angle. This fact puzzled the geologists for a great many years, but by care- ful examination and by physical experimentation, it has been found that this "slaty cleavage" is always at right angles to the lines of greatest pressure during the alteration of the

rocks. 1 1 ding plane cc, et. etc. formed at

Fig. at. Fig. 39 the lines a 6, cd, ef represent the bed-

hich the material was deposited, represent joints which have subsequently been ight angles to the bedding planes, and which are present in all stratified rocks. The diagonal lines g h and g h represent a cleavage which is neither at right angles to the bedding planes nor to the joints, but which cuts through both at an angle independent of the original formation of

mIm, %bfTwitii( the maaeT in these fa hitvr. t,e/-y>m crimped or bent by the pnasnrc wlaA dend- 'tfMttl (atjr (.iearaiEC. Fig. 31 iDiKtrates a otf aadala. (iftK Mrata and ritovt tbc manner in which the cleavage win

he (laralll thrmffhont the entire formation, regardless of t dneftU/n '4 the ntrata at anjr partictilar point. It is probable that tb f(reat jireimure which caused this cleaTagc was due In the hfinkas;c (rf the earth's crust, and that this action ftirtxA the continenu and the mountain ranges into, approx- imately, their present position. In manr cases the action ienH Uf have been accompanied with very little rise in Icmperature, %n that the material is practically unchanged, while in other rases this action has taken place in rocks bare been altered by heat. The geologist or pros- pertoT raant be careful not to be deceived by slaty cleaTage, which may l>e easily mistaken for the strati6cation of the rock.

S3r

Geology.

65. Nodular or Coacretloaary Structure.- — In

nearly all rocks, balls or masses of material are found which have been formed after the rocks were laid down. Frequently the stratificalioa passed right through the ball, while in other cases they are indepandent of the stratification. These balls or nodules are called clay balls, iron balls, lime balls, or aulphur halls, according as they are composed of the different materials named. They are really all nodules or concretions, and may be composed of a great variety of materials. In limestone they are usually composed of silica, while in sandstones the composition will be Hmc. iron, or sulphur. The sulphur balls are really iron pyrites, and arc usually found in coal-meas- ures. Sometimes the balls are hollow and lined with crystals, when they are called gcodfs. tions assume very peculiar foi

taken for fossils, being called hands, feet, or whatever they may happen to resemble. Fig. 33 illustrates one of these peculiar shaped concretions. As a rule, the concretion is formed about some foreign particle as a base. This may be a fossil fish, leaf, shell, or some similar bit of foreign matter which occurred in the formation.

letimes ns and are frequently r

Oft. FosbII*. — As has already been mentioned, stratified rocks are composed of material which has been deposited in water, and hence such deposits would naturally contain any shells, bits of coral, leaves, logs, or other material which might happen to be dropped upon the material when the deposit was being formed, or which might be washed from the land into the delta of a river or into a lake. Bodies of animals from the land were also washed into the water and their bones deposited and covered with the sediment, together with the bodies of fish and the various living forms which inhabited the water. Animals walking over the soft

42 Geology. § 87

ground or mud left tracks which became corered with aedi- ment and are now found in the rocks. These evidences ci the previous existence of living beings are called fossils.

67. Condition of Poaalls and Their Uao. — Where the fossil consists of all or a part of an organism, it may be presented in any one of a number of forms. In the older rocks the material of the bones or the tissue of the object is rarely ever present, but the fossil consists of a cast or impression of the object, or the object may have been replaced, particle by particle, with solid matter in such a manner as to form a perfect model of the original. This latter class of fossils are said to have been petrified, and one of the best examples of this class is petrified wood. Fossils are useful in determining the relative age of the rocks, and it is by this means that the rocks of different countries can be compared. When life first appeared on the earth, it was of the simplest form, and the organisms on the different continents differed but little, but in each succeed- ing geological period greater differences appeared between the different continents, until the conditions existing at the present time came into being.

68. Development of Life. — Animal life, and espe- cially higher forms of animals, can not take nutriment or material to live upon directly from the minerals, and hence vegetable life was naturally the first that appeared, and was probably in the form of seaweeds. These simple forms were soon followed by shells, coral, etc. At first animal life could not have existed on the continents for several reasons. (1) The animals could not have obtained food necessary for them, on account of the lack of vegetation and other animal life on which to feed. (2) It is probable that the atmosphere of that period was so heavily charged with carbonic acid gas that no animal breathing through lungs could have existed upon the earth.

69. Geological Section. — As has already been stated, the different series of stratified rocks are separated by periods of elevation and erosion, and hence there is no place

Annricxr lfia

iifmaii Ceiiiraltin.

aonBZtmBF

t-i

,/utr'.-":i viii-a, r

'

</-mj;/'/;,5' tilt Csinuriicc

/

k

n

' " ' "' ' "" ''/f; ',f ;/:;jM.-, *r'j'.h as , which

"" " ' - /NO* '/f i)j-: fat that the atmosphere

"' ' """;/''i /r.i), /.M l;.,r,,/ ;,M'I ;/;iv. This rank vegeta- '' " ' '""" i/M.,t r |/;.r! of thc'oal which we now |/..MH|/ H,i |,,Hi |mM ',f I 111. p-rjod the first reptiles "I'l""'"' '"♦! Um y .nw Moi h*won,ir j/li-iiliful Until the ''' ' '' '' "1" n M J: |/mwIm;i fn';i! sizr, and were the I'lMhi, (Hill In ihi< Uiiairniary jHTiod man ♦l'l'"H.' IW.'Mi IhiM II uill JK' .i..n th.it the earth was

g 37 GEOLOGY.

continents suitable for him to live upon; by gelling rid of tlie poisonous carbonic acid gas of the atmosphere and slor-

46 Geology. § 37

and, last of all, by collecting the minerals and metals into forms in which he could make use of them, as will be shown under the consideration of metalliferous veins and deposits. Fig. ',\4: is a section of the rocks present in the State of Colo- rado. From this it will be seen that the Devonian rocks are entirely wanting, and that the series is not complete in several other respects.

The fossils of the different periods will be treated later.

Unstratified Or Igxeous Rocks.

70. General CharacterlntlcH. — The unstratified rocks are distinguished from stratified rocks by (1) the absence of stratification; i. e., they are not laminated as the result of being sorted by water; {'Z) there is a total absence of fossils; (:J) the general structure of the rock is more or l(?ss crystalline or glassy ; (4) the general mode of occurrence is usually characteristic, as will be explained later. Most of th(! unstralifi(*d rocks liave evidently consolidated from a fused or scnii-fustrd con(liii(n, and it is for this reason that lluv arc called i'''ncous r)(ks. also fretiuentlv occur in dike nr tortuous veins cutting tlirougli the regular strati- fied a!i(l {producing ctTccts u{)on the stratified rocks which show tiiat tlie material was hot at the time the dike or vein was formed. In many (\ises the igneous rocks closely rescnihle the modern lavas in tlicir mode of occurrence. Sonietinics wiiere thert* liave been several successive flows of volcanic material, the different fiows will have a stratified aj>j)earanc<-, but the lann'tia* will be absent; aKo the character of the material aii<l its ionnection with tlic surroundinjr formations will usually show that it has not been deposited by water.

71. Mo<lcs of Occurrence. -- I'ig. I).") illustrates a number of the c)iumon forms in which igneous rocks occur. They may utidcrlie <.ther rocks forming masses, as at <r, or form a ridge or (ore of mountairi ranges, as at /'. They frecpieutly appear as vtuaical sheets, filling fisstires or

§ Ur GEOLOGY.

cracks in the rocks, forming dikes, as at h, g; i, or w. They siinietimes occur as beds of material forced in between the strata, as aty, or as overflows on the surface, as at i. or the overflciw may form a volcanic cone, as at o. Frequently the dikes or fissures which are filled with eruptive material do not break clear through to the surface, as shown at rn. When such is the case, the existence of the dike would only

Fig. SS.

be known after the overlying strata were removed by erosion, or it is possible that such dikes might be encoun- tered during the raining operations,

72. ClasKlflcation of luneouit RockH. — Igneous rocks are classified by their physical characteristics rather than hy their relative age. The common divisions are phi- tonic, or massive rocks, and volcanic, or true eruptive rocks. The rocks of the first class include the great masses, and those in the latter the nicks which are injected into fissures or outflow over the surface. The plutonic rocks are entirely crystalline and are usually coarse-grained. The volcanic rocks are imperfectly crystalline, or are partly or wholly glassy, and seem to have solidified in the place which they at present occupy, while the plutonic rocks have apparently sometimes been forced into their present position while in a partly solid condition. The two groups pass into each other by such gradual changes that no sharp distinction can be drawn between them.

Pluto.Mc Or Massive Rocks.

73. General Charncterlittlctt. — These are character- ized by a close-grained, mottled, or speckled appearance, resulting from the fact that they are composed of an

Geology.

aggregation of crystals of different materials and colors. These rocks are usually made tip of a mass of crystals without any ground mass or amorphous or glassy material between them. The minerals which compose practically all the rocks of this class are quartz, feldspar, mica, and hornblende. In the speckled mass the opaque white, or reddish, or grayish crystals with the glistening surface are feldspar; the trans- parent bluish, glassy spots are quartzite, and the black specks are usually hornblende. The mica can be easily detected as glistening scales of various shades. The prin- cipal kinds of rocks of this class may be taken as granite, syenite, diorite, diabase, and its variety, gabbro.

74. Granite. — Granite may be considered as a type of this class of rocks, and it consists of quartz, feldspar, and

mica, or of these together with hornblende. Sometimes the mica and hornblende are want- ing and the quartz exists in the form of bent plates embedded in feldspar. Sometimes all the crystals are small and evenly granular, but as a rule they are fairly coarse. Fig. 36 shows the general appearance of a piece of fairly coarse granite,

75. Syenite. — Syenite is a term used in America and England to distinguish rocks of the granite group in which the mica is replaced by hornblende, and where both mica and hornblende are present the rock is called syenite-granite; but on the continent of Europe, and especially among the Germans, the term syenite is applied to a rock composed of feldspar and hornblende only, and when the quartz is present (American and English syenite) they call the rock quartz- fiyenite. The general aspect of the rock is similar to granite. In the rocks thus far mentioned, the feldspar is the potash feldspar (orthoclase).

76. niorlte. — Diorite is a dark speckled, greenish-gray rock, and is composed of a crystalline aggregation of plagio- claae {soda, lime, feldspar, and hornblende), and therefore

§ 37 GEOLOGY. i9

differs from the German sytnite only in the form of the feldspar.

77. Diabase. — Diabase is a dark, greenish, crystalline rock, usually fine-grained, but sometimes having a coarse- grained structure. In general appearance it is similar to diorite, but differs in the fact that augite replaces the horn- blende and it often contains olivine.

78. Gabbro. — Gabbro is a granular diorite or diabase in which the augite takes the form of diallage.

79. Subdivisions of Plutonic Rock.— These differ- ent forms of rock merge into each other so insensibly that it is frequently difficult to determine the various classes. Diorite and diabase frequently form dikes of fine-grained material, so that they are sometimes considered intrusive rocks rather than massive rocks, and are often treated as an intermediate class between the two. The plutonic rocks can be divided into two sub-classes, one called acid, and the other basic, rocks. Quartzite is composed of silica, and is acid. The orthoclase feldspar is acid and the plagioclase feldspar basic. In the acid rocks quartzite and orthoclase feldspar predominate, while in the basic rocks hornblende or augite and plagioclase feldspar predominate.

The acid rocks are usually somewhat lighter than the basic rocks, the specific gravity of the former varying from 2.6 to 2.7 and of the tatter from 2,7 to 2.9. The acid rocks are also usually lighter in color than the basic rocks. Granite is the best type of the acid class, and diorite and diabase, and especially gabbro, are good examples of the basic class, while syenite lakes an intermediate place.

80. Mode of nccurrence of Plutonic Rocks.—

The plutonic rocks, and especially the granite and syenite types, occur in large masses forming the axes of great mountain ranges, as, for instance, the Sierra and Colorado Ranges, as shown in Fig. 37, or they may appear in ronnded masses in the midst of the stratified rocks, as in several of the New England States, around Lake Superior, and in

60 Geology. § 37

various parts of Canada. The rocks of the plutonic group are never found in connection with scoriae, glass, ashes, or other evidences of rapid cooling in contact with the air. They have never been erupted on the surface, and have

Fig. 87.

evidently been cooled or solidified under pressure in great masses and at great depths. Hence, when they are found on the surface they must have been exposed by extensive erosion.

81 . Intermediate Series. — Between the true plutonic rocks and the volcanic rocks there is an intermediate series, the rocks of which are sometimes placed in one group and sometimes in another. They are called the trappean or intrusive rocks. They occur mostly in the older and middle rocks in the form of dikes filling great fissures, or as beds between the strata. In the acid group of this class of rocks perhaps the most typical is fchitc. This rock is a very compact, fine-grained aggregation of quartzite and orthoclase feldspar, and therefore it is liglit-colored. Chemically, it has the same composition as granite, but differs from granite in the fineness of its texture and in the abscMire of the mica. When felsite rock contains embedded in the fine-grained mass large, well-f(jrmed crystals of feldspar or hornblende it is called por{)hyritic. Tf quartz crystals arc also distinctly visible, then it is called (juartz-porphyry. The word por- phyry " or p()rj)hyritic " is often applied to any rock in which distinct crystals are visible in the fine-ground mass ; thus, there may be porphyritic granite, porphyritic diorite, etc. The porphyritic structure is probably fonn(Hl by the material being in a fused condition and the lari::: crystals separating out. When partially cooled, and after the crys- tals had been separated, the material was forced into its

§ 37 Geology. 61

present position. Intrusive rocks of the basic group are usually called greenstones or traps. This term usually includes the intrusive diorites, diabase, etc., which differ from the massive crystalline rocks of the same class only in being finer grained. The difference is probably due wholly to the rate of cooling, and the differences between the massive and intrusive diorites may be due to the same cause. When a mass of lava is cooled rapidly, it will result either in a fine-grained material, or, if the cooling is very rapid, may form a glass-like mass or obsidian. When the cooling is slower, the crystals of the various constituents have an opportunity to separate, and the result is a coarsely crystallized rock, more like the porphyries or the granites.

Volcanic Or Erupt I Vb Rocks.

82. General Characteristics. — In texture these rocks either appear minutely speckled or are usually of a grayish shade, on account of being composed of crystallized or only partially crystallized and fine-grained material. Sometimes their structure is amorphous or glassy, on account of the fact that they have cooled very quickly. They consist for the most part of some form of feldspar with hornblende or augite. Free quartz and mica are sometimes present, but are not necessary and are not common. Other minerals, such as magnetite, are frequently associated with some forms of lava. Volcanic or eruptive rocks are also divided into the sub-classes, acid and basic. The acid rocks consist of an ortho-feldspar which usually takes the form of sanidin or glassy feldspar, while in the basic class the feldspar is plagioclase and is associated with hornblende or augite.

83. Trachyte. — Of the acid group, trachyte is one of the most common forms. It is usually a light-colored rock, and has a peculiar characteristic rough feel, on account of the fact that the ground mass is composed of sanidin in which there are needle-like crystals of the same material which give the rock its peculiar rough feel. Augite is

Ul "M:

iBut 2( TssatLSJT . ixL s:

-XL XiOXXXL ZXl'JUt

fC apCCTfttlTJ.

vxxlSl saa z

a;ii4 3uit% toojiCrTh kciC acocacaawc As a rak; it is Laiy4 -f i*!::s.-pa*c jboQcrit rxycSae -or irKlnrtc in the

T-

fbSTit'rra 2iryi has a >nraj5ar rir die

wttyJk h :ts najne cs pbooojlhc or cfinkstooe.

ftfsuuli crrstals of feldspar can be seen in the

Mi# fteMiltp — Of the liasic sisb-onp. basalt is the most

t/j/j'ii It a 'I'Ar'tu. a'.rr.vi ilick. n3:"eral when freshly hrok,!., T(i'-:at:i':r5 to a ruty brown o>ior on exposure to olivin': j; a jIa v ;<ro';:.'; '/ th': same material. Magnetite ir- /f'/jti<Tj)tl/ ]fT*'.\''U\ 'ori-i'I-rabie cuantitfes in the basalt.

H7# l>oirlt. l}'A:rilK is a composition very similar io l/a:-,a)f, l/iit. iaoks ih*; olivine, and is somewhat more ' f y:;t;illifM' in -itrii' liin:.

fifi, /\ffileftc Atidesiic is so named because it was iittit found in !li*; And#rs Mountains. It is a dark greenish- riiy <onhitlinj *;ssentia)ly of plagiodase with horn- \iU'iit\f t,t aiirilr. It is similar to dolerite, but is slightly I yt;t,illin', Ilk*' basalt, and often has a rough feel like lliiliyli', JMMMf it is honirtinies called trachy-dolerite.

MK Hptfclfal lrfiiH CatiHcd l>y Rapid Coollnn;. —

All ihi- MM k'i both iIm* acid and the basic group), and frt|iri liilly the niDtc typical ones, have their scoriaceous and

§ 37 Geology.

glassy nr vitreous varieties which compose the light-colored scoria: and the obsidians on the one hand and the black scoria: on the other.

90. Modes of Eruption.— There have been two gen- eral modes of eruption in genlugicai times. In one case great fissures have been opened up during extensive crust movements, and if they extended to the surface great sheets of lava have flowed from them. At times fissures were simply filled, even though they did not come to the surface. The other general mode of eruption has been where lava came to the surface through chimneys or openings and flowed away as streams. The first form are called fissure eruptions and the second form crater eruptions, or are vol- canoes proper. There are no records of fissure eruptions, either at the present time or during very recent periods, and hence, in dealing with the subject of modern volcanoes, only the chimney or crater eruptions need be considered.

91. Positions In IVhlch Lava May Occur — The lava may occur in any one of several positions, and especially when they have been produced by great fissure eruptions of the past. (1) They may appear as vertical sheets filling great fissures, which by subsequent erosion have been made to outcrop as dikes, or else they may fill small radi- ating volcanic fissures as volcanic dikes. (2) They may occur as sheets between the strata (intercalary beds), as if forced between the separated strata or else outpoured on the sea bottom and subsequently covered with other deposits. (3) They may occur as great sheets or streams which have been outpoured on the land, (4) They may occur as great domes or masses between the strata.

92. Dikes. — Dikes are fissures filled with igneous material. They may outcrop for great distances (some of them being more than 100 miles long), and may vary in width from a few inches to over 10(1 feel. They extend down to great, but unknown, depths. If the dike is com- posed of hard material, it will resist erosion and appear as a rough stone while rising above the surface, as illustrated in

S-~

.iT .*T '

r.Iwtr i.i

§37

Geology.

in northwestern North America covered northern CaH- fornia, northwestern Nevada, the greater part of Oregon, Washington, Idaho, part of Montana, and extended into British Columbia. In places this overflow is cut through by the Columbia River, and is shown to be from 3,000 to 4,000 feet thick, and it covers, approximately, 150,000 square miles of territory. The Des Chutes River has eroded cafions from 1,000 to 2,500 feet deep in this lava field without reaching the bottom. About a dozen e.ttinct volcanoes can be found over this area, but it is evident that such a large amount of lava did not come from these small volcanoes, but must have been the result of great fissure eruptions.

f>4. Ase. — The age of lava Hows can only he determined in a relative degree. For instance, if two dikes occur in such a manner as to cross each other at an angle, the one which cuts through the other must of necessity be the younger. Where beds of igneous material occur between stratified deposits, their age can often be determined by the character of the deposits above and below them. It is evi- dent that the igneous material must be younger than the stratified deposit beneath it, and if it has altered the material over it by heat, it is evident that it was injected between the formations or beds; but if the material on top of the igneous rock is unaltered, it is likely that the flow occurred on the bottom of a lake or sea, and was subsequently covered by other deposits of a sedimentary nature. Where one stream or sheet of lava has flowed over another, it is evident that the upper must be the younger. By comparing the adjacent sedimentary rocks and the relative position of the different flows or seams, some idea as to the age of the igne- ous deposits may be formed.

95. Columnar Structure. — Many of the eruptive

rocks exhibit a remarkable columnar structure. This is most conspicuous in basalt, probably on account of the fact that basalt has evidently been heated much hotter than the other eruptive rocks; that is, it has been superfused, for the melting-point of basalt is lower than that of many other

Geology.

lavas, and that it was exceedingly hot can be seen from ihe manner in which it flowed out into thin sheets. Fig. 39 illustrates a rough columnar structure as exhibited in the basalt rock on the shore of Lake Superior. Sometimes the columns are more perfect prisms than those shown in Fig. 39, and they may be regular hexagons. The columns are often of considerable length {varying from a few feet to from 50 to 100 feet), and varying in diameter from a few inches to a foot or so. Where a structure of this nature has been eroded by the sea, by the action of a river, or by atmospheric agencies, it often results in very bold and picturesque i The Palisades on the Hudson, some of the cliffs at Mb|

Holyokc in Massachusetts, and the cliffs on Lake Superior, and a number of places in the Rocky Mountains furnish illustrations of this structure. In Europe, the Giant's Causeway on the coast of Ireland, and Fingal's Cave on the island of Staffa, on the west coast of Scotland, may be mentioned as especially noted localities for this form of basalt structure.

96. The direction of the columns is usually at rig! angles to the cooling surfaces, hence in horizontal ! the columns would be vertical, while in a dike the columns would be formed horizontally, and if the dike was subse- quently exposed by the erosion of the adjoining strata, it

§37

ould stand oi an illustratio

Geolooy.

h like a pile of cord-v

Fio. W.

97. There is little doubt that this columnar structure is produced by contraction while the rock was cooling, but it is not known why the structure should be more irregular in basalt than in any other known substance.

9S> Volcanic Conjclnmerate and Breccia. — If a stream of fused rock from a crater or fissure runs down the bed of a stream, it will gather up pebbles in its course, and after solidification, will form a conglomerate, which differs from the true conglomerate in the fact that the uniting paste is of igneous instead of sedimentary material. In the same manner a stream of igneous material flowing over a surface with broken rock or rubble would take up the mate- rial and form a breccia; or the front and upper surface of the lava may become cooled, and subsequently be crushed and broken by the flow of liquid lava from behind. This broken lava would become mixed with the molten lava and

us form a breccia. The disintegration of volcanic rock and the transportation and depositing of the pieces would give rise to an aqueous conglomerate or breccia composed

of volcanic material, and it : such a deposit from the I breccias and conglomerates which ciinsist of the materi,

:.Ogy. % 37

i often difficult to distinguish

rue volcanic breccia. These

graduate into volcanic tufas,

thrown out by volcanoes of

the explosive type, and which have flowed down the sur* face of the mountain or valley as a volcanic mud.

99. Amyedaloldal Structure. — Another form of

structure very common to igneous rocks or lavas is called amygdaloidal. The rock called amygdaloid greatly resem- bles volcanic conglomerate, and is apparently composed of almond-shaped pebbles in an igneous paste, but it is formed in a very different manner. The streams of lava or trap always contain more or less gas, and this results in bubbles or openings being left in the material. The gradual flow of the slowly hardening stream elongates these bubbles and gives them their almond shape. In the course of time these bubbles become filled with silica, carbonate of lime, or some other material, by infiltra- ting water holding these mate- rials in solution. Sometimes the filling has taken place very slowly, successive additions being composed of different colored materials. It is in this manner that the beautiful agate pebbles are formed. The most common filling is silica, on ac- count of the fact that the waters percolating through igneous

rocks are always alkaline, and hence hold silica in solution. Sometimes very fine opals ;ire found in this amygdaloidal material. Fig. 41 illustrates a mass of amygdaloid toi'

J

The Origin Of Igneous Rocks.

lOO. There are some reasons for thinking that igneous rocks are not all eruptive portions of the origild fused magma or mass of rock. Among these may be stat

§ 37 Geology. 69

the following: The lavas erupted in the same locality, but at different times, differ very greatly in composition and structure. It seems hard to account for this difference if the material was all drawn from the same source, but the action of water in producing stratified rocks has resulted in extreme differences of material, with pure silica for one extreme and pure lime for the other. If these were re-fused it would produce greater differences than existed in the lavas, but as pure silica or pure lime is practically infusible, when considering the limits of ordinary fusion, the range of possible lavas is reduced to those actually found. Some evidences to prove this theory will be given under the head of metamorphic rocks, where it will be shown that rocks having precisely the same composition as many of the igneous rocks are frequently produced from sedimentary rocks.

lOl. Metamorphic Kocba. — Metamorphic rocks were evidently originally sedimentary deposits which have been subjected to heat and other agencies which have changed their structure, sometimes entirely destroying the fossils and laminations and inducing a crystalline in place of the stratified structure. Evidence of the sedimentary origin of metamorphic rock is found in the gradual grada- tion into the true igneous rocks on the one hand and into sedimentary deposits on the other. For this reason they are called metamorphic. Metamorphic rocks are more common among the older formations, and become less and less com- mon as one passes from the earlier lo the later periods. They seem to require a great depth of strata and are gen- erally associated with more or less folding, tilting, inter- secting of dikes, and other evidences of igneous agencies, Metamorphic rocks are mostly found in mountainous regions and they extend over large areas of country. Nearly all of Canada and Labrador, a large part of the Eastern Appala- chians, and much of the Western mountain regions are covered with metamorphic rocks, and they probably underlie all or ne;irly all the stratified deposits. The Laurentian

series of Canada is probably over 50,0(>0 feet in thic and is met amorphic ihroughoul.

102. The principal kinds of metamorpliic rucks are 1 gneiss, mica-schist, chlorite-schist, talcose-schist, horn- , blende-schist, clay slate, quartzite, marble, and serpentine. J

1 03. Gnelsa. — Gneiss is the most common and charac- '

teristic of the metamorphic rocks. It has the general! appearance and contains the samel minerals a.B granite, but has a bedded i or stratified appearance, and in the'] case of banded gneiss, the light and 1 dark constituents are arranged in distinct bands, as shown in Fig. 43. J ns by insensible gradations 'j e hand into granite, and on '] ratified forms into sandy j

Gneiss

on the

through the more

lays or clayey sands.

the

oraposed of practically the .

104. Sic hist.— Schist same constituents contained in granite or gneiss, but the crystals of mica, hornblende, or the similar constituent, all lie in one direction, so that thi material has a laminated appearance and i be split into thin leaves in the direction of i crystals of mica, feldspar, or similar mattn il According to the preponderance of ceriaiii minerals, the rocks arc known as mica-schists, hornblende-schists, talc-schists, etc. Both gneisses are frequently very much contorted shown in Fig. 43.

hists and folded, as

105. Serpentina

gray magnesian rock. line rocks is that manj regions of

, — Serpentine is a compact, greenish- One peculiarity in regard to serpen- , if not all. of the platinum -bearing J are found where serpentine rocks I

abound, and serpentine has been supposed to be the parent rock of platinum deposits. The other metamorphic rocks,.! such as marble, etc., need no especial description.

% 37 GEOLOGY. Rl

lOH. Connection Betwreen Metamorplilc nnd Other Hoclts. Hornblende-schists run by insensible grada- tions into clay slates on the one hand and into diorites and syenites on the other. All the metamorphic rocks can be regarded as changed sands, limestones, and clays. The great variety in metamorphic rocks is due to the differences in the original sedimentary rocks and to the degree of meta- morphic action. Pure sand or sandstone forms quartzite; pure limestone forms marble. Clays are usually impure and contain sand, lime, iron, magnesia, etc. Such impure clays, if sand is in excess, form metamorphic gneiss, mica-schisS, etc., while if lime or iron is in excess, they form horn- blende-schists or clay slates; if magnesia is present in con- siderable quantities, talcose-schists are formed. The origin of serpentine is not well understood, but it is probably frequently formed by the change of magnesia clays, and in some parts of the Western mountains all stages of the change can be seen, from the clays to the serpentine. In other cases, it seems to have been formed by the change of igneous rocks which contain large amounts of olivine.

107. ClaasBs of Metamorphic Rocks. — In con- sidering the cause of metamorphic rocks, they may be divided into two classes: those produced by local causes and those produced by general causes.

108. Local Metamorphlsm. — Local metamorphism

is that produced by the direct contact with evident sources of heat, as when dikes break through stratified rocks. The fact has already been stated that when dikes come in con- tact with certain rocks, changes are produced along the face of the dike. Impure sandstones become schists or gneiss; clays are changed into slates, or if they contain much sand they may become jasper; limestones become marbles; bitu- minous coal becomes coke or anthracite, etc. It is evident that the cause of these changes must have been the intense heat of the material in the dike at the moment it was filled. Such local metamorphic effects usually extend to a compara- tively few feet from the walls of the dike.

Geology.

109. General Metaiuorpliism, — In many cases, the changes can not be traced to any evident source of heat, for rocks thousands of feet in thickness and covering great areas are thoroughly metamorphic. The principal agents of this general metamorphisin seem to be heat, water, alkali, and pressure. That heat is a necessary agent isevident from the general similarity between local and general meta- morphism, but that the heat was not so intense as in the case of local metamorphism is evident in many cases, for meta- morphic rocks are often found interstratified with unchanged rocks, and intense heat would have changed all alike, or nearly alike. Also, minerals are found in metamorphic rocks, which will not stand intense heat; as, for instance, carbon has been found in contact with manganite iron ore, although it is known that this contact can not exist, even at a temperature of red heat, without the reduction of the iron ore. The effect of simple dry heat has been shown, in the case of local metamorphism, to extend to a comparatively few feet, while the general metamorphism penetrates very thick beds.

1 lO. The fact that heat combined with water seems to be the agent has been proved both experimentally and by observation. Water in contact with most rocks at a tem- perature of 450° F. reduces them to a pasty condition, and at this temperature, quartz, feldspar, mica, augite, and other crystals are formed. It has been found that only a very small amount of water is necessary to produce this result (from to 10 of the bulk of the rock), and as this amount of water is probably present in all sedimentary rock, it is evident that a sufficient amount of water would be present to produce this result,

111. Solutions of alkaline carbonates or silicas common in all waters, and experiments show that their pre ence greatly reduces the point at which aguco-igne< fusion takes place.

112. In order to produce the high temperature nece sary, the water must be under considerable pressure, and ug

§37

Geology.

has been found that water at a temperature of from 575° to 750° F. win produce the same effect that dry fusion at a temperature of from 000° to 3.000° F. would produce, while if a small amount of alkali is present, a temperature of from ;10U° to 400° F. will produce the same result.

113. All the necessary factors are found associated in the deeply buried sediments. Series of outcropping strata are often found from 20.000 to 40,000 feet in thickness, and the lower strata of such a series would, by the regular increase of the interior heat alone, reach a temperature suf- ficient, with the included water, to produce aqueo-igneous pastiness, and therefore by cooling they would become crys- tallized and regular metamorphic rocks. Fig. 4i illustrates

Flo. 44.

a case in which the original rock surface vrasatid, but a great thickness of sediment A has been deposited on the bed of the sea. The two lines or isotherms of temperature for 400° and S00° F. are drawn in the original rock. Now, as time passed and the sediment became thicker, these lines would evidently rise into the sediment until they assumed the positions as shown by the upper dotted lines. It is evident that where this were the case the temperature in the lower part of the mass of sediment A would be sufficiently high to produce complete metamorphism. It is probable that even as low a temperature as 200° F. in the presence of alkali may produce considerable change in the characteristics of the rock formations.

Geology.

114. Effect of Horizontal Pressure. — Allhougl

simple pressure resulting from the weight of tlie strata i not cause heat, it is evident that horizontal pressure which crushes the strata will cause heat by the conversion o£ mechanical energy into heat. Now, in all cases of meta- morphism ample evidences exist of horizontal crushings andl foldings, together with cleavage of the strata'. This crush-' ing of the rock sometimes produces a schist structure, not only in stratified rocks, but even in igneous rocks, and hence this has been called mechanical or dynamical metamorphism, and the rocks of this class are very diflficutt to distinguish from the truly metamorphic rocks formed from sedimentary deposits.

115. Effect of Percolating Waters. — At oihetl times percolating waters carrying silica at slightly elevated* temperatures and under heavy pressure may fill up the spaa in sandroek, and thus produce a perfect quartzite, whiclia would be another form of metamorphic rock.

116. Definition of Metamorphism. — Prom whal has preceded, we may describe metamorphism as a changi in the structure of rock formations, without a change place. This change may be so extensive as to completely destroy the original characteristics of the rock and anjj fossils which it contains, or it may simply induce a crystal line structure without destroying the fossils, as is th in some marbles.

117. General Remarks on Metamorpblsm.- The explanation of metamorphism gives some of associated phenomena as follows: The fact that grei pressure was necessary and that heat was also necessar-fl explains the usually association of metamorphic action witll great thickness of strata. This also explains why the oldei rocks are most commonly metamorphic, since they ha<£ newer rocks piled on top of them and have only been exposed by subsequent erosion. The newer rocks are some- times metamorphic, but it is usually only when the forma- tions are very thick or in volcanic regions. The fact that

§37 Geology. G5

some beds in the series of metamorphic rocks are unchanged can be explained by the fact that some rocks are more easily afTecied by hot waters than others, and the composition -of the water in the different strata may be somewhat different ; for instance, some rocks would not be liable to contain an alkaline solution. The definition given also explains the reason why metamorphic rocks are usually found associated with mountain chains and with the folding and bending of the strata.

1 18. OriKin of Granite.Thc origin of granite was formerly supposed to be entirely igneous, but there is strong reason for believing that much of it was produced by the raetamorphism of highly silicious sediments without any accompanying eruptions. In many locations in the mountain regions, every stage of gradation may be ob- served between the clayey sandstone and gneiss and between gneiss and granite. So perfect is the gradation that it is impossible to draw sharply the distinction, and eve'l geolo- gists who believed that granite was entirely derived from the igneous rocks have been compelled to admit that there is also metamorphic granite which it was practically impos- sible to distinguish from the primitive granite. It seems almost certain that granites have not been formed entirely by dry igneous fusion, and yet that this rock has been in a liquid or pasty condition is certain from its occurrence in tortuous veins. Therefore, it has evidently been rendered pasty by heat in the presence of water and under great pressure, which always exists in deeply buried strata. The weight of the overlying strata, or else the pressure pro- duced by the folding and crushing of the strata, has forced the pasty material into the cracks or fissures.

119. Orlsin of Some Otber of the Massive

RockH. — Not only have granites been formed in this man- ner, but such rocks as gneiss, diabase, gabbro, and many, if not all, rocks of the trap group seem to have been formed in the same manner. Some geologists have suggested that this was the manner in which eruptive rocks were

6G

Geology.

produced, and that the additional heat necessary to fore them forth as lavas resulted from the mechanical action ij the folding or bending of the earth's crust ; and tf this correct it is possible that every portion of the earth's has been worked over many times, being forced out as iguft ous rocks, eroded from the continents and deposited i sedimentary rocks, only to undergo metamorphism and ult| mate re-ejeclion as volcanic or eruptive rocks.

STHLCTtHE COMMON TO ALL ROCKS.

120. Common Peculiarities. — Thus far a brief de- scription of ihe different classes of all rocks has been given, but there are certain peculiarities or formations which an common to all rocks. These are joints, fissures, and veiiu

121. Joints. — All rocks, whether stratified or igneou are divided by cracks or division planes, which run in thref directions and separate the material into irregular prismati blocks of various shapes or sizes. These divisions arecallet cracks or joints. Fig. 2!) illustrates the bedding planes and joints in a mass of rock, as well as the secondary or slate cleavage which has been induced by pressure. In stratified rocks the planes between the bedding constitute one of the series of cracks. In igneous rocks all division planes are of the nature of joints. In sandstone the blocks arc large and irregularly prismatic. In shale they are long and parallel

divisions In slates they are small and confused plates, th 1 i,h s metimes I imt nature s h tl Inl mestonOi

g37

Geology.

umnar structure, as shown in Figs. 39 and 40. In granite Ihey are large and frequently divide the material into rough cubes. On account of these divisional planes and the way in which they divide the rock, perpendicular or rocky cliffs often present the appearance of huge masonry walls laid up without cement, as shown in Fig. 45.

122. Cause of Joints. — The cause of joints is prob- ably the shrinkage of the rock while it is consolidating from the condition of sediment or while it is cooling from the previous condition of high temperature in the case of igneous or metamorphic rocks,

123. Fissures. — Fissures or fractures must not be confounded with joints. Joints pass through the individual strata or beds only, while fissures are fractures in the earth's crust that may pass through many strata, or even through several formations. As has been previously stated, joints are probably caused by shrinkage. Fissures arc the result of movements of the earth's crust, and they may vary from a few inches to 50 or 100 feet in width, and may extend for a great number of miles. Fissures are on record which extend along the surface from 50 to 100 miles, or even more, and they may continue down to great but unknown depths. They are sometimes filled with material of igneous origin, in which case they are called dikes. In other cases they are filled with material which has been deposited from solu- tion, and then they are called veins,

124. Cause of Fissures.— The cause of great fis- sures is evidently connected with movements of the earth's crust, either by foldings or by lifting. In either case there would be formed a parallel system of fissures in the direc- tion of the folds. For this reason, fissures are often found running parallel to the mountain ranges. In most cases the walls or two sides of the fissures do not correspond with each other, but one side has been pushed up higher or dropped down lower than the other. Such a displacement is called a fault, a slide, or a dislocation. A fault may occur in connection with a fissure in any kind of rock, hut it

68 GEOLOOY. g 37

is easier to detect faults when they occur in stratified deposits.

125> MonocItneH. — When the strata are sufficiently flexible, they may be bent into a single fold in place of being

broken by the favilt. '-uih l fold is lalkd a monoclinal fold, and is illusirate.l Tig 4(, Monoclinal folds have been known to run into faults when the pressure became greater than the flexibility of the strata could accommodate, and one fold may run into several parallel faults.

126. Throw of Faults. — The throw or displacement of faults varies fnmi a few inches to 20.000 feet, and may be eveti greater than this.

Faultn.— The directio

of

iiietimes perpendicular, !

line, and the matei

usually it is at an anf,'le, and in the major- ity of cases the upper portion of the material (hanging wall of the fault) has slipped down upon the lower portion ft (foot-wall of the fault). Such a fault as this is called a normal fault and is illustrated by Fig. 47, in which cd is the fault 3 the right or hanging-wall side of e

B37

Geology.

has moved down. Of course, ihe effect would have been the same if the ftiot-wall had moved up in reference to the hanging wall, and this is probably the case in many faults. When faults follow the usual rule and arc normal faults, the law of finding the continuation of the bed or vein is to follow the greater or obtuse angle when the fault is encountered; for instance, if the bed (xAwere being worked from the direction a towards the fault, when the fault was encountered the rule would be to follow the greater angle, which would be in the direction of J, and would take the operator to the continuation of the vein or bed. In the same manner, had the work been progressing from d towards a when the fault was encountered, the greater angle would lake the operator in the direction of c, which would also find the continuation of the bed towards a. Sometimes faults drag portions of the vein material and distribute it

Fio. ta. along the plane of the fault, and this may give an indication as to the continuance of the deposit sought. If the strata of a region are known, it is possible to find the continuation of a bed by breaking through and examining the material on the opposite side of the fault ; as, for instance, in Fig. 47, if work had been carried on from a towards the fault, upon breaking through the fault the limestone bed e/ would have been encountered, and as it was known that this bed ordinarily lay above the vein, the operator would sink along the fault to find the continuation of the deposit. Fig. 48 illustrates a scries of faults in Nevada, all of which are normal faults.

128. Heverse Faults. — In some cases, and especially in strongly folded strata, such as occur in mountain regions, the hanging wall seems to have been pushed or

70 Geology.

made to slide up on the fout-wall. Such a fault is c reversf fault.

129. Cause of Reverse Faults.— Fig. 49 illustrates the manner in which a reverse fault may be formed, (a) illustrates the bent strata before they had become faultedij

{fi) represents the strata after the pressure had become suffi- cient to cause faulting. Sometimes faulting planes are very flat, and in such a case they are called thrust planes, as illustrated at (r) in Fig. 4!i.

130. Dratts. — Sometimes the faults out through tin veins squarely, as illustrated in Figs. 47 and 4B, and some- times they drag the ends of the strata down, as shown in Fig. 40. This bending of the strata near the fault is called a drag, and usually gives indication as to the direction of the fault, though sometimes motion may have taken place along the faulting plane at several different periods, so that the rocks have slid alternately up and down upon each other, and when this has been the case it may be very diffi- cult to determine the direction in which the material has been carried,

J

Geology.

131. Cause of Xormal Faults. — The explanation of normal faults is not quite as plain at first sight as that of reverse faults, especially when the latter are along thrust planes, but by reference to Fig. 50 the manner in which they may be caused can be seen. At a the original form of the strata is shown, together with a series of breaks or fissures previous to faulting. Now, if the underlying mate- rial were forced up, it would cause this portion of the strata to take an arched form, as shown at b, and this would separate all the faulting planes, as shown in the illustra- tion. Now, if. by the escaping of the pressure stored beneath, either as molten material through the faults ur by the relief

of the pressure of the steam and gases, the material were allowed to fall back once more, the blocks would naturally tilt over onto each other, as shown at c, and this would result in a series of normal faults. Another possible cause maybe as follows: If the material were broken, as shown at a, and pressure brought to bear upon the under side of it, the portions having the broad bases would naturally be forced up on account of tlieir having greater areas of base exposed to the pressure, and for the same reason the portion with a narrow base would drop down beneath them, causing, in both cases, normal faults. In many cases subsequent erosion has removed the higher side of the faulted material.

r

Geology.

and hence the fault may give no evidence of its existence on the surface. In some cases it is probable that the slip has not been all at once, but has occurred slowly through a com- paratively long period of time. Where fissures were caused by lateral pressure, reverse faults would naturally be expected, but where they were formed by lateral contrac- tion or by a stretching of the surface owing to upheaval, normal faults would be expected. Frequently the faces of a fissure rub against each other during the faulting, so that one or both of the surfaces become polished. These pol- ished surfaces are called slick-insides.

lUINRRAL Vi:i!V9 ANp ORB nEPOSITS.

132. DiHtinctloa Between Veins and Diked. — All

regions that have been subjected to faulting and bending (as most mountain regions) are seamed and scarred in every direction with veins or dikes, as if the surface of the country had been broken and mended, These breaks are, as a rule, along the lines of fissures, and whc-n filled with material of igneous origin they are called dikes. When filled with material which had been deposited subsequent to the formation of the fissure, they are called veins. Sometimes the term "vein " is applied to either class, but the distinction above made will save a great amount of confusion.

133. Veins. — True veins are accumulations mostly in fissures of certain minerals which are usually in a purer condition than the surrounding rocks, and often in a sparry or crystalline condition. The accumulation has, in all cases, taken place after the fissure was formed and by a slow process. At times the veins follow no distinct fissure, but the material has been deposited along the lines of crushed or broken rock or at the contact of beds or rock formations.

1 34. Different KIndsof Veins. — The different kinds of veins may be divided into veins of segregation, veins of infiltration, and fissure-veins.

Geology.

135> Veloa of Scffreifation. — Veins of segregation do not differ materially from the surroimding or country rock, but are usually composed of the same elements or minerals; as examples, the veins or streaks of coarse-grained granite in granite may be mentioned, which differ only in the color and texture of the contents, or the irregular veins of feldspar in granite and in gneiss. Such veins have no distinct cause, and were not caused by the filling of a crack or fissure, but by the collecting of the material along cer- tain lines, either while the rock was cooling from the fused or plastic state or by the subsequent action of percolating waters, much as ioncretion.s or balls of iron ore are formed in some rocks. Such veins may sometimes contain valuable ores, but in small quantity.

136. Veins of Inflltratlcm.— Veins of infiltration may include gash-veins and siockwork. They may be siraply deposits in the joi planes which occur in all rocl or they may be deposits in I the bedding planes of rocks. Fig. 61 illustrates the occur- rence of gash-veins in joint planes. Sometimes the veins of infiltration occur simply in broken or crushed material. """' ""

They are commonly filled with silica or calcium minerals, and sometimes contain very rich ore, though they are never of great extent. The term "stockwork" is applied to such veins when they are so intimately associated with the country rock and cross each other in such a net- work that the entire formation has to be mined to obtain the material in the veins. Usually veins of this class have distinct walls, and frequently the material deposited in them has a ribl>on or banded structure very similar to the bands in the agate, and this structure was probably caused by the material being deposited at different periods and very slowly, in the same mannir that agates or opals

g 37 GEOLOGY.

marked, on account of the fact that tlie vein has resulted from the filHng of a previously existing fissure. At times this line is marked by a deposit of clay or other material along the face of the vein between the ore and the rock. This dividing deposit is commonly called selvage or gouge. 139* Mlneralii Found In Veins and Beda. — Iron occurs principally in beds or large deposits, and in many cases seems to have been dependent upon organic matter for the formation of the deposit. Lead and zinc occur mostly in flat beds or deposits in or on limestone. Man- ganese also occurs in a manner similar to iron ore. Most of the otner metals occur in veins, and the majority of large deposits occur in fissure- veins. If the outcrop of a vein is soft, subsequent erosion may form gullies or valleys where the veins outcrop. Fig. 53 is an illustration of a mountain- side on which two series of veins cross each other, and erosion has formed a series of valleys appro.\imately follow- ing the outcrops of the veins,

-. f 1 ,!

PocketH

Id Horses. — When rock is faulted, it break into perfiictly straight or smooth

planes, but frequently the surface of the break is irregular n the direction of the dip of the fault and decidedly crooked n the direction of the strike of the fault. If the fault stops n such a position as lo leave the projections on the opposite walls together, it results in a set of conditions similar to that illustrated in Fig. 5:}. Such a case may give rise to pinches or narrow places and to the wide places or pockets in many veins. Sumetinies masses of rock become broken from the walls and are subsequently surrounded by vein matter. Such masses arc called irses, and one is illus- trated in Fig. 54.

141. Gantcue. — The contents i ( ail mineral veins may be divided into two parts: the vein stuff or gang ue, which is usually composed of barren material, and the ore or mineral of value. The principal gangiie minerals are quartz, car- bonate (if lime (calcspar), carbonate of baryta, carbonate of iron, sulphate of baryta (heavy-sp r), fluoride of calcium (fluorspar). Sometimes various manganese minerals, or other lime compounds than those mentioned, such, for instance, as dolomite, occur in the gangue material or veins.

142. Ore. — In the case of practically all ores the mineral of value occurs either in small bunches or particles scattered through the gangue in certain small streaks and leaders, or it may occur in pockets of considerable magni- tude where the vein is intersected by other veins or dikes, or where the conditions have favored the concentration of the ore material. Nearly any of the metallic minerals described in the Paper on Mineralogy may occur in veins as ore.

1 43. Arrangement of Materials In Veins. — Occa- sionally the minerals in the vein are associated so as to form an ordinary rock, and hence the vein has considerable resemblance to a dike, but in most cases the material filling the vein has been deposited in successive layers or bands. Fig. 55 illustrates this banded, or, as it is sometimes expressed, ribboned structure. The central vein a is com- posed of galena; the bands b, b of fluorite; c, c of baryta;

Geology.

(/, li of quartz, wliich has crystallized as shown in tlic illus- tration;/', /are the gouge or selvage; the hanging wall and A the foot-wall of the deposit. This banded structure is not always as phain as shown in the il lustration, for the mineral or some of the gangue constituents may be pinched out in a portion of the vein, only to reap pear again as pockets in a

At times the narrow portions of the deposit contain the richest mineral, and these narrow portions are sometimes called ore leaders or stringers.

144. Contact Deponltti. — Deposits of ore frequently

r at the contact between igneous rocks and the adjoin- ing country rock, or between joints or cracks of country rock, especially where two kinds of rock join,

Fig. 5G illustrates a number of these cases. In the lower part of the figure the original country rock was gneiss. This was cut by a large porphyry dike, and subsequently contact veins fi>rmed at t m and n II on each side of the dike. The

/becaiT

Farther dowi e an ore bed, ;

Blankrt falnl

g limestone became o] A? chutes. The contai ? ///between th

tissiire r was filled as a reyiilar or true lissure-vein. Subse quently the surface was eroded and the deposit of quartzite.l // /X-yiaid down, probably as a sandstone. Then on top ofJ this the limestone was deposited; subsequently the region f was again disturbed and the intrusive porphyry dike c forced f into the iiraestone. After this, contact deposits formed along both sides of the intrusive sheet of porphyry, as aX ad in the limestone the bedding plane J nd the vertical joints all through the J limestone became ore I e contact j the I quartzite and the j limestone also came a contact de- posit, the ore ex- , tending slightly into 1 P'o the joints

quartzite, but no contact ore-hody being formed along the 1 liney it between the quartzite and the gneiss. It is evident j that the porphyry played an important part in the formatio of these ore-bodies in the limestone. Fig. 57 illustrates J another case in which a dike and an overflow of porphyry J have been instrumental in forming contact veins between I the porphyry and the limestone.

145. Vein Formed In a Dike. — Frequently a vein consists of a de- composed dike of some eruptive rock which is highly impregnated with mineral, the impregna- tion taking place most strongly at the contact between the dike and the country ruck. such a case.

?37

Geology.

146. Peculiar Occurrences of Ore.— In the Silver Cliffs region at the Bassic mine, the ore deposit seems to be composed of the throat of an extinct volcanic crater filled with lava pebbles, the spaces between the pebbles being filled with very rich ore. At the Bull Domingo mine the same formation occurs, only the pebbles are all granite and are coaled with a layer of galena rich in silver, the pebbles themselves being entirely barren. Sometimes per- colating waters have mineralized some certain bed or stratum ia the formation, and thus formed the blanket

deposits or the saddle reefs. Subsequent metamorphic action may change these strata into quartzite or other solid mineral, without destroying or changing the value of the formation as an ore. The great low-grade gold mines of the Black Hills and the Treadwell mine in Alaska are exam- ples of this class. Also, the blanket gold deposits of Africa and the Saddle Reefs of Australia. Fig. 59 illustrates a saddle-reef formation occurring in an anticline, the ore deposit being situated between the sandstones and slate rocks.

147. Age of Ore Deposits. — The age of veins or ore deposits can not in many cases be accurately determined. In the case of veins, it is evident that the ore deposit must be younger than the rocks through which the vein or lissure cuts. Then, too, the relative age of two or more deposits can frequently be determined by observing which of the

Ik

iM.:.i\i'r: wuft '-n<6*r ii-.ct-iiTiiii'jt fcj.cc iitt :iin.ir:c \i5.:r-*: ".irf T'-rr, '".ni --liic r iirt: bi-Urr ' t::i iz i

0 A

9

-r. V

—

,

, .

t

f.'! .1, .' . m;ili'T''d ' ofjditi'i".. S- 'ni-tiin*;< the rirh '!';/',.)♦ I. I'//.ii#l of on: wall nior; ihan on the other; at

§3?

Geology.

extends entirely across the vel of surface waters. Fi

in at or near fiO illustrates

oilier tir

the draii

these conditions, a is

the outcrop or blossom

of the vein; b is the

gossan; d represents

the rich deposit of

secondary mineral; c the unaltered portion ft" of the vein; e the hanging wall and y the foot -wall. The per- tion of the vein b undoubtedly origi- nally contained the mineral in practically F"-

the same condition in which it is found in the portion e, but the action of the surface water has leached out the copper and redeposited it at li. The deposit (/ may represent not only the copper from the portion of the vein b, but from a greater portion, for it is undoubtedly true that the process of erosion has gone on simultaneously with the process of leaching, and hence a considerable [lurlion of the leached ore may have become removed by erosion. Sometimes where gold or silver ores occur associated with the copper ores, the gold may remain in the gossan, together with a portion of the silver, so that the outcrop of the vein appears to be a gold or silver ore rather than a copper ore. This was especially true of most of the mines at Butte, Montana. The rich deposit of secondary mineral may occur quite near the surface or may be several hundred feet from the surface, depending largely upon the topography of the country and upon the depth to which the effects of surface agencies extend.

150. Lead Deposits. — The natural or original form in which lead occurs seems to he as a sulphide of lead or galena, but along the outcrop of the veins it is commonly

GEOLOGY. g 37

foui a carbonate, The explanatiou seems to be that the galen.t (/W) is decomposed by atmospheric agencies and becomes a Bulphate {P6S0,), and then the sulphate, by reaction with carbonate of lime derived from the wall-rocks or from calcspar in the gangue materia], becomes carbonate of lead. In proof of this, it is stated that the galena thrown onl from lead mines in England along with the rubbish of limestone has all in the course of time been changed into carbonate. Moreover, it is common to find in lead deposits masBCS of sulphide changed " utside to carbonate.

161. Gold Dei found largely associated

with iron pyrites o ; sulphides. In many

cases, gold seems lo ht mi c : state even when con-

tained within the crystals ulphides. Now, at the

outcrop of the vein the sulpJ become oxidized and

reduced to sulphates, which are hed out by the circula- ting waters, leaving (in the case iron) some peroxide of Iron and free gold. On this accou :, the gold in the outcrop of most vcinn is in a free condition while at greater depths H large jmrlion of the value may lie cuntaiiifd in the sul- jthidcN. The quartz of the vein which originally contained the sulphide is left in a granular or porous condition by the kachin); mit iif the sulphide, and it is frequently colored red by thi; ojtide of iron which remains. As in the case of the iirvH ]neviously described, the effect of these surface agencies lUiiy i;xli;nd to a depth of several hundred feet, but below that ]ii>iiit the gold is usually found associated with the HulphidoH.

1 S2. I'lncer DepOHits. — During the process of erosion

and diwiiilcuration of the rocks, it has been seen that the material eroded undergoes a sorting action while being transported and deposited in the water. During this sort- ing action the heavier particles settle first. Now, certain heavy minerals or metals are unaffected by tiie atmosphere, and hence would naturally collect into deposits near the places from which they were eroded. Among this class of material may be mentioned native gold, platinum, tinstone,

§37

Geology.

or oxide of tin, monazite sands, and some precious stones. These deposits containing material of value, but especially those containing metallic gold, are termed placer deposits. It is probable that many of the placer deposits contain prac- tically all the gold from very large areas of strata which have been eroded, and the greater part of the contents of which have been washed to the sea. leaving the gold or heavy minerals deposited comparatively near the rocks from which it was obtained,

1 53> Some Facta Concernlns the Occurrence and RlcbnesB of Metalliferous Veins. — Metalliferous veins occur mostly in regions where the crust movements have produced tiltings, foldings, and the resulting fissures. This action is usually accompanied by more or less metamorphism of the rocks, and these conditions seem to be necessary for the formation of most mineral veins, hence most minerals are found in mountainous regions or in regions which have undergone the greatest metamorphic action. Lead and zinc seem to be an exception to this rule, and these exceptional occurrences will be considered separately. Metalliferous veins occur mostly in older rocks, but the principal reason for this seems to be that these rocks have undergone the greatest amount of change or metamorphism, hence the age of the formation is not as much of a criterion as to its value as is the location of the formation and the amount of change it has undergone.

154. Pay Chutes or Cblmneys. — The contents of any vein, whether it be a gold or silver vein, or whether the precious metal be associated with other materials, is liable to vary greatly from point to point, and the rich ore will usu- ally be found iu chutes or chimneys. Sometimes this ore can be delected by a slight change in color or character of the gangue material, which is probably due to the slightly different solution from which the ore was deposited; but these indications may, and often do, vary in different parts of the same mine, and hence the exact value of any gold or silver ore and the limits of the pay ore can be determined

J

r

84 GEOLOGY. g 37

only by assaying. It has already been stated that regions which have iin<Ivrgone mctamurphic action are those ia which goki or silver and other metals arc most liable to be foimii.

16S* Hurnllttl VelnH.— Usually parallel veins contain similar ri res, though veins at right angles frequently contain similar ores, on account of the fact thai there is the usual secondary series of fissures at right angles to the principal fissures caused during any crust movement. Veins at other angles than those which are practically parallel or at right angles usually contain different ores.

156. EfTosct of Wall-Rock on Vein Contents. — In fissure-veins the country rock seems lo have less effect upon the contents of the vein than in the smaller deposits and gash-veins, and yet it is not uncommon to find a fissure-vein carrying one form of mineral while passing through one rock formation, and other forms of mineral while passing through other rock formation.i. Metallic veins are usually richer at points where they arc intersected by granite or dikes of igneous origin, and this is especially true where the strata adjoining the dike have undergone considerable metamor- phism from the heat of the material in the dike. When two veins intersect, the point of intersection frequently contains richer ore than either vein does in its ordinary course. Sometimes veins are barren, as far as mineral value is concerned, except where they intersect dikes or igneous rock. The Silver Islet mine in Lake Superior is a good illustration of this. The vein occurs in a fissure cut- ting through the unaltered flags of that region, and at the point where it intersected and faulted a dike which had pre- viously been formed, the vein became filled with valuable silver mineral.

157. Faulted Veins. — When veins are faulted or slipped, the continuation is searched for by the same rules employed in searching for beds which have been faulted ; that is, that the foot-wall of the fault has usually moved up in regard to the hanging wall, or, in other words, lo find the

§37

Geology.

coiuiniiation of the vein, follow the greater angle. As has already been stated, the surface indications of veins vary in different regions, and the prospector must of necessity become familiar with the region in which he expects to operate.

158. The Theories

parties have held that vf Igneous injections; other: result of deposits fr<

of Vela Formatloa. — Some

ins, like dikes, were filled with , that the vein contents are the Lpors containing minerals which

; ascending through the fissures; and still others have held that electric currents traveling certain fissures or veins have been influential in forming the deposits. All these theories seem to lack positive proof, and while each may apply in certain instances, practically all scientists are at present agreed that, in general, the vein filling has been the result of the circulation of percolating waters. The manner in which smaller amygdaloids may be formed in cavities has already been noted, as has the method in which the waters may obtain minerals from the country rocks, and it is probable that small gash-veins, etc., are practically all filled by this method of lateral infiltration from surface waters; but in the case of deep fissure-veins it is probable that most of the deposits are the result of heated alkaline solutions which have ascended through the veins and which contained the minerals or other material in solution. The waters may have derived a large portion of their contents from the adjoining country rock, or it may all have been derived from great deposits.

159. Gaosue Material. — The ribbon structure and the net-like system of crystals as exhibited in many veins indicate that the material was deposited in successive bands or portions from solutions. Fig. 55 illustrates this banded or ribboned structure. Silica or quartz is the most common of the gangue minerals, and it is evident that the beautiful crystals frequently found in veins could not have been formed in any other manner than from solutions. The material in the veins often contains small cavities in the

Geology.

crystals or in the body of the gangue minerals, and these cavities contain fluid which has been enclosed at the time the vein was formed. The cavities in quartz are easily observed on account of the transparent nature of the mineral. These cavities could not have been formed if the veins had been formed under any other conditions than from aqueous solutions. Also, many of the minerals found in veins will not stand fusion, and hence have evidently been deposited without fusiim.

160. Mot Solutions. — It is evident that the solutions were heated from the following considerations; Deep fissures would naturally become filled with water, and the lower por- tion of the fissures would naturally reach to depths where the waters would be hotter than the surface waters, and hence an ascending current would be set up in the fissure, the water to supply the current gradually settling down through the adjoining country rock. But one of the best proofs as to the temperature of the water can be derived from the fluid cavities found in the gangue minerals. The fluid doesnot always fill these cavities, showing that there is a vacuum in the cavity and that the fluid was deposited at the higher temperature. By heating the material until the cavity is filled, the temperature at which the deposit was made can be approximately ascertained. By this means it has been determined that the temperatures varied from ordinary temperatures to from 300° to 350° F. Veins are almost inevitably associated with regions where metamor- phic action has occurred, and hence it would be expected that the waters contained in the veins or fissures would ! hot.

161. Alkaline Solutions.— That the solutions whi effected the filling of the veins were alkaline is evident trot the following facts: Alkaline carbonates and sulpkatts a the only solvents for silica or quartz, which is the moj common of the gangue minerals, and if these waters contain an excess of carbonic acid gas, as is usually the case, th<d would also naturally dissolve the carbonates of lime, baryttfl

§37

Geology.

iron, etc. In California and Nevada such hot alkaline car- bonate and sulphide springs abound, and are now depositing silica as quartz, together with carbonates of lime and iron, and some of them are even filling fissures.

162. Oriffln of Metollic Ores.— It is probable that the metallic ores were deposited in the same manner that the gangue materials were deposited, and probably at about the same time. Metallic sulphides are the most common form of ore, and many of the other forms in which the ore occurs can be traced to them. Metallic sulphides are slightly soluble in alkaline sulphides, and these latter are often found associated with alkaline carbonates, as, for instance, in many of the hot springs in California and elsewhere. Such waters would deposit both the gangue materials and the ore upon cooling, or the mineral might be precipitated by the meeting of different solutions or by the presence of organic matter, It is also not unlikely that the enclosed walls of country rock had more or less to do with the depositing of some minerals.

163. The view that metallic sulphides and their ores were deposited fnun hot springs receives considerable sup- port from the fact that the hot springs of California and Nevada, and especially the Steamboat Springs near Virginia City. Nevada (so called on account of the periodic eruptions of hot steam and water), are forming such deposits at the present time. The waters of the Steamboat Springs are strongly alkaline and deposit silica in abundance. This deposit tills fissures, some of which are practically filled, and now form veins. The filling materia! exhibits a perfect ribboned structure in some cases. Moreover, the sulphides of several metals, i. e., iron, lead, mercury, copper, and zinc, have been found in the quartz gangue material. In this case, then, a true metallic vein is being formed at present. Practically the same process is going on at the Sulphur Bank, Lake County. California, where hot alkaline sulphide waters coming up from beneath are depositing silica and cinnabar in small irregular fissures and cavities.

Ding quarti veins contaioing cmnabar. The deposit is so rci.jni thit nsucli of the silica is in a soft hydraied ooDditioo and can be cut l&e diecM.

104. Perctdating waten travcSiq; m any Erection may cany or depomit material at value, iMtt the aaoendhv waters are most likely to prodnce eztensJTe dosks. Hmce, the large fismre-veiiu are the most lisUe to be paying mineral depositiL It is eridcat that the fissures would fnmidi free watercourses, and that the waters would naturally tend to ascend, and in so doing to become ooider. Sometimes, in place of the formation of a nngle lissurc, the rock is simply crushed, so as to form a series oi small parallel seams, which ultimately become filled with mineral. The cinnabar bodies of California are particularly gonti illustrations of this class of deposit. At other times the fissure brealcs or crushes quite an area of rock, and the vein material cements this broken country rock together, thus forming a kind of breccia. At other times, certain soluble rocks, such as lime- stone, have passages dissolved in them by the circulating waters, and these passages or spaces are subsequently filled with ore by the same agencies. Even a porous rock, like sandstone, may become a place for ore deposits, as, for instance, the silver and copper bearing sandstones of New Mexico and Utah. The exact chemical reactions which took place in the forming of mineral deposits are not fully under- stood, but there seems to be no doubt that the greater part of our supply of mineral has been deposited in this way from hot alkaline solutions.

166. It is known that the sea-water contains most metals in solution and that they are deposited in smalt amounts over the sea bottom and become scattered through all sedimentary rocks. Volcanic rocks also contain small amounts of different metals disseminated through them. Circulating waters may subsequently dissolve these particles of mineral and then redeposit them in veins or beds. In this way it is possible for waters to contain metals, even though they have not ascended from great depths, and the

Geology.

solutions may curae from almost any kind of rock forma- tion. After tlie material is in solution, the water may descend to a great depth, and subsequently deposit its burden of mineral while ascending through some fissure.

106. A Study of the Drift Gravel Mlnea.Some

evidences as to the method of formation of mineral veins

can be obtained from a study of the drift gravel mines of California. These are placer deposits in ancient river-beds, which have been covered with subsequent lava flows. Fig.Ul illustrates such a condition. The original river-bed was in the hollow a a, and its gravel or placer deposit was subse- quently covered by an overflow of lava c and c are the present river-beds. The lava in these overflows was frequently underlaid by a deposit of volcanic scoriae or mud, and the lava itself was not of iho thoroughly fused type. The gravel in the ancient river deposit usually con- tains more or less driftwood and other organic matter. Waters percolating through the lava deposit have become alkaline and have taken silica and various sulphides in solu- tion, which they have subsequently deposited in the old river channel. Some of the logs or other organic material have been petrified, the silica taking the place of the wood. Iron pyrites has been deposited in some parts of the gravel for- mation, and these pyritic crystals frequently carry gold very similar to that found in the ordinary gold vein. But prob- ably the strangest part of the deposit consists in the growth of gold nuggets. The placer gravel undoubtedly originally contained small gold nuggets, and in many cases they seem to have been enlarged by the subsequent deposits of gold

pon the outside, until they have grown u some eases weigh lieveral ]M>uDds.

1R7. lad and Zinc Deposits. — Lead and zinc de- posits frequently occur in comparalively flat or unaltered limestone formations. In such cases the mineral soroelinies seems to have been derived from adjoining rock formations, while ill others they may have come from circulating waters which have ascended through the fissures and then traveled laterally out through the ne, where they deposited

their burden of ore.

168. VuKS* — Ore veil '. deposits frequently con-

tain vugs or openings which ha not been filled with ore or gangue material.

169. Richness Wltta De| tfa. — There have been many claims in regard to the ehccl of depth on ore de- posits, some claiming that fissure-veins become richer with

depth, while others liolil to the opposite theory. There seems to be no particular ground or reason for either belief, and as far as is now known no definite law can be stated con- cerning this point. Some veins have been explored to a depth of about one mile, and have not been found to change to a considerable extent in value, while others may have a number of alternate changes, first becoming richer and then poorer. As has already been stated, the walls enclosing a deposit may possibly have some effect upon the value of the vein, as, for instance, it is not uncommon to find a vein containing good ore while passing through limestone, but upon following it into the underlying granite it may be pinched out and become barren or almost barren, or it may carry some other mineral than the one which formed the principal value of the ore in the limestone. From this it will be seen that the statement so often met with in the prospectuses of different mining companies that fissure- veins always become richer as they gain in depth has no foundation whatever.

Geology.

Fossils And Characteristics Of The Periods.

1 70. Before taking up a detailed study of the materials of economic importance which are recovered by mining or quarrying, It may be well to consider the principal fossils and remains of life found in the different geological periods, as these remains are all of great assistance in determining the age of any given rock formation, and this age is fre- quently of considerable local importance.

171. Artthean. — The Archean rocks contain no dis- tinct fossils, but the presence of masses of graphite indi- cates that there must have been some form of organic life from which the carbon was obtained, and the existence of exten- sive beds of limestone is evidence that some form of organism may have existed to form these deposits.

172. Cambrian. — The Cambrian period contains a number of marked or characteristic fossils. Pig. 62 illus- trates a few of the most important and character- istic of these. J, 2, and 3 represent three forms of trilobites which were one of the first forms of Crus- tacea. The Crustacea in- clude our modern crabs, lobsters, etc. 6 and represent two forms of shells which are corapar- Btively common in some of the Cambrian rucks. 4 represents the tracks made by the Crustacea while q traveling over the soft sea ' bottom or beach. 5 represents the tracks of worms. The burrows of worms are also frequently found and consist of small round holes which the worms had drilled or bored in the earth and in which they lived. These holes have become

t, Ploropod -. Hyo

; a, Lingulu Anttqiu

Geology.

filled with other matter, and can frequently be seen upon breaking open rocks of this period.

173. Silurian. — The Lower Silurian, and probably a portion of the Upper Silurian, belongs to the period before vertebrate life came the earth, but in the ' Upper Silurian a few fishes appeared, though the Devo- sreallylhe age of fishes, h The Silurian period is char- acterized mainly by the large number of shells and coral which were developed during le. Figs. 63 and Gi illustrate some of the most 1 Silurian fossils. In Fig. (53, the figures 1 to 6 show some of the charac- teristic shells of the period. 7fl represents a trilobite open, and represents the same species when curled up or closed. S and 9 are two of the simple coral forms, though the majority of the coral of this formation were not of the branchy type, : such as exists so commonly I at the present day, but were more of the form shown at Fig. G4, which represents a cup or horned coral, or at (i"), Fig. G4, which represents a coral which was composed of long ceils joined together in a series of chains, as shown in the illustration. It was during this period that the form from which the modern nautilus and cuttlefish have descended first appeared. The nautilus has a shell com- posed of chambers as shown at Fig. O-l, which i

Fio. M.— SILURIAN FOSSILS. -1. Orthis-DavfdBonif: I. Pntani. KniKhiii; J and J iBtHtiK ; 5, Pleura Uurchinonla gracili menaBlunienbBchtl S. Coral ChocUies Ottbocem* [>u>Bti.

SpirKer Cumber- 7a and 7A. c'lily-

Geology.

sents the modern nautilus. The chambers are connected by a tube running from the animal back through all the chambers, though the cham- bers themselves are emp- ty. WheQ the animal out- grows the forward chamber in which it lives, it advam the shell and leaves another sealed chamber behind it. The first shell of this type was chambered in the same manner, but was not coiled as is the nautilus. 11. Fig. c;!, illustrates this shell, which was called the orthoceras. {b). Fig. 64, represents a species ' of curved chambered shell which also came into existence before the end of the Siluri period. Another important form of life which appeared during this time was the cri- noid. This is illustrated at Fig. 04. The crinoids were practically all attached to the sea bottom by long stems; the head of the crinoid was shaped considerably like a lily or flower, having five or moru fingers or plates, which it could open or close while searching for food. In fact, the crinoid was a good deal like a starfish on the end of a stem. One very characteristic little fossi! which is found in the Silurian rocks, but not found above them, is shown at HI, Fig. V.i. This is called the graptolite.

.-SILURIAN KO.SS1LS. arly Nnutilus; UtiiitM itls; icl. CHnofd; (d). Za- llaleralts: irt, Halyidtei cn-

174. Devonian. — Fig. G5 illustrates a few of the most important of the Devonian fossils. 1, 3, and 3 are three of the common form of shells. is one of the common forms of chamber shells belonging to the nautilus family which existed during that time, B,G, and 7 are three of the com- mon corut forms. The corals of the Devonian period were

Geology.

also more massive than those of the present time, and thl cup coral, as shown at Fig. Gi, continued throughouffa this period, though in a slightly different form, S, 9, and J

represent the teeth of fislifl and H and 13 scales i plates from fish. The-1 Devonian fish were of thefl intermediate type largely,! and were in many caseS-fl different from most of thef modern fish. The earliest forms did not have scalei such as most of the mod-J ern fish possess, but thai bodies were covered with| irregular horned plates; some species only the forvj ward part of the bodics| was covered, and it is prob- able that these fish lived! in holes in the mud of thofl sea bottom, only dashing) out and exposing their sof bodies when actually pur suing prey. The modern garpike has scales or plates on ite body very similar to those of most Devonian fish, and macjB of the Devonian fish had teeth similar to those of the sharla of our day.

Both the Devonian and the Silurian rocks frequently coi tained pockets of graphite, pitch, or asphallum. which seen to have been derived from organic remains of some These organic remains may have been either seaweed e animal remains. It is also probable that the natural ( and oil derived from these formations come from the slotfi distillation of these organic remains after the rocks ha(fi become buried under their strata and the internal heat o£j the earth has had an opportunity to act upon the remai contained in the rock.

FlO. n.— DEVONIAN FOSSILS.

1. Splrifer perexleniui : t, Cnmncardium

I. Orthis LIvaii. Gunialiici; 5, Acervulurii

Davldionii ; Crepidophyllum An-hiel ; 7

Corat ; S. s, and IB. Fiih teeth i II and It

§37

Eoc

175. Carboniferous. — Fig. 66 illustrates a few of the most common fossils found in the Carboniferous formations. Numbers la, lb. Ic, S, a, 6, 7, S, 9, and 13 are shells which occur com- monly among these rocks. Figs. and 10 represent two of the common chambering shells of the nautilus type, as existing during the Carboniferous pe- riod. 6, 5 illustrate cri- noids, though this type is sometimes called bias- tids, on account of the fact that the fingers are not well developed, but are replaced by five petal - like projections. Near the crinoids in the center of the picture can be seen two small disks which are sections bro- ken from crinoid stems. Both these sections and short pieces of crinoid stems are of very common occurrence in all rocks in Paleozoic times. 11 and m are characteristic coral forms of this period.

Some trilobites are found in the Sub-Carboniferous, but they disappeared during this period. The orthoceras or straight-chambered shells disappeared with the end of the Paleozoic time, and are practically, if not quite, extinct dur- ing the Devonian Age, though the curved or spiral cham- bered forms continued in great abundance.

During the Carboniferous period, fishes had become more abundant and had attained a higher stage in the scale of development than during the Devonian times. Before the end of the Carboniferous the first amphibians appeared.

noldi (Pbi K. GuniU

CAR BON I FERGUS FOSSILS. id Ic. Prodiiclus; t. f. Spirrfen: cnni-LU; t, Euamptxuliis : J, 6, Cli- DinltcK ; e. Pleurnlomarln ; 7. Bel- , Atbytis Sobilllia ; p AsurtclU; en; II. Coral (Archimedes War- :nra1 (Cllsloiibyllniim tiabbi); U.

A

y throughout life both

These are animals most of which c lungs and gills, and hence car breathe either air or water. But the characteristic of the Carboniferous period was, as its name indicates, the great abundance of vegetable life, which resulted in the formation of coal deposits. The vegetable life of the Carboniferous period was of the lower forms, such as our club mosses, ferns, etc., of the present

There were no fruit-trees and no flowers, but the

)wth of vegetation in the swamps and on the low

suited in great peat -bogs, which finally became the

lis of the present day.

ol the characteristic fossils of the vegetable remains

Sarbonifcrous period are illustrated in Fig. 07. J,

ferns (tf the coal period, while 4 is a very tommon

§37

Geology.

form of vegetable life, and a small leaf. 6 and 7 are fruit from the carboniferous trees. S, 9, and 10 are impressions of the bark of the larger plant forms, while Jl represents the lower end of the stem of a calamite. These are very common in the fireclay underlying the coal-measures, while ferns, bark, and fruit are more common in slates which over- lie the coal or any thin seams of slate in the coal-measures. At the end of the Carboniferous period the thick deposits of sediment which had been so long accumulating in the Appalachian regions were folded and forced up to form the Appalachian Mountains. At the same time, or very soon afterwards, the Utah Basin region was upheaved to form land, while the Nevada Basin region sunk to become sea. In fact, the Pacific shore line was transferred eastward, but there still remained a narrow sea between the Appalachian Mountains and what are now the Rocky Mountains.

176. Permian. — The Permian is usually classed with the Carboniferous period, but is in reality the transition period between the Paleozoic and the Mesozoic time. In North America the transition between the two periods was marked by great changes in the continent. The Appalachian Mountains were forced up from the sea bed, and many exten- sive changes took place in the western portion of the country; hence in most places the Permian is entirely want- ing in this country, though in parts of Illinois, Kansas, and some other localities it is present.

177. Jura- Trias. — In the greater part of North America it is impo.ssible, or practically impossible, to deter- mine the dividing line between the Triassic and Jurassic periods, hence they are usually considered under the one name of Jura-Trias, and the deposits of this period consist of a narrow strip along the Atlantic Coast, to which belong the sandstone deposits of the Connecticut River, similar deposits in New Jersey, and the coal deposits of North Carolina and Virginia, Also during this period there were extensive deposits both east and west of the principal range of the Rocky Mountains, During this period fish

J

mW

Geology.

developed into a form more like that known at the present' I tine. True reptiles appeared, and also reptiles which very ] doeely rc&imbli'd birds, and finally birds which did not fty and probably hail teeth. The vegetation approached more ] ttcarly that of the present time. In some parts of the world t this is marked by extensive salt deposits, and Mhem by extensive gypsum deposits. This is especially J true of much of ihe formation of the ca.stern slope of the Rocky Mountains. Insects also became common during j this period and some forms of land animals were developed.

At the close of the Jura-Triafi, the eastern portion of the i continent was elevated so as to bring the northern part of' the Atlantic beds above the sea. Portions of the deposits i in the Central Slates east of the Rocky Mountains were elevated, while other portions became covered with fresh- water or brackish lakes. The Sierra Mountains and the Cascade range were formed at the close of this period, thus moving the Pacific shore line westward again.

178. Cretaceous. — Thc .ceous |>eriod is mainly characterised by a general transition of the animal types, from those of the Jura-Trias to those of the Tertiary. The deposits of this period in America are confined to the Southern and Southeastern States of the United States, the central portion of the continent east of the Rocky Mountains, and the strip along the Pacific Coast. During this period the entire peninsula of Florida was under water. The chalk formations of Europe and England belong to the Cretaceous, and were formed from the remains of certain small shells which lived in the deep seas. The Cretaceous formations in the United States contain some quite extensive coal-fields, which are mainly situated in the Rocky Mountains, though the coal of this period, unless altered by metamorphic action, is liable to be rather soft. The plants approach more nearly to those of the present time. Great reptiles still lived in the sea and on the land, but the fish of the shark and whale family appeared. During this period the form of shell-fish of the nautilus or chambered order developed a great variety

§37

Geology.

of curved and crooked shells, some of thein having the form of a trumpet or spiral spring, but many of them had very beautiful shells. The birds seem to have ail had teeth set in distinct sockets similar to those of the reptiles, and great reptiles ruled both the land and the sea. At the close of the Cretaceous, the Wahsatch and Uintah Mountains were elevated, and the portion of the country which had formerly been a sea dividing North America into two continents was elevated into land.

179. Cenozoic. — At the close of the Mesozoic the greater part of North 'America was above water, but the Coast range on the Pacific side had not yet been formed, and the interior of the country contained great fresh-water lakes; also the Gulf or Southern States were still under the sea. During this period the land was ruled by great mam- mals and the sea by great fishes of the whale or shark order. These were so plentiful that in some places iii the Southern Slates whole beds of sharks' teeth are found, and bones of the gigantic whale are frequently found in Alabama and Georgia. In the deposits of the great fresh-water lakes of the West many mammals, both large and small, are found, and the animals seem to have undergone a rapid evolution during this period. At the end of the Miocene the Pacific Coast underwent an extensive revolution, the coast chain being forced into existence and at the same time great fissures opened, which resulted in extensive lava flows over much of western and northwestern North America. At the end of the Cretaceous period practically all the area of North America was above water, as was al.so the greater part of Europe. During the Tertiary period there were a large number of coal deposits formed, but in most cases the coal is of a soft nature (lignite). The rocks of the Creta- ceous and Tertiary periods of the extreme western portion of the continent have undergone metamorphic action, and hence are firm, solid rocks, while in most other locations they are not completely solidified. The soft rocks of the Mesozoic period have given rise to the pecidiar formations

100 GEOLOGY. Sa

Imovn M the Bad IniU of the West, which cmsisi of irreffuUf tublc'Unds having vallcjs eroded throagh them. Pre>|uently their irregaUr nnssesof material, vhldi have been left in the pr<x!e9a o( eroskm, look tike distant cities Iff vilb)(e<i, or like great ca<itleL I>Driog the Tertiary peri<il the mammals developed to an enormous size, but in ulMe<|uent perirvdit most of the mammals hare disappeared. time daring the (Quaternary period man appeared, but he did not liccome ruler fif the universe at oncv, but has developed as all other forms have. This period seems to have been character! se<] in the Northern Hemisphere by an elevation of the northern part of the continent, so that it became much colder than in the previous periods and was with a great ice sea which extended far south, forming the glacial period. Subsequently the continent wa<i |i>wercd a whole to a point somewhat lower than that which itn northern part now occupies, and after this gradually liflcd til its present piution. During the Mesosoic time anil the Tertiary time the temperature of all the northern countries seems to have been very much warmer than at present, while during the glacial period the temperature very much Iowlt than at present.

Economic Geology.

1 80. MuterlalH uf Cummerclul Importance. — The

general form of mineral deposits and the mode or manner of occurrence <if most minerals have been considered under the head of Structural Geology, but there are some materials of commercial importance which should have separate con- sideration.

Among these arc the following; (1) The metals, gold, silver, iron, copper, lead, zinc, manganese, nickel, cobalt, tin, mercury, antimony, and platinum, (a) Mineral fuels, petroleum and natural gas, bitumen and asphaltum, salt, building stone and slate, clay, gypsum, phosphates, sulphur, silica and other materials for the manufacture of gl

Geology.

pigments or the materials for the manufacture of paint, graphite, asbestos, mica, monazite, alum, borax, the soda and potash salts, and precious stones and gems.

Goi.D.

181. Occurrence. — Gold, as stated in the Paper on Mineralogy, occurs in nature both as native or free metallic gold and as various minerals principally associated with tel- lurium. Gold deposits may be divided into three general classes: placer deposits, deposits which are mined for gold or gold and silver only, and from which the metal or metals are obtained by some milling or lixiviation process, and ores in which the gold is associated with copper or lead, from which it is obtained by means of a smelting or refining process. The surface changes that occur in gold deposits have been treated in Art. 151.

182. Placers. — PlacershavebeendescribedinArt. 1S2 as resulting from the decomposition and erosion of various deposits and the subsequent accumulation of the gold {owing to its great specific gravity) by the sorting power of water. The methods of prospecting for placer deposits, of testing various gold ores by panning, and of working placer and hydraulic mines, do not come under the head of geology, but should be treated in works pertaining to these subjects.

183. The ores of gold in which the metal is associated with copper or lead, and which require smelting, are usually considered as copper or lead ores carrying gold, and hence would naturally come under the head of those ores and be treated according to the methods usually pursued for the recovery of such metals.

184. Special Occurreaces. — Gold occurs not only in veins, but in beds or blanket deposits, as has been noted in connection with the subject of Structural Geology, Some- times these beds or blanket deposits are undoubtedly placer deposits which have accumulated either in river-beds or on or near old sea or lake shores; or the gold in the rock may

10 GEOLOGY. S 3fl

lutTC been deposiled from circulating waters which havl flowed through sandstone or other open formations anA deposited gold, together with various minerals, there, subse> J quent to the time that sandstone was deposited. Owing to-l the fact that some of the gold reefs have in places films o£| gold oti the outside of grains of sand or mineral matter, has bten thought probable that their gold was not deposited. at the time the bed was formed, but was the result of subsexl quent deposits from circulating waters. The principal.1 values in gold deposits generally occur in pay chutes orj pockets as described in Art, 154.

185. Gold occurs in almost all countries, but is alwaySJ more common in the regions that have undergone the i change.

Silver.

18t). Occurrence. — The silver minerals and the mao ner in which the silver occurs have been spoken of in th'l Paper on Mineralogy, where it is stated that native or metal- lic silver may be found under certain conditions, but most silver occurs as silver mineral. The distinction between dry, or milling, ores and smelting ores, and the distinction between free milling and refractory ores, was also explained in the Paper on Mineralogy. Silver minerals in the ore can frequently be detected by the eye or be determined by means of the blowpipe, but in the majority of cases an assay is necessary to determine the value of any given ore.

187. As in the case of the gold, the principal values in silver veins usually run in chutes or chimneys, and silver is not always found in veins or associated with other metals, but may occur in sandstone, as was the case in both Utah and New Mexico, where the organic remains of the fossils in the sandstone seem to have played an important part in the deposit of the silver. In the Laie Superior copper mines, nuggets of pure silver are frequently found associated with metallic or native copper. The copper and the silver are, as a rule, not alloyed, but occur in separate nuggets,

§ 37 Geology. 103

which may be joined with each other so as to form one mass of metal, the nugget being copper on one end and silver on the other. A large portion of the world's supply of silver comes from the argentiferous lead and copper ores, and in fact the silver often forms the principal value of such ores. Frequently the outcrop of a copper vein carrying silver con- tains silver, but no copper, the latter having been leached out and deposited farther down in the vein, as described in Art. 149.

188. Silver, like gold, is found in nearly all countries and in nearly all geological formations, but usually occurs in the regions which have undergone the greatest amount of metamorphism. The silver ore itself may occur in dikes or veins in nearly any kind of rocks or as pockets in lime- stone deposits.

189. Requisites for a Good Ore. — The principal

iron minerals have been given in the Paper on Mineralogy. The requisites for a gO"d iron ore for making cast iron or for making Bessemer steel are that it should be very low in phosphorus. No iron or steel should contain over.l phosphorus, and hence no iron ore for this process should contain over .05;* phosphorus. The ore may be consider- ably higher in silicon, as this does not injure its quality, and the silicon may assist in the Bessemer process. For making basic iron, the ore should be high in phosphorus and contain practically no silica, as in this process the phos- phorus is burned out in the steel converter, while in the Bessemer process the silicon is burned out. It is impossible for a prospector to determine the percentages of iron or of impurities in the iron ore, hence the assay or analysis should always be made by a good chemist.

190. Mode of Occurrence. — Iron ores very rarely, if ever, occur in true veins, but are found in lenses or beds, and organic matter seems to have played an important part in their formation. Ores of iron are especially abundant in

Geology.

coai -measures, but these deposits are practically all com- ised o( ferrous carbonate, which occurs mixed with clay, mid hence it is called clay ironstone. Often the ore is nodular or mainmillated, and is called kidney iron ore. When it occurs Intimately mixed with carbonaceous matter, it is called black band ore. Deposits of this latter class arc found in Pennsylvania and Ohio, and some of the deposits have furnished a considerable portion of the supply of ore in England and Scotland.

I 91 . Most of the iron deposits in formations other than the coal-beds occur in the form of ferric oxide. They may be hydrated, in which case they form brown hematites or limonites, or they may be anhydrous, in which case they are red hematites. The deposits also often contain magnetic oxides. The outcrops of pyritic veins are often oxidized, forming deposits of hematite and limonite. In the West such deposits frequently carry gold and silver, and as iron is required as a flu.t in the lead smelters, this class of ores is especially welcome, f"r !hf gold and silver will be recovered during the smelting process. Deposits of pyrite are of value when located in a mining region as a fuel for pyritic smelt- ing, or the pyrite may be employed to form a matte with dry gold and silver ores. When the deposits occur in regions where large amounts of sulphuric acid are employed, they are valuable for the manufacture of this acid, and sometimes the resulting iron oxide has been employed in making certain grades of iron. As a rule, however, iron ores containing large amounts of sulphur are valueless as ores of iron, but sometimes ores containing some sulphur, especially when low in phosphorus, are roasted to expel the sulphur, and then employed in the manufacture of iron.

192. Ores of iron occur in most geological horizons, but different formations seem to contain the best deposits in different regions. The great iron ore deposits of the Lake Superior region are practically all in the Archean rocks, while many of the deposits worked in other parts of North

§37

Geology.

It origin. As a rule, the largest older rocks.

America are of more r deposits seem to be in

ld3. Most, if not all, of the deposits of magnetic iron ore appear to have been formed from the other oxides by meta- morphism, and this also seems to he the origin of a large num- berof the deposits of hard hematite. Frequently the rocks containing these hard ores are not conformable with the strata containing the soft ores, and the latter frequently occur in valleys between the hills of the older rocks, and appear as though the deposits had been formed in the valleys which they now occupy,

194. The sharp competition in the iron industry and the extremely strict demands as to the purity of the ores have hut many deposits out of the market, so that now most of the supply of iron ore in North America comes from the Lake Superior region and from Alabama, though quite a large amount is produced in Pennsylvania or other por- tions of the East, and in Colorado. Good ore has also been furnished from various other points of the Rocky Mountains, from Missouri, from several of the Eastern and Southern States not previously mentioned, from Cuba, and South America. Iron ore is mined in several localities in England and in a large number of places on the continent of Europe, ranging from northern Sweden to southern Spain. Ore of good quality has been discovered in Africa and many parts

Copper.

195> The ores of copper are given in the Paper on Min- eralogy. The world's supply of the metal comes from two sources: (1) The mines producing native copper only; (2) the mines producing some of the ores of copper, with possibly a small amount of native copper near the surface.

The mines producing native copper only are limited to those of the Lake Superior region in the United States. Where the copper occurs as fine threads or grains in trap or conglomerate rock, occasionally large masses are found, and

Geology.

the native copper is accompanied by small amounts of r silver, the silver as a rule not being alloyed with the coppeiS and occurring as silver nuggets, which are nearly pure silver and a strange feature of the deposits is thai frequently a nugget may be composed partly of silver and partly of copJ per, as though the two had been welded together. A con sideratile portion of the world's supply of the metal coma from these Lake Superior ores. They have the advantage over all other ores that the metal, being in a pure stat simply has to be crushed and washed free from rock; alstl on account of the fact that such impurities as sulphufjif arsenic, etc., are unknown in these deposits.

196. In veins or deposits where the copper occurs i: mineral, it is not uncommon to find a considerable quantit] of native copper near the surface, but this seems to haw always resulted from the decomposition of sulphide or through the action of surface agencies. Fig. GO, Art. 149 illustrates the manner in which the upper part of a vein carrying metallic sulphides or other metallic compounds-* may become leached out and a secondary deposit formed.

b represents the leached portion of the vein, d the secondary deposit, and c the unaltered portion of the vein. In thi case of copper minerals, this enriched deposit usual consists of native copper, together with the rich oxidci carbonates, and sulphides of copper, and occasionally native silver. Sometimes the copper has been leached from tlw upper part of the vein, leaving only silver and gold, i of the metals alone, in the weathered portion of the deposit At times the outcrop of the copper veins shows no signs C copper, all the metal having been leached out. At oth times a small amount of the metal has been reduced to tin form of a carbonate, and has so stained the rock that !jq gives the appearance of a very much greater deposit of t metal than really exists.

197. In western North America there are

deposits which follow in a general line the mountain systei all the way from British Columbia to the Isthmus. Thi

.Geology.

richest of these deposits occur at Butte City, Montana, and at various points in New Mexico, Arizona, and Old Mexico. Colorado also furnishes considerable copper, must of which is a by-product from the concentrates of gold and silver mines, or as matte from the lead smelters, the copper minerals having been associated with the other constituents of the ore and the copper being recovered as a by-product during its treatment. Practically ali the copper ores of this section carry gold and silver, which in many instances form the principal value. A small amount of the copper mineral has been obtained from the lead and zinc mines of the Mississippi Valley. At Sudbury, Ontario, there are rich deposits containing copper, nickel, and cobalt. In the Eastern and Southern Slates of the United States, deposits of copper are often worked, but in most cases they are secondary ores resulting from the decomposition of veins by atmospheric agencies and the concentration of the ore in certain portions of the vein, as illustrated .by Fig. tiO, Art. 149. For this reason, though many of the deposits, may be rich, they are of small extent and are soon exhausted. The copper deposits of South America follow the Andes Mountains, much as those of North America follow the Rocky and the Sierra Mountains. Copper is also produced at various points on the continent of Europe, especially in Spain, and in other portions of the world, as Japan, Aus- tralia, etc.

Lkau.

198. The ores and minerals of lead are given in the

Paper on Mimralogy. Lead ores are divided into two gen- eral classes, depending upon their contents of silver. The silver-bearing ores are called argentiferous. Those which do not carry silver are called non-argentiferous. Lead ores occur in veins and also in bedded deposits mainly in or on limestone rocks, and, in fact, deposits of both lead and zinc are rarely found separated from limestone. The outcrop of lead veins or deposits rarely consists of galena, but is composed of a carbonate or sulphate ores which have

108 GEOLOGY. j

resulted in the decomposition of the galena. Such ores i ally carry practically the same per cent, "f silver or yold that are found in the original galena. With depth, these I deposits run into galena. The general surface changes which are most common in lead deposits have been described in Art. 160. In some localities lead and rinc ores are mixed together in such a manner that they require sep- aration by means of a concentrating plant This is espe- cially true of certain portions of soathwestera Missouri.

199. Deposits of lead which are more or less argen- tiferous occur in eastern North America, following, in a general way, the line of mountains parallel to the seaboard, but as a rule these deposits tiave proved too small to be of commercial importance. Similar deposits occur in the Lake Superior region, but so far no really large lead mines have been developed in this portion of the country. The Missis- sippi Valley, contains large deposits of non-argentiferoua galena, located in western Illinois, Wisconsin, Iowa, Mis- souri, and Kansas. It'is from these Hources that a consider- able portion of the supply of lead used in the United States has been derived. In the western portion of the continent, all through the mountain region, veins or beds of argentiferous lead ores occur, and they produce large amounts of lead as a by-product during the process of gaining the silver. Argentiferous lead ores also occur all through the Andes Mountains in South America and in a number of countries, such as Japan, Australia, etc. In North Amer- ica the most important deposits of argentiferous lead ore are found in Colorado, Utah, Idaho, British Columbia, Ari- zona, Nevada, and Old Mexico.

Zinc.

200. The ores and minerals from which zinc is pro- duced are given in the Paper on Mincralogj', and may occur as gash-veins in nearly horizontal country rock or dissemi- nated through limestone formations in practically bedded deposits on top of, or in, limestone formations or in true

g 37 GEOLOGY. 109

fissure-veins. At times the zinc mineral is so finely dis- seminated in the limestone that it is difficult to distinguish the ore from the country rock.

If the ore is high in silver, zinc forms a very unwelcome constituent, as it will interfere seriously with the smelting of the ore and the recovery of the lead, gold, and silver, though of late such ores are treated hy forming an oxide of the zinc and a portion of the lead which is collected and employed as a pigment in the manufacture of paint, the gold and silver being collected in a small amount of lead bullion.

201. In most cases zinc-blende seems to have been the original zinc mineral, and surface deposits which are com- posed of carbonates, oxides, silicates, etc., seem to have been derived from the sulphide ores. In localities where the surface has been subject to decomposition or weathering, the sulphide ores of either lead or zinc are rarely found

202. Zinc deposits of importance occur in North America in the following regions: In New Jersey, Pennsyl- vania, Virginia, and other Eastern States, in Iowa, Wiscon- sin, Kansas, Illinois, and Missouri, in the Mississippi Valley, and in various portions of the Rocky Mountains. As a rule, zinc ores of the Rocky Moiintains are associated with argentiferous galena, and may themselves carry gold and silver. Zinc ores are also mined in a number of European countries and in North Africa. Large deposits are known to occur in a number of countries which have not yet become producers.

Makganksb.

203. Manganese minerals are rarely found pure in nature. The ores consist mostly of carbonates or oxides,

and are often associated with iron or zinc. Manganese ores are employed in the manufacture of spiegeleisen, which is a highly crystalline compound of iron containing from l(i;( to 15;* of mangant-se and a large amount of carbon.

204. Some of the manganese used in the raanufactui of iron or steel is derived from the manganiferous iron oresl i. e., from iron ores containing from to of manganescLl Some zinc ores, as, for instance, some of those occurring' j in New Jersey, contain both iron and manganese, and after the zinc has been volatilized the resulting mixture of iron and manganese is employed in the manufacture of spiegel-

205. Deposits of manganese ore are worked in Colo, radu, Arkansas, California, Georgia, New Brunswick, ; number of other locations in North America. It i: produced in Belgium, Greece, and other countries on the I continent of Europe, and mines arc operated in South America. Deposits are known to exist in Asia and various other portions of the world, which have not as yet been brought to a producing state. In general, manganese ores are found in practically the same horizons as those of ii and they usually occur in beds or lenses similar to the t of iron.

206. Some of the manganese ores are silver-bearing (as those mined in Colorado), and are worked for the silver they contain. Manganese ores are also sometimes employed in place of iron ores as fluxes at lead smelters.

207. The dioxide or black oxide of manganese (pyro- lusite) is employed in bleaching, and its value for this purpose depends upon its ability to give up oxygen, so that when it is treated with hydrochloric acid it sets chlorine free, and the chlorine is employed for bleaching. Manganese dioxide is also used in the manufacture of glass to do away with the green or brown color due to the presence of small amounts of iron in the glass. The name pyrolusite comes from this ability to remove or wash away the color in the glass, and the action depends upon the fact that the dioxide can give up free oxygen.

208. Nickel and Cobalt.— Nickel and cobalt are usually associated in nature. Cobalt is never found in a

OU5 .-een

'4

Geology.

native or metallic stale. The ores arc siilphiiles, arsenides, arseno-suiphides, an oxide, a carbonate, a phosphate, and an arsenate. Nickel is found also associated with cobalt in the sulphides and arsenides. The ores of nickel are sul- phides, arsenides, arseno-suiphides, an antimonial sulphide, a sulphate, carbonate, silicate, arsenate, and the metal is a constituent of several cobalt ores and also of pyrrhotite (magnetic pyrites). Metallic nickel has been found alloyed with iron in certain meteorites. Nickel ores are usually associated with those of copper or other metallic sulphides. The deposits are usually found in veins or in contact deposits at the sides of dikes.

209. At present the world's supply of these metals is practically all derived from two localities : First, the Sudbury district, in the Province of Ontario, Canada, where the metals occur associated with copper in sulphide and arsenide ores, which also carry platinum, and second, in New Cale- donia, where the nickel occurs as a silicate associated with some cobalt and practically free from copper. At one time the "Gap" mine in Pennsylvania was the largest single producer of nickel in the world, but at present these work- ings are closed. Some nickel and cobalt are derived as a by-product from the lead and zinc mines of Missouri and from mattes at the various reduction works throughout the world. Deposits of nickel silicate occur in Oregon and in California, but thus far practically nothing has been done towards their development. Small amounts of nickel have been obtained from gash-veins or other small deposits throughout the Eastern United States, but none of these deposits has been of sufficient magnitude to warrant mining on a large scale. Nickel ores are also mined in various parts of the continent of Europe.

210* As stated in the Paper on Mineralogy, the princi- pal ore of tin is cassiterite, or oxide of tin. This is usually found in irregular or gash veins, in granite, in quartzose-

iia

Geology.

gneiss, or in mica-schist. It is often associated with wo!f3 ram, pyrite, and other minerals. The species of granite usually associated with tin is called greisen. So far, no regular veins or true fissures carrying tin ore and extending to great depths have been discovered. Owing to the fact J that the mineral has such a high specific gravity (frc 6-1 to 7), when deposits of this mineral are eroded, the tiii*| stone is collected in placers much as gold is, and a larg< portion of the world's supply of this metal is derived from these placers; the tin thus recovered is commonly callei stream tin, on account of its having been washed from th sands or gravel of the streams,

211. Practically all of the world's supply of tin come) from the mines in Cornwall, Australia, the Island of Banc: in the East Indies, and from Malacca. Deposits of tin c are known to occur in the eastern portion of North AmericaJ but not in sufficient quantities to justify working. Therea are also deposits in various portions of the western mouniaiU'J regions, especially in the Black Hills of South Dakota, atj San Diego, California, and in various portions of Idaho anij Montana and in Old Mexico. Deposits are also reported a occurring in South America, but thus far none of thes has been worked on a commercial scale.

Hbrcurv.

21 2. Mercury occurs native alloyed with silver, formis a natural amalgam, in combination with sulphur, selemuai chlorine, or iodine, and with sulphur and antimony in som tetrahedrite; the ore which is of the greatest commercial importance, however, is the sulphide. While m occurs in widely different geological horizons, yet the cood ditions under which it occurs are usually similar. TheJ Spanish deposits are in Silurian strata, the Austrian fi lower Triassic, while the deposits in California are in thoi'1 Cretaceous formations. The sulphide (cinnabar) is tbQ.l principal ore, though it is usually associated with many o the other mercury minerals. The ore usually occurs in slatei

§ 37 Geology. 113

or sandstones and in broken or shattered rocks which have been broken or shattered by faulting; that is, in place of the rocks being fissured, they have been simply crushed along certain lines. Mercury occurs in Oregon, California, Nevada, Old Mexico, and British Columbia. At present the only producing mines in North America are situated in Old Mexico, California, and British Columbia. Deposits of ore are known to exist in several other States, including some in the eastern part of the continent, but the deposits are too small to be worked. In Europe, Austria and Spain furnish the main portion of the supply. Some is also derived from Russia and Italy. China is said to contain rich deposits of the ore, but thus far they have never been worked.

Antimony.

213. Antimony usually occurs in pockets in veins pro- ducing silver, lead, zinc, or iron, and sometimes the ore is disseminated through the minerals carrying the above named metals. Antimony is also a constituent of a number of different ores, but the ore from which practically all the commercial supply of the metal is derived is the sulphide (stlbnite). This compound can always be distinguished by the readiness with which it fuses. It can be melted even in the flame of a candle. It can also be distinguished by its characteristic reaction before the blowpipe. The Stales producing antimony at present are California, Utah, Mon- tana, Idaho, and Nevada. Some ore is also produced in New Brunswick and in Old Mexico, but most of the antimony of commerce comes from European ores. Some is also derived from Japan and from Australia.

Platinum.

214. Practically all of the world's supply of platinum is at present derived from placer deposits, in which it occurs in the metallic state and usually alloyed with a small amount of some of the other minerals, as silver, copper.orsomeof the

Geology.

heavy metals of the platinum group. Platinum is known to a constituent of several different ores, and especially of thn nickel and cobalt ores. In the Sudbury district in Ontario,! some of the metal has been obtained as a by-product durinJ the electrolytic refining of the nickel and cobalt ores from these deposits.

When the platinum occurs in placers with gold, the tw0i metals can always be separated by inspection, for the smatll amount of other metals alloyed with either of them does not W materially change their respective colors.

MINEHAL Pt'Et.S.

2 IS. Coal Formation*.— The minerals which com under this head are considered under the subject of coal i; the Paper on Mineralogy. No coal of commercial impor-1 tance is found below the Carboniferous period, owing to Ihqfl fact that up to this time there was not sufficient vegetatioal to produce carbonaceous matter in any large quantities-. I All the formations succeeding the Carbonaceous period con-J tained beds of coal when the conditions for its formatioi were present. The beds in the later periods are liable to be composed of lignite or brown coal, but in some cases meta- morphic action has changed these into bituminous, or often* to anthracite, coal.

316. Impurities. — The value of coal to a large Octenfl depends upon its freedom from impurities. These impurt- ties may be considered under three heads : (1) Those whicltl take heat from the coal or reduce its beating efficiency.J without leaving any residual components, such aa ash, without having any special effect upon the furnace or o chamber in which the fuel is bumed. To this class belonj moisture or water and nitrogen gas. (2) Ash, or the residit which remains after the coal has been burned. (3) 1 terious elements which pass into the gases and attach t] furnace or chamber in which the fuel is employed,

217, Ash, — Under the second head of aah must be ci sidered all the materials composing the residue left Jiftei

§ 37 Geology. 115

the coal is burned. When the ash is practically silicious and has a gray color, it is, as a rule, harmless. If colored red or brown, it indicates the presence of iron, and the presence of iron, lime, or alkalies usually produces an ash which fuses into a slag or*cinder, thus stopping up the grates and possi- bly attacking the grate-bars or walls of the chamber in which the coal is burned.

218. Sulphur and PhoHphorus. — Under the third head come sulphur and phosphorus. The sulphur is gener- ally present as iron pyrites, and the sulphur passing into the gases attacks the furnace or boiler, thus doing consider- able damage; and in case the coal is used for domestic pur- poses, it may give rise to foul-smelling and deleterious gases, which find their way into the dwelling. Sulphur is also sometimes present united with calcium to form gypsum. Both the iron and the calcium pass into the ash and become unwelcome constituents of the same. Phosphorus is usu- ally present in small quantities, and it enters the gases in much the same manner as sulphur does, but if the coal were used in the manufacture of iron, both the phosphorus and sulphur may enter the iron and so reduce the quality of the resulting product.

219. Value of a Coal Deposit. — The commercial value of a coal deposit depends upon the purity of the mate- rial, the thickness of the seam, and its location, both in regard to the adjoining rock and property, which aflfect the facility with which it can be worked or mined, and its location with regard to the railroad market, etc.

pktkom:um.

220. Petroleum is a general name given to a class of hydrocarbon oils of varying composition and degrees of fluidity. Sometimes the oil occurs in such a thin and pure condition that it can be burned for lights without subse- quent refining, while in other cases it is of sut'h a character that it can be used for lubricating without previous refining.

116 Geology. § 37

Most of the illuminating and lubricating oils, together with such products as vaseline, paraffin, etc., are derived from petroleum during the process of refining. Petroleum usually has a disagreeable odor. It is found in much the same geo- logical horizon as coal, though it may occur in*paying quan- tities in rocks below the Carboniferous. The petroleum usually occurs in sandstones or conglomerate or limestone, filling the pores of the rock very much as though it were contained in a sponge. The porous rock is usually underlaid and overlaid by clay or shale formations, which are imi>er- vious to the petroleum. In the Province of Ontario, in Canada, petroleum is found in the Corniferous, which is the Lower Devonian ; in Pennsylvania it occurs in the Upper Devonian; in West Virginia and Ohio in the Carboniferous or Upper Devonian; in California in the Tertiary. Hence it will be seen that petroleum may be looked for in most geological horizons, providing the conditions for its forma- tion and storage are present.

Natural Gas.

221. Petroleum is usually associated with more or less hydrocarbon gas. which is commonly called natural gas. In some rcijions there apjKirently was not a sufficient amount oi carbonaceous matter to form the petroleum, and it has all been rediued to natural ias and some heavy carbon compound as bilunien or a form of coal.

222. Hiiunu n a.vi .isphaiiuni are names applied to car- bvMuieevnis evMnpouiu'.s v f a pitv :--;:ke nature which occur in var:vi:s pans of : iu- w vv'.vi. Aspr.altum is especially abun- daiu a:vu:u! :!u iVav: Sea. :- A-ia, and in the island of Ti:n:.:.iv!. v:Y ilu o! S;:h Arneriea. In the latter of solivi :v:v:\ Iv- v:. in.iivx.i: :n ::;e center vf the lake is Kn:;nv; .n,.;v ; :a: vf :hc sa-o or similar com-

§37

Geology.

position are found in a number of places in both North and South America, and usually find a ready market, providing they are situated so that the material can be transported from the deposits with ease. Deposits of grahamite (gilson- ite) occur in Utah and have been quite extensively worked. The material is used for making varnish, insulating electric wire, etc. Deposits of sandstone or limestone containing bitumen are also found in many localities, and are worked for use as paving material. California furnishes the most of the asphaltic limestone.

Salt.

223* Salt occurs in nature, both in solution, as in the sea, salt lakes, springs, or wells, and in deposits of halite or rock salt. Both are of commercial or economic importance. Salt occurs in all rocks, from the Silurian down to those of the present time. There are extensive deposits of halite in Europe, North Africa (where it occurs as great hills and extended plains), in Asia, South America, and in various por- tions of North America, as western New York State, West Virginia.Louisiana, Michigan, Kansas.andmost of the Rocky Mountain States. It also occurs in Canada and Old Mexico. At present salt is being produced from the rock-salt deposits of Louisiana, Kansas, Michigan, New York, Utah, Nevada, and California. It is also produced in various por- tions of Europe and Africa and in other parts of the world. Much of the salt of commerce is obtained by the evapora- tion of sea-water, of saline solutions obtained from springs, wells, or lakes.

Gvpsl1M.

224. GcoloKlcnl Occurrence. — Gypsum deposits are usually associated with those of salt, but have a wider range than the salt deposits. Gypsum is found in the rocks of all geological formations, in some cases even occurring in con- nection with volcanic formations.

118 Geology.

225. Productive Regions. — Gypsum is produced Michigan, Kansas, New York, Ohio, Texas, Iowa. Virginia* ' South Dakota, and small amounts have been derived from California, Colorado, Oklahoma, Montana, Utah, and Wyo- ming. It is also produced in Nova Scotia and Mexico. The material is of widespread occurrence and is mined in nearlw all civilized countries.

226. Alabaster.— Alabaster is pure massive gypsum] and when of good quality is employed in the manufactur&jl of statuary. The greater portion of the alabaster used for j statuary and vases is obtained from Italy, though some of] the gypsum deposits of North America contain sufficiently I pure varieties for this purpose. At times, pure massive 1 gypsum is treated chemically and thus made to represent variegated marbles. In this form it is employed fof J internal decorative purposes in buildings, etc.

Bt'Il.DING STONK.

227. Rsseotlal Quallflcatlons. — The essential quali- '

fications necessary in any stone to render it a good building stone are a firm texture, a cementing material that will not be softened or disintegrated by exposure to the atmosphere, and that will not undergo chemical changes such as break or split the stone. The stone must also be free from par- ticles of material which would undergo chemical changes, either breaking or staining the material. Among such materials may be mentioned especially iron pyrites. A fine texture is also desirable, and stones are often considered better fitted for this purpose when they will receive a high polish.

228. Varieties of Bulldlns Stone.— Among the

most common building stones obtained from the stratified or unaltered rocks may be mentioned sandstone and lime- stone. Occasionally a sandstone is employed which con- tains considerable argillaceous material.

229. Among the varieties of building stone obtained from the massive metamorphic or altered rocks may be

§ 37 Geology. 119

mentioned sandstones which have been converted into quartzite, or have only been partially reduced to quartzite, gneisses, granites, etc., which have been derived from sand- stones or argillaceous states, and marble which has been derived from limestone.

230. Marble. — In the case of marble, sometimes the metamorphic action has not been sufficient to destroy the fossils contained in the limestone, and they may add to the beauty of the marble. Marble varies in color from white to black, and includes all shades of red and blue, the color being caused by impurities, mostly. iron, contained in the original limestone. Statuary marbles are white, hard, semi- transparent, fine-grained, and are derived from the fine limestones of the older geological formations which have undergone thorough metamorphic action. The best marble for this purpose comes from Italy.

231. Granite. — Granite varies in texture and shades of color according to the size and character of the grains composing the same, and according to the color of the vari- ous ingredients and the proportion of each in the stone. In color it varies from light gray to red, and for building or monumental purposes should have a fine texture and be capable of receiving a high polish.

232* Sirpetttine. — Frequently serpentine or similar rocks are found capable of receiving a high polish and are used as building materia), especially for internal ornamenta- tion.

233. Sandstone. — As a rule, the brown or red sand- stones in which the cementing material is largely composed of iron are more durable than those in which the cementing material is composed of argillaceous or lime material.

234. Linifstonc. — This should be firm and, as a rule, close-grained to be a good building stone.

235. Flagstones. — Frequently deposits of argillaceous sandstones occur which will split into large flat slabs suitable

120 Geology. § 37

for flagstones. The splitting occurs along the laminations or bedding planes.

236. Slate. — The slate which is employed for roofing and similar purposes is composed of a hard argillaceous slate which has undergone thorough metamorphism, and, as was stated in Art. 64, the slaty cleavage is frequently inde- pendent of the bedding planes of the deposit, as illustrated by Figs. 29, 30, and 31. In the United States most of the slate quarried comes from Pennsylvania, New York, Ver- mont, Maine, and Virginia, though good deposits occur in many other States where the rocks have undergone meta- morphism, and some slate is produced in a number of Western States. Fine slate is also produced in England and on the continent of Europe.

Clay.

237. Under the head of clay may be considered all the forms, ranging from pure kaolin, which has been derived from the decomposition of feldspar and is used in the manu- facture of porcelain or for glazing paper, to the more imperfect varieties employed in the manufacture of brick, tiles, drain-pipes, heavy crockery, stoneware, etc. The presence of iron in the clay makes the resulting product red or brown.

Ordinary firebricks are made from clay and silicious material or from clay containing sand or silica.

Most of the supply of clay for commercial uses is obtained from surface openings or clay banks, but in order to obtain more uniform products, a number of works are operating underground clay mines.

238. The products manufactured from clay vary in the percentage of clay they contain, all the way from porcelain, which is made from practically pure kaolin, to the silicious firebrick called dinas brick, and which are made from silicious material or crushed quartz, together with a little

§ 37 Geology. 131

milk of lime or a very small percentage of clay in the water employed for moistening the material before it is molded into the bricks. Such bricks may cohtain as high as silicious material.

Phosphates.

239> Phosphates occur in nature in two forms, in one of which they are available for plant life, and in the other of which they require treatment with acids before phosphoric acid is liberated. Some marls, as the greenstone or glau- conitic of the Cretaceous and Tertiary, of New Jersey, con- tain phosphoric acid in such a form that it is available for plant food.

Phosphorus also occurs in the mineral apatite, which is a phosphate and chloride uf lime. This occurs in many parts of the world, and has been mined in Canada, Massachusetts, New York, and some other locations. It requires treatment with sulphuric acid to render the phosphoric acid free or soluble.

Most of the phosphates employed in the manufacture of fertilizers are obtained from beds of calcium or lime phos- phates, and require treatment with sulphuric acid. The material is produced in Florida, North and South Carolina, and Tennessee, in the United Stales, while in Europe it is produced in a number of countries, but the majority of the foreign product comes from Algeria.

240. On the continent of Europe, the regular phosphate rocks have been, to a large extent, displaced in the manu- facture of fertilizers by the use of basic slag, resulting from the basic process for the manufacture of iron and steel, and in which many iron ores high in phosphorus are employed.

241. Guano.— Guano is a natural fertilizer in which the phosphoric acid is available for plant life. It consists of the excrement of sea-fowls and is found in dry islands in the Tropics, especially off the coast of Africa and Australia.

Geology.

8Ul.Phub.

242. Sulphur is found in a free condition in volcani regions, where it has been deposited by sublimation. also occurs at some sulphur springs, where it has beeafl deposited by the decomposition of the sulphur gases, bad the greater part of the world's supply comes from deposit! found in gypsum, bituminous marl, or hmestone. sulphur is also manufactured from iron pyrites. Sulphur in ordinarily obtained from the ores by distilling, or by setting fire to the material so that the sulphur melts and flows out! of the lower part of the furnace or kiln. In the Island of J Sicily, in the Mediterranean Sea, sulphur occurs gypsum in the Tertiary deposits, and it is from this source j that the greater part of the world's supply comes. The j sulphur exported from Japan is found in volcanic regions ' and was deposited by sublimation. Deposits also occur in ' California, Nevada, Wyoming, Utah, and New Mexico, in most of which the sulphur is free. In Louisiana extensive deposits have been discovered under the swamps in or near the delta of the Mississippi, but they are so situated that it is practically impossible to recover the sulphur by ordinary mining methods. These deposits are either Cretaceous or Tertiary. As has been previously mentioned, iron pyrites are frequently mined for the manufacture of sulphuric acid, [ and sometimes a portion of the sulphur is obtained in a frea ] state.

Silica Pou Glass.

243. Glass is, generally speaking, a double silicate of " potash with lime or lead, or a double silicate of soda with lime or lead. If the glass is to be pure or clear, the silicate must be free from iron and other impurities. Sands fit for this purpose are obtained on the seashore and in certain sandstones of almost all ages, from the Silurian up to the present. Glass has been manufactured on a large scale from sandstones which occur in Illinois, Wisconsin, Missouri, Penn- sylvania, Ohio, Minnesota, New Jersey, and other localities' J in North America. Sometimes glass is manufactured from

§ 37 Geology. 133

flint which has been crushed and is used in place of the sand or silica. This makes what is called "flint glass." For the manufacture of a common or coarse glass for making bottles, a granite containing only quartz and feldspar, with practically no mica, may be used in place of the silicate.

Pigments.

244. Pigments are materials used in the manufacture of paint. Among them may be mentioned the following:

245* Ocher. — Ocher, which consists of an oxide of iron containing water and gives various shades of yeDow, brown, and red. This is found in almost all geological for- mations, and occasionally as surface deposits of recent origin,

246. Umber. — Umber is a variety of ocher, contain- ing oxide of manganese, which gives it a brown color, and upon being calcined it takes on a reddish brown color which is known as burnt umber.

247. Sienna. — Sienna consists of oxides of iron and manganese, together with clay.

248. Barytes. — Barytes is a common constituent of the gangue material of many mineral veins and is used in the manufacture of white paint, together with zinc while or white lead. The supply come.'i mostly from Virginia and Missouri, though it has also been produced in Pennsylvi Michigan, Tennessee, and !

249. Zinc White. — Zinc white is an oxide of zinc which is made from various zinc ores and is usually called zinc pigment. Sometimes zinc ores carrying lead are treated in such a way as to form a pigment composed of zinc oxide and some lead oxide.

Graphitic.

250. CbaracterlstlcB and Uses. — Graphite, or, as it is commonly called, plumbago, is mentioned in the Paper on Mineralogy as being carbon in a higher state of metamor- phosis than is thu case with anthracite coal,

124 Geology. § 37

251. Occurrence. — Graphite occurs in the oldest for- mations or in those which have undergone the greatest metamorphic action. The principal mines producing graph- ite at present in America are situated in New York State, although it is found in greater or less quantities all the way from Canada to the Gulf of Mexico, mostly in the Archean rocks along the mountain ranges. It also occurs in Michigan and in various portions of the West. Graphite is also pro- duced in several locations in Europe.

252. Plumbago is pure graphite, and it is usually found associated with various impurities. It is employed in the manufacture of lead-pencils, and it is from this that it has derived its name of plumbago. It is infusible and is not changed by high temperatures, and hence it is employed in the manufacture of crucibles for the melting of brasses and other alloys. Pure graphite has a greasy feel to the touch and is employed as a lubricant.

Asbbstos.

253* Asbestos is a variety of the minerals hornblende, pyroxene, and serpentine, and is usually found associated with the hitler. It occurs in crevices in the crystalline rocks, but often to a limited extent. When found in long, fine, toiiili fibers, it becomes valuable for commercial pur- poses, for it is infusible and is unaltered by ordinary fire. It is employed as a covering or protecting material for steam-pipes and other surfaces exposed to a moderate degree of heat. The most extensive asbestos mines are situated in Canada, though it is found in a number of the Middle and Southern Atlantic States, in California, and several other of the Western States. Asbestos is also produced in several other countries, a peculiar blue variety being found in South Africa.

Mica.

254. Mica occurs crystallized in veins of coarse granite in the oldest (Archean) rocks. The variety known as muscovite, or white mica, is of commercial importance, and

Geology.

as the plates become larger, the irregularities fewer, and the transparency greater, its value increases. Owing to tlie fact that mica is infusible and is lough, it is employed as windows or for closing openings where it will be exposed to a considerable degree of heat, and yet where it is desirable that the interior can be observed, as the peep-holes in blast- furnaces and cupolas or for the doors in stoves. Mica is also employed for insulating material in electrical construc- tion, and the ground or pulverized mica is employed in con- nection with some lubricants.

lUOKAXITK.

255. Monazite is a phosphate of cerium and lanthanum

containing small quantities of didymium and thorium {TfiO,). The latter is the valuable constituent of the mineral, for it is used in the manufacture of Welsbach, or incandescent gaslights. Monazite is found in various granitic rocks, and owing to the fact that it is a very heavy mineral, it collects in placer deposits similar to gold or tin- stone. Considerable of the material has been obtained from such deposits in North and South Carolina, and it is known to exist in some of the Western States, but at present practically all of the world's supply comes from South America.

250. Alum is obtained principally from alum shales, the most desirable of which are pyritous and clay rock con- taining disseminated coaly matter. Such deposits occur in the coal and lignite regions of Europe, and it is from them that the principal supply is obtained. Alunite, or alum- stone, is another source, and is found in volcanic regions, though it is not common. There are valuable alum shales in a number of locations in Western North America, but thus far nothing has been done towards their development.

126 Geology. § 37

Borax.

257. Native borax is found in several places, but it is also obtained from native boracic acid and from the mineral ulexite. The usual occurrence is in the mud at the margin or at the bottom of saline lakes, also as incrusta- tions in marshes which are dry at times. In the former con- dition it is found near Clear Lake, in California, and in the latter, to a considerable extent, in Nevada, from which most of the product for the United States is obtained. Sev- eral marsh localities in California are yielding good supplies.

Soda And Potash Salts.

258. Soda and potash salts occur in nature in a number of forms; the most common soda salt, that is, halite or common salt, has already been described. The other salts of soda, as the carbonates, sulphates, etc., are found in the beds of dry lakes or in marshes which are dry a portion of the year. Such deposits exist in a number of places in western North America. Nitrate of soda occurs in vast deposits in Chili, in South America. Small amounts of it have also been found in caves in all parts of the world. Potash salts arc ' found in a number of locations, but at present practically all of the world's supi)ly comes from Stassfurt, in Germany, where it occurs in connection with deposits of halite or common salt.

Gems Anh Gkm Stoxes.

259* The most important precious stones have been mentioned and described in the Paper on Mineralogy and the location in which most of them occur has been given, but there are a few points worthy of notice. Most precious stones belong to the older rock formations, as granite, gneiss, porphyritic rocks, etc., and are generally found in the debris resulting from the disintegration of such material. Certain

Geology.

diamond- bearing soils are of comparatively recent age, but they are made up of the constituents of older rocks.

260> Corundum not only furnishes the valuable gems, but also the material employed as an abrasive. Corundum of good quality for this purpose has been found in several of the Eastern States of the United States, previous to which most of the world's supply came from Asia.

261. Diamonds. — Diamonds have been referred to in the Paper on Mineralogy as being pure crystallized carbon and as representing the highest or purest form in wiiich carbon occurred in nature. In India, diamonds are found in a conglomerate made of rounded stones cemented together; in America a few have been found in flexible sandstones, mostly in the southern portion of the United States; in Australia they occur in gold-bearing conglom- erate ; in Brazil the greater portion of the supply is obtained from a conglomerate of white quartz pebbles and light- colored sand, sometimes containing yellow and blue quartz and iron sands. In South America the diamondiferous alluvial deposits consist chiefly of nodules of granite, basalt, and sandstones, in which are found garnets, jasper, agates, etc., associated with diamonds. In the East Indies, diamonds are often found in the river gravel, associated with topaz, garnets, zircon, spinal ruby, native gold, tinstone, etc. At the Kimberly mines, in South Africa, the diamondiferous ground forms a pipe or chimney surrounded by formations totally different from the payable rock. The country rock is made up of red, sandy soil on the surface, underneath which is a layer of calcareous tufa, then yellow and black shales, and below this hard, igneous rook. The diamond- bearing ground consists of " yellow ground " (really decom- posed "blue ground "), which is comparatively friable, and, deeper down, the " blue ground," which is a hydrous mag- nesian conglomerate, which is usually so hard that it requires blasting with dynamite. The blue ground is of a dark bluish or greenish gray color and has a greasy feel. It is mixed

Iss

J I

Dortions at bouldars of v&riuus ranlc such an BeCEieo-

vitb portions of boulders o£ various cocks, sack as eerpeo- tine, quartzite, granite, etc. All the blue ground has evidently been subjected to heat. The gems are in the material which binds the rocks together and not in the rocks themselves. Diamonds have been found in America, Rusua, Australia, New Zealand, Borneo, etc.

Prospecting.

Preliminary Education And Preparation.

1. To save a vast amount of time and futile labor, the would-be prospector should acquire all the knowledge he can, both theoretical and practical, pertaining to his chosen calling. He should learn in what rocks and under what conditions he may reasonably hope to discover certain min- erals, so that he may not be found looking for coal in granite, nor for gold and silver veins in the unaltered rocks of the flat prairie. Hence, a knowledge of the elements of geology, of the different kinds of rocks and minerals, their appear- ance, associations, and value, and also some knowledge of panning, assaying, and blowpiping, are essential.

2. One of the best preliminary educations is actual work in the mines and mills, where the student may get an idea of the ores, how they occur in nature, and their relative value. A good plan is to go from district to district, study- ing the ores peculiar to each district, their peculiar mode of occurrence, and, in fact, the entire geology of each district. He will find, for instance, that the ores and mineral condi- tions occurring in different formations, as limestone, granite, and volcanic rocks, vary as widely as the rocks themselves, and also that the character and mode of occurrence of ores in the same class of rocks are subject to local variations in the different districts he may visit. This varied experience will prove invaluable to him, and there is no other way of acquiring it. Many valuable and well-defined ore-bodies were overlooked in the early days of mining, and are even now, because the prospector's experience had been confined

§38

t sRosPEcrnre. § m

tt a fev peculiar vBrietioB of ritck iKxiuTiiip hi tht* panicu- ]ar be vraF zaiaed, and hr {rtes tiiroujrb 'thc mountains diligentlv seardiiQcicir a duiiicau of the deposit ti) vrfaicfa fais slodv faaf bcsen cunfined, frequenth' passins; iivtrr niu(di riciMn* deptwhs, wiiicdu Id his iimiitd idcn of are depusils. prewmi nt> mineral siirns at all.

3L £k will al0i find h tS |n%at advanxapt- ii> kit- alik* to retxgniae the varitms rocks, mil onlj In- cliMe cxaminaxicm uf hand aptscimcais, taxt Inr tfacir fyencra] apjHmTHim- hx the field and the (dtasaxrtenstic fimuB tfarv assuntt- in lai masiiies. Thnfi, lulk buih of Jimcfiiimt:, sandsiont:. or otfaer ivtsdimtmtanr rock Ixave an-entirehr dxfferem aiiiKuiranrxiram tbosr tximposed ti rugged giKsdi and areas (C inrrttly tTig>- iiv rock difiplaj' cSuractcrifdJcs dxSeriniiiToixi hoih of xhcjie. UiUs made up ttf aedimffntairr rock nsualhr huvt- fonorah, rounded nalUxwfi, or fiow Iud distinru miruui: ridires; of istxaia. GraxoMr apt to be in inasisiivr iaiirrTi. irxdi bold, ncpod imtlixMSB. Lara Anrvare aju iv apjituc rjQK ijS JMOg, ]erl taUe-Sa&dfu villi the peculiar rvirumTuir lure more or Itses prxntonnoed. Tbrir bitri.mTii! profile ivff ibem a striking ibou mibrr id.o.:.o.ii::. lApitrAT-

ft. Th<r btu'JtrKi >h'/uld learn the use f : i.k. .Ir. ., Mji?>t:rij<-|/'/w::r By workinjj arour.i a o. ::ce:::ra::r: r.r.'." h: w:-i I:arn lo <hstiri'ui>h between mineral an-i ganiv. r.vk, itiA \ty S'tzXMV 'fTK in a mine he will acquire an ir.v.v.izve fa< iilty of r.'r/j{nizin;{ rih re from {.NM.r .re vr Kirrxrn gangue alrn'st at sight. A little knowledge ut cari'rntry

r

§ 38 Prospecting. 3

will enable him to make a hand-winch, and a few lessons in blacksmithing will teach him how to temper and sharpen tools. These are important qualifications, for his calling frequently takes him to places miles from the nearest carpenter or blacksmith shop. He will soon learn to crush quartz and pan it to see if it carries any gold, and from other prospectors he will pick up all sorts of labor-saving dodges and makeshifts, such as are used bv them in the field.

VSE OF GBOIGICAI. MAPS AlVH SBtTIOIXS.

6. As soon as a mining district comes into any promi- nence, the Government causes a complete geological survey of it to be made, and from the notes of this survey a report is compiled on the district. All important geological and mineralogical features are shown in vertical sections. The student will find these reports a great assistance in his study of the various regions. If in the vicinity of one of the noted sections, he can not take a better lesson than, with map in hand, to follow the section through all its details, noting carefully the appearance of the various strata, the occurrence of veins and faults, etc. This will familiarize him with rocks and practical geology. Fig. 1 is an example of a geological section, showing a generalized section of the Rocky MoTintains in Colorado, with the economic products in the different horizons and strata. Fig, 2 in a similar manner presents a generalized vertical section of the earth's crust in Colorado. Such an example is rarely, if ever, found complete in any part of the world, but portions of it may be found in various cliff sections and caftons. A remarkable example is that of the Grand Cafion of the Colorado River, where a thickness of the earth's crust is exposed for over a mile in depth, yet even this great cafion shows but a few of the great formations composing the whole upper crust of the earth; hence, many sections, in many places, must be studied and put into a generalized section like Figs. 1 and 2 if we would get a complete idea of the whole.

Prospecting.

7. A general section, giving the different geological for.l

mations and periods as they would occur in a perfect section'l

made up from different parts of the earth, has been givetta i'l the Paper on Gfology.

§3

Prospecting."

8. The use of fossils for determining the different geo- logical ages or periods has been treated in the Paper on Geology, and illustrations of some of the fossils which are most characteristic of the different periods given.

9. A good example of the use of fossils occurs in con- nection with certain limestone beds occurring at Aspen and Lcadville, Colorado. Certain of the beds carry very rich lead-silver ores, and they are distinguished from similar lime- stone in the same State by the fact that they carry certain characteristic fossils of the lower Carboniferous age. The prospector will find fossils useful in giving a general idea of the geological horizon in which he is operating, but to deter- mine the age of any particular bed in a given locality, he will have to become familiar with the fossils of that region.

Phospectou'S Outfit.

10. The prospector's outfit is very simple; the simpler the better. It usually consists of a donkey or pony packed with a couple of heavy blankets, as the nights in the moun- tains are nearly always cool, a small, portable "A" tent, cooking utensils, etc., such as are found in every mining town, a supply of flour, sugar, bacon, salt, baking-powder, and coffee sufficient to last usually about a month, an ax, and prospecting tools. These latter consist of pick, shovel, pan, or horn spoon for separating the gold, hammers, three or four drills of assorted lengths, a "spoon " or scraper for cleaning out drill holes, a few pounds of blasting- powder or dynamite with fuse and caps, an iron melting ladle, a pocket magnifying (ore) glass, and sometimes a blowpiping outfit or even a small mufBe furnace, for assaying, packed on an extra animal. A rubber blanket will be found handy, as the prospector is apt to be exposed to violent and frequent rain- storms. A rifle or shotgun is also considered indispensable where game is plentiful. Carry no unnecessary articles.

11. In the new part of the Lake Superior region, in much of Canada, and in Alaska, there are so many swamps

Prospecting.

that it is impossible to use packhorses, and in such a cas< th prospector has to take one or two men as porters, or, ; they are called, packers. Each one of these men will carryi from 100 to 125 pounds.

PROaPBCTING FOR PLACBR DEPOSITS.

12. Prospecting may be treated under two heads: hunt*! ing for loose gold, platinum, or tinstone in placers or alltt vial deposits, and hunting for metal-bearing ores in place lodes or veins.

13. Placers are deposits resulting from decora positioife and wearing away of metal or mineral bearing rocks by* natural agencies, and the accumulation of the fragments in beds lower down in the mountains, where they have been carried by water, glaciers, etc. The principal materials obtained by placer mining are metallic gold, metallic plati- num, tinstone or oxide of tin, monazite, and precious stones; these all being of sufficient specific gravity to become con- centrated by the action of water, and at the same time being sufficiently stable to resist the action of the atmos- phere. Water soaking into the surface and cracks of rock expands on freezing and causes the rock to crack and flake off, and the scales and dust resulting are carried down by streams and freshets into the rivers below. The action of the water separates the mineral portion from the lighter material, and its greater specific gravity causes it to sink to the bottom, while the dirt is carried along with the stream until it reaches some point where the current slackens, when it is deposited. Naturally, the larger particles of mineral sink first, accompanied by the coarser portions of the gravel, so that it would be unreasonable to expect coarse gold or mineral deposits at any great distance from the mother-lode, though fine gold and mineral may be carried great distances, particularly in streams having the steep grades and high velocities of mountain creeks, which will carry even quite coarse gold some distance. In a somewhat similar way, glaciers wear away the rocks over which they pass, and.

Prospecting.

melting, deposic the debris in moraines and windrows along their paths. These deposits are worked over by the streams which take the place of the glaciers, and from them many of our richest placer beds are formed. The prospector, fol- lowing up an ancient river-bed which the water has long since subsided, can, from his observations of modern streams, recognize places where there must once have been an eddy, where the stream took a sudden drop over a bench, or where it hollowed out a pot-hole under a waterfall; these places he should carefully prospect. When possible, he sinks at once to bed-rock, as there the mineral is naturally thickest, and on reaching it he examines it closely, searching with his knife or pick for scales or grains of mineral hidden in the crevices of the bed-rock. He also has an eye for rusty streaks in the gravel bank or for dark lines of "black sand " or magnetite, as the iron minerals forming these streaks are, from their great specific gravity, commonly associated with gold and other valuable minerals in placer deposits, and hence each one of the streaks represents a possible zone of " pay dirt."

14. Thus far, the world's supply of platinum has been derived from placer mines. The prospector, looking for gold placer deposits, should examine any heavy particles of white metal, to see if they are not platinum, since platinum is as valuable as gold. The metal can be distinguished from native silver by its not being attacked by any single acid.

15. Pannlne. — The prospector tests the bank from time to time as he descends, by "panning." The pan he uses for this purpose is about 10 or 12 inches in diameter on the bottom, 10 lo 20 inches at the top, and ai to 3 inches deep, pressed out c single sheet of Russia iron (see Fig. .'i). The rim is sometimes strengthened by turning it over a wire. The manipu- lation of the pan, while quite simple, requires considerable practice before one can become expert. The manner of testing is as follows; The prospector fills the pan about half

Prospecting.

full of water, throws into it a shovelful of dirt, first picking out the larger pelibles, and works the whole mass thoroughly with his fingers till all the clay is reduced to a fine sand and mud. The muddy water is then carefully poured off and the pan refilled with water. Now he takes the pan in both hands, one on either side, and, inclining it slightly away from him, gives it a peculiar circular motion. At each revolution a portion of the water slops over the depressed edge of the pan, carrying with it some of the sand and lighter minerals, the gold, owing to its greater specific gravity, remaining at the bottom. He continues this until there i only about a teaspoonful of sand or matter left, in which hel can see the specks of gold shining. He then pours nearly all the water off, and moving the pan to and fro, the gold gradually collects, and a slight tilt and jerk of the pan to one side will carry the sand off towards the other, leaving the gold in an orange-yellow streak. This orange-yellow color J of gold usually suffices 1 to distinguish it from iron pyrites, which fe brass-yellow, or copper I pyrites {chalcopyrite) which is bronze I However, if the opera- 1 tor is still in doubt, the' ! malleability of gold and ' 1 its insolubility in any single acid, in connec- tion with its color, are infallible tests. The ' operation of panning is

soniewiiii lacLliiated if one edge of the pan is kept sub- merged beneath the surface of a pool or quiet stream of water during the entire operation up to the separation of the "color" from the heavy sand in the pan (see Fig. i).

charge

By

ting roughly the le value of gold

veight of dirt in a pan extracted therefrom, an

g 38 PROSPECTING. 9

approximate estimate can be made of t!ie amount of gold in a ton or a cubic yard of the placer dirt, and from this a rough estimate of the yield of the entire placer may be made if desired,

Locating Placer Claims.

17. The location of a mining claim, either placer or lode, consists In defining its position and boundaries, and in doing such other acts as indicate and publish the intention to occupy and hold it under the laws of the government within whose domain it lies.

United Staters Practice.

18. Area and Shape of Placers. — The amount of ground which may be located as a placer is limited to 20 acres to each individual or person, a corporation being con- sidered as an individual, regardless of the number of its incorporators. An association of persons {not incorporated) may locate a claim in common, not exceeding 20 acres to each individual, or l(iO acres for the entire association. It requires at least eight bona fide locators to lawfully claim lUO acres.

19. The shape of the placer claim is immaterial, it usu- ally following the course of the stream or deprjsit. Unlike lode claims, the exterior lines of placer claims can not be extended over other placer claims. The dimensions may vary as much as desired so long as they do not include more than the legal area. One acre equals 43,5S0 square feet, the area of a square 208.71 feet on a side,

20. Discovery or Knowledge of Mineral Value. — It is necessary for a valid location that the land be known to have mineral value, either by discovery or previous knowledge, and in the case of an association a separate dis- covery is required on each 20 acres.

21. Location Notice. — Having discovered a placer deposit, the prospector is alloweJ 30 days from the date of

10 pRospBcmra ts

discovenr to complete the locatioo amd record. He posts a preliminary notice similar to the one here shorn:

Pretty Joe Placer Cladl

The underMgned claims 90 acres for placer-miniiis pnrpoaeSh with to dajs from date to complete location and record.

Sept. SO. 1807. Jammb E. UvmMAY.

m

This notice is posted conspicuously at the center of the claim or at some point where prospecting pits give evidence of actual work.

22. Having completed his location, the prospector replaces the preliminary notice with the regular location notice, of which the following is the common form:

Pretty Joe Placer Claim.

The undersigned claims 20 acres for placer-mining purposes, as BUlced on this ground. Date of discovery. Sept 20, 1807.

Jambs E. Murkat.

23* The dimensions of the claim, instead. of its total area, are sometimes specified. In IdahxO, posting and sta- king must be done within three days after discovery.

24, Staking:. — The locator is required to mark each angle of his claim by a substantial post, sunk into the ground at that point. In Idaho the size of the said sub- stantial post " is fixed by law at 4 feet high and 4 inches s(juare, and these dimensions are tacitly accepted through- out the country. Where posts are not obtainable, the monuments usually consist of mounds of stone 3 feet high and ;j feet in diameter at the base. These monuments must be tied, or referred by distance and direction, to permanent monuments or natural landmarks, so that thev can be readily located in case of controversy.

25. The labor or improvement necessary to hold a placer claim is the same as that for a lode claim — worth annually. This must be actual work in developing and improving the property. Where several claims are being worked as a group, all the work may be performed on any

S38 Prospecting.

one of the group. The record of location must be placed with the recorder of the county or district in which the claim lies.

British Columbiah Practice.

26. The laws of the Canadian Government in reference to placer mining are much narrower and more stringent than those of the United States. Miners or mining com- panies are obliged to take out "free miner's" certificates, at an annual expense of for individuals, t50 for cor- porations capitalized for 8100,000 or less, and tlOO for corporations with over tlOO.OOO nominal capital, before they are entitled to the privilege of prospecting and mining in Canadian territory. This regulation also applies to lode mining. Violations render miners liable to a fine of |35 and costs.

27. Size of Claims. — One hundred feet is the uniform length of all individual claims, except those granted to the discoverers of districts. Such discovery claims may be 400 feet in length for a single discoverer, IjOO feet for a party of two discoverers, 800 feet for a party of three, and 1,000 feet for a party of four. For larger discovery parties only the ordinary length of claim will be granted for each additional person above four. A "creek discovery "includes all ground to the top of the hill on each side of the creek, so long as the total width does not exceed 1,000 feet.

Creek elaims extend laterally from base to base of hill or bench on each side, unless this distance be less than 100 feet when they are 100 feet square.

Bar diggings are in width the distance from high-water mark to the edge of the stream at its lowest water-level.

Hill diggings 3. 100-foot base-line parallel to the main direction of the stream, and the side lines extend to the summit of the hill, at right angles to the base-line. All other diggings are 100 feet square.

28. 8laliin(£, — The method of staking and posting notice is similar to that in vogue in the United States. The

claim must be as nearly rectangular as possible, following the general course of the river, and the corners marked by "legal" posts, 4 feel high and 4 inches square. One of these posts must be marked " Initial Post," and on it must be posted the location notice, similar to the American form previously given. If any side line exceeds lOtJfeet in length, additional posts must be placed along such line, not more than 100 feet apart.

29. RecurdlOK. — The Canadian mining law, somewhat like that of the United States, requires that the location be recorded at the Mining Recorder's office of the mining division in which the claim is situated. The claim must be recorded within three days after the location is completed, il the claimant is within ten miles of the recorder's office, or one additional day for each additional ten miles or fraction thereof.

30. Unlike the American practice, however, the Cana- dian law does not give the miner permanent ownership of

the claim. Placer claims are recorded for a term of one or more years, and may be re-recorded for another term of years, and during the existence of a record or a re-record the term may be extended one or more years, the fee for recording, re-recording, or extension being $2.50 per year.

31. Abandonment. — If, after recording a location,

and before the expiration of the record, a miner desires to abandon his claim, he is obliged to give notice of such intention to the Mining Recorder, together with a fee of 12.50. His interest in the claim ceases from the date of recording such notice.

32. Work on Placer Claims. — Every placer claim must be worked continuously during working hours, in the open season, by the holder or his representatives. If left idle for a period of seventy-two hours, in the working season, without valid excuse, the claim is considered abandoned and forfeited. A miner is, however, entitled to one year's leave of absence from his claim upon proving an expenditure

§ 3!5 Prospec

equivalent to $1,000 on each full interest in any claim or set of claims, without reasonable returns, or in case of a set of claims, on application signed by all the holders. Such leave of absence will not exempt the holder from the provisions respecting free miners' certificates, records, etc.

33. Free Miners' Prlvllefcet! — Any person holding a free miner's certificate may locate not more than one placer claim on any creek or hill, and not more than two claims in the same locality. He may, by purchase, however, hold any number of claims. He may kill game for his own use, while prospecting or mining, at any season of the year, and may cut timber for mining purposes on any public lands.

Prospecting or mining without a free miner's certificate is illegal, and renders the person so doing liable to a fine not exceeding ic25 and costs. A certificate may be extended for one or more years on the payment of $5 for each year, and if lost will be replaced for (il.

Prospecti\G Lodes Or Veins.

34, In searching for mctai-bearing deposits in place, the prospector meets with conditions quite different from those of the placer deposits. Placer mines differ very little from one another in general characteristics, one placer being practically an example of the whole class; but in the case of veins or lodes, very seldom are two claims found on which the conditions are identical, even in the same district. The prospector is obliged to trust much more to his intuition, and at the same lime more knowledge of geology and min- eralogy is required, if he would work to the best advantage.

35. Having selected a district for prospecting which, for geological or other reasons, he considers "likely," the prospector's first effort is to find '"fioat," Float is vein matter which has become detached from the " mother-lode "

Prospecting.

by nattiral agencies. The fragments roll down-hill, or are carried by waier and snowslides, sometimes great distances from the original ledge. Some of this float may be barren quartz iif other vein rock, while some may be more or less mineralized. Commonly, float is a rusty, spongy mass of rock, stained red or green from the oxidation of the iron or copper sulphides it originally contained. The spongy char- acter of the mass is generally due to the cavities left by the metallic sulphides when they oxidized and dissolved out. These sulphides are also sometimes found in the float in their original state,

Utt. Having discovered float, the prospector endeavors to trace it up to the ledge from which it was broken. Natur- ally, it will have come from a point above that where he discovered it, and rolled down-hili; so up-hill he goes, fol- lowing the course of the stream or slide, which is marked by pieces of float, gradually increasing in size and number as he ascends, till he comes upon the mother-ledge in full view, or a zone where the float ceases abniplly. In the latter case he starts a trench across the probable course of the vein — as indicated by the direction of the float zone— and prolongs this trench up and down the hill until he strikes the vein or becomes discouraged and concludes that "the game isn't worth the candle." If he finds float in the bed of a cation or watercourse, he follows it up the stream till it turns off Up-hill, and then proceeds as just described.

Sampling The Outcrop.

37. Suppose the prospector is fortunate enough to find the vein and trace its outcroppings; he next makes an approximate estimate of the value of his find. Breaking off at intervals along the outcrop fragments of likely-looking rock, he crushes them up to about the size of peas, or even coarser if he has a large sample or the ore is thought to be low grade. He then mixes the sample well on a piece of canvas and " quarters " it down to half the size. This half he further crushes and again "quarters," repeating the

Prospecting.

operation till he has left only a, few ounces of finely pow- dered ore, which, however, represents quite accurately the average value of the samples he has taken from the vein.

38. QuarterInK- — The operation of reducing samples takes the name "quartering" from the peculiar way in which it is performed, the sample being spread out into a flat circular pile, divided into quadrants by lw'> (iimnetrical lines at right angles to each other: two alternate quarters are saved, the other two are thrown away. The method is as follows: The crushed sample is placed in the center of a can- vas sheet and thoroughly mixed, either with a shovel, or, if the sample is small, by drawing the corners of the cloth, one after another, up and over, rolling and mixing the ore within. When ''"' °-

thoroughly mixed, the sample is heaped up in a conical pile. If the sample is large, the operator walks slowly around it, scraping the ore from the apex of the cone towards the outside with his shovel as he goes. This he con- tinues till the sample is re- duced to a flat pile. Through the center of this pile he draws two lines at right angles to each other, which divide the sample into quadrants. ; then shovels away two al- n;rnale quadrants, preserving 1 he other two for further treat- ment. Thus, if, as in Fig. 5, ivc consider the quadrants as n limbered consecutively from

k dt C Md

mmenai get tmaHkr u

pMM'flliVVMVP ftK4L n 1

fnamnA rfiwmt rfifctfy tfceafc af the e

tfirta* ft KAftlf arnrnwl. the pbte , jniai

jM 4ffitaH4 Ciirt Iliii irii.rhi Jii iiM liiing, niiiTiif liltlhc ! M teAwnA l*i the doind itJtfcaewu Ths vedaod of fffrltKtnit Motpln baa been dmod by expcrnacnc to cnv wc-flrmi* rrMlu if carefnlljr done. Tbe roaftins saniplc he mt i'4t in hU paa tor irvt gold mc preacm to be assajed

fW, C'tirft h'juld be tajten to thoroaghlv dean the AtintffllnK rl<'lh aftrr aing, nr the fine and valaable purtkin of ttief)r<<, wliif-h hm Mtlled to the btftiHn and adhered to

the 4 >ilh, may make (he next batch sampled appear valo- aM oViFfi lhntif[)i it htr a trtally larren niek.

Ihwmiku.

4(l> When Ihi: protipcctor finds the rock of the hillside ho witihcB I" i'xartiiiK; fovcn-d with a hier of drift, it is often pimNlliic ri-iti()V(! the oiirlh and expose the rock by the pl-ijcrsti idllcd lioornirijf. This is really ground sluicing to rriiiovi' ihr rarlli. Thi; water is either confined in a reser- viilr iii'ur ihi' Inii, and Hiid<lenly released to plow its way tluwn to llif valh'y. carrying nuich of the earth with it, or a illli-li lit diiK fi''iiii H"i"" iTwk and carried along the hillside until ll KiiiriM ii siillirii-nl height above the valley, when it is nllowi'd t" ll-.w over the hill. Frciiuently the earth in tin' coiHNi' of the water is loosened with a pick, and the BtiTiint niaili- to carry it away. Under favorable circum- Blt>nct". ti man can niovr more earth in a day by booming limn hi' coiilil in several weeks with a pick and shovel.

Prospecting. Locating Lode Claims.

irslTEO STATES PRACTICE.

41. SJe of Claim. — If, as the result of his investiga- tions, the prospector considers the deposit a promising one, he proceeds to "locate " it according to the laws of the dis- trict in which the property lies. The mining laws of the United States limit the dimensions of a lode claim to 1,500 feet along the course of the vein by 600 feet wide, horizon- tal distance — 300 feet on each side of the center of the vein at the discovery shaft. In Colorado, the State Legislature has fixed the legal width of a claim at 300 feet, except in the case of Gilpin, Clear Creek, Boulder, and Summit Coun- ties, where the limit is 150 feet. In all the other Statesand Territories the dimensions specified by the Act of Congress of 1872 — 1,500 feet by 000 feet— hold, and can under no cir- cumstances be exceeded for individual claims. The only provision in the United States mining laws in regard to the shape of the claim is that the end lines titnst be parallel. The side lines may run in any direction so long as they are nowhere more than the legal distance apart, and the location will still hold. They are usually surveyed parallel to the center line, however, and at the maximum legal distance from it, when such a course will not bring them into conflict with other properties, as it is not human nature to give up any land which might be had without additional expense.

42. DIscctvsry Shaft. — To render a location valid in Colorado, Idaho, Wyoming, New Mexico, Arizona, and Mon- tana, a shaft or equivalent opening must be made which shall expose the ore-body at a depth of at least 10 feet below the lowest point of the surface at the opening. In those Slates in which the depth of the discovery shaft is not fixed by law, an exposure of the vein is all that is necessary, and if the vein outcrops on the surface, no digging at all is required. The "discovery shaft" is not necessarily the opening by which the lode was discovered, but merely a con- dition of a valid location, subsequent to discovery, and may

: JMsCam IK9C ai'wtSiSated j£

pffftiminary nr.cirj! at the p;inc disa)Tery. .jf die f-iUow- insf f'-rrei :

Tare blue u>de:

7 Ki iifwlirriii[nft -.Uunia itT liaj -Ui suk. fjacmerr shaft, and thie Iin<'>n(h4 t'. f-'"/'! '>n thia itia.

tinvinx <"m\i\KV-A dLsovery 5ha£c and decided oo the I i/iit. 'li hii ' laim, he substitutes for the preliminary notice, Ht ttn: (Kjinr f'f 'li:'ivery, 'ne of the following fono — the f*'(£"''"' l"'Jili"'i ri'.tj(:

'Ml*- '(Ki:J'. tSJ-i:K UjrK.ilJscoveTedbyMichael A. Kelly,Sept.27, IW7 (liiliri yri f''t northerly and 750 feet w>uthtr1y /rom discovery-. Michael A. Kelly.

'IIm'

IIHlifC

iKiliirf itt nifttomary, Init not necessary. This iilil i'(in>>|ti(:ui)nHly [xisted, either on a post, tree,

§ 38 Prospecting. 10

45. Staking. — Having decided as to the course of his claim, the prospector proceeds to mark its boundaries by means of stakes, or, if these are not obtainable, by monu- ments of stone or earth. A stump or boulder properly marked fully answers the purpose of a stake. The stakes should be at least 4 inches in diameter and 3 feet long, and set 18 inches in the ground. One such stake is set at each

qEhL . —ofW*.. fPoH.

F]G. 7,

corner of the claim, blazed on the side towards the claim, and marked with the name of the lode and the number of the corner. When the center line of the claim is a straight line, a similar stake is set in the middle of each side line, blazed on the inside and marked. If the center line is a broken line, stakes are set at all angles of the side lines and oCBriMC. Ctnter<?Stak.

Dlteovriu.Sha/1 .

CenUr<MalDe.

numbered continuously around the claim, starting with one of the corner stakes as No. 1. Only the stakes at the angles are numbered, center stakes, when present, being merely marked as such. In the Dakotas and Arizona a stake is required in the middle of each end line. Fig. 7 is a diagram of a lode correclly located imder the present law in Colo- rado and most of the other mining Slates and Territories.

Prospecting.

Fig. 8 shows the lines which it is nectrssary to run for the prospect survey.

When a stake can not be driven on account of bed-rocic, it should be 6d in a pile of stones. If, on account of prc- cipitouK ground, it is impossible I" set the stake where it belongs, a 'witness state should be set at the nearest avail- able point along one of the lines of the snrvej-, suitably marked to designate the position of the comer.

Rl|[hlN of Locator. — Having properly located ind rccnrded the location with the Recorder of the

t'jiinly ur district, the prospector is eiilitled to all veins] (ipexihg within his binindaries that arc not already claimed, and may work such veins on their dip, to their full depth,> fcir tilt! iliiitance between the parallel vertical planes of thol end lines. Under no condition, however, can he follow thsV vein outside of the vertical planes of the end lines. If the I vein, in itn di]), turns and crosses the end plane, he loses all I further right to follow it on its dip beyond where it crosses. I Thus, the miner may follow the lode down indefinitely if, asJ in Fig. 9, it rctniiinn within the end planes, Init if it turm

§ 38 Prospecting. 81

and passes out through either end plane, as in Fig. 10, he has no claim to any portion of the lode beyond the end plane.

47. The terms a/tcx and outcrop mMst not beconfounded. Flat, stratified deposits, such as coal-beds, the zinc -ore beds

of Missouri, or even blanket veins, can not fairly be consid- ered to have an apex, or highest point, though they may have a well-defined outcrop. In the cases of coal and zinc beds and stone quarries, no extralateral rights are ever granted, the locator being enlilled only to that portion of the bed vertically underneath his surface location. The case of flat veins and blanket deposits, though coming under another statute, would appear analogous, and is generally so con- sidered by the courts. A location on the outcrop of a vein with a dip of 8° w-is held to give the locator no extralateral rights, and subsequent locations made on the dip of the same vein were held to be valid, with the same restrictions.

cnects the

as a Fig. 13 — is Uk

irf tfce ni5n£, "sohstan- tiiliT ai right angles" — so thai th distance between the end lines, if m'ved in, vould be less than the legal width of the claim, the side lines Ift-come in effect end lines, and the rights of the loca- anes of both side and end

All, // t/>. .f/<,

Cm II, iIm< I... mi

CHH tvlililn llio VHiicU |i].ii

litlr

I'lH one siiif iiii

I ily that p

of liiH Hide lines

twice, as in irlion of the

Prospecting.

Such cases as the preceding are, however, more or less in the hands of the courts, and mining cases are always in doubt till the final decision of the highest court is made. The construction a court may put upon certain phrases and conditions of the statutes is frequently totally unexpected and without precedent, so that the prospector should exer- cise the utmost care in locating his claim, to have it incon- testable. Otherwise, if it shows well on development, he is almost certain to have a few lawsuits over it.

51. The form of the mining claim does not have to he a rectangle, but may be laid out as shown in Fig. In. in which case the line A f/B a is supposed to approximately follow the vein, and the entire length of which must not be over 1,500 feet. The end lines through the point A and B can not be over the full width of the claim as allowed by law, and these end lines must be parallel to each other; that is, the line a d, passing through the

point A, must be parallel to the line r (/, passing through the point B. The side lines are parallel to the center line, and in no place should the perpendicular distance between them be over the allowed width of the claim. These angu- lar claims are used to overcome the difficulties illustrated in Figs. 11, 13, 13, and 14. The stakes are numbered as in the case of rectangular claims, and may start as from the point (T, and be numbered in order, as shown in the illustration.

52. For location notice, it is not necessary that the survey of the claim be tied to a special government monu- ment, patent corner, or section corner, but it is sufficient for it to be tied to natural landmarks or to monuments which can be easily identified. When the claim is finally

Ml la lw cMten fl

jKfMbW. Ar MCMMAT ii Si*

*0xmit Irom iW OovcrwaoaC: M il h;- f

IMTibM*, hr ittay vvUmt [MrickaMr it or otaaia iW pr/rlt- of Mii9MiK irf ytjiag rofahj or a dtfiaitc leaae- la tfc f*lfi/vri, ihr mini2 muM Iw coofioed to the ravcaU plasMs iht'mgh the lnvundaries of Uie property: in otlier W'ltt, IIm; miner in nut attoired to foUov fan rcia under tUiU:T ffen/ti't itrmxtty.

IIMI'MMH t'fl.l'HHIAN PRACXICE.

AA HlxM MiMl (if Clulm. — A mineral (lode)

iliiliii, iiM'.t'llitK I.. iniftiriK laws of British Columbia, iiniv I"-, I'lil 'tin iK-i i'xi...'.l, l/iOO square. v4// angles mint hi- 1 1,1; lit ,111,1; /is ; I hill it. llic rlaiiii must be rectangular. 'I'wii bIiIiiq I.] tliK I liilii) iiiuhI liriiM nearly as possible parallel

Mt.

IIUviivw<',v of Vwlii. T" make a location valid,

I'M' Iii!

1-.I 1.1' iliB.i'Vrir'l 111 |.lmT, (IS iu the American laws,

I'll! till

I'U' nil' III' ii'unliiiJniKt iiH In ..]H-iiint;s, A "discovery

I'l'Ml "

until I'l' I'liui'.l in lu-rti- US iKissiMo to the point of

'H 'riiWuiim |..Mlli'i>iililUiry "Ical post "described

'l.-t

l'l,iM'i luliiiitu in Hiiiith rotiuul'iit.

T.

(tit(i(Mti, lUyuU'* llu- dixo.-v.-ry tvv-i. the Cana-

'xjnU'i n vl'lj'd wl lwv".>ihpr (HVits, (See

Fig. l(j. ) These are set along the line of the vein, not more than 1,500 feet apart. They must be "legal posts," and numbered respectively No. 1 and No. 2. Upon No. 1 post there must also be written the words "Initial Post," the approximate compass In'orini or direction of No. l po.st, and

7ffO"

Iso-

Dlteov

Pott

lao'

no'

m

tPntt

jrrapMt

1100'

Post

DU.Ptt

laso'

iioo'

iOO'

S'l

.Pott.

.VI Pott.

a statement of the number of feet the locator claims on each side of the line between the two posts, known as the "location line." Thus:

Initial Post. Post No. 2—1.500 feet northeasterly. 900 feet of this claim lie on the right and 000 feet on the left of the line from No. I to

No. 3 post.

He is obliged to so mark the location line that it can be plainly seen. If the country is timbered, he blazes the trees and removes the underbrush along the line; if it is open, he sets legal posts, or monuments of earth or stone not less than 'i feet high and 2 feet in diameter at the base, so that the line can be easily traced.

Once set and recorded, No. 1 post can not be moved or tampered with in any way. If the distance between No. 1 and No. 2 is found to be more than l,5{f() feet, the Provincial Land Surveyor can move No. 2 in to the proper point; if, however, the distance is less than 1,500 feet, it can not be changed after the claim is recorded.

S8. RecordloB- — The miner is given fifteen days from the date of location in which to record his claim, if within ten miles of the Recorder's office, and one additional day

PROSPECTING. g 38

tor each ten mllen or fraction thereof beyond this distance. A rlujin not recorded within the lime prescribed wiD be cn*iilrri-d iibandonvd.

AH. Abandonmeat. — The law rcgardingabandonnieiit U the aiiiQ an for placer claims (see Art. 31 ), except that it not tieceiary to work claims continuously ia order to hold them. A free miner can not relocate a claim which he bn* uhundoticd nr forfeited without a written permit from the fioM CummisNioner.

W>. Annual Labor. — Work must be done on theclaim or ill pfojiiinity to it, with intent to develop it. to the nmouni of |ill>0 a year, from the date of recording, and an nflidavlt filed with the Gold Commissioner setting out a detailed ntatemcnt of the work done, before the expiration trf each year from the date of rei:ord. Unlike the American law, lurveyinit done on the claim within one year from the date iif record, to an amount not to exceed tllXi, is counted u development work. Two or more miners may work their claims as a group, after having filed a notice of such inten- tion, and all the work for the group may be done on one claim.

Tunnel Sites.

61. In the United States, any person or persons desiring to do so may claim a tunnel site for the purpose of running a tunnel for the discovery and development of lodes, with the right to hold and work, for a distance of 1,600 feet along their length, all veins not previously known to exist, which may be cut by the tunnel within a distance of 3,000 feet from its "face" or mouth. All lodes cut must be staked and recorded exactly as if discovered from the surface, with the exception that the tunnel discovery renders the discovery shaft unnecessary. The location notice should be set on the surface at a point directly above the tunnel, on the center line of the claim. To set the surface stakes, the approximate dip and strike of the vein are noted where it is

Prospecting.

ar

cut by the tunnel; these are projected up to the surface and the stakes set accordingly.

02. Dump Room. — Each tunnel-site location carries with it the option of locating an additional space 850 feet square at the mouth of the tunnel for dump room, upon the specification of such claim in the location notice and record.

Location Of Tunnel, Bite.

63. The courts are at present considerably at variance in their interpretations of the timnel-site statutes, and no absolute rules can be given for locating and recording claims. It has been practically settled thai the legal "line of the tunnel " means a parallelogram 1,500 feet wide, par- allel to and including the actual line of the tunnel. The

latter need not necessarily be midway between the boundary- lines. If, however, a vein be oblique to the tunnel, the 1,600 feet will have to be taken along the vein, as in Fig. 17; hence the width of 1,500 feet for a tunnel site has no par- ticular legal value.

64. Staking.— The location notice is placed at the mouth of the tunnel. A substantial stake is placed verti- cally over the ultimate end of the tunnel, 3,000 feet from the mouth; this is the end stake. Three or four stakes should be set at intervals along the line of the tunnel

Prospecting.

Is

between the mouth and the end stake. The four corners O the tunnel site are marked by the ordinary "substantial? stakes. Dump ground is marked by stakes at the foun corners.

65. Location Notice and Certiflcate. — The locaticH notice and certificate, in all their essential features, practically the same as the notice and certificate for ordt<9 nary lode claims. The notice must contain a description of the claim, the bearing of the line of the tunnel, and the claim of all lodes discovered in the tunnel and not previously known to exist, with the distance claimed on either side of the line of tunnel. The end stake should be tied to promi- nent landmarks or fixed monuments, and such ties should be indicated in the notice. If dump room is claimed, the claim should be added at the bottom of the notice, thus:

Dump 250 feet square, as slaked.

The location certificate also contains all these features,

but greatly elaborated, with bearings and distances to corner

stakes, distances to intermediate stakes along the line of

tunnel, etc.

66. Annual Labor and Abandonment. — The work done or money expended on a tunnel is counted as annual labor on all lodes opened and developed by it, for each of which HOO worth of work must be done yearly. Neglect to work a tunnel for a period of six months constitutes an abandonment of the rights of the owner to all veins aloi the line of the tunnel, though not of the tunnel itself.

Mill Sites.

67. A (f// Ji>(- is a grant of non-mineral land for poses incidental to mining. The United States statutf further divide mill sites into two classes, according to purpose for which they are to be used. The first claj mill Nlte with lode, is of most interest to the prospecto] Such a mill site is a grant of land, which may be adjacet to the claim of the locator, but not on the lode nor on knon

§88 . Prospecting. S9

or supposed mineral land, not exceeding five acres in area; in some districts the area is still further restricted. It may be used for any purposes incidental to the working of the claim, as for storage room, boarding-houses, ore bins, etc., or for mills for treating the ore from the mine. The crea- tion of this class arose from the necessity, in largely operated mines, for more surface room for the purposes mentioned than is usually to be had, suitable for such pur- poses, within the limits of the claim proper. The applica- tion for a mill site of this class must be made by the owner of the lode claim for which it is to be used.

68< The second class, mill site Tor mill or reduc- tion vrorks, covers all claims in which the application is made for the mill site alone, independent of any particular lode claim. Such a mill site must be used for the purpose for which it is claimed, i. e., a site for a mill or reduction works — incidental uses are not sufficient.

The British Columbian laws do not make any such distinc- tion. Their only provision is that the land be unoccupied public land, and, as far as known, non-mineral. British Columbian statutes entitle the owner of a mill site to : face rights only, reserving all minerals which may be subse- quently discovered on the land, together with the right to enter the property and mine such minerals, for the Govern- ment and its licensees. They also require that the milt site shall be as nearly square as possible.

Location And Recording.

American Practice.

69. stalling. — Mill sites are located, like lode claims, by placing a substantial post at each angle (the British Columbian laws stipulate that such posts be "legal posts ") marked with the name of ihe mill site and the number of the corner. The corners should be tied to natural land- marks or permanent monuments, and, in fact, their location should conform in every way to the requirements of a

Prospecting-

mineral -claim location, except in the matter of mineral values. A location notice must be posted on some prominent poin on the claim, which should read substantially as follows: LOCATION NOTICE. 1 claim the Little Eva mill site (500 feet south by 400 feet north) i staked on this ground. Date of location, Oct- fi, 1

J. K. Hawlst.

70. Recording. — The record of a mill-site location i practically the same as that of a mineral claim. The prop- erty should be so described in the cenificate that there can be no difficulty in relocating it in case of litigation.

British Lolcmbian 1>Ractick.

71. Aside from the differences already mentioned, British Columbian statutes in reference to mill sites are v similar in intent to those of the United States.

Area aad Staking. — As in the United States, the an of a mill site is limited to five acres. The i marked by "legal posts," with a notice on each post stating

1. The name of the locator. 2. The number of his free minor'jf certilicate. 3. The intention, within sixty days from date of notice, I apply for the land as a mill site, i The dale of r

72. Application for Lease. — Having properly locate* and staked his mill site, the locator, within the sixty dayi specilied, applies lu the Provincial Land Surveyor for a ' lease on the property, and, on depositing duplicate plans and making affidavit as to the location of the claim, is granted

a lease for one year. If in that time the lessee has placed or constructed machinery or done other work on the pr< erty, for mining or milling purposes, to the value of tSdl he can obtain a Croivn grant (the equivalent of the Unitf States to the mill site, at the expense of 95 per actt

The interpretation of the term " mining purposes " so broad as in the American practice. It includes only ttti erection of machinery and buildings for transporting, redffi cing, crushing, or sampling ores, or for the transmission power for working mines.

Prospecting For Gems And Precious Stones.

73. Most gems are olitained in the debris of the older rock formations, that is, frum the gravels or sands of rivers. The prospector looking for goid or other placer material can examine the gravel for precious stones, the gold pan being used to separate any stones from the clay or fine sand which may be associated with them; but if a person intends to prospect especially for gems, it is better to be provided with a more extensive prospecting outfit. The following has been recommended as an outfit for a person searching for gems: A shovel and pick with which to loosen and move gravel; two sieves, one having two or three meshes to the linear inch and the other having twenty or more meshes to the linear inch (the coarser sieve should be arranged so that it can be fastened onto the top of the finer one); a tub of sufficient size to enable the prospector to submerge the sieves in water during the washing process; an oilcloth for sorting the gravel upon ; several stones as a scale of hard- ness; a small pocket magnifying-glass, and a dichroiscope. In some cases, more or less of this paraphernalia is dispensed with. The process of prospecting is as follows: Having discovered a promising location, the prospector fills his tub with water, fastens the coarse sieve on top of the fine one, and places a shovelful of the material to be examined in it; liien immersing the sieves in the water, he works all the clay and fine material through the upper sieve with his hands. This leaves only the larger stones above. The upper sieve may now be removed, the stones examined and thrown away. Then the material in the lower sieve is washed until all the clay and fine sand has been separated from the gravel. After this, a little quick jigging motion will carry the heavier and coarser stones to the bottom of the sieve. The sieve is then removed from the water and suddenly turned over upon the oilcloth, so as to bring the material that was at the bottom onto the top of the pile. The prospector now examines each piece with his glass or

32 Prospecting.

scale of hardness, and if he is in doubt about any of thi gems, he may be able to settle their identity with the dichroiS scope. Few of the precious stones are of sufBcient specifiq gravity to cause them to concentrate into decided deposit! as in the case of gold, tinstone, and some other heavy com pounds, but, nevertheless, they are usually somewhat cot* centrated. Garnets are frequently found in pockets on t bed-rock or in patches, where they have been carried by' eddies or other disturbances in the flow of the streams. These patches of garnets are considered a good indication of the possible presence of more valuable gems.

THE UlCHROtSCOPe;.

74. To settle the identity of a stone, the dichroiscopi (in shape a cylinder 3 inches long and 1 inch in diame ter, and so easily carried about) is most useful, taking fori granted that some practice with the various kinds ofW translucent or transparent stones of various shades and i colors has been acquired. A preliminary examination of aj few sapphires and rubies, spinel rubies, garnets, topazes tourmalines (green, brown, red), zircons of various colorsJ andalusite, water sapphire, colored quartz (includin; amethyst), etc., will impart a confidence very much moraj than any tabulated results of dichroism, which depend) much on the intensity or depth of color in the stone.

75. Fig, 18 illustrates the dichroiscope in position

I the tweezer,

hile Fig. 19 illustrates..! the manner in which the two colors appear. When a semitransparent J stone is examined, the j color of the square a will sometimes be of different, f shade from that of th4 J square li, and these dtffer>4

caused by the dichroism of the stone being:

Prospecting.

76. Placing (by means of tweezers) a translucent or transparent stone close, to one end of the instrument where the two square images are seen when the instrument, held skywards, is looked into, and turning it ahout in various directions, and at the same time turning the instrument around, the observer will notice whether the '''°-

color of the two squares is one and the same. If the stone is amorphous, such as glass, flint, obsidian, etc., or crystal- lizes according to the cubic system, such as diamond, spinel ruby, garnet, etc., the two squares will be of the same color. In other cases the color of one square will be of a different color to that of the other when the colored stone is exam- ined in certain directions, though it may be the same in certain others. Thus, a true ruby, which affords two shades of pink, can be distinguished from a spinel ruby or garnet without dichroism, or from a pink tourmaline (rubellite), which gives two colors, but somewhat differently to those of a ruby; so, too, a sapphire, which gives a blue shade in one square and a light shade of color without any shade of blue in the other (though sometimes in a dee ply -colored stone what might be considered as a greenish blue is noticed), can be distinguished from an amethyst, which afifords two shades of purple, or from a blue spinel (which does not show any twin coloration), or from an iolite (or water sapphire), in which the coloration is of its own kind.

77. A tourmaline (very frequently associated with other gems, especially in Ceylnn), either the green or brown, can be recognized directly (indeed, often without using the dichroiscope) by the color of the one square being quite dark compared to that of the other.

78. An emerald affords two distinct shades of green (one bluish) easily remembered (quite distinguishable from the dichroism of a green tourmaline); so a green garnet, which does not show twin coloration, can not be mistaken for it.

3-1 Prospecting.

79. With the dichroiscope and two or three minerals such as the sapphire, topaz.-and rock crystal, to lest ' hardness, and a little practice — the more the better — and i slight knowledge' of the crystallization of minerals, which,J though frequently found water-worn, not uncommc retain traces of the original crystal edges and faces, prospector can examine his specimens with a very m easier mind than he would do without them.

80. The following gems display dichroism when exam ined with a dichroiscope: All the corundum minerals, topaz, emerald, amethyst, iolite (water sapphire). tourraa*j line, and zircon. The following gems do not display dichroism: Diamonds, spinel, and garnet. Cat's-ey quoise, and opals, not being transparent, can not be teste< with the dichroiscope.

GENERAL KBMARKS C<>KCEHKIXG l>KOHI>ECTINIj.

81. When the prospector discovers mineral in place ina vein, he must not be too sure of its character or value until it has been prospected to the point below the influence of the surface agencies, or, as is commonly stated, to belotr the water-line, for it is quite a common occurrence to find a deposit containing free milling gold ore in its upper por- tions, rich oxides of copper or other minerals near the water-level, and farther down such a small amount of base sulphides as to render the material valueless as an ore.

82. The term ore is used in this work as signifying any material that can be extracted with profit. It will be seen that this definition would rule out material in one region as being worthless, while in another location it might be classed as an ore.

83. Sometimes the prospector discovers what appears to be the outcrop of a bed of hematite or limonite, but which proves to be the weathered outcrop of a pyrite vein, and hence valueless as an ore of iron.

Prospecting.

Underground Prospecting.

84. At times, especially in precious-metal mines

tfae

vein becomes lost, and prospecting has to be carried on underground as well as on the surface.

In reality, the openings of the mine become simply an extension of the surface exposures, and the prospecting is carried on very much as it would be from the surface.

85. When exploration is being carried on in advance of the regular raining, this work is usually called exploration and development work, and is considered in connection with the mining.

86. When searching for a lost vein from the under- ground workings of a mine, the exposed surfaces are exam- ined and a careful study made of the geological conditions, both underground and on the surface.

In cases where the vein has simply pinched out or become barren, it may be found again by following such indications as stains or rusty streaks in the rock, small leaders of the mineral itself, or veins of material other than the country rock.

After having examined all the indications, as exposed ia the mine and on the surface, if the ore is thought to be in a certain direction the work must be continued in the desired direction, either by drilling or by actual mining operations.

87. When the vein Or ore-body has been cut by a fault which has thrown the rock either up or down, it may be dis- covered once more by breaking through into the formation beyond the fault and carefully examining the rock to ascer- tain whether it is the formation above or below the body sought. If the fault has thrown the vein or deposit to the right or left, or up or down at an angle (that is, so as to carry it up or down as well as to one side), it will be neces- sary to make a careful study of the geology of the region, and to determine the probable direction of the throw by the rules for the throw of faults as given in the Paper on Geology, together with any local characteristics in that respect. If,

d

after examining all the indications iioth above and beltf ground, it is thought probable that ihe mineral lies in i certain direction, work may be continued in the desired direction either by regular mining operations or by drilling.

Prospecting With A Diamoxi* Drill.

88. Deposits which do not outcrop lu the surface, the outcrop of which gives no definite idea as to the posi- tion of the deposit, may be prospected for by drilling. The diamond drill is the best machine for operating in rock. The machines and their working are described in /Vj sive and Rotary Boring, but the following points are of interest in laying out the prospecting of any particular pi of ground.

89. There are many cases in which the deposits arc t of a regular nature, and are so located that the diamoi

drill is practically the only means by which they can be prospected. Fig. 2(Jillustratcsan ore-body occurring beneath a bog or lake. This is very common in the case of the ores of iron or manganese. There is a slight outcrop at a, but, owing to the nature of the ground over the deposit, it would be impossible to prospect by means of test pits or shafts without their being excessively expensive. In such a case, a diamond drill may be placed upon the surface when it is frozen, the stand-pipe being driven through the soft materiid

S3

Prospecting.

to bed-rock, and the drilling accomplished as though there were no soft material over the deposit. Drilling has been done in this way from the ice of lakes in the winter, and very valuable discoveries have thus been made. After the ore has been found, it may be possible to drain the bog or lake, and thus recover the deposit.

90. It may be stated, as a general rule, that where the strike and dip of the deposits sought for are fairly well known, the diamond-drill holes should have a direction practica!l\ at right angles tu the d e p o s i t s sought, as illustrated in Fig 21, c d being the di a mond-drill hole and a the deposit.

91. Sometimes, where it is possible to Fio.ai.

sink to bed-rock around the edges of the deposit, test pits are put down, and a series of holes drilled from the bottom of the test pits, the drill being placed on the bed-rock. Such holes are commonly called fan holcn. Fig. %% illus- trates a case in which a property has been prospected by three sets of fan holes drilled from three shafts or test pits, A, and C. The long lines a, a, a', a', a', a', etc., repre- sent holes drilled at a comparatively flat inclination, while the shorter ones ii, fi, b', b' . b', b', etc., represent holes drilled at a steeper angle. It is best to do the work from more than one shaft or test pit, if possible, in order that thelines of the diamond-drill holes may cross each other, as shown in the illustration. The drill pits, or test pits, in which the diamond drill is to be placed, as shown at A, B, and f, are situated at such points that they will not have to penetrate the bog or extremely wet ground immediately adjoining a lake, and for this reason they are usually situated at the foot of the hills, as shown in the illustration. It may be

Prospecting

cheaper to sink pits snnte <listance in the rock at the foot of tbe hill than H would be to keep the water pumped out, had

the pit been placed in the softer material of the swamp or bog.

92. It may be stated, as a general rule, that when the dip or general direction of the formation is not known, the ground should be blocked off into approximate rectangles and the holes drilled in such a manner as to cross each other, thus, if possible, discovering any small or irregular deposits

Prospecting.

3ft

of valuable material. It is not always safe to depend upon a rectangular form for the system of blocking out the ground for diamond drilling. Fig. 23 illustrates a case in which a lense or body of ore occupies a trough, and had two dia- mond-drill holes been drilled as shown attiand, they would

give very erroneous indications as to the size of the deposit, while if they had been drilled as at c and if, they would have

tirely.

ough an

If the holes are drilled close enough together and in rec- tangular form, they will give a fairly close idea as to the form of the deposit, but ver- tical holes should also be drilled as at c, for the prob- abilities arc that the inclined hiilos wfiuld drift up as in- dicated by the dotted lines, and hence give a false idea as to the location of the deposit, which the vertical holes would correct. 93. A single hole drilled

1, as shown in Fig. 24, may

Prospecting.

give a very false idea as to the dip of the strata, for while the dip, with regard to tlje center line of the hole, will be clearly indicated in the core, as shown by Fig. 25, the core may, and probably will, bi;come turned in the core-barrel while being drawn from the hole, and hence will give ] idea as to the true dip of the formation.

94. In order to determine the dip of any given depositT it is necessary to drill a number of holes and compare the records; as, for instance, in Fig. 2, if holes were drilled at a. b, and c, and their re- sults (.ompared, it would be easy to tell that the vein J c had a uniform dip in ihe direction in-

iSBtn

" 1

ziii

T

W

r

-r'

&i

dicated

95. Sometimes it] necessary to drill faoli very close together 4 ai-iijunt of the fact thj formations maybe v Pio, v>), erratic, as illustrated 2

Fig. v.. In this caai the hole b has passed perpendicularly through a small b of ore, thus giving indication of a large deposit, while td hole C( has passed through a thin portion of a large body, thus giving indication of a small deposit, prospecting for material which is liable to occur in irregi pockets or lenses, it is necessary to put down a number holes, and to place them in a somewhat regular order; instance, if other holes had been drilled from the positio occupied by the machine while drilling a b and c d, aa in(S cated by the lines from a and c, it is evident that a fair good idea as to the dimensions of the deposits in this pla would have been determined ; and if another series of had been drilled from the position c, as indicated, a vef much more definite idea of the form of the deposit wou]

have been obtained. By means of a careful and systematic exploration of the ground with a diamond drill, it may be

possible to obtain

all the data necessary f<jr layinj ig a new portion of the deposit.

96. One advantage of prospecting with a diamond drill is that the work can be done at a very much less cost per foot, and so several diamond-drill holes can be put down for the amount of money it would require to sink one shaft or drive one tunnel, and the results obtained by means of the diamond driil may render it possible to so locate a shaft or tunnel through which the ore is finally removed that it will be very much more effective, and permanently reduce the cost of mining; hence the diamond drill is one of the best methods of prospecting certain forms of deposits.

Hand Algers For Drilling.

97. While the diamond drill is preeminently fitted for drilling in rock formations, it is sometimes necessary to prospect in comparatively soft material near the surface,

ii

Prospecting.

as, for instance, when searching for iron ore in ctay beds or for deposits of manganese ore, bog-iron ores, phosphate rock, clay, etc. For this work a simple auger may be used, as shown by Fig. 28. This is usually composed of a bar of steel, or of iron with a steel tip, which is twisted to a spiral form and the point of which is split and sharpened. A good length for the auger is about 13 inches, with a diameter of 2 inches. The auger should have about 4 turns in a distance of 13 inches. For the operation of the tool, it has a piece of 1-inch pipe welded to it, and as the boring progresses, other pieces arc screwed on by means of ordinary pipe-couplings. For the turning of the auger there is a handle arranged with a central eye so that it can be slid up and down the pipe and fastened at any desired point by means of a set-screw. In case hard rock is encountered when prospecting with this outfit, it is possible to continue the work by means of a churn-drill, formed by a piece of If-inch octagon steel having a 2-inch cutting edge, and with a piece of pipe welded to its upper end. For the first section of rod above the steel chop- ping bit, a piece of linch round iron may be sub- stituted for a section of the pipe. This has the advantage of giving the necessary weight to the churn-dril! for driving it through the formation.

Prospecting has been carried on to a depth of over 60 feet with such an apparatus as this, the Pic. w. churn-drill being used when hard rock was encoun- tered, and the auger-bit while working in soft strata. One great advantage of this outfit is that it costs but little, and can be made or repaired at any blacksmith shop. When using the chopping bit, the material drilled may be worked stitf enough to remove the debris by means of the auger- bit, or a sand-pump made from a piece of pipe with a leather valve at its lower end may be employed. During the work sufficient water is introduced into the hole to keep the tools cool and to render the cutting somewhat easier.

Prospecting.

Percissive, Or Churn, 1>Rili.S For Prospecting.

88. Sometimes large drills of the percussive type, such as are ordinarily used for boring wells, are employed in pros- pecting, but the results obtained are not nearly so good as those obtained with a diamond drill, owing to the fact that the entire product is broken up into fine grains, and the valuable portions may be broken so small that it is impossible to tell the exact character of the material passed through. Machines of this class are illustrated in Percussive and Rotary Boring.

Magnetic Prospectixg.

99. When prospecting for bodies of magnetic iron ore, both the ordinary compass and the dipping-needle, or miner's compass, can be employed. The miner's compass is illus- trated in Fig. 29, and con- sists of a magnetic needle so mounted that it can move in a vertical plane. Fig. 30 illustrates the manner in which the ordinary compass would behave in passing about a body of magnetic ore situated at a. If a pros- pector were to start at b, the com pass, instead of point- ing due north, would be de- flected slightly towards the ore-body a, and as he ad- vanced towards the position c the deflection would become greater and greater until it reached the maximum oppo- site, or nearly opposite, the body of ore a, and after pass- ing this point the attraction fiq.

would become less and less. Similarly, in passing from d to e, the magnetit; needle would deflect towards the body a. By this means some idea as to the position and extent of the

center of attraction may be determined. After having gone over the ground with an ordinary compass, the pros- pector may use the dipping-needle, or miner's compass, and obtain the results shown in Fig. 31, which is a vertical section on the line N S, Fig. :iO. If the dipping-needle

were taken from the point S towards the point N, the dip would vary until, if the body of ore be large and near the surface, the needle would point directly down, or might often assume a reversed position as shown at a and Ir, where the needle is taken beyond the ore-body towards the north. After the center of magnetic attraction has been determini

J

Prospecting.

prospecting can be continued either by sinking or by the use of the diamond drill. Sometimes beds or bodies of material containing magnetic sand may cause magnetic dis- turbances which would produce ihe same effect as a body of magnetic ore, and on this account magnetic prospecting may possibly give false ideas as to the position of ore-bodies and as to their extent.

Examples Of Prospecting Regions.

PROSPECTING REGIONS OF COLORADO. lOO. If we study the geological map of Colorado {Fig. ,i'i) as a type of the Rocky Mountains generally, we see that the two main crystalline bodies of rock, the granitic and eruptive rocks, have somewhat definite positions. The granite areas are very large, and are arranged along certain definite lines from north to south across the State, preserv- ing a rough parallelism to one another and corresponding to the three principal ranges, and are separated from one another by intervals of surface matter or by overlapping sedimentary rocks. The first of these granitic areas on the east, bordering on the great plains, is the Colorado, or Front, Range, extending from beyond the Wyoming bound- ary south to the Arkansas River, and continued southward under the name of the Wet Mountains. Some miles to the we.st, and irregularly separated from the Front Range by the depressions of the North, Middle, and South Parks, and the Wet Mountain Valley, is the Park, or Mosquito, Range, a narrow range whose granite base is overlaid at intervals by old, metamorphosed, sedimentary rocks belonging prin- cipally to the Cambrian, Silurian, and Carboniferous series. This range is continued southward, tinder the names of the Sangre de Cristo and Culebra Ranges, to the southern boundary of the State. A little west of the Mosquito Range is the great, massive, but comparatively short, granite

Prospecting.

of the Sawatch Range, separated from the Mosquitu by the depression of the Arkansas Rivr VMr-y.

101. These are the main great outcrops of the grani system in Colorado. Not that this fundamental granite j confined to these areas, however, for it underlies elsewhere, - at varying depths, the rest of Colorado and the whole Rocky Mountain system, but in these areas it is brought most prominently to light by uplift and erosion, while elsewheCft

§ 38 Prospecting. 47

it is buried out of sight by superficial and sedimentary rocks, sometimes of enormous thickness, or by broad sheets and deluges of lava. In other parts of the mountains we find the granite here and there exposed by great local denuda- tion, where a caHon has bitten deeply into the earth's crust, as in the San Juan region; here great areas have been cov- ered up to a depth of 3,000 to -I.OOO feet by deluges of lava; profound caflons cutting through these sheets of lava will sometimes reveal the granite in the bottom of the stream- bed.

102. If we turn to the map to look for the areas of erup- tive volcanic rocks, we observe that they are much more irregularly and indefinitely distributed than the granites. They are not quite so abundant towards the north as towards the south of Colorado. They appear most plenti- fully in a rough line from north to south, through the cen- tral-western regions of the mountains. They seem to follow principally an irregular line west of the Parks, the Mosquito and Sawatch Ranges culminating towards the southern-cen- tral portion of the mountains, in the prodigious eruptive mass of the San Juan region. These dark patches on the map represent, however, more the great sheets and broad eruptive overflows than the multitude of narrow dikes and local intrusive sheets of volcanic matter to be found scat- tered here and there over the entire mountain region. These latter, though unimportant and too small for repre- sentation on a map, may be of great local consequence in connection with ore deposits in local mining centers, as, for instance, at Central, Idaho Springs, Boulder, Leadville, and Aspen.

103. Let us next consider where the older Paleozoic series of sedimentary rocks, commonly metamorphosed by heat, are most prominently shown. These "old-life," or "Paleozoic," rocks He generally close upon the primitive granite, and comprise three divisions. The Cambrian, com- posed of hard, vitreous, white quartzites, lies right upon the granite. Upon this comes the Silurian, mostly of drab-

48 Prospecting.

colored, thin-bedded limestones, and on this the Carbonifer- ous, composed of dark-gray, or "blue," heavy-bedded, massive limestones below, and a great thickness of shales and conglomerates or grit-stones above. The Lower Carboniferous "blue limestone," when overlaid or pene- trated by intrusive sheets of porphyry, gives us the most important lead-silver deposits in the State, as, for example, at Leadville and Aspen. The united thickness of this Paleozoic series in Colorado is rarely more than 2,000 feet to 3,000 feet.

104. As these rocks were all laid down by the ancient seas as successive shores and sea beds when our great gran- ite ranges were merely a series of islands in oceans almost universal, we would naturally look for their outcrops along the borders of those island ranges, or capping, as in the Mosquito Range, even their highest and once submerged summits, while the rest of their broad sheets pass under the more recent sedimentary strata of the parks and prairies and lie deeply buried beneath them. In the latter position they are unaltered and uncrystallized by heat; in this con- dition we find them along the eastern border of the Front Range at Perry's Park, Manitou, and CaBon City. A glance at the geological map shows this class of rocks outcropping along the Mosquito and Sangre de Cristo Ranges at inter- vals, also down the Wet Mountain Valley to the Culebra Range at the southern extremity of the State. On the western slope of the Mosquito, at various points in the Arkansas Valley below Leadville and above Leadville to Tennessee Pass, then down the valley of the Eagle River to Redcliff and beyond, it appears and occupies large areas about the Grand and White Rivers and in the White River plateau.

105. Again, it skirts the old Sawatch Island on both sides, going north and west from Leadville, round by way of Frying-Pan and Lime Creeks, to Aspen, outcropping in several places in the region occupied by the volcanic peaks of the Elk Mountains. To the southwest it outcrops here*

§ 88 Prospecting. 49

and there from under the lava overflows of the San Juan and La Plata Mountains, and locally here and there in other parts of the Stale where the Paleozoic seas laid it down around the primitive granite islets, or where exposed by the removal and erosion of overlying and more recent forma- tions.

106. Such is the general sketch of the geological and geographical distribution of these eminently metalliferous rocks in Colorado. Of course, it is only occasionally that these rocks are productive of precious ores, and then only under certain peculiar, and often local, conditions. But it is well to point out to the prospector that these are the likely rocks in which to look for precious metals, to prevent him from wasting his time on other areas and among other classes of rocks, often widely represented in Colorado, which experience has so far shown to be unproductive.

OTHER PROSPECTIKG REGIONS. 107. We have taken Colorado as our type of the Rocky Mountains, because very similar geological structures are found all over the Rocky Mountain region, in Montana, Utah, Nevada, in the Black Hills of South Dakota, and also down in New Mexico and Arizona, Not but what there is an infinite diversity, not only in every region, but in every principal mining district, to describe which individually would take many volumes. In the California region we find, too, many of the same formations and the ores under very similar conditions, so that if any one knew well how to pros- pect Colorado, knew all its geological structure and the pre- vailing habitat of the ores, lie woidd not find himself very much at sea in any other of the Rocky Mountain regions; for instance, in the Black Hills of South Dakota. That little mountain range is a miniature of the great Rocky Mountain system of Colorado. The Black Hills consist of a granite nucleus, once doubtless a granite island, over- laid by ancient slates and schists of a period intervening between the Archean and Cambrian, called by geologists the

50 PROSPECTING. g 38

Pre-Cambriaii period. This is also found in some parts of Colorado, particularly near Ouray, where the Pre-Cambrian schists and quartzites are upwards of 14,000 feet thick. Through these schists come up long dikes and veins of granite and porphyry, in which, or at the contact of which with the schists, are found ores of tin, silver, and gold. Resting upon these schists are the Paleozoic formations, traversed, as in Colorado, by eruptive, intrusive rooks. So a man conversant with Colorado geology and accustomed to prospect there would very soon learn the indications of the new camp.

1 08. In Utah he would again find much the same struc- ture as in Colorado. The main mountain mass, the Wah- satch Range, is of granite, with Paleozoic limestones, etc., dipping off from it and much faulted. He would look for fissure-veins in the granite as in Colorado, and silver-lead deposits in the limestones, especially when traversed by porphyries. As for gold, he would look for that in decom- posed dikes of porphyry, or in quartz veins in the granite, or else in placer deposits in the stream-beds.

109. In Montana he would have mainly a granitic type of rocks to prospect, traversed by porphyry sheets, and, in connection with the latter, would look out for the ore signs.

110< In Idaho Territory he would meet largely with great masses of eruptive and volcanic rock, and some of the richest gold mines there are in decomposed dikes of por- phyry.

111. In Nevada he would find a series of isolated moiin* tains and mountain chains scattered about, and in some places, as at Eureka, he would find Paleozoic limestones tilted up on granite and traversed by eruptive rocks. He would find many of the silver-lead deposits there in cavern- ous deposits in the limestone as at Leadville, Colorado. In the Washoe district, where the great Comstock lode is, he would be in a region composed of many different kinds of eruptive rock, and at the junction of some of these with

Prospecting.

each other he would observe the great Comstock quartz fissure-vein running through the country and spHtting up into Httle branches at either end.

After this great fissure was discovered, extensions of it were prospected, but without much success. It is some- times a good thing to follow up the extension of a noted lode, but it has been observed that frequently Nature seems to have exhausted all her resources in the main part of the fissure where the ore has been found most abundant, so extensions are not always to be relied upon as good proper- ties. Again, the Comstock is an example of the fact that a particular kind of rock, producing good ore in one district, may not be at all productive in another and distant district. The Comstock miners hunted up the same porphyry all over Nevada and other regions as is found in the Comstock, yet without success. The mere existence of a certain variety of rock can never be safely considered as a guarantee of ore; Other conditions are necessary, such as Assuring, accompanied by evidences of ancient hot springs, volcanic eruptions, and many other phenomena of less importance generally, but often of great local importance.

112. In California we have the Sierra Nevada and Coast Ranges abounding in ores. The gold is generally found in quartz veins traversing the slates, but often in little scattered pockets, and sometimes in dikes of eruptive rock. There is one mineral that is almost peculiar to Cali- fornia in America, and that is cinnabar, the sulphide of mercury. The ore is found in crevices or in Cretaceous sandstones, which it impregnates, sometimes in fissure-veins in slates, and not infrequently associated with a green ser- pentine rock, which may have once had an eruptive origin. In the New Almaden mines it was found mostly near evi- dences of faulting, associated with signs of movement and friction in the rock, such as fragments of rock more or less rounded by attrition, or polished and slicken-sided. The ores are brownish-red or brownish-black to vermilion in color, according to their purity, and give a scarlet streak. There

are a great many red ores which might be taken for cinna- bar, but on heating a specimen of the latter in a tube with carbonate of soda it gives off quicksilver, which condenses in the upper part of the tube, this reaction readily distin guishing it from minerals of similar appearance.

113. The ore deposits and geological formations of Ni Mexico are very similar to those of Colorado : granites, erup?! tive rocks, Paleozoic limestones, etc., with gold, silver, and lead ores, and some copper.

114. In Arizona there are many fine prospecting fields, largely in granitic and eruptive rocks, producing much gold, silver, and copper. Towards certain portions of Arizona are areas of Paleozoic limestones, etc., traversed by porphy- ries, producing ore-bodies of lead-silver in much the same way as in Leadville. Some of these ore-bodies occur in the great cliffs of the Grand Cafion of the Colorado, and are rather inaccessible to railroads. Rich gold placers are also said to abound in the beds of old streams, but are at present worthless because of the absence of water with which to work them, This state of affairs is quite common both in Arizona and New Mexico, the sands in some cases being very rich, but the placer valueless because of the scarcit] of water.

Prospectors' Tools.

115. The most essential of the prospector's tools are picks, drills, hammers, and shovel, and these are kept down to the minimum number and weight, in order that the pros- pector shall be as free and unencumbered as possible in climbing around the mountains.

For his trip as a whole, the prospector may carry a more or less complete outfit of tools, packed upon a burro or pony, but when he arrives in a likely-looking region, he makes a temporary camp, pickets his pack animal, and taking only a light prospecting or geological pick, weighing probably three or four pounds, he starts out on a genera! recon- noiter. The pick he lakes is a little single-hand affair, about

Prospecting.

S3

10 inches long, with one end a square-faced poll or hammer

and the other a pick-point; the handle is abaiit 15 inches

long. The edges of the poll are sometir

square, sharp-cornered face is better,

as the sharp edges and corners are

better adapted for breaking rock than -

the rounded or beveied ends. The

pick should be all of good steel, with

a good-sized eye to admit a strong

and springy hickory handle. [See (i).

Fig. 33.]

Armed with this little weapon, the prospector climbs the hillsides, hunt- ing for float or for the rusty outcrops of ledges. Loose pieces of float he cracks open with the hammer end; ""'

softer rock in place he explores with the pick. Old pros- pectors consider this little pick indispensable for preliminary search. If the prospector finds anything likely "' in place," he marks the spot and goes on ; when he returns to camp at noon or evening, as the case may be, he unpacks his heavy digging pick and shovel, and in the afternoon or next morn- ing goes back to his "find " with these tools and proceeds to "open up"; then, if the ledge appears to be worth further exploration, on his next visit to camp he brings up drills, hammers, and blasting outfit, and goes systematically to work.

Picks And Drills.

116. Picks and drills that are used on rock rapidly become dulled, and the prospector, at a long distance from blacksmith shops, is forced to become his own blacksmith and sharpen and temper his own tools. The kind of sharp- ening and the nature or degree of tempering depend upon the kind of rock to be worked, whether hard or soft, loose-

64 Prospecting. § 38

grained or fine-grained, silicious or clayey. Drills, for example, would have to be differently sharpened and tem- pered for hard, vitreous quartzite than for soft sandstone or limestone or hardened clay. The same remark applies also to picks. Picks may be either double-pointed or poll picks, with one point and a hammer head which can be used for breaking rocks. The essential points of a good pick are strong cutting tips, a stout eye, and a tight handle. The little prospecting pick is made of the best steel throughout, but in the heavier picks only the wearing parts, the tips, are made of steel, and these should be made replaceable; an all-steel pick soon becomes shortened and useless working among , while an iron pick-eye may be made to last indefinitely by welding on steel tips from time to time,

117. SharpeninK.For mining purposes, both tips of a pick are usually made pointed or pyramidal. The lips are forged into points on an anvil, the character of the point varying with the nature of the ground in which it is to be used. Thus, for hard, dense rock the point is made on a blunt taper; for loose, fissured rock a slim taper is used; if the ground is soft, tough, or clayey, one tip is usually sharp- ened to a chisel-point for cutting the ground.

Drills.

118. By far the most important of the metal-miner's tools are his drills. Drills are made from round or octagonal steel bars, the latter form being preferable, as it is more easily turned. The bars are cut into the desired lengths, and then one end of each piece is forged to a cutting edge, slightly wider than the diameter of the bar to save weight and prevent the drill from sticking in the hole, and the other, the striking face, is left flat. Drills vary in length from 1 to 4 or 5 feet, or even more for special purposes, and in diameter from jf inch to 2 inches, the larger size being used exclusively for double-hand or three-hand work, one man turning and another, or two others, striking. The ordinary sizes for single-hand work are J-inch to -inch steel.

Prospecting.

and for double-hand J-inch to 1-inch steel, the smaller sizes being too springy and the larger sizes too heavy.

The flare of the cutting edge, as well as the angle, varies with the kind of rock to be worked. For soft rock, like limestone or sandstone, a drill with a tapering edge is used, the bit fiaring tosome- times twice the diame- ter of the stock, while as the rock gets harder the edge angle is made flatter, and the flare is diminished, till for very hard granite or porphyry it is as low as 'j inch on each side,

cutting a hole aliout

inch greater in diameter than the stock of the drill. The drills used in soft rock are usually straight-edged, as in / and Ja, Fig. 34, as the straight edge cuts more freely than the curved edge, shown in the other cuts in the figure, but it is weaker, and the corners are more apt to chip off; hence, for harder rock the edge is slightly curved. This curving also keeps the center of the bit in advance of the corners, and thus tends to equalize the work, which in the straight-edged bit increases towards the circumference in proportion to the distance from the center. As it is, the corners of the bit receive the brunt of the wear, and straight bits naturally tend to wear to a curve or an angle with its apex at the center.

In a set of drills, to insure the longer drills working freely in the hole, the width of the bit is very slightly reduced in each successive length. For all-around work, such as a prospector's tools have to stand, the bits should flare to about inch or f inch greater width than the diameter of the stork.

1(9. Sharpnlnit. — To sharpen a blunted drill the bit-end is first placed in the forge and heated to a working

heat; it is then tiiken nut and hammered to n width a little greater than the diameter of the hole to be hored; the cutting edge is next hammered up with a. light hammer to the requisite angle, and the corners hcalcn in In give the exact diameter of the bore hole desired. The edge is touched up with a file. Heavy hammering and high heats should Ite avoided, and tlic steel should be kept well covered with coal while heating to protect it from the air, Overheated or "burned " steel is liable Ui fly, and drills so injured arc use- less until the burned portion has been cut away; a cherry- red is the heat for steel — no higher. Care is required in forming the cutting edge to get it even and of the full form. If the corners get hammered, as in .'la, Fig. 33, they are said to be "nipped," and the drill will not free itself readily in cutting. A bit is ""bankward" when there is a depressi<jn in the edge, as in SA, and "odd-cornered " when one of the corners is higher than the other, as in 3<r. Either of these defects causes the main force of the blow to be thrown upon only a portion of the edge, which is apt to become over- strained and break.

Bl,Acksmixh1Ng.

120. Blacksniithing is an art by itself, and one can become expert at it only by long practice. The prospector can, however, learn enough in a short time to enable him to sharpen and temper his own picks and drills.

121. Fuel. — The best fuel for blacksmithing is a slightly caking coal, which gives an open fire, considerable flame, and a high heal. Coke gives a greater heat, but is harder to keep fire in. Whatever fuel is used, it should be as free as possible from sulphur, phosphorus, and shale, or slate. The two former corrode the steel, and the latter forms a pasty cinder that sticks to the drill, clogs the fire, and is a nuisance generally. Iron in the ash (red ash) also renders the coal liable to clinker. Away from civilization, charcoal is frequently used as a fuel, or even chips of wood, which should be blown with a small bellows.

Prospecting. 87

I'Zll. Prospector's Forge.— A prospector who is obliged to be his own blacksmith wants to keep his outfit down as light as possible, and hence resorts to many make- shifts to lighten his luggage. A simple blacksmith's forge that is quite commonly used by prospectors is made up of one, two, or three blasting-powder cans with the heads cut out of all but the bottom one, and one head must be cut out of this; these are placed one on top of the other to make the furnace. A 1-inch hole is punched in the side of the lowest can, close to the bottom, for draft, and to put the points of the tools in to heat them. Some prospectors carry a small bellows to furnish a blast. A chunk of steel or railroad iron about 6 or 8 inches long can be made to serve as an anvil.

123. Hardening find Temperintc- — Steel is iron containing carbon, the presence of which gives to steel its well-known property of hardening and "tempering" on being suddenly chilled. The hardness of steel depends upon the proportion of carbon present, the temperature from which it was chilled, and also on the presence of other elements, as nickel and chromium. As the percentage of carbon increases, the melting-point of the steel decreases, and this greater fusibility reduces its welding quality. A steel that has been suddenly cooled from a very high tem- perature and has become as hard as possible is called "hardened." Hardening is accomplished by heating the iron to a cherry-red color and then plunging it suddenly into some liquid which extracts the heat from the tool. The quicker it is cooled and the greater the difference of tem- perature, the harder the steel, but, on the other hand, the more sudden the cooling the more brittle the steel. Either oil or water is used for the chilling fluid; both volatilize at a temperature much below that of the immersed tool, sur- rounding it with a vapor, so that the hardening really takes place, not in a liquid, but in a gas. Oil-hardening gives a tougher steel than water-hardening, as on the first plunge the metal becomes coated with soot, which tends to retain the heat in the steel, so that the cooling is slower.

Prospecting.

124. Hardened steel is too brittle for tools, and the hardness has to be reduced, or "tempered," to a degree varying according to the purpose for which the tool is designed, the toughness increasing as the hardness decreases. Hardening is the extreme of tempering, as the word is com- monly used, and tempering is merely "drawing the tem- per "of the hardened steel down to any desired point by reheating the chilled steel up to a certain temperature, the heat partially removing the effect of the chilling. The relative temperatures of the steel are indicated by the colors of the film of oxide which forms on a clean steel sur- face. When a piece of hardened steel is slowly reheated, its surface will be observed to gradually assume different colors, beginning with a light straw-yellow and passing through successive shades of yellow, brown, purple, and blue, up to a cherry-red; at cherry-red, the color before hardening, the eflfect of the chilling will disappear entirely. Each one of these shades corresponds to a definite temperature of the steel, and by noting them the expert smith can tell just how far ihe tempering, or reduction of hardness, has pro- ceeded, and having previously determined just what temper the tool should have for any certain purpose, can obtain that temper by stopping the reheating when the proper color is reached.

125> Razors, springs, knife-blades, and any other arti- cles which require tempering throughout, are first hardened and then tempered, as above, in a separate operation, but for tools like drills and picks, which require only the point or edge hardened, the two operations are combined. The point and a few inches of the stock of the tool are heated up to a cherry-red — the operation may be performed imme- diately after sharpening, if desired, with the same heat — and then plunge the tip, for about an inch or two, into the water or oil; this chills and hardens the point. The tool should not be held in this one place gently back and forth, and worked ii for some distance above the temper 1

but should be waved id out of the water so that'the change

§ 38 Prospecting. 69

from hard steel to soft steel will not be too abrupt, as other- wise the internal strains set up by the hardening renders the tool apt to break very easily along the line of change. While there is still considerable heat left in the stock of the tool, the point is withdrawn from the liquid and the scales rubbed off on wood or brick, so that the colors can be carefully watched ; the heat is noted to draw gradually towards the edge from the hotter portion above. As soon as the desired tempering color is reached, the tool is again immersed and completely cooled. The idea that steel is cooler at a blue than at a yellow color, in the final drawing, is errone- ous, for more of the heat of the stock is conducted to the point than is radiated out into the air in the same time, and the first heat to the edge produces only a yellow color; with more it becomes brown, purple, and so on. In temper- ing drills, the tool is usually plunged when a copper color is reached; for picks, the reheating is continued to a light blue.

' r

V

i

Placer and Hydraulic Mining.

History Of Placer Mining.

The Uuigin Op Gold Pl,A.Cers.

1. The fragmentary deposits carrying gold, known as placers, have been formed by disintegration or breaking up of rocks and the subsequent sorting of the resulting mate- rial by water. This disintegration or breaking up may have resulted from any one of several causes. The rocks may have been ploughed or broken down by glaciers, water fall- ing on the surface may have soaked into the cracks and sub- sequently frozen and expanded, thus rending or breaking the rocks.or water percolating through the rock masses may have dissolved the softer portions, and so caused the disinte- gration of the entire mass. If there had been no disinte- gration of the rock masses, the mountains would be simply vast smooth rolling billows of strata, broken occasionally by great cliffs, the result of faulting. As mineral veins are mainly due to the action of circulating waters, which pass through the faults or crevices and appear at the surface as hot springs, geysers, fumaroles, etc., the monotony of the landscape would have been broken by an occasional mass of calcareous or silicious matter along the line of some fault or fissure, similar to the masses now seen at the Hoi Springs in the Yellowstone National Park and elsewhere. These masses would indicate the points at which veins were being formed below, or points where they had already been formed.

If upon this surface the various agencies of erosion had been set at work, our present rough and jagged mountain system would be the result.

Placer And Hydraulic Mining.

2. Work of Glaciers. — The glaciers are s;reat ice sheets which fill every fold and undulation of the surface, and press forwards, planing oS the tops of the muuntaJns an cutting great valleys and gorges down their sides. Thj material or debris cut from the mountains is piled in valleys, or on the flanks of the mountains and hills as moraines, to be subsequently winnowed and distributed by the action of streams and rivers, the finer material being carried on and distributed on the plains to form soil, washed to the ocean, while the heavier and coarser materi has settled near the point where the glacier left it, and thi

naturally contains the greater part of the gold. Owing 1 the fact that changes of temperature between the differca Bcasons of the year affect the active work of glaciers, these agencies are most effective in the high or moderately high latitudes only, and in the tropics we must look for some other series of forces as the principal agents in the duction of placer deposits. Fig. 1 shows the mi which the glaciers flow from the mountains down through valleys.

3. Kffect of Frost and Erosion by l\'ater. — In thi

higher mountains of the tropics, frost has played ati importai part by freezing water in the pores of the rocks, thus Bplij ling the material, as it has done all through the higher lag tudes. The material thus quarried or broken loose has b

§39 Placer And Hydraulic Mining. 3

subsequently washed away by the force of the streams resulting from the rainfalls or from the melting of snow. In the tropics the rainfall is frequently very heavy, and this heavy rainfall furnishes enormous quantities of water, which rush down the mountainsides, cutting and tearing everything before them, and carrying great masses of debris on to the plains below. In many places the humid air, assisted by the rank tropical vegetation, has disintegrated the rocks to great depths, and during the heavy rain-storms great gulches are washed through this soil, and the material thus eroded is winnowed and deposited in the valleys.

4. Orlaln of Drift or Placer Gold.— The materials eroded from the rocks by the action of glaciers or atmos- pherii: agencies, such as frost, percolating waters, etc., con- tain not only the gold from the veins of quartz or other material which existed in the rocks eroded, but also any gold which may have been disseminated through the formation in minute particles. It is well known that the crystalline rocks, such as granites, porphyries, lavas, and other igneous rocks, contain small amounts of gold disseminated through them, and by the concentration of this over an extended area it would be easy to account for the formation of placers. If all the gold that has been spread far and wide in minute grains through the rocks could be collected, it would far exceed all that has been, or ever will be, obtained by man in his puny efforts at placer mining and sand washing, for not only do the massive rocks contain gold, but it is found in small quantities in many of the stratified rocks and in minute quantities in the waters of the sea.

5. Ancient Placer FurniatlonH. — Though modern placer deposits are generally conceded to have been laid down by the action of comparatively recent glaciers, streams, and other bodies of water, in more or less loose, incoherent banks, yet there are other far older formations firmly con- solidated into rock, which may be considered as ancient

placers having had the same alluvial origin as modern placers, and withal gold-bearing, such, for instance, as the

maiWH 'jC 'itibris by die water? of rratrs aad stnaiBS. and iii-fi :rf 'Tase. An.)CE.;r ta.:tor vEiicb. Sas aa importan.: parr in turning the attend)?!! naa to placer '-sit.'i in hi'h U.tita(ie3 !:i the foirt thai aev not cntir.ealeii ur.rfer detijie j'jngles or trT]pn:aI TrgttMioa, as is the cse in the tmpics. and a mle the variation betvcn winter ami summer aifopi-> a better ')pp)Ctnnity for placer operati'on*. during; a few niT'tiths the year, than can be found at any time in m.iay t'.'Catiocs in th tropKS For these reaji.,.ns the re-oai which haTC fcwMja affected by tbe glaciers have n'lC ualy pniuced m-.'st oi the known placers of the present time, but have alfurded a better opportonlty for working the same than is the case in the tn>pics.

7. reason why the placers in the tropics hare not beea worked more is because the Ii,>w river-bottoms in

g 39 PLACER AND HYDRAULIC MINING. 5

which they occur are often infested with germs of fevers and other diseases, which render it practically impossible for white men t<J work placers in such climates. The prin-

cipal placer areas of North America are shown by the shaded portions on the map, Fig, 3.

8. The simple fact that a region is covered with disinte- grated material or glacial drift can not be taken as evidence

6 PLACER AND HYDRAULIC MimNG.

that placer deposits of value vill l>e found there. As, for instance, the entire northern portion of North America ia covered with glacial drift deposits, which in the Central States often aggregate 300 to 700 feet in Ihiclcness, and the material of which has been winnowed and rewashed by the modern rivers, and practically all this region is barren of placer deposits, on account of the fact that the rocks from which most of the glacial material was derived did not carry gold in any appreciable quantities. In most cases it is neces- sary that the action of the glacier has been succeeded by that of running water, in order that the placer deposits may be of value, because the glacier simply acts as a plane for quarry- ing or breaking the material, while the water sorts it and con- centrates the gold,

Placer Mining.

Form Of Deposits.

9. Shallow or Modern Placers. — As has already been stated, placers are deposits of material which has been eroded from rock formations, and the heavier portions of which have become concentrated by the action of water in such a manner as to form deposits rich in gold. The placer deposits which are most accessible are those occurring in beds of modern or recent rivers. These have been worked from the dawn of history, and the greater part of the gold that has been obtained in all ages has come from these modern placer deposits. The material of the deposit may consist of sand, gravel, loam, or clay.

Shallow deposits may occur in the beds of rivers, or 'as bars along the banks or shores of rivers, or on the seashore where the waves have gradually concentrated the gold in the sea sand into a richer deposit than the average sand. Any of these deposits may become deep placers by being subse- quently buried under lava or debris.

1 0. Mode of Occurrence of the Gold. — These deposits contain metallic g<)ld in fragments ranging from

Scer And Hydraulic Mining.

the finest dust to nuggets which weigh more than 100 pounds. The gold is also associated with more or less metallic plati- num, and occasionally with metallic silver, lead, and copper, and the heavier iron minerals, tinstone, jud precious stones.

1 1. The velocity of the current and the amount of mate- rial carried by a river will determine whether it will erode its channel or deposit material. If the river is carrying less sediment in suspension than it is capable of carrying, erosion will take place, while if it is overloaded, some of the material in suspension will be deposited. Just at the point where a river begins to deposit some of the heavy material it is car- rying, a concentrating action will take place and particles of different density will be separated. As the bed-rock of most rivers is rough and forms a series of natural pockets or riffles, one would expect to find the best deposits of precious metal at this point, and such is usually the case. All changes in direction of the course of a river, depressions or holes in its bed, changes in its width, or the character of the bottom, usually form places for the deposition of gold.

This is illustrated by (a), (d), and (c), Fig. 4. A pocket at one side of the bed of the stream, which would form a

jiwwfi-.

likely receptacle for gold, is shown in (,7). In (/') ami (.-) arc a series of pockets formed by the upturned edge cif the strata, as illustrated at A, A; these would probably contain rich deposits of placer material. After the current has

PLACER AND HYDRArLIC UINING.

comnienced to <]posit material, it sometimes dejiositj rapidly that there will be a stratum which contains but a small amount of gld as compared with that concentrated on the bed-rock. Then if this be succeeded by a period somewhat more rapid current, a richer rata will be formed with the gravel preA-iously laid down as a bed-rock, or if the current slows down a bed of clay may be deposited which will later form a floor on which a deposition will take place. These flrwirs or beds on which later depositions occur are called false bed-rocks, and frequently a mass of gravel will have a series of rich streaks running through it parallel to bed-rock. Rivers which change their courses back and forth through broad sandy beds act in the same way, and often form rich pockets in the material of the bed.

12. Even though the pockets on the bed-rock are usu- ally rich, the holes at the feet of waterfalls are sometimes barren and contain only a small amount of gold on the lower rim of the pot-hole. This fact is to be accounted for by the manner in which the water plunging over the waterfall would wash everything, coarse or fine, heavy or light, out of the hole, and then by some sudden change llie pot-hole may be suddenly washed full of gravel or other debris, without an opportunity for i ir.iii.ii 1.. take place.

I 3. Distribution of Gold In

I he Deposit E\-cn where the

, li.] is fairly uniformly distributed .l.n)ughoHt the materia] of the placer lieposit. ii is usually richer at or near I>ed-rix:k, and the different layers of gravel, sand, or other material will usuallv have a somewhat different average 'alue. Fig- Sis an example which will illustrate this point. The figures opposite the different strata

represent the value per cubic yard of the materials com- posing the several strata, as obtained by a careful series of tests ill the particular case under consideration. It is not to be supposed that all cases will be exactly like this. Some- times the richest deposit may occur fairly high up in the for- mation on a false bed-rock, and at times the surface of the deposit may be entirely barren.

14. Deep L.evel or Ancient Placers. — Placers may

become deep by successive deposits of material, and finally the river which formed them may be diverted from its course, or entirely lost by changes in the elevation of the continent, or by lava flows in the upper portion of its course. Such placer deposits may subsequently be cut by modern riv- ers, and they will then form bench or hill placers or diggings. In some cases the deposit is from 400 to 500 feet in thick- ness, the upper portions of it being as a rule composed of lower grade material than that of the portion near bed-rock.

In other cases the old river-bed has become filled with lava, which has covered the placer gravel to a greater or less depth. Subsequent erosion may form new channels which frequently cross or cut into the old deposits.

The deep placers, whether covered with lava or not, fre- quently become cemented into a kind of conglomerate, either on account of the presence of oxide of iron, silicious matter, or calcareous matter, which has been carried into the deposit by percolating waters.

The deep or buried placers were first discovered at points where they were intersected by the courses of modern rivers, and were explored by drifts or tunnels along their courses.

APPARATUS AND METHODS USED IN PLACER AM> HYDRAULIC >HNING. 15, Ancient MetbodH. — Gold was originally washed in a crude manner in all parts of the world, and all the primitive washing apparatus imitated as nearly as possible the methods Nature employed in the production of placer

10 Placer And Hydraulic Mining. § 39

deposits; thai is, they provitied some kind of dish or appa- ratus in which the gold-bearing mntcrial i-ould be subjected to the action of water, so as to wash away the lighter portion and leave the gold Iwhind. These efforts resulted in a number of washing devices, some of which are used at the present time.

1 d. VuHhilK Trough. — In China, among the Malays, and in the I'hili[pine Islands a kind of shallow trough, like a reversed house roof, came into use for gold washing. This is rocked backwards and forwards in such a manner as to cause the water to flow up one side and then up the other, carrying the lighter sand with it. This action gradually works the gold down into the bottom of the trough. The device is easy to handle, but is very slow, it being necessary to repeat the operation several times before fairly clean gold-dust can he obtained.

1 7. Balea. — In South America, a round wooden vessel called the batea came into use. This is a wooden bowl, usually about 20 inches in diameter and ?i inches deep. The sides of the bowl, which is turned from a single piece of wood, slope at a uniform angle from the outside to the center. The batea is sometimes used floating in water, the barren material being worked over the edge and the gold concentrated at the center. As a rule, the batea is much belter fur the saving of fine gold or for. concen- trating pyrites than the pan which is to be described later. This is on account of the fact that the surface of the wood is belter adapted for the catching and holding of fine material, and also it is easier to concentrate some classes of fine material in the point of the batea than in the edge of the pan. The balea is sometimes made of enameled iron and has a small hole in the, center of it, fitted with a plug or cork. This form is extremely use- ful for ore concentration tests, as after a heading has been obtained near the center, the richest portion of it can be washed through the hole, the cork replaced, and the concentration continued until another small portion is

'k

Placer And Hydraulic Mining.

ready to wash through the center of the pan. The wash- ing can be accomplished by pouring a small stream of water from a dipper in such a manner as to carry the desired por- tion of the material through the center of the pan.

18. Pan. — The pan is used mostly for washing gold by hand in North America and Australia, It consists of a pan 10 or I'i inches in diameter at the bottom, 1(1 to 20 inches in diameter at the top, and from H to 3 inches deep, pressed out of a single sheet of Russia iron, as shown in Fig. 6. The rim is sometimes strengthened by turning it over a wire. The pan is mostly used in prospecting, in cleaning gold-bearing sand, collecting amalgam in the sluices, and throughout placer mining gener- ally, as a test or check on all the work. 1 1.. Its manipulation requires considerable skill. A quantity f-f dirt to be washed is placed in the pan, occupying about two-thirds iif its capacity. If water is plenty, the pan with its contents is immersed in the water and the mass stirred so that every particle may become soaked. All lumps of clay should be broken up, and the coarse and worthless stones thrown out. The

pan is then taken in both hands, one on each

jl side, and without allow- j ing it to entirely emerge from the water, is siis- 1 pended in the hands, ' not quite level, but tip-

ping slightly from the t operator. In this posi- tion it is given a slightly rotary or shaking mo- tion, which allows the

'"' water to discharge all

light, earthy particles over the edge of the pan. Fig. 7 shows two men in the act of panning. After the light or

Placer And Hydraulic Mining.

earthy material has l>een worked off, there will remain a certain amount of i;old-dust, heavy sand, small stones, etc. The small stones can be picked out, washed i)ff and thrown away, and by carefully turning the wrist so as to give the pan a slight rotary motion, the muddy water is allowed to escape over the edge, a little at a time, with- out carrying the heavy sands with it. By repeating this operation, the material can be washed until nothing remains in the pan but gold-dust and heavy blai'k sand, with possi- bly a little earthy matter. By carefully working with plenty of clear water, the earthy matter can be completely removed, but the heavy iron sand can not be gotten rid of by simply washing, owing to the fact that its specific gravity is so near that of the gold. If the iron sand be magnetic, the grains can be removed by means of a magnet. If there are fine particles of pyrites in the pan, they can generally be distinguished from the gold by their lighter color, thaj gold being commonly a rich orange.

19> Horn Spoons. — Horn spoons, cut out of black ori horn or made from black rubber, are sometimes used by prospectors, especially for finishing the work begun in the pan. The surface holds the gold well and the colors shos very plainly upon it.

20. Tli Puddllne Box.— The puddling box wooden box, which may be either square or round. If round, it is usually formed by sawing a barrel in two, though pud- dling boxes are sometimes made six or eight feet in diam- eter, and are sometimes made square or rectangular. The box is provided with a series of plugs in the side, and its object is to remove clay from the gold-bearing material before it is panned or worked in a cradle. The bo.T is filled with water and gold-bearing clay and then stirred, either by means of a rake or, if round, by a rotating drag. When the clay has become thoroughly mixed with the water, one of the plugs in the side is removed and the muddy water allowed to run off. After this the plug is replaced, more water is introduced and the process repealed, with possibly

Placer And Hydraulic Mining.

the additionof some more material, until the box is filled, with grave] and black sand carrying guld-dust, up to the lowest plug. The contents are then shoveled out and worked in pans or cradles by hand. The water from the puddling box is frequently trapped, allowed to settle, and used over and over. Round boxes have the advantage that the water can he given a rotative motion, which has a tendency to keep the fine clay material in suspension, and thus make a better separation than can be accomplished in the square boxes.

21. Cradle or Rocker. — The rocker probably orig- inated in Georgia, and was introduced into California during the early days of gold mining. It is a box about 10 inches long by 16 inches wide and 1 foot high, with t. or two rifRes across the bottom the box being set on rockers, fio. s.

as shown in Fig. 8, which gives an end view and a longitu- dinal section of the rocker. On the upper end there is a removable hopper. 18 to 3(1 inches square and about 4 inches deep, with an iron bottom perforated with holes about J inch in diam- eter. Beneath the hop- per, beiow the perforated plate, there is a light frame placed on an incli- nation from front to back, and on this frame a can- vas or carpet apron is stretched. To use the rocker, material is thrown

into the hopper, water is poured on with the dipper held in one hand, while with the other hand the cradle is kept rock- ing. The water washes the finer stuff through the bottom of the hopper, and the gold or amalgam is either caught on

Placer And Hvdraulic Mining.

the apron or collects in the bottom of the rocker behind the riffles, while the rocks or stones are picked out from the hopper by hand, washed ifff, and thrown away. The lighter and worthless material washes over the riffles and dis- charges at the lower end of the rocker, while the gold or amalgam collects behind the riffles. Sometimes the entii bottom of the apparatus under the riffles is covered with 1 carpet. Rockers were used in placer mining before the introduction of sluicing. Now they are mainly employed ( in cleaning up placer claims and quartz mills and for col- lecting finely divided particles of quicksilver or amalgam. Fig. 9 shows a man operating a rocker.

22. Tlie l>ong Tom.-— The " Long Tom "' is a rough

trough about Vi feet long and from 15 inches to 20 inches wide at the upperend, inches wide at the lowei tnd, and about 8 inch< deep. It is set or Iiers or stones, with ; inclination of about 1 inch jier fool. The lower end of the box is cut off at an angle of 45°, and closed by iddle perforated with i-inch which a represents the Long Tom proper, (/the sluice which feeds it, and d the rifBe box. The material from the sluice flows down over the Long Tom a, where it is worked by means of a rake or fork so as to break up the lumps of clay. The finer material passes through the holes in the riddle or screen at the bottom of the Tom, while the gnivel or large stones collect against it and are removed periodically by means of a shovel or fork. The liner material which passes through the riddle into the riffle box is washed through the box, and the heavy parti- cles, such as gold-dust or black sand, collect behind the riffles. The old-fashioned Long Tom was about 14 feet long. It was followed by the '"Victoria" and the "Jenny

holes, as sh(

§39

Placer And Hydraulic Mining.

Is

Lind," or " Broad Tom." The latter is only C feet to 7 feet in length, 13 inches wide at the tipper end and 3 feet at the lower end. From two to four men work at one washer of this class, one man being required to rake and work the mate- rial in the portion a and discharge the coarse gravel and stones which collect against the riddle, while the others are employed in digging materia! and shoveling it into the trough a. The riffle bos b is placed at such an inclination that the water passing over it will just allow the bottom to become and remain covered with a thin coating of fine mud. Sometimes a little mercury is placed behind the riffles to assist in retaining the gold, and at times the riffle box is sup-

plemented by a series of sluice boxes, which may be pro- vided with blankets in the bottom for catching the very fine gold. Toms are cleaned up periodically, the gold and amalgam from the riffle box being washed or cleaned with cradles or by means of a pan. Fig. U shows three men working at a " Broad Tom."

23. Gold Adhering to Stones — Frequently the large stones or boulders have more or less gold adhering to them, and possibly attached to them by means of clay or the cementing material which held the gravel together. To free the boulders of this gold, it is necessary that they

Placer And Hydraulic Mining.

be rubbed together mth each other aad with tine stono in the presence of water. This may be accomplished byi allowing them to flow together through a long sluice by pass- ing them through a trommel, where they are tumbled over and over against each other in the presence of water, or by working them backwards and forwards by manual labor, is done in the " Long Tom."

24. Sluices. — When washing gravel by mean; Tom, the material is broken up and disintegrated in thja Tom proper by means of a fork or rake, and only i paratively fine sand or gravel is fed on to the riffle box. OnV this account quite a good separation can he made with a I short series of riffles, but it was found that even here it was I usually best to add one or two riffle boxes, and thes4a practically form a short sluice. Owing to the fact that tbfil capacity of the Tom is rather small and that the labor involved in breaking up the material and shoveling out tb big stones is considerable, this form of apparatus is totalljl unsuited for working large masses of comparatively iowJ grade material. For working this class of deposits, sluicesl proper were introduced. In the sluice all of the material a dug is passed through a series of boxes, and the coarse J stones are depended upon to grind up and disintegrate thd masses of clay, etc.

25. The term "sluicing" is applied to the washing c material down any channel, whether it be boxes, a ditctj dug in the ground on bed-rock, or a natural ravine; bu when the material is washed over natural surface, it is callet 'gri_mnd_ sluicing," and when washed through boxes it i called "box sluicing," or simply "sluicing." The sluicel boxes are made of boards, and vary in" width from 1 foot to over 5 feet, and in depth from 8 inches to 2 feet, or morea The boxes are usually made in sections from 12 to 14 feed long. For working shallow deposits where the material id shoveled into the sluice, the boxes are ordinarily from 16 t 18 inches wide and from 8 to 13 inches deep. The boxei are frequently constructed with the bottom narrower i

§39 Placer And Hydraulic Mining. 17

one end than the other, so that they will telescope one

into the other. This construction has the advantage that the sluice box can be quickly taken up and replaced in a different position. The line of troughs or sluices rests on trestles or stones, and usually shows a uniform grade throughout the whole series, the grade varying from 8 to 18 inches in 13 feet, depending upon the char- acter of the material being washed. It is important that the sluice should be conveniently near the level of the ground at the point where the pay dirt is introduced, and 1 this has an influence on the grade, as has also the character ,lof the pay dirt and the length of the sluice. The steeper /ithe grade, the quicker the dirt is washed away by the / Iforce of the water. The tougher the dirt, the steeper must be the grade, as tough clay does not break up so quickly in a slow current as in a rapid one. In short sluices the grade should be comparatively light, as there is more danger of the fine gold being lost in the short sluices than in the long I ones. The steeper the grade the more material can be put through a sluice. As ordinary pay dirt is generally com- I pletely disintegrated in the first 200 feet of a moderately ( low-grade sluice, the extra length beyond this is useful only I for catching the gold. Sometimes, therefore, the grade of , the last part of the sluice is reduced. When the grade of I the sluice is very low, say 1 foot in 40 or 50, the gold is I easily caught, and much of it would rest even upon the smooth floor of the sluice, but additional means, such as riffles, are usually employed. In case the grade of a sluice changes, particular attention will have to be paid to the point of change, as the larger stones are liable to lodge at such points and block the course, so as to cause the sluice to overflow. Frequently all stones as large as the two fists are thrown out of the sluice by means of a fork having several prongs (sluice fork).

20. Riffles. — If the wooden sluice were not lined with any material, the gravel would very soon wear through the sides and the bottom; hence false bottoms and sides ar

Placer And Hydraulic Mining.

necessary. The sides are usually simply planked linings,

htit ttie f;il?c h"Hnm i'? i<.'ncr;il!y in the form of riffles which iissist in the catching and :|ihng of the gold.

27. I K if fie

aici t udinal

-Longitudinal, bar. riffles are composed if bars or slats running if thj sluice. They arc such a length that it This would make

in the direction of the length usually fitted up in sections r requires two sections to each sluice bf the riffles about 0 feet long. The slats are held apart by small wedges or blocks placed one or two feet apart, and are frequently provided with strips nailed across the ends. They are held down in the sluice boxes by wedges. and sometimes by having the side linings placed on top of

them and then spiked to the shows the arrangement of a composing the riffles may b 4' X 4', or 4' X C scant- i-±l ling-

28. Block MlfncB.

— Where there is a great

quantity of pebbles and bouUlers running through the sluice, the longitudinal riffles are - sometimes worn away very rapidly, and hence their place is frequently taken by block riffles. In the block riffle the timber is sawed across the grain instead of with it, so that the blocks stand with the grain as it was in the original

set

n;uii

of the sluice. Fig. Vi f riffle bars. The bars f X 4". i' X 6',

§ 39 Placer And Hydraulic Mining. 19

tree, and the material rubs across the surface of the grain.

In the upper part of Fig. 13 are shown a series of block

riffles formed from sawed material. The riffles are held in

place by having strips of wood nailed to them by means of

headless nails, as shown in the illustration. These strips

form narrow spaces between the blocks, which spaces are

effective in the collecting of gold.

Sometimes round blocks are used

in place of square blocks, as shown

in Fig. 14. Where round blocks are

used, they are held in place by

being nailed to transverse strips, as

in the case of the square blocks,

and one series of blocks is started

from one side of the sluice and the

nest from the opposite side, so that

if the sets of blocks do not go clear

across, the spaces left will not form

a channel.

The blocks used for lining the bottom of sluices, whether square or round, are usually from 8 to ISinche iintii worn down to 3 or 4 inches thick, regarded. The sides of the sluices are i plank.

; high, and are flsed hen they are dis- tsually lined with

29. Roct Riffles. — Sometimes sluices are paved with rock in place of wood. These rock riffles may be of two

kinds, dressed, or squared rock riffles, which are blocks of rock that have been quarried and dressed approximately square, like paving-stones, and are arranged in the sluice in sections of 5 or 6 feet in length. Between each section of rock riffles a piece of timber should be securely fastened across the bottom of the sluice, so that in case some of the stones should become loosened, the flow of the material through the sluice could not rip up the entire series of riffles from one end to the other, and thus carry the gold already caught into the tailings. The other class of rock

g 39 PLACER AND HYDRAULIC MINING.

e 8 feet of such riffles, made in sections of about 15 inches each, were placed at the head of a line of sluice boxes 100 feet long; 98 per cent, of all the gold caught was found in these iron riffles, and the remainder was distributed throughout the wooden block riffles which occupied the remainder of the sluice. Iron riffles are usu- ally cast in short sections of 15 or 16 inches along the length of the sluice, and having a width, or, as is the case with a transverse riffle, a length, equal to the width of the sluice, the succeeding riffles being held in place by plates cast across the end of the block mentioned, {d) represents a series of angle-iron riffles as frequently used. This consists of ordinary angle-irons which are secured at the ends either by riveting them to a longitudinal strip or by any other simple device, such as placing blocks on the sides of the sluice so as to hold them in place. These riffles have proved very effective in catching gold, and have been used in a great many instances, especially in Australia, New Zealand, and South America, (c) represents a form of cast-iron rifHe in which the width of the riffie is equal to the width of the pocket; the pocket has vertical sides. The advan- tage that these riffles possess is that they are strong and resist wear well when used in sluices where great amounts of heavy material are run, but for some reason they have not been as close savers as some of the others, (ti) shows a riffle in which the width of the riffle is only one-fifth that of the pocket; these riffles have been used in cases where all the coarse material has been removed from the gravel by means of a trommel, and they have proven to be exceed- ingly close savers, for they retain nearly all the gold in the gravel.

31. Hallroad-lron Rimes. — Where heavy cement gravel is being washed, longitudinal riffles are sometimes made by placing railroad iron in the bottom of the sluice. This greatly reduces the wear and tear on the sluice and forms a good surface for the steep portion of the sluice, where the greatest part of the grinding takespiace while the

cement gravel is being reduced by means of the boulderS in the materia!.

32. Zigzag Riffle*. — Where considerable quantities of fine gold are present in the gravel, xigzag riffles are some- times employed. These extend only partially across the

sluice and from alternate sides, so that the current is made to pass backwards and forwards from side to side of the sluice. This character of riffles is supposed to assist in amalgamating the fine gold, the amalgam being caught by means of ordinary riffles farther down.

33. General Remarks In Regard to Riffles.— In

selecting the kind of riffles to be used in any particular case, it will be necessary to consider the form of the riffles, the character of the material which is to be run over them, the amount of material to be passed through the sluice, the amount of water, and the grade of the sluice. Some riffles which are especially adapted for dealing with large amounts of coarse material are not as effective as others would be for the fine material, while some riffles which are especially adapted for fine material are not well suited for coarse material; for instance, the form shown at d. Fig. 15, is intended primarily for fine material, while the forms shown at a, b, and Fig. 15, are intended for handling coarse or fine material as it may come. Block and stone riffles are about equally efficient on coarse or fine material, but the stone riffles wear longer when very large rocks are run through the sluices. Where much of the gold is saved by amalgamation, block riffles made of soft wood seem to be most effective, as they broom up and thus retain the smajl particles of amalgam and the gold. Where block riffles are employed, the crevices or cracks of the old blocks frequently cont.iin a considerable amount of gold, and hence it pays to save the old blocks, burn them and pan the gold out of the ashes.

34. Undercurrents. — In order to catch the fine gold running through sluices, it is necessary that the velocity

g 39 PLACER AND HYDRAULIC MINING. 83

of cUrrcntaiid depth of the flow be reduced. To accomplish this, it is necessary to separate the fine from the coarse mate- rial and to increase the width of the flume for a distance. Undercurrents are established for this purpose. They are really wide sections of a flume. Into the bottom of the reg- ular flume is introduced a grating composed of iron bars, set from half an inch to an inch apart across the flume, as shown in Fig. 16. The fine material drops through between the bars, while the coarse stones and a portion of the water continue in the main flume. The floor or pavement of the sluice above the gratinjf should be at least 1 inch higher than

the grating, for if this is not the case the grating is liable to become clogged. In order to maintain this condition, it

is necessary to renew the portion of the pavement immedi- ately before the grating quite frequently. In the under- current illustrated in Fig. 10, after the material passes through the grating at a. it flows through a box or sluice

placed at right angles to the regular sluice, and provided with block or cobblestone riffles. This transverse sluice b has a slight grade as il recedes from the main sluice, and it also becomes slightly narrower. It is provided with wings or distributing boards (not shown in the drawing), which distribute the flow over the various sections of the under- current proper. In the undercurrent shown in the illustra- tion, the two outside sections are paved for a short distance with cobblestones, and for the balance of their length with longitudinal riffles, while the two central sections are paved entirely with cobblestones. Such an undercurrent as this would be intended to handle anything that would pass through the spaces of a grizzly or grating. The grade of the undercurrent may be greater or less than that of the sluice. It usuaily depends very much on the character of the riffles employed. Where several undercurrents are employed, the upper one may be constructed as shown, or may have cobblestones, block or iron rifHes throughout, and have a grade somewhat steeper than that of the siuice, the depth of the flow being reduced to 1 or 2 inches. The material which passes over the undercurrent is, if possible, returned to the main sluice, and frequently the coarse stones which will not go through the grating a are passed over a drop in the main sluice, which has a tendency to pulverize any balls of clay or to break up any portions of cement, gravel, etc., which may have been carried to this point. The next undercurrent would probably be provided with a some- what flatter grade than the first, and possibly with a different form of riffle. Sometimes the last undercurrent is made much wider than the first, given a very flat grade (sometimes as little as 3 inches in 13 feet) and lined with carpet, blankets, plush, or burlap. The width of the undercurrent is usually from five to ten times that of the sluice, and its length may vary from 20 to 50 feet. Sometimes it is possible to arrange an undercurrent at such a place that the coarse stones which pass over the grating or grizzly are discharged over a precipice, while all the material which passes through is taken to the undercurrent.

ir

Placer And Hydravuc Minixg. § 39 '

3S. Gold-Having Tables. Soineti cues undercurrents are constructed in sections, and arc often called gold-saving tables. Fig, 17 shows such an arrangement. The sluice above the table is made double, so that either portion of it can be cleaned up separately, or the gates above a can be removed and both portions employed at the same time. The portion of the main sluice from a to d has no pavement, but is pro- vided with an iron floor perforated with small holes. The fine material passes through these holes and on to the tables at the right and left, flowing in the direction of the arrows. These tables may be covered with canvas, carpet, burlap, or may be provided with fine riiSes. Ustiatly they are covered with some 6brous material. After the fine material has passed over the tables, it is taken up by the branch sluices and returned to the main sluice lower down. Below the point the main sluice has a series of drops, as shown in the side elevation. These drops are paved with iron riflles, and serve to disintegrate any material which has not been broken up above the point d. Any section of the tables may be stopped at any time by turning the material from it on to the adjoining sections by means of deflecting boards under the main sluice, and the section thus exposed for cleaning. Gold-saving tables similar to those shown in the illustration are very largely used in South America, Australia, and New Zealand. The riffles are usually made similar to those shown at Fig. IS, and the main sluice is provided with a lining i)f cocoa matting before the riffles are put in place. This cocoa matting serves to hold any fine gold which might otherwise escape, and also prevents currents from flowing under the riffles.

36* Grade of Sluices. — As a rule, in working com- paratively tough or cemented gravel, especially when it contains much clay, it is best to set the sluices on consider- able grade and provide numerous drops to break up and disintegrate the gravel, depending upon the undercurrents to catch possible gold rather than upon the sluices proper.

Placer And Hydraulic Mining.

37. BuomliiE. — Buoming is ground sluicing on a larger scale, by means of an intermittent supply of water. The water is frequently collected behind a dam with an automatic' gate, working somewhat like that shown in Fig. Iff. When the dam is full of water, the overflow fills the small tank which operates the gate. The weight of the water in the tank opens the gale, -sO that tne entire mass of water in

the

wn through the gulch.

: reservoir e; a rush and carries the ma terial before it into the stuic The rush of the water lets the heavier particles of gold and magnetic iron or black sand settle on the bed-rock or in the sluice, and these are subsequently collected and washed in pans or cradles. When the small tank containing the water drops, a trap-valve in its bottom is opened, allowing the water in the lank to escape, and when this takes place the gate closes of its own weight, thus returning the tank to its former position.

Chabginu Thg S1.L'1Ces.

38. When commencing operations at a large placer mine, the sluices are made ready and are examined to see that they are water-tight. Then water is turned into the pipes and material run through the sluices for a day or two, so as to pack them with sand and gravel. The water is then shut off and a charge of quicksilver put into the upper portion of the sluices. In the case of very long siniccs, quicksilver may be put into the first two or three hundred feet of the boxes and a small quantity distributed through all, except the last 41K) feet of the line. In the case of a 0-foot sluice, the first charge may require as much as three flasks. The undercurrents arc charged at the :;anie time, and a small

S8 Placer And Rvdraulic Mining.

amount nf <)uicksilv(.-r i>iit itim the tailings sluice. Quick- silver is added daily during tlic run, in gradually lessening quantities, the object being tn keep the surface of the mer- cury uncovered and clean on the riffles in the upper portion of the sluice. : the (juautity chiirjjed is regulated by the amount exposed to view, A 24-foot undercurrent may be given from 80 to 00 pounds of quicksilver. In charging the riffles, the quicksilver should not bo sprinkled or splashed, as by this action the mercury is reduced to such small par- ticles that they are readily carried off hy the swift stream, and if broken sufficiently fine will be carried away. The surface of the water from mining sluices often yields minute par- ticles of quicksilver, and sometimes also float gold. In large placer-mining operations as much as 'i or 3 tons of quicksil- ver are sometimes required, a portion being in the sluice, a portion being held in reserve for use as needed, and the remainder being in the form of amalgam.

In the United States a flask of quicksilver is supposed to contain 76J pounds; the quicksilver is shipped in iron flasks.

Methods Of Excavating Material.

39. Manual Lul>or. — Originally the placer gravel was

loosened with pickaxes and shoveled into pans, rockers, Toms, or sluices. The sluices ran so much more gravel than the men could shovel that the operators found it nec- essary to adopt some more expeditious means of handling material.

40. Ground Slulcinfc- — Ground sluicing is much more rapid than manual labor, and has been used in a great major- ity of cases to feed the material into the sluices. The opera- tion consists in the carrying of a stream of water along the surface of the ground and into the end of the sluice. This stream hmsons and carries with it much of the gravel and earth. Its action is often assisted by men who stand in the stream or on the sides of it and loosen the material with

§39

Placer And Hydraulic Mining.

pickase:;, bars, tir shovels. By lliis means one man cuii HLinietimes run more gravel into the sluice in a day than he would be able to shovel in a month. Ground sluicing naturally partakes of the natnre of flume sluicing, and the current tends to sort the material, leaving the bonlders, coarse gold, and black sand on the bed-rock. The streams of water which flow over the bank and effect the ground sluice are sometimes called we uuiterfulls.

HVnRAV LICKING.

41. Origin of liydraullu MInloK-— The origin of hydraulic mining is usually credited lo Edward Mattison, of Connecticut, who was working in the placer mines of California. He conceived the idea of directing a stream of water under pressure against the gravel bank from a nozzle, and so doing away with the pick and bar nec- essary in ground sluicing and flume-waterfall work. He conveyed the water through a rawhide hose with a wooden nozzle, and discharged it againtit llie bank in the mannersln iwn in Fig. 19. Others soon took up the method, and the size of the hose and nozzles rapidly in- creased; but these pipes gave a great deal o f trouble by bucking, knocking the men down and causing considerable damage, the evolution finally resulting in the invention of the Giant or Monitor, which is shown in operation in Fig. 20.

BVOLVTiON or the: giant.

42. Goose-Neck. — The original form of nozzle for use on the end of the metal pipe was the Goose-neck, as shown at (n). Fig. 21. This consisted of two elbows turned in opposite directions, the upper one being provided with a nozzle. The trouble was thai the pressure of the water caused the joints to leak, and when the pipe was turned so as to make an angle with the direction of the supply-pipe, it would buck or fly back, endangering the lives and limbs of the operators.

43. Globe Monitor. — The Goose-neck was succeeded by the "Craig Globe Monitor," as shown at Fig. '21. This consisted merely of a ball-and-socket joint, to which thi nozzle was attached. The pressure of the water in 1 joint nude it very difficult to operate.

44. Hydraulic Chief.— Mr. F". H. Fisher invented the" Hydraulic Chief, which was the next in advance. This ma- chine is shown at (c), Fig. 21. The main improvements con- sisted in the use of two elbows placed in reversed positio

§3E1

Placer And Hydraulic Mining.

when in a straight line, connected by a ring in which there were anti-friction rollers. The ring was bolted to a flange in the lower elbow, but allowed the upper elbow a. free horizontal movement, while the vertical motion was obtained by means of a ball-and-socket joint in the ontlet of the upper elbow. The interior was unobstructed by a bolt or other fastenings, and the man at the pipe could operate it by means of a lever without danger to himself. Riffles similar to those shown at (g). Fig. 21, were inserted in the discharge-pipe to

prevent the rotary movements of the water caused by the elbows and to force it to issue in a solid stream. These machines soon became leaky at the joints, but the riffles have remained as one of the features of the Giants ever since. If the water issues from the nozzle with a rotary motion, it will spray and not form a solid stream.

45. Dictator. — The Hoskins Dictator was the next step in advance. This was a single-jointed machine with clastic packing instead of two metal cases. The joint

Placer And Hydraulic Mining. § 39

worked up and down on pivots, and in rotating it, small wheels ran arniind against the flange. 1

46. Little Giant.— The Littie Giant, a subsequei invention of Mr. Hoskins*, on account of its simplicity arnii-l durability, superseded all previous machines. This is illus- trated at {d), Fig. 31. It is a two-jointed machine, portable and easily handled, having a knuckle-joint in the nozzle to give it a vertical range, and a swivel-joint in the pipe for the horizontal movement. The nozzle was provided with riffles.

47. Hydraulic Glantti. — The Little Giant was suc- ceeded by the Hydraulic Giant, one form of which is shown at (f), Fig. 21. In this form the pivot or knuckle-joint is placed between the two elbows, the swivel being at the top of the lower elbow. The joint has no bolts passing through it, as was the case in the Little Giant, thus giving a free passage to the water. The pipe is provided with a balance weight similar to that shown in connection with the Little Giant.

48. Monitors,— The Monitor is a form of hydraulic

machine invented by Mr. H. C. Perkins and shown at (y"). Fig. 31.

49. DeflectliiK Nozzle. — In the earlier forms of Giants it was necessary to drag the pipe backwards and forwards, or lift or depress it by manual labor, and this was extremely difficult and coupled with more or less danger to the open tor, Mr, Hoskins invented the deflecting nozzle, which is: simple device by means of which one man can easily hand: the largest (iiant. The attachment is shown in connectia with the machines illustrated at (c) and (/), Fig. 21, : may be described as follows: There is a small extension to the regular nozzle, which in some cases is slightly larger, and in others practically the same diameter as the nozzle. The extension is connected to the main pipe by means of a ball-and-socket joint, as shown at n, Fig. 21 (c), and at A, Fig. 21 The deflecting nozzle is operated by means of a handle c, which ordinarily rests on a support J. When the

§39 Placer And Hydraulic Mining. 33

handle c is on the support d, ihe two nozzles are in line. If the deflecting nozzle be moved in any direction by r of the handle c, one side of it will be brought into contact with the stream as it issues from the regular nozzle, and the force of the stream reacting against the deflecting noz- zle will force the entire pipe in the direction of the interfer- ence. In order to cause the pipe to travel in any given direction, it is only necessary to thrust the handle c in that direction. If the pipeman is cool and collected, this deflect- ing nozzle gives him absolute control over the pipe at all times, and removes much of the danger formerly connected with this part of hydraulic mining.

£0. General Remarka In Connection 'with Hydraulic Nozzles. — Monitors or Giants of any descrip- tion have to be securely fastened down by bolting them to timbers, and weighting the timbers and the first joint of pipe with rock; for if the Giant can get in motion and once starts to trembling, it is almost sure to buck, and frequently tears loose from the pipe, so that the Giant and the man at the pipe are both washed away by the flood of water from the supply-pipe. In using the pipe for hydraulicking or washing down banks, considerable skill or e.tperience is required. If the bank contains a stratum of clay, together with a considerable quantity of large boulders, it is possible to cut the clay down in such a manner that it will practi- cally lubricate the way for the boulders, so that they wi!l slide over the bed-rock and into the sluices as though the way had been greased. On the other hand, the mixing of the boulders and clay will facilitate the breaking up of clay balls. This is especially true where the sluices are provided with drops. Considerable skill is required for the operation of the Giant, and a good pipeman, as the men who operate the Giant are called, is much more valuable than several less experienced men would be about a placer mine, on account of the fact that he knows just how to take advan- tage of the different classes of material to be washed and to get the most work out of the water.

Placer And Hydraulic Mining.

Cavixu Bakks.

51. In opening up a placer mine, the work is comtneoci near the sluice. As the bank recedes, bed-rock cuts or ground sluices have to be advanced to the face, to facilitate the washing of the gravel into the sluice proper. The banks are ordinarily caved by turning two or more streams against any one point in the bank in such a manner as to under- mine it, as illustrated in Fig. 22. The water is delivered,

with a force of from 150 lo 2U0 pounds to the square inch; rapidly undermines the bank, washes away the material, am carries the debris into the sluice. If the bank caves readily one pipe may be used for cutting, while the stream from th other will be employed for washing the gravel through th) bed-rock cuts into the sluice. The face of the bank should' ' be kept square, advantage being taken of any corners which may be left, and under no circum.stances should a horseshoe shape be formed. When the cut is rapidly pushed ahe< and the work not squared, the men at the pipes becoid

§39 Placer And Hydraulic Mining. 86

enciri;led by the high walls and their lives are in danger. Where the banks exceed 150 feet in height, the deposit is usually worked in two benches. When the men at the pipes see that the bank is about to cave, the water should be immediately turned away, for if the cave falls on water, a rush of debris is liable to follow, which may bury the pipes and force the men to run for their lives. In mines which are only operated by day, caves are usually made just before quitting time at night. Where possible, the washing should be continuous and no water allowed to run to waste; hence it is desirable to have several faces or openings, so that the stream may be diverted from one to the other while the bed- rock, cuts, or sluices are being lengthened. The cuts or bed-rock sluices are trenches made in the bed-rock near the face, to collect the water and material and convey them to the sluices. Sometimes these cuts are as much as 00 or 70 feet deep. As a precaution against theft, where claims arc worked intermittently the sluices are run full of gravel before closing down.

Trommels.

53. In many placer mines tnimmels are employed for disintegrating or breaking up the gravtl and for separating the fine material from the coarse stones. The rolling action of the trommel, together with the water which is discharged on to it, thoroughly washes or cleans all the boulders, and removes all clay or gold from them before they are discharged. Trommels are especially useful where the amount of water is not sufficient to carry the boulders through the sluice, or where it is impossible to obtain a sufficient fall for a length of sluice that would disintegrate the material and then sufficiently concentrate it. Trommels are used very largely in the Siberian placer mines.

Lighting.

53. Where mines are worked night and day, some form of artificial light must be employed for the night-work. In some cases, locomotive reflectors or bonfires are employed, but must <'f the large mines now use arc lights.

Placer And Hydraulic Mining.

Of Taii.Ikgs.

54. General Uemarkn. — In large placer mines dispi sition of the tailings has always been a serious question In many cases they are simply washed into some rapidi] flowing river, but sooner or later they are liable to worlQ down the stream and to block the course of the river, caii ing serious floods and the burying of much valuable land iq the agriculiiiral districts. On this account, a permanea injunction has been granted against certain classes of placen mining, work in California. To overcome this difHcultfj several devices have been resorted to.

55. Brush Dams — Dams of brush or logs are fr&-l

quently constructed in gorges or canons, and the tailingl allowed to accumulate behind them. As the level of thef tailings reaches that of the lop of the dam, the height of the I dam is increased. By carefully constructing the dams and J by keeping them up to full height, the tailings may bcv indefinitely held in the caBon or gorge by this means; but iit'l many cases the level of the tailings would soon reach that of the ground from which they were being excavated, and hence work would be brought to a standstill. To overcome this, some form of elevator became necessary. In some cases tailings have been elevated mechanically by means i bucket elevators, but this is expensive and is rarely i sorted to.

HVURACLIC ELEVATOHS nLOWUPS.

56. The Ludlum Elevator. — One of the first hy- draulic elevators that was constructed to raise tailings is illustrated in Fig. 23. The principle is that of the ejector. A stream of water under considerable pressure IS discharged through a nozzle similar to a Giant nozzle, as shown in the illustration, and gravel mixed with water is fed to the opening around the nozzle, the force of the stream carrying the entire mass up the discharge-pipe to a consld erable height. Similar elevators or ejectors are also 000.1 structed for removing water from workings in the beds o]4

Placer And Hyuraulic Mining

rivers, or other places which have a tendency to become flooded.

57. Evans Elevator. — Fig. 24 illustrates the Evans

elevator, which works on the same principle as the ejector. The water under pressure enters through a and is discharged through a nozzle The suc- tion for the grave] is through a large opening in front, and the rapid flow of the water draws the material in and ejects it tip through ihe contracted por- tion and on through the dis- charge-pipe. One great advantage claimed for this ele- vator is the introduction of the two auxiliary suctions 6 and c. These are placed at the sides of the main suction and may be employed for draining the pit of water, for drawing in fine material, or even for draining places in bed-rock at some dis- tance from the elevator. One great advantage in the use of these auxiliary suctions is that the space back of the nozzle is thu

Placer And Hydraulic Minino.

water, and the boulders and other material drawn in through the main suction prevented from rushing around into this space with a great force, which they would otherwise have a tendency to do. These elevators are built with a capacity to handle stones 18 inches in diameter and lift materia] 15 feet high for every 100 head of water.

S8.

Auxiliary Appahatus.

l>erricU(t.Strong derricks are used in hydraulic' mining to remove heavy boulders. The mast is frequently 100 feet high and the boom over 90 feet long. The mast is held in position by guy wires and is provided with the proper tackle both for raising and lowering the boom and for rais- . ing any weight attached to the bofjm. Such derricks usually operated by means of water-wheels of the "hurdy-j gurdy " pattern, the wheels frequently being as much as feet in diameter and sometimes being connected to the drum which operate the ropes by means of gearing.

S9. Water- Wheels. —The "hurdy-gurdy" or son form of impact wheel which can be moved by a stream (

jet of water issuing from a nozzle under pressure, i

g 39 PLACER AND HYDRAULIC

striking open buckets on the circumference of the wheel, is frequently used for operating the derrick, or furnishing other power around the placer mine. One form of Pelton wheel is shown in Fig. 25. Undershot water-wheels are also fre- quently employed for operating the Chinese pumps or bucket elevators in connection with wing-dams in bar

Wikg-Dams.

60. The material below the level of a stream may be worked by means of wing-dams similar to that shown in Fig. ao. The stream is dammed and the water carried along

side

in a

ditch or flume. The portion of the bed thus separated from the current is pumped out, and the gravel removed and sluiced. The water may be removed from the por- tion isolated by means P"* of hydraulic elevators, power pumps, or by means of water- whi;els or Chinese pumps. In Fig. 2(i a modified form of Chinese pump is in operation. On the right of the figure will i>e seen an undershot water-wheel which operates a Chinese pump at the left of the figure. This pump, consisting of a large wheel around which passes a chain-bucket system, lifts the water and dumps it into one of the sluices shown at the left of the figure, thusdraining the workings. The other sluice shown at the left of the figure is the gravel sluice, which is supplied with water from the stream above the dam, and is used for sluicing the gravel taken from the opening. In the examples of placer mining at the latter part of thi.s Paper there is a description of the Roscoc placer, which was exposed by a wing-dam.

:

Placer And Hydraulic Mining.

nniFTiKG.

61. In tne case of deep placers overlaid with lava caps, it is sometimes necessary to resort to drifting in order to obtain the material on the bed-rock. In some cases, only the bed-rock gravel will pay for excavating, while in others it is possible to work the material for some distance above bed-rock, and occasionally it would be found profitable to work the i;ravcl nn tirn difFrrcnt levels, there being a false

nr

bed-rock some distance above the true bed-rock. In work- ing these drift mines, the entrance may be effected either through a shaft or tunnel. In some cases an old river-bed is cut by a modern river-bed in such a manner that the drift or tunnel can follow the old bed, but in most cases it will be found necessary to drive a tunnel from some adjacent val- ley or to operate the mine through a shaft. Operating through a shaft has the disadvantage that the water must be removed, and this would often render the mining opera- tions unproductive. Fig. 27 gives a plan and two sections of the " Sunny South " drift mine in California. This mine is operated through a tunnel driven from an adjacent val- ley in such a way that it passes under the lowest part of the ancient river-bed, and access is obtained to the gravel by

Placer And Hydraulic Mining.

means of raises. Drifting is only profitable when the pre- cious metal has been concentrated in well-defined strata or portions of the channel. The location of the tunnel through the " rim rock " is a matter of great importance. However, if it is not located below the lowest part of the deposit, it will be necessary to pump the water and raise the gravel to the tunnel, and hence the main object sought in drifting

Ibe r

ssed.

62. Handling and Treating the Gravel. — The

gravel is removed in mine-cars to the mouth of the tunnel, where it is dumped on the floors and washed in sluices, if not loo firmly cemented. If the material is firmly cemented, it must be crushed in stamps previous to washing. These stamps differ from those used in gold and silver mills in that they have a double discharge and use a very much coarser screen than is common in mill-work, the screen usually being at least --inch mesh. An attempt is made to amalgamate the greater part of the gold in the battery, but copper plates outside of the battery are also employed, and these are usually followed by sluices. As a rule, no attempt is made to save the gold-bearing sulphides contained in the gravel. In some mines, steam locomotives are used for transporting the men and materials through the tunnel, which in some cases is over a mile in length.

63. Timbertnfc and Method of Minlne- — The tun- nel is timbered like an ordinary drift by means of sets simi- lar to those shown in Fig. Sf. The gravel is mined much like coal is worked, the deposit being divided into panels or divisions, which are subsequently worked either on thepillar- and-stall system or by means of square work. When worked by the pillar-and-stall system, the pillars are sometimes robbed clean, the entire deposit on bed-rock being recovered. This is accomplished by building packs or pillars of the larger boulders in the worked-out rooms, and also by sup- porting the roof temporarily by means of posts and breast caps similar to those .shown in Fig. 29. If the gravel is com- paratively soft, it fhay be necessary to timber the entire roof,

Placer And Hydraulic Mining.

S3

and in thai case the posts may support stringers, which in turn carry the lagging, or a series of drift sets may be used

side by side. When the square-work system is employed, the drifts or breasts are carried in both directions at right angles, leaving the pillars as illustrated in Fig. 30. It will be seen that by this means three-fourths the deposit can

§ 39 Placer And Hydraulic Mining. 43

64. Tunnels as OutUttt for Hydraulic Minea.

— Some placer deposits occur in ancient river-beds where they are not overlaid with lava caps, but are so situated that they have no natural dumping-ground. An outlet for these deposits is frequently provided by driving a drift or tunnel to some neighboring ravine or caf5on. A shaft is sunk to connect with the inner end of the tunnel, and the gravel washed down through the shaft and out through the tunnel. Sometimes siuice boxes are placed in the tunnel, while in other cases the material is allowed to run on the rock bottom of the tunnel, the floor of the tunne! forming a natural ground sluice. When this latter process is followed, the material is liable to wash the floor of the tunnel into very irregular hollows, and may in time cause very serious caves. There is one advantage in having a sluice inside of a tun- nel, and that is the tunnel can be provided with doors, which can be kept locked in such a manner as to prevent the stealing of the gold which has accumulated in the sluices. After the work has progressed for sometime and the gravel has been removed to bed-rock, at the point where the shaft descends to the tunnel, it may be possible to place a portion or all of the sluices on the bed-rock above the pfinl where the material enters the tunnel. The introduction of hy- draulic elevators has furnished a means for working a large number of deposits which were formerly operated by means of tunnels, as just described.

65. Worklng Frozen Ground. — In Siberia and Alaska the ground is frozen to a considerable depth, and the summer season is so short that, as a rule, it would not thaw sufficient gravel to give the miner a fair season's work, and in some cases would never thaw to bed-rock. On this account the material is mined during the winter, while frozen, and is thawed and washed during the summer. The frozen gravel is much harder to work than ordinary rock, owing to the fact that it is so tough that it resists drilling, blasting, or picking, so the miner thaws the ground before attempting to break it down. He accomplishes this by

44 PLACER AND HYDRAULIC MINING. gS

building a fire against a portion of the ground to be removed. In sinking his shaft, if the surface is frozen, he builds a fire of wood where he desires to sink, and the heat from this thaws the ground for a little distance. The fire is often rendered more effective by a cover of charcoal, so as to con- fine the heat. When the fire dies down, the miner scrapes aside the embers, and shovels away the loosened ground beneath until he comes once more to a frozen i>ortion, where another fire is built, and the whole operation repeated. This is continued down to bed-rock. The sides of the shaft are given what support is necessary by means of timber cribbing or rough square sets with lagging. From the bottom of the shaft the drift is started, every foot having to be thawed. A strong wood fire is built against the face of the drift and covered with charcoal, as before, and allowed to burn out. After the material is thawed, it is removed and another fire built. All workings must be tightly, though not necessarily heavily, timbered, owing to the fact that the constant use of the fires underground soon softens the roof, and portions of it are liable to cave and cause seri- ous results. Some simple ventilating device is usually necessary to remove the gases generated by the fire. This may be accomplished by means of a brattice until the mine has been extended a sufficient distance to drive an air- shaft. The work is usually carried on by means of the square-work system, as shown in Fig. 30. The effect of the fires in the drifts is to raise the temperature to an oppressive point, so that in some large Siberian mines the minerswork naked, though the temperature outside may be several degrees below zero. An amount of wood equivalent to the thickness of 1 foot across the face will thaw about the same depth of gravel, and 14 inches is practically the maxi- mum depth which can be thawed with one fire.

66. Blasting — When working cement-gravel mines by the hydraulic process, it is frequently necessary to loosen the gravel by means of blasting. For this purpose, a tunnel is driven into the bank some distance, and drifts turned to the

§ 39 PLACER AND HYDRAULIC MIKlNG.

right and left, parallel to the face. Boxes or barrels of pow- der are packed into these drifts and connected with the surface by means of wires, so that they can be ex- ploded when desired. The tunnel is then carefully tamped with fine gravel or clay, so as to prevent the escape of the gas through this opening, and thus increase the effi- flc. si.

ciency of the blast. The tamping should be thoroughly rammed in with wooden mauls. Occasionally blasts are fired by means of fuses, and when this is done, two or three lines of fuse should be laid, so as to avoid misfires. The general arrangement of the tunnel drifts and charges is shown in Fig. 31, in which a it and i/(/ are the wires con- nected with the two poles of the battery, and d b are the charges to be fired. Comparatively soft cement gravels of black powder, which is simply what disintegrate the bank. Where extremely hard, it is sometimes blasted lite or giant powder. In el, 50 to 150 feet high.

are best blasted by ii

used to lift and ;

the cement gravel is e

by means of low-grade dyn

banks of ordinary cement gravi

recommends that the main drift should be run in a dis- tance of two-thirds the height of the bank to be blasted. The cross-drifts from the end of the main drifts should be run parallel to the face of the bank, their length being deter- mined by the extent of the ground to be removed. The powder required is from 10 to 20 pounds of black pow- der per 1,000 cubic feet of ground to be loosened. Even when black powder is employed for the blast, the ex- ploders b, b are usually inserted in cartridges of giant pow- der and placed on top of the paper covering the black powder. By this means a much more powerful detona- tion is obtained, and the action of the black powder is made more effective.

46 Placer And Hydraulic Mini]

Cleaning Up.

67. The length of the run depends upon the pavement or riffles and upon the value of the ma put through the sluices. Some claims are cleans twenty days, others every two nr three months only once a season. All pavements should be soon as they begin to wear in grooves. Where titles of gravel are washed, it is advisable to cle 1,000 or 3,000 feet of sluice about every two wee ing sluices being only cleaned once a year. Un should be cleaned up whenever quicksilver is fo over the lower riffles, with a tendency to dischal end into the tailings. The gold-saving tables an every few days without stopping the work in sluice, by simply diverting the water from oneb is being cleaned up, and repeating the operatl of the tables have been cleaned. When it is decii a general clean-up, the bed-rock and ground washed clean. No material is turned into the s water alone being run until the sluices are free A small quantity of water in which a man can work is then turned through the sluice, the blod out with crowbars, washed, cleaned from amalgi alongside the sluice. This is done in sections oi so. One row of blocks is left in the sluice betwe tion. These rows serve as riffles to prevent til quicksilver from passing down the sluice. Aft section of blocks is taken up, the men follow th dirt as it is slowly washed down the sluice and quicksilver and amalgam with iron spoons am sheet-iron buckets. As each riffle is reached, tl and quicksilver are collected, the blocks remo' residue washed down to the next riffle, etc., dow line of the sluice. When this operation is finishe is turned off entirely and workmen go over the small silver spoons, digging the amalgam out holes and cracks. After this, the side lagging iai

J

Placer And Hydraulic Mining.

and the blocks are replaced. Very long sluices are usually lined in the lower portion with heavy rock riffles, which can be used for a longer period without cleaning np than is the case with the smaller riffles used farther up. In some cases it is customary, where mines are run night and day, to clean up as long a section as possible during the day, to replace the lining, and resume washing at night, proceeding thus until the entire sluice is cleaned up.

Aualgahation.

68. Although heavy gold may be arrested by the vari- ous contrivances described, such as riffles, undercurrents, etc., much fine gold might escape in the absence of mercury or quicksilver. When this is present, it instantly seizes and amalgamates any gold coming in contact with it. When using zigzag riffles, a vessel containing quicksilver, and pierced by a small hole which allows the metal to escape drop by drop, is sometimes placed at the head of the sluice. The quicksilver trickling down from riffle to riffle over- takes, absorbs, and retains the fine gold, the amalgam thus formed being caught in the regular riffles farther down. Where the sluices are provided with longitudinal riffles, after starting the washing, more mercury is poured into the head of the sluice and finds its way down with the current, though the larger proportion of it will remain in the upper boxes. Small quantities of quicksilver are sometimes intro- duced at intervals farther down the sluice, the quantity being increased, in direct proportion to the amount of fine gold present. Where block riffles are employed, an attempt is sometimes made to impregnate the pores of the wood with mercury. This is accomplished by grinding the end of a piece of gas-pipe to a thin edge, and driving it into the wood. The gas-pipe is then filled with mercury, and the pres- sure of the column will force a certain amount of the fluid into the pores of the wood. As the wood gradually wears away, this mercury becomes exposed and amalgamates any gold that may come in contact with it. When cleaning

PLACER AND HYDRAULIC MINING, fi

itc, the amalgam remaining Ti ply scraped off.

, ihe surface of tin

69. Copper Plates. — Where gold is very fine, amalg; mated copper plates are sometimes employed. These are usually at least 3 feet wide by 0 feet long, and sometimes the stream is split and carried over two or three such plates, so as to reduce the speed of the current on the plates as much aspossible. The plates are placed nearly level and at consid- erable distance from the head of the sluice, as it is intended to catch only the fine gold ; and for this reason also a screen is placed above the plates in such a manner as to remove allJ the coarse material and allow only the fine material to pass over the plates. The screens employed for this purpose arfl.B frequently perforated with holes inch by -jY inch, simila] to the slotted screens used in the stamp batteries of gold aiid silver mills. The copper plate is amalgamated by first cleaiiTJ ing its upper surface with dilute nitric acid, and then apply:>] ing some mercury which has been treated with dilute nitri< acid to form a little nitrate of mercury. The current mus) be slow and shallow, so that every particle of gold may cotnoi in contact with the surface of the plate. A freshly amalgaJ mated plate may become coated with a green slime of sub* salts of copper. This must be carefully scraped off and the plate carefully rubbed with fresh mercury. To remove the amalgam in ordinary cleaning up, the plates are sometimes , cleaned by means of a whisk-broom, the bristles of wh have been cut very short, or are scraped with a knife scraper. If it is desired to remove practically all the amalr gam, this may be done by gently heating the plate and thei scraping off the amalgam; but plates always catch gold t ter when there is a little amalgam remaining on them, ; the warming of the plate makes it more difficult to re-coat. For these reasons, it is not always advisable to resort 1 these means during a clean-up. The copper plates sin not be less than j'- inch thick,

70. Amalffain Kettles. — Amalgam kettles are ordt nary sheet-iron buckets or porcelain kettles. They are used'l

§ 39 Placer And Hydraulic Mining. 49

as receptacles in which to collect mercury and amalgam while cleaning up sluices and undercurrents, and also for flnating amalgam to free it from foreign substances before

it is strained and retorted.

71. Cleaning the AmalEoni. — The quicksilver and amalgam obtained in cleaning up the sluices and under- currents are well stirred in buckets, if necessary, with the addition of mercury. The coarse sand, nails, and other for- eign substances which float to the surface are skimmed off. This residue of sand, which always retains some amalgam, is concentrated by working in pans or rockers, and the con- centrates are ground in iron mortars with some clean quick- silver to free the amalgam. Any base material floating on the surface after this second cleaning is melted separately to a base bullion, and the clean quicksilver and amalgam are added to the clean portion from the first. The quicksilver is then separated from the amalgam by straining through canvas, chamois-skin, or buckskin, and the dry amalgam is

treated in iron retorts.

72. Retorting. — When the amount of amalgam to be treated is small, hand retorts answer all requirements. These are simply cast-iron pots having a cover that can be fastened on, and through which a bent pipe passes. The iron pot is partially filled with amalgam, placed in an ordi- nary forge fire, and the end of the bent pipe immersed in water. In this way the mercury is driven over and into the water. Care must be taken that at the end of the retorting the heat of the fire is not allowed to fall in such a manner as to form a vacuum in the retort; for in such a case the water would rush back into the iron pot. form steam, and probably result in a disastrous explosion.

Where large amounts of amalgam are handled, stationary cast-iron retorts are used. If the furnace were to be left unattended for a short time, and it were placed immediately above the fire, it is apt to become overheated. In this case, the weight of the metal inside of the retort would cause it to "belly, "thus ruining it completely. To prevent this, the

' : I

.. -.ri mIj -l. il lit-

1 ,

§ 39 Placer And Hydraulic Mining. 51

allowed to cool, and when cool is opened. During the oper- ation the condenser coil at the back of the retort should be kept cool by means of a continuous supply of fresh water, which enters from the lower end of the box containing the condenser, the warm water discharging from the upper end of the box. For the purpose of cleaning, it is better to have the condenser in the form of a straight tube than in the form of a coil, for it is impossible to run a rod through the coil for the purpose of cleaning ; it is also impossible to satis- factorily inspect the coil and see if it is clean. The retorted bullion is cut or broken into pieces and melted in well- annealed black-lead crucibles, and the gold cast into bars.

Distribution Of Gold In Slcices.

73. In sluicing, the greater part of the gold (usually at least 80#>) is caught In the first 200 feet of the sluice. For example, in a claim yielding $03,000 on a 100 days' run, *54,000 was obtained from the first 150 feet and 3,000 from the undercurrents. The first undercurrent, 7!0 feet from the head of the sluice, yielded 50 per cent, of the total amount taken from the undercurrents; the second undercurrent, containing per cent, of the gross undercurrent yield, was 78 feet distant and 40 feet below the first. The last under- current was 98 feet from the second, with a drop of 50 feet between them, and its yield was about toOO. The balance of the gold was obtained from the bed-rock above the sluices. Another case has already been spoken of in con- nection with the iron riffles, in which 8 feet of iron riffles were employed at the head of the sluice, and ',18 per cent. of the gold caught was found in these 8 feet of riffles, the other 2 per cent, being distributed over the !I3 feet of block riffles.

Preliminary Investigation Of Placers.

74. The value of the gravel deposit is the first con- sideration. Its determination involves the ascertaining of the course of the channel, the deptli of the deposit, and the

Placer And Hydraulic Mining,

I position of lied-rock, which in some cases may be under I hundreds of feet of materia!. The total size of the deposit 1 must be determined, and an estimate made of the yield 1 which the ground can make and of the cost required to j work it. The geology and topography of the deposit and its surrounding must be considered, as they will assist in determining the course of the channel and the depth to bed-rock; the conditions for dump should also be considered. The value of the gravel may be approximately determined by making shallow pits and washing the material obtained from them and from other available places, as where the bank has been exposed by the cutting of streams. Deep placers and large enterprises frequently require prospecting by shafts sunk to bed-rock and by drifts. The water- supply conditions and the length of the working season should likewise be carefully considered. Different-colored gravels, as red, rusty, and blue, are sometimes cortsideredI good signs, but they are not reliable. Black sand is fn quently accompanied by gold, but it may be barren.

The careful prospecting of a large placer deposit fre- quently involves the expenditure of a large sum of money, as, for instance, in the case of the Malakoff property in Cali- fornia, where it was found necessary to sink four shafts and to drive over 1,200 feet of drifts, making in all, counting shafts and drifts, over 2,000 feet of exploration workings. The average assay of the samples from the various drifts was #3.01 per cubic yard, and the actual yield obtained by treating 21,000 tons of the material extracted was at the rate of t3.75'per cubic yard. The cost of the preliminary work in this case was ttiO, 050.20. From this it will be seen that large and deep placers are certainly not poor men's mines.

When investigating placer deposits in arid or dry regions the following facts should be borne in mind : The greatei part of the gold in such a region was not deposited by con- stantly running streams, but by intermittent flows, most of which were of the character of cloudbursts or floods. On this account, the gold will not be found concentrated, as t:

§ 30 Placer And Hydraulic Mining. 63

the beds of streams which have a comparatively even flow, but will usually occur on false bed-rock above the true bed- rock, the pay gravel being in irregular patches, which, as a rule, do not extend over large sections of country. Fre- quently the soil just under the grass roijts is the richest portion of the entire deposit. This fact may be accounted for as follows: In regions which have wet seasons, the soil becomes soft to a considerable depth, and any particles of gold tend ultimately to find their way to bed-rock, while in the arid regions the rain-storms usually soften but a few inches of the surface, and hence any gold contained in the soil accumulates a few inches from the top of the deposit, the first few inches being thus freed of the gold, which will settle through to a lower point. The barren surface soil is blown away as dust during the dry season, or washed away during the rainy season; as this process continues, the gold gradually works its way downwards, always remaining within a few inches of the surface. Such occurrences of gold high in the deposit should not lead the prospector to believe that the material will become richer and richer until true bed- rock is reached, for these formations are frequently barren in their lower portions.

Water-Supply.

75. Source of Water. — The water-supply for placer operations is obtained from running streams, melting snows, and rains. The snow accumulates on the mountains during the winter, and the heavy rains of the spring cause rapid thawing of the snow-banks, and enormous volumes of water rush down the gullies and ravines. In case the country is timbered, the streams may furnish a sufficient supply throughout the year; but near the timber line or in a sparsely timbered country, the water usually rushes off in the spring, and the streams are dry later in the year. In order to provide a supply of water for hydraulic mining in such a region, it becomes necessary to collect the water in a reser- voir, from which it is drawn for use during the dry s

54 Placer And Hydraulic Mining. § 39

Reservoirs.

76. Reaervolr Site. — In selecting the site for a reser- voir, the following points should be observed:

1. A proper elevation above the point at which the water is required.

2. The supply of water furnished by all creeks and springs and the catchment area, or area drained into the reservoir, should be carefully determined. In this connec- tion, one point must be observed, and that is that usually all streams and springs within the area are fed by the rainfall within such area, and hence the total amount of water can never exceed the amount which falls on the surface, and owing to evaporation and other losses will always be much less.

3. The average amount of rainfall and snowfall should be carefully determined.

4. The formation and character of the ground with reference to the amount of absorption and evaporation should be determined.

The elevation of the reservoir depends upon the location of tlic mines and the extent of the country which it is pro- posed to supply l)y means of the ditch. The reservoir should he located below the snow line if possible, and at the lowest point of the catchment area or watershed, in order to obtain the maximum sup})ly of water. The average mini- mum su})ply (jf water from all streams should be carefully determined. The rainfall is often greater in the mountain districts than in the lower countries, and is greatest on the sK>pes faciui;- the direction from which the moist winds blow. Snow measurements are taken on the level, and a given amount of snow is reduced to an equivalent amount of water, tlie total year's fall being calculated as rain.

77. .Absorption unci Kvaporntion. — The most

desirable formation kA ground for a reservoir site is one of compact rock, like granite, gneiss, or slate. Porous rocks, like sandstone and limestvuie, are not so desirable, on account

g 39 PLACER AND HYDRAULIC MINING. fiS

of the fact that they may absorb water. Steep bare slopes are best, as but little water escapes from them. The greater the slope, the more rapidly will the water flow into the res- ervoir. The presence of vegetation causes absorption, but at the same time the rainfalls are often greater in regions covered with vegetation, and the streams have a more uniform flow. At the Bowman reservoir in California, 76 per cent, of the total rain and snowfall (reduced to rain) is said to be stored in the reservoir. A reservoir must be made large enough to hold a supply capable of meeting the maximum demand. The area of the reservoir should be determined, and a table made showing its contents for every foot of depth, so that ihe amount of water available can always be known. Besides the main storage reservoir, all hydraulic mines have distributing reservoirs, which receive the water from the main ditch and deliver it to the claims through the pressure pipes. These auxiliary reservoirs act as safety devices which protect the ditch and flumes from being overflowed, as they are usually capable of holding sufficient water for about a day's run, and if operations should suddenly cease, they could be depended upon to take care of the water until the flow in the main ditch could be stopped.

Dams.

78. Dams are used for retaining water in reservoirs, for diverting streams, and for storing debris coming from placer mines in canons and ravines.

79. Foundations. — The foundation for a dam must be solid to prevent settling, and must be water-tight to pre- vent leakage under the base of the dam and wear in front by water running over the top. Whenever possible, the foundation should be solid rock. Gravel is better than earth, but when gravel is employed, it will be necessary to drive sheet piling under the upper toe of the dam to pre- vent water from seeping through the formation under the dam. Vegetable soil is unreliable, and all porous matter.

56 Placer And Hydraulic Mining.

such as sand, gravel, etc., should be stripped off until hard pan or solid rock is reached. In case springs occur in the area covered by the foundation of the dam, it will be neces- sary to trace them up and confine their flow to the inner or upper side of the dam, so that they will have no tendency to ultimately become passageways for water from the upper face of the dam, which might ultimately wash holes through the foundation and destroy the structure.

Woodek Uam.

80. Wooden dams are constructed of round hewn or sawed logs one or two feet in diameter, laid in a series of cribs 8 or 10 feet square. The logs composing the cribs are pinned together by means of treenails, and the individual cribs are attached by the same means, or by bolting. The cribs are usually filled with loose rock to keep them jn place, and in many cases are secured to the bed-rock by means of bolts. A layer of plank on the upper face of the dam makes it water-tight.

81. Aprons. — Where water discharges over the top or crest of a dam, it will be necessary to provide some surface to receive the impact of the falling water, for if this is not done the dam may be undermined and thus destroyed. If the dam is on firm bed-rock, the upper surface can simply be extended slightly and the water allowed to fall on the bed- rock, which will not be badly cut ; but where there is danger of the foundation being washed away, it will be necessary to provide some form of apron or water cushion. An apron may he formed by providing small cribs, which are set on the lower side of the dam and are covered with a plank floor, on to which the water falls and from which it is discharged into the stream below. Sometimes the plank of the floor is made to pitch back towards the dam in such a manner as to form a tank, into which the water falls, the impact of the fall being taken by the water cushion in the tank, A simi- lar result may be accomplished by building a low dam just

§ 3ft PLACER AND HYDRAULIC MINING. fi7

below the ntain dam, so as to form a small between the

two, wbii-h acts as a water cushion and protects bed-rock or foundation.

82> Abutments and DlGliar([e Gateti. — Abut- ments are the structures at the ends of a dam, and may be constructed from timber, masonry, dry rock-work, or wooden cribs. If possible, abutments should have a curved out- line and should be so placed that there is no possibility of the water overflowing them or getting behind them during floods. If the discharge from the dam takes place from the main face, the gates may be arranged in connection with one of the abutments or by means of a tunnel or culvert through the dam. In either case, some structure should be con- structed above the outlet so as to prevent drift-wood, brush, or other material from stopping the discharge gates. In I'ig. Xi the water is discharged through three pipes which pass through the upper face of the dam and are protected

by a timber, screen, or strainer. Each pipe has a valve in the tunnel or culvert, as shown in the illustration, and these pipes dischitrge into the wooden flume which conveys the water to the face of the dam, and from here it flows down through a flume to the mine When the discharge gates are placed at one side of the dam. they are usually arranged outside of the regular abutment, between it and

Placer And Hydraulic Mining.

§39 '

another special abutment, the discharge being through a series of gates into a flume or ditch.

83. Wastewraj. — Wasteways are openings provided in dams for discharging the water during floods or freshets. In the case of timber dams, they are usually surrounded by solid cribs filled with rocks, and the waste-gates each have 40 or 50 square feet of area. There are two general forms for constructing waste-gates. One consists of a com- paratively narrow opening in the dam, extending to a con- siderable depth. Water is allowed to discharge through this ' during flood-time, but when it is desired to stop the flow, planks are placed over the upper end of the opening in such j a manner as to close it. The opening, which is usually not ' over 3 or 4 feet wide, is provided with guides on the upper I face of the dam, between which the planks are slid down, the individual pieces of plank being at least a foot longer than the opening is in width. Another device which is fre- quently employed consists in providing a spillway to one I side of the regular spillway, with a crest 2 or 3 feet lower j than he regular crest of the dam. The crest of this spill- way is composed of heavy timber. Four or five feet above I the crest timber is placed a parallel timber, and the space I between these two is closed by what are called flash-boards. These are made from pieces of 2 or 3 inch plank, about 8 or 10 inches wide. The planks are placed against both I timbers so as to close the space. The individual planks are ] made sufficiently long, so that they extend from 1 to 2 feet I above the upper timber, and through the upper end of each [ plank is bored a hole, through which a piece of rope is passed and a knot tied at the end of the rope. These I ropes are secured to staples in the upper timber. When it 1 becomes necessary to open the wasteway, men go along with peevies, cant-hooks, or pinch-bars, and pry up the plank i such a way as to draw the lower end out of contact with the ' lower timber, when the force of the water will immediately carry the plank down the stream as far as the rope will ' allow it to go. After the first plank has been loosened, the j

S39

Placer And Hydraulic Mining.

succeeding ones can be pulled up with comparative ease, and two men can open a 25 or 30 foot section o£ wasteway in a very few minutes. The ropes keep the plank from being lost, and the space can be closed once more by pass- ing a plank down at one side of the opening and then mov- ing it sideways in the current. Some skill is required both in opening and closing the wasteways.

Stokb Dams.

84. Dry-Stone Dams.— In regions where cement or lime is expensive and large quantities of suitable rubble- stone can be obtained, dams are frequently constructed without the use of mortar. They are rendered water-tight by a plank facing on the upper side of the dam. Fig. 33 illustrates the Bowman dam, constructed as the main dam for the Bowman reservoir in California. There is another dam at this reservoir which is used as the waste dam, and it is supposed that the water will never have to pass over the top of the large dam, but, owing to the fact that there are several other reservoirs farther up the stream and that these may break at some future time, thus flooding the reservoir, the dam had to be constructed so that it would be able to take care of a heavy and sudden rush of water over its lop. Originally the dam consisted of unhewn cedar and tamarack logs notched and firmly bolted together, and solidly filled with loose stones of small size. A skin of pine plank was constructed on the water face to form a water-tight lining. This dam was 72 feet high. Subse- quently the dam was increased to a height of 100 feet by building a dry-stone structure below the main dam. This is composed mainly of angular stones taken from the moun- tainside and carefully laid up in irregular range-work so that they break joints. This range-work was faced with quarried stones on both the upper and lower faces. Part of the lower face was made practically vertical, being given a baiter of only 15 per cent, for KJ feel in height. This vertical wall was composed of heavy stones carefully laid and

60 Placer And Hydraulic Mining. § 39

securely bolted together and to the structure behind them. The face of the dam above was given less inclination, as shown, and was also built of quarried stones laid up dry. ! The dam was made water-tight by means of a plank facing

on the upper side, as shown. Many of the dams in Cali- fornia have been made of dry-stone work, being rendered water-tight by means of a plank facing on the upper sur- face. If water ever flows over the top of such a dam, a great deal of it is liable to pass through the interstices in the slanting stonework, thus subjecting the lower portion of the structure to considerable hydrostatic pressure. To overcome this, the vertical portion is provided with open- ings through which this portion of the water would find a ready exit, and, as has been stated, the stones in the vertical port ion are securely bolted together and to the rest of the dam.

85. Manonry l>ainH. — Masonry dams are not much used for placer and hydraulic mining, on account of the fact that the length of time during which the dam will be required is rarely sufficient to warrant an expense sufficient

to construct a masonry clam. Masonry dams are usually thinner than those (N)nstructc(l of dry-stone work, and their shape is carefully (Urterniined accordinj to known laws, on account of the fact that the cement renders stonework one solid mass, while in the case* of dry-stone dams, each indi- vichial slone in the inrc of the dam has to resist beini washed awav 1)V its \vci*iii. In either niast)nrv or dry-stone dams the slone should not he laid in iiorizontal cotirses extending from front to rear.

i:arth n.vMS.

HH. liartli dams are used for reservoirs of moderate depth. They should be at least In frc-t wide on the top, and a height of more than On feet is unusual.

H7. l*ucJdlc Wall. — Where the material of wliich the

dam is he (N)nstru(aed is un{ of itself water-tight, as, for instan(M', iravel, sand, etc., it is sometimes necessary to constru(t what is called a })ii(ldle wall. This consists c)f a

Placer And Hydraulic Mining.

narrow dam made of clay mixed with a certain proportion of sand. If the foundation of the dam is open gravel or sand, the puddle wall should be carried to bed-rock or to an impervious stratum. The puddle wall should not be less than 6 or 8 feet thick at the top of the dam, and should be given a slight batter on each side, so that it will be some- what wider at the base. It is constructed during the building of the dam. and should be protected from direct contact with the water on the upper face by a considerable thickness of earth, for water will slightly dissolve and wash it away. The upper face of an earthen dam is usually pro- tected by means of a plank lining or a pavement of stones.

88. Masonry Core. — Sometimes earth dams are pro- vided with a masonry core, in place of a puddle wall, to render them water-tight. This consists of a masonry wall carried to an impervious strata and up through the center of the dam. This masonry core should not be less than a or 3 feet thick at the lop, and should be given a batter of at least 10 per cent, on each side.

Debris Damb.

88. These are dams or obstructions across the beds of streams to hold back the tailings from mines and to prevent damage in the valleys below. They may be made of stone, timber, or brush. The difference between a debris dam and a water dam is that no attempt is made to render the debris dam water-tight, the only object being that it shall retard the flow of the stream and give it a greater breadth of dis- charge, so that the stream will naturally have to drop or deposit the sediment which it is carrying. This sediment soon silts or fills up against the upper face of the dam, so that the area above the dam soon becomes a flat expanse or plain, over which the water finds its way to the dam. When these dams arc constructed of stone, the individual stones in the lower face and crest of the dam should be so large that the current will he unable to displace them, while the upper

Placer And Hydraulic Mining.

face and core of the dam may be composed of finer mate- rial. In case a breach or break should occur in a deltris dam, it will not necessarily endanger the region farther down the stream, as is the case where a break water dam. The reason for this is that the debris dam is not made water-tight, and hence there is never much pres- sure again.'it it. In case a breach should occur, the only result would be that more or less of the gravel held behind the dam would be washed through the breach and down the stream.

90. For turning streams from their courses, wing-dama : sometimes employed. Wing-dams may extend partly across the stream and then down one bank, forming a course for the stream, or it may simply extend partly across the stream, so as Iqi turn the water into a sluicd or flume. Inlhecaseof coni' paratively small streams, wing-dams are usually of a temporary nature, and aro constructed of brush

PlO. H.

light cribs filled with stones, which are subsequently backed, up with earth, stones, or some timber-work. Fig. 34 illuBtraies one method by means of which wing-dams may be constructed. In this case, hags filled with sand were piled across the course of the stream and backed up with gravel and pebbles. The sand-bags and earth turned the course of the stream, and enabled the operators to con- struct triangular wooden bents or frames behind the bank, as shown in the illustration. These frames were subse- quently weighted down with stones and their lower face covered with a riprap of drift boulders, etc., so that in case the water ever came over the dam, it would not wash away and destroy the work.

ot wash iti

8 30 Placer And Hydraulic Mining. 63

Measurement Of Floiv Of Water.

91. Various forms of meters are used for this purpose. Some of them are so devised that they measure the actual quantity of water flowing through the weir; others simply give the velocity of the current, and from this and the size of the channel through which the water flows, the quantity is determined.

92. GauRlag by Rleht-AntTled V Notch. — A right- angled V notch, cut from thin sheet iron, is frequently used for gauging comparatively small flows. The notch is fitted in one end of a box, as shown in Fig. 35. The edge of the plate forming the notch must be sharp, and the bevel must be on the lower side of the plate, the inside face being at right angles to the surface of the still water, To prevent

surface currents in the box, baflte boards are placed some distance back, as shown in the illustration. The distance a of the surface of the water below the top of the weir and below the top of the box is taken at a point some distance back from the notch (at least IS to 24 inches), where the water surface is level. This distance subtracted from the total depth //of the notch gives the head // of water pass- ing over the notch. This head may be obtained as follows: A Straight-edge or level is placed on the weir plate P, so as to extend back over the surface of the water in the box. The distance a between its lower edge and the surface of the water is measured. This distance subtracted from //

Placer And Hydraulic Mining.

§39

Table I.

IHHCHAROR OF WATBR THROUGH A RIGHT-A!liGI.En

V >Jotch.

Q

ft

(Juaiit.

h

Quant.

h

Quant.

h

Quunt.

A

Quant.

Heaa. Inches

per Min..

Head, Inches.

per

Min.,

Head. Inches

i)er 1 Min.,

Head. Inches..

per Min..

Head. Inches.

per llin..

Cu. Ft.

Cu.Ft.

Cu. Ft

Cu. Ft.

().3Ss4

' 3-35

0.4S27

6.523 '

1 5.65

1 5.70

0.64 So

1 3-55

54-53 :

0. 70<)6

3.()0

5.S5

0.S432

, 8.058

57-14 ;

<).(ji53

58.03 '

; 10.35

3. So

S.613 ;

1 6.(x)

5S.92 ,

I.<)7(K)

3.S5

8.899 '

60.73 '

I.24(K)

h 3-95

9.4S9 1

().i5

I. So

i.33(M>

().20

io.6<:)

1 1.4240

1 4-05

10. I(K)

().2 5

29.8ft

63- 5 r

' 1.5220

30. 4 S

6445 '

1 14.(<)

! I. (.2 50

1 10.730

S.55

1-731"

I I . ( X )

, S.(K)

10. So

1 1.3''

10.S5

1 5' '

I 1.73"

I Kt "2

I j.o7'

3 v()0

2. 2" )

2. I ';'" 1

-4- i"

S.x)

7( ). 3c

I 22. Si

4 4r

1J.7-M

34- "'i

13. 14"

1 25. (Jl

J . ' )' X 1

1

I ; . 5 I I

3(..2 3

J. 7 V '"

74- 3''

J'-'"- 4 5

37-5"

2.5')

1-7"

14. ''50

9.1?

1 77-4')

132. M

i3-44'

7-"r

4'i')

I I 2' K '

71"

0-3"

11.50 ;

.J 1.-3

l"i t"

1 7. 1 I"

I I.(M.

' 7- 54"

43-3"

I I. (.5

7-3"

."'5. 12

1 4 3 . 2 s

2..J5

4--7-V'

I "'.42'-

44-"-

1-77""

7- 1"

4-0"

140.3(,

l''7i"

I-;. 320

7-4

1 1 . s 5

147 oi

7-5"

0-7"

I I.()0

()2.uo

I cubic foct ct'Utaiiis 7.46 U. S. KiiH'' ; i l'- S. alluti weighs S.j.\ ixunids.

g39 PLACER AND HYDRAULIC MINING.

leaves h, which is the depth or head of water in the notch. This head may also be obtained by measurements from the bottom of the box, in which case the height of the bottom of the notch above the bottom of the box will be subtracted from the depth of water in the box. This depth may be obtained by measuring with a rule or scale which extends to the bottom, or by means of a hook gauge, as explained later.

The discharge in cubic feet per second is equal to 0.0051 times the square root of the fifth power of the head expressed in inches. Table I gives the discharge in cubic feet per second through the right-angled V notch for heads k varying from 1.05 inches up to 13 inches.

Weirs.

93. A weir is an obstruction placed across a stream for the purpose of diverting the water so as tn make it flow through the desired channel. This channel may be a notch <.ix opening in the obstruction itself, and it has been found that when properly constructed and carefully managed, such a weir forms one of the most convenient and accurate devices for measuring the discharge of streams. Many care- ful experiments have been made to determine the quantity iif water that will flow over different forms of weirs under various conditions. As the result of these experiments, two forms have come into general use, and the amount of flow over either can be determined by simple formulas and coefEcienis that depend upon observed conditions.

94. A Weir Wltfa End CoatractlonH.— Such a weir

is shown in Fig. 30 {a). The notch is narrower than the channel through which the water flows, thus causing a con- traction at the bottom and two sides of the issuing stream.

95. A ' WItbout End Contractioas. — This is also called a weir with end contraction suppressed, and is

shown in Fig. .1(i (b). this case, the notch is the full width

PLACER AND HYDRAULIC MINING. § lently the streai

of the ch;innel leadhig to it, and conseq issuing is contracted at the bottom only.

9. Crest of the Weir.— The edge a. Fig. 36 (c) am Fig. 3(i {d), is called the crest of the weir. The inner edgi of the crest should be made sharp, so that the water in pass ing over it touches only a sharp edge. For very accuratt work, both vertical and horizontal, edges should be madi

from tbin plates of metal having a sharp inner edge, a shown at (f ) Fig. 3G (r), but for ordinary wori: the edges o the board in which the notch is cut may chamfer off, a shown in Frequently this edge is not made absolutely sharp, but is left flat for about i inch, so as to increase thi strength of the edge and lo decrease the liability of its being damaged. The bottom edge of the notch must be straighl and set perfectly level; the sides must be at right angles tc the bottom. The inside or upper edges of the notch musl always be in a plane at right angles to the surface of still water. The head //jjroducing the flow is the vertical dis' tance from the cri:st of the weir to the surface of the water, as shown in Fig. HO {c) and Fig, 3C. (rf). This head must b) measured at a point sufficiently back from the crest so that

§3

Placer And Hydraulic Mining.

the surface of the water is not affected by the curvature of the stream flowing over the weir.

97. The distance from the crest of the weir to the bot- tom of the feeding canal, flume, or reservoir should be at least three times the head, and with a weir having end con- tractions, the distances from the vertical ends or edges to the sides of the canal should each be at least three times the head also.

98. The water must approach the weir with little or no velocity. To accomplish this, it is sometimes necessary to provide means for reducing the velocity of approach, such as baffle boards similar to those used in connection with the V notch.

99. Fig- 37 shows a simple form of weir located in a small stream for the purpose of measuring the discharge.

A plank dam is put across the stream at a convenient point, care being taken to prevent any leakage around or under the dam. The length of the notch is great enough to

Placer And Hydraulic Mining.

provide for a flow having a head oi from 0.5 to 1.5 feet, but at thi same time the length i>f tlie cresi fcir accurate work should never bi less than three or four times ihi head. If it is desired to measti: smaller amounts of water, the notch can be used. A titake E driven firmly into the ground at point alwut G feet up-stream from the weir and near the bank, shown. The stake is driven down until its top is exactly level with the lop of the weir. The head ia the vertical distance from the top of this stake to the surface of the water, and it may be measured by means of a 2-foot rule or a square, as shown in the illustration. For very accurate work, the hook gauge is used.

Uoou Gavgb.

I OO. For accurate measure* , such as are made when testing the efficiency of water. wheels, the head is measured with an instrument called the hook gauge, shown in Fig. 38. Ahooktr is attached to the lower end of a sliding scale the scale is gradu ated to Iiiindredtlis of a foot, and providL'd with a vernier, by means of which readings can be made to thousandths of a foot. The scale and the hook can be raised or loW' ered by means of a screw s. Th instrument is fastened securely

J

§3a PLACER AND HYDRAULIC MINING. fi!>

tosome substantial structure at a point a few feet up-stream from the weir, and where the surface of the water is quiet and protected from the influence of winds or eddies. The hook is so set that the gauge will read to zero when the point of the hook is at the same level as the crest of the weir. When the point of the hook is raised to the surface of the water, it lifts the surface slightly before breaking through. To use the gauge, start with the hook slightly below the sur- face of the water and raise it slowly until a slight pimple, caused by the lifting of the surface, appears over the point of the hook. The reading of the scale for this position of the hook gives the head of water.

DI9CH:VRGE OF n'EIRS.

lOl. When the dimensions of the notch and the head on the crest of a weir are known, the discharge can be com- puted by means of the following formulas and tables of coefficients:

Let / length of the weir in feet; H measured head in feet ; V velocity with which the water approaches the

weir infect per second; k head equivalent to the velocity with which the water approaches the weir, or a head which would produce a velocity equal to c coefficient of discharge; Q actual discharge in cubic feet. The actual discharge for weirs with end contractions is given by the formulas:

2 5.347f/(jV+jA)*. (I.)

which is used where the water approaches the weir with a velocity equivalent to the height b, and

Q=5.Si7ciN*, (2.)

where the water has no velocity of approach.

70 Placer And Hydraulic Mining. §30

The actual discharge (or weirs without end contractions is given by the following formulas:

Q=!i.W}cl{f/+\A/i)*, (3.)

which applies in cases where the water has a velocity of approach, and

Q=b.W!clIf\ (4.)

which applies where the water has no velocity of approach.

102. Velocity of Approach. — By this term is meant

the velocity with which the water flows through the canal leading to the weir. This may be obtained by finding, appro."cimately, the amount of water discharged in a given time and the area of the cross-section of the canal leading to the weir. Then the velocity of approach will be equal lo the given amount of water divided by the area; or, if

A the area of the cross-section of the canal in sq, ft., the velocity of approach in ft. per sec, Q the quantity of water in cu. ft.

e have

Q may be obtained approximately by assuming that v is equal to zero and applying the formula for the class of weir in question, as given above. Having obtained this quantity Q and from it the value of v, the equivalent head // may be found by the formula

h 0.01555 1''. (5.)

Since v is small with a properly constructed weir, it is usually neglected unless great accuracy is required.

103. Table II gives the values of the coefficients of discharge c for weirs with end contractions and diflferent values of H and /, In this table the head given is the effect- ive head // + //. When the velocity of approach is small, A is neglected and the head becomes simply H, but this change will not affect the coefficients in the table.

§ 39 Placer And Hydraulic Mining.

Table H.

VALUES OF THB COBFFICIBNT OF DISCHARGB FOR TVBIRS TVITH BND CONTRACTIONS.

Eflfective

Length of Weir

in Feet.

Head in

Feet.

; 0.601

0.G08

104. Table III gives the values of c for weirs without end contractions. Weirs with end contractions are more often used and are to be recommended in most cases. Values of c corresponding to values of // and / between those given in the tables can be found by interpolating or taking an average between the desired figures, assuming that the variation is uniform between the values given. In Tabic III the head given is the effective head //+ //, which, when // is neglected, becomes simply H. This does not affect the value of the coefficient in the table.

w

Placer And Hydraulic Mixing. Table Iii.

Effective

Length of Weir in Feet.

Feci.

Ib

iij

0,fl57

0.Gs9

O.Gw

0.G44

0.G49

0.6oS

0.S35

0.R37

O.G37

0.G42

o-dis

o-as

0.tl30

O.04I

0.C2G

o.(!ai

0.fi33

U.636 0.H34

O.'Jo

O.Cl'J

0,039

o.i;2o

u.oaa

o.an

l.(!(l

0.tl23

105. The tables and formulas thus far given require the measurements to be taken in hundredths of a foot. Frequently operators are not provided with apparatus for accomplishing this, and iience Table IV is given, which gives the cubic feet of water per minute for every inch in length of the weir corresponding to the depths given in the table, the table giving the depths by eighths of an inch 1 inch to 25 inches. This table is not accurate for weirs whose depths are great compared with their lengths, and should not be used unless the length of the crest of the weir is at least three or four times the depth of the water on the weir.

§ 39

Placer And Hydraulic Mining. 73

Table Iv.

WEIR TABLK GIVING CUBIC FEEX UtSCHARGED PEK MIPS-

UTE FOH EACH INCH IN LENGTH OF WEtH FOR

DEPTHS FROM l-S INCH TO ZB INCHES.

Inches

t

L9e

3,68

G.09

6,86

10,18

13. G7

15,43

17,78

18,05

33, 33

23,51

24,86

36. Go

27,27

1!)

34,00

37,28

40,04

6. As an illustration of the use of Table IV, suppose

that

we had a weir 5 feet in length and that the water

It K.

J. 74 Placer And Hydraulic Mining. §

J'

I upon it stood at a depth of 10| inches. Then the amou

I of water passing for each inch of length of the weir wou

be found by noting the figure 10 in the left-hand colun

of the table and passing along this horizontal line un

the value under was obtained, which would be foui

to be 13.03 cubic feet per minute, and as the weir w

GO inches long, the total amount passing per minute w

be 13.03 X 00 835.8 cubic feet per minute.

107. The following examples are given to illustra the use of the formulas and tables:

Example 1. — What is the discharge of the stream in Fig. 37 if tl length of the weir is 5 feet, the head lOA inches, the coefficient of di charge J){)', and the velocity of approach 0 ?

SoLCTioN. — Applying formula 2, we have

y .003 X 5.347 X 5 X .H75' 13.1934 cu. ft. per second. Ans.

Example 2. — What is the discharge from a weir with end contrai tions under the following conditions: The length of the weir is 4 fe< inches and the measured head 10 inches. Assume that there ;

no velocity of approach.

SoMTiox. — The length /of the weir feet H inches 4.12.") fed

and tli- lie. id // inclies .S4 foot. From Table II we find th in llu- (i.rnk-icnt "i" — .<inih -i- .— .(Mr2 for each increase of 1 fcwi in len.s;th. Tlie ( (t]i( ient a weir 4.\'2o feet long is, therefore .<;(M) . , 1. rj."i .(H)2t .no-J'J."). The rate of increase for a head of .Jl fo.. is (Jio:; - .."iiJS)-: -j .Oo-J."), and the coelVicient for a weir 4. r.") ffe ..V.> -r 1.1'2'> y .one:)) - JKMisi. The decrease in the coefticien for an increase in liead .1 foot is .00225 — .0001 =.00144, and for ai

increase in head of .(II foot tlie (h-crease is .00144 X .00057. Thi:

snblrat ted from tlie c<)cfiieient for .S foot gives .({022.") — .()(Mr7f> - .OOHm I a- the t oelVK ient di--(liari;e for a weir 4.rJ.'> feet long and ; lieatl foot. I'ing but four decimal plate's, the discharge !)y for niui.i 2

n 5.:MT X .<5017 X -1.12."") X >43 - 10.22 cu. ft. per second. Ans.

ICx.xMi'LH I). — If the canal leading to the above weir is 10 feet widt and feel deeji below the crest of the weir, wliat is the head eqiiivalen' to the velocity f approach ?

/

Solution', — The depth of water in the canal is the depth lielnw the crest plus the head 3.84 feet. The area of the cr<ias-section of the water in the canal is A 3.H4 X 10 38.4 square feet, and the -Velocily is j'= .896 toot per second. The head h equivalent to the velocily v is, according to formula 5,

A .01555 X -288' .001 1 foot. Ans.

Note. — This value of h is so small that its influence on the discharge is much less than the probable errors in measuring the head H. and so need not be considered in finding the discharge.

Mixer'S Inch.

108. The miner's inch varies in different districts and is by no means a definite quantity of water, as the methods of deriving it vary in different places. Merriman states that the miner's inch may be roughly defined as the quantity of water which will flow from a vertical standard orifice 1 inch square when the head on the center of the orifice is inches, and determines this amount of water to be equal to 1.53 cubic feet per minute, and states that the mean value of the miner's inch may, therefore, be taken at 1.5 cubic feet per minute. Bowie states that in different counties in Cali- fornia the value of the miner's inch varies from 1.20 to 1.7(j cubic feet per minute. The reason for these variations is mainly due to the fact that when water is bought in large quantities, it is discharged through large areas; thus, at Smartsville a vertical orifice or opening i inches deep and 350 inches long, with a head of 7 inches above the top edge, is said to furnish 1,000 miner's inches. At Columbia Hiil an opening 13 inches deep and 12| inches wide, with a head of C inches above the upper edge, is said to furnish 200 miner's inches. In Montana the common method of measure- ment was formerly through a vertical rectangle 1 inch high, with the head on the center of the orifice 4 inches. The number of miner's inches was said to he the same as the number of linear inches in the rectangle; thus, under the given head an orifice 1 inch deep and 60 inches long would be (JO miner's inches.

u

76 Placer And Hydraulic Mining. §

109. The State Legislature of Montana has now pass a law defining the miner's inch as a certain amount of wat flowing per second regardless of the pressure or size of t opening through which it passes. The statement is I, follows:

Where water rights expressed in miner's inches ha been granted, 100 miner's inches shall be considered equi alent to a flow of 'Zk cubic feet (18.7 gallons) per secon 200 miner's inches shall be considered equivalent to a fie of 5 cubic feet (37.4 gallons) per second, and this proporti< shall be observed in determining the equivalent flow repr sented by any number of miner's inches."

llO. If this amount be reduced to cubic feet p

minute, it will be found to be equal to a flow of 1.5 cub feet per minute as the equivalent of the miner's inch, whic is the value given by Merriman. In some states, or son portions of states, the miner's inch is defined as tl amount of water which will flow through a certain siz€ opening, the thickness of the plank and the character i the faces comprising the opening being mentioned i some cases; but no two of these definitions seem to agre In some countiits in California what are known as t>4-hou I'-i-hour, 11-hour, (r in-hour inches are in use, and repr< sent th( amounts of water which would flow through jiven o[)eninij in these lenjths of time. For convenience i converting; cubic feet into iallons, it may be stated that cubic ft)ot is e([ual to 7.4S V. S. gallons.

I)ITCHi:S AM) FIAWIKS.

111. Tliousands of miles of ditches have been made i j)lacer-mininij districts for carrying water from reservoirs t locations where it was to be employed. On account of th rocky character of thec<nnUry in su(di districts, steep grade are necessary, and high trestles with Humes and wrought iron or wooden pipe are frec[Uently built for carrying th water across cafions or ravines.

§ 39 Placer And Hydraulic Mining. 7!

112. For the construction of ditches, Bowie recom- mends the observance of the following rules:

1. The source of supply should be at a sufficient eleva- tion to cover the greatest range of mining ground at the smallest expense, great hydrostatic pressure being always desirable.

2. An abundant and permanent supply of water during the summer months should be secured.

3. The snow-line, when possible, should be avoided, and the ditch, especially in snow regions, should be located so as to have a southern exposure.

4. All watercourses occurring on the line of the ditch should be secured. Their supply partially counteracts the loss by evaporation, leakage, and absorption, and fre- quently furnishes an additional quantity of water during several months of the year.

5. At proper intervals waste-gates should be arranged so as to discharge the water when necessary, without risk of damage to the ditch. In regions of heavy snow,these waste- ways should be provided at intervals not greater than one- half a mile.

C. Ditches, when practicable and the cost not excessive, should be preferred to flumes.

Ditches.

113. Surveylna a DIteta Line. — A preliminary examination of a ditch line can be made by means of care- fully compared aneroid barometers. By this means, the elevations, not only of the termini, but of any intermediate points, can be approximately determined. Subsequently sur- veying parties may be started from these various points for the appixiraate location of the line.

114. After the survey line has been carried through and the various necessary points are established, the line is constructed and the leveling done. In leveling, all turning- points should be made on grade, if possible. The stations

78 Placer And Hydraulic Mining. § 39

should be properly numbered and staked and pegs driven to grade. Bench-marks should be placed every one-fourth or one-half mile for convenient reference. The bench-marks should be to one side of the regular ditch line, so that they will not be disturbed during subsequent work.

All details of tunnels, cuts, and depressions requiring flu- ming or piping should be worked out in full. In this work the hand level can often be employed with advantage for fill- ing any minor details. Complete notes should be made of the character of the ground along the center line, and also of any possible changes.

115. The size of the ditch is regulated by its require- ments. Its form will be modified often by circumstances according to the judgment of the engineer. The smallest sec- tion for any given discharge is when the hydraulic depth is one-half of the actual depth. The hydraulic depth is the quo- tient obtained by dividing the area of the cross-section of the stream at any point by the wet perimeter at that point the wet perimeter l)eing that portion of the outline of the cross- sertion whicli comes in (N)ntact with the bottom of the ditch l)elow the surface of the water. Tra[:)ezoidal and rectan- gular forms are a(l()])te(l for ditches and Humes, res{>ectivelv The resistances due to formation in the latter forin is the smallest when the width is twice the height. Half of a r(\i;'ular hexaion is a common form for ditches. In a moun- tainous country with a rocky soil, narrow and cUep ditclies with steep cjradcs are adopted in ])reference to wider ditches with ifullcr slopes, as they are chea{)er to excavate and kecsp in repair, ditches with in-ades of from 1<) to 'O feet i)er mile heinu (piite couimon in mountainous reiions. Before commencMni work, tli ' ditch line must be ("leared of trees and brush. Where llinncs are to he constructed, the brush for at least 10 feet on each side is burned off. On a hillside the line should be iraded so that the ditch may have walls of solid tmtouched round, and not mud banks. The banks should ]:>e at least '] feet wide on top. In momitain reii:ions where the material excavated is of a com[)aratively firm nature, the

§39 PLACER AND HYDRAULIC MINING. 7i>

upper side of the ditch in hillside work is frequently given an angle of 00° and the lower bank an angle of 50°. This varies with the nature of the ground. Contracts for the dig- ging of ditches are either let out so much per unit of length or at so much per cubic yard. The material excavated from the ditch is piled on the lower side and ultimately consolidates into firm ground, thus raising the height of the sides of the ditch and increasing its capacity. If ditches are not so steep as to scour or erode their bottoms, they will ultimately become lined with a scum or silt of fine clay which closes up the pores and openings in the soil, thus stopping leakage and increasing the carrying capacity of the ditch. Bowie states that the annual cost of running and maintaining ditches in California averages $400 per mile. A number of the large California ditches cost nearly half a million dollars each, and many of them are more than 5(1 miles in length.

116. Fig. 39 illustrates a cross-section of the

North Btoomfield ditch in t...,y.''M

California. The dimvii sions of this ditch, as u 1 1 1 be seen, were 5 feet in width at the bottom, 8 0 feet at the top, and 3ifeet in depth, with the upper

side at an angle of 65° and the lower side at 00*.

Fll'Mbs.

117. In general the use of flumes is to be avoided wher- ever possible, for long experience has demonstrated that they are not economical, being loo liable to destruction by fire. wind, and snow-storms, or by decay ; hence they are a source of continual expense.

118. Flumes vs. Dltcbes. — There are instances where the formation of the country requires the use of flumes rather than ditches. For example, in cases where the water must be carried along ihe face of vertical cliffs;

Placer And Hydraulic ]

there are also certain conditions of ground, topography, where a ditch can not be empli ically as a flume; for instance, when the posed either of very hard or of porous and I Likewise, where the water Is scarce and absorption are great, flumes must necessari In such cases as these, either flumes or pipe) tageously used.

118. Grade. — Flumes are usually set than is possible fur ditches, the grade fre<3 much as from 25 to 30 feet to the mile. Th increase in the velocity of the flow, and I tiona! decrease in the cross-section of the flu

1 SO. Construction of Flumes. — Flu

constructed of seasoned pine plank from thick, froml3to24 from 12 to 16 feet I joints are battenei with pine strips fro wide and inch thi tiire is reinforced e frame consisting ot two posts. A fludl :t feet deep requii ;nul caps, i" X 6' si siiingers. Posts I he sills with the deep and are no The sills are alloi from 13 to 20 inches beyond the posts, and are usually introduced, as illustrated in shows a cross-section of a flume and trea are usually made of suflUcient length so that of 3 or 4 inches between the top of the sid the cap. In carrying a flume along a hillside, be graded out and the flame placed in close as to avoid danger from snowslides, etc. Tha

g 89 PLACER AND HYDRAULIC MINING. 81

graded and the stringers laid in place. The sills are subse- quently laid on this and the flume constructed. The string- ers prevent the sills from coming in contact with the earth, and thus protect them from rotting. Another advantage of having a flume close to the bank is that in cold weather the snow usually stops up the space at the sides of the flume, thus preventing the circulation of air under it, and its sub- sequent chilling effect.

121. Curves. — Curves should be laid with care to insure the maximum flow of water and to prevent splashing, as where splashing takes place excessive freezing is liable to occur in cold weather. The box must be cut into two, three, or four parts, necessitating more sills, posts, and caps. For good curving, the side planks are sawed partly through in places so as to make them bend easily. Where the water passes around the curve, it has a tendency to rise on the outer side of the curve, and hence the flume must be blocked up on this side. This is usually accomplished by judging the amount of inclination first and changing it after the water is running by wedging the flume up until all splashing ceases.

122. Bed and Joints. — In constructing a flume, the bed is carefully prepared, the stringers are laid, and the sills placed upon them proper distances apart; the bottom planks are then nailed to the sills, the end joints being carefully fitted. The side planks are nailed to the bottom ptank and the posts set in gains in the sills, an occasional cap being placed on the posts to hold the flume in shape. Sixteen- penny and twentypenny nails are used for fastening the material together. The joints are battened with thin material nailed on with sixpenny nails. Each box when complete is set on grade and wedged into place.

123. Connection with Ditch. — Where a flume con- nects with a ditch, the posts for a distance of several boxes back are lengthened to permit the introduction of an addi- tional plank on each side. The end boxes of the flume are flared to permit a free entrance and discharge of the water. At the junction of the flume with the ditch, or where a flume

S2

Placer And Hydraulic Mining.

passes through the bank of earth, an outer siding' may be nailed on the outside of the post to protect the flume. The lumber should be prepared in exact sizes at the mill, so that rapid work can be done in the construction. The lumber is usually delivered ;it the head of the flume and enough water turned in to float the material down as the work progresses. Where trestles are employed, the supports are usually placed from 8 to 12 feet apart. The life of a flume will usually not exceed 20 years at most, and is generally little more than 10 years.

124. Wale-GateB. — Waste-gates should be placed every half mile to empty the flume for repairs or in c;ise of accidents. Waste-gates are also useful in running snow out of the flume. In snow belts, flumes are frequently covered with sheds in exposed places to protect them from snowslides. If anchor ice freezes on the bottom of a flume, the water should be immediately turned out. If snow fills

e flume when gotten rid of by tui before it has time t

through it, it may be and flushing it out „

125. Bracket Plumes. — When it becomes nee to carry a flume along the face of a cliff at such an elew tion that a trestle is practically out of the question, bracket

§39 Placer And Hydraulic Mining.

may be employed. Fig. 41 illustrates a bracket flume which was employed in Butte County, California. The Clitf is a perpendicular wall of basalt, and for a distance of 600 feet the flume is carried on brackets 118 feet above the bed of the ravine, and at one point 232 feet below the top of the cliff. The brackets are made of 30-pound T rails bent in the shape of an L; the longer arm (10 feet long), on which the bed of the flume rests, is placed horizontally, having the end next the cliff supported in a hole drilled in the rock. The short arm stands vertically, and has in its upper end an eye into which is hooked one end of a J-inch round iron rod connect- ing with a ring-bolt soldered into a hole in the cliff above. The brackets were set 8 feet apart, and were tested to stand a weight of lij tons. The flume is 4 feet wide and 3 feet deep, with a capacity of 3,000 miner's inches.

Pipes.

126. Wooden Pipes. — For moderate heads, wooden- stave pipes are commonly used. They are practicable for any desired head, but are only economical to the point where the pressure necessitates such close banding that the cost exceeds that of iron or steel pipe of the same strength. If kept full of water, the stave pipe will last indefinitely, and the bands may be protected from rust by a coating of asphaltum or mineral paint. The amount of iron in the bands for each foot of pipe is the same as that required for a foot of sheet-iron pipe of the same diameter calculated to withstand the same head or pressure with a considerable margin of safety. Fig. 43 illustrates a wooden-stave pipe in which the bands are composed of round steel rods. One advantage of a wooden-stave pipe is that it can be made to conform to the irregularities of the ground more easily than is the case with an iron pipe.

127. Wooden for Tunnels. — On some extensive ditch lines it has become necessary to carry water through tunnels, and owing to the fact that the irregular rock lining of the tunnel interfered considerably with the

PLACER AND HYDRAULIC MXa

flow of the water, it has been found best to li wilh timber. This has been dune by buile

pipe inside the tunnel, the pipe being backc4j and no bands l)eing; employed. In fact, it bq

§ 39 Placer And Hydraulic Mining. 86

a wooden lining for the tunnel. Where such linings are employed, the tunnels are sometimes driven below the water- level of the ditch, so that they really become inverted siphons, and in case the water should be turned off in the ditch, the tunnel would always be filled, and hence there would be no tendency for the lining to dry out and crack. Such a lining always remaining under the water will last indefinitely.

128. Iron Plpe. — Wrought-iron or steel pipes are exclusively used for high heads. For low heads, either wood or iron may be employed, the choice between them being a matter of location and cost. Pipes are used as water conduits for replacing ditches or flumes, as the supply or feed pipes passing water from the pressure box to the claim, and as distributing pipes taking water from the distributors or gates at the end of the supply-pipe line and delivering it to the discharge- pi pes, Giants, or nozzles. Pipes used for carry- ing water across depressions and placed so as to follow the natural surface of the ground are called inverted siphons. The thickness of the metal for pipes is determined by the pressure of the water and the diameter of the pipe. The pipe, when put together, soon becomes water-tight from the foreign matter in the water. This result may be hastened by throwing in a few bags of sawdust. The pipes thus rendered water-tight will remain so when subjected to a pressure as great as 200 pounds per square inch. In jhe Texas pipe line, Nevada County, California, there is an inverted siphon 4,4;J8.7 feet long, constructed of riveted sheet-iron pipe l? inches in diameter. Its inlet is 304 feet above the outlet and at the full head will discharge l,2yO miner's inches. The maximum head is 770 feet, which is equivalent to a pressure of 3:i4 pounds per square inch on the pipe at its lowest point,

129. Joints — Ordinarily, pipes vary from U to 40 inches in diameter, and are constructed of sheet iron or steel, varying in thickness from No. 8 to No. 14 or Ifi (Bir- mingham Wire Gauge). The sheets are riveted together into

sections of frr turn inl'. Icti-i

RAULIC MINliG.

in length, and these in feet, or into convenient lengths for transporta- tion. These longer pieces may be put tn- yeiher by a number of different devices.

S.,in

the

this style of jui

simply put together stMvcpipe fashion, nei- tlier rivets, wire, nor any oLher contrivance being . necessary to hold the I juint in place. Where re is great pressure, n collars or lead joints are frequently used. Fig. 43 {a) shows ; it is frequently used; / is a wrought- iron collar about 5 inches in width and -,'f inch thicker than the pipe iron. The inside diameter of this collar is of an inch greater than the outside diameter of the pipe; / is a joint composed of lead which is run in between the collar / and the pipe and then calked tight from both sides; is a nipple about C inches in length which is riveted in one of the sections by means of |-inch rivets. Sometimes, owing to expansion and contraction of the pipe, the lead in the joint has a tendency to work out, and to replace this lead or force it back into the joint, the clamp shown in {b). Fig. 43, has been devised. At a is shown the clamp and its method of application for forcing back the lead which is worked out. The clamp is shown both in side view and in cross-section. At the lower part of {b). Fig. 43, will be seen another clamp which is driven over the joint to keep the lead in place after it has been forced in by means of the clamp a.

130. Sometimes wrought-iron pipes are provided with hooks, which are riveted near the ends of the pipe and are

§39

Placer And Hydraulic Mining.

fastened together by winding wire about the hooks on the adjacent lengths of pipe, thus counteracting the tendency which the pipes have to work apart, owing to expansion and contraction.

131. Elbow*. — Sharp bends should always be avoided in pipe-lines when possible, and all turns should be made

by gradually bending the pipe, if this can be accomplished. When short curves are necessary, elbows similar to that shown in Fig. 44 may be employed. In this case, a, a are the angie-irons riveted on to the elbow and connected by straps to similar angle-irons riveted on to the adjacent sec- tions of pipe, as shown in the illustration These angle- irons and straps are necessary to prevent the pipe from pull- ing apart at this point, owing to expansion and contraction.

132. Air and Blow-Off Valves Blow-off valves

are provided to allow the escape of air while the pipes are being filled, and also to prevent the formation of a vacuum, and the conse- quent collapse of the pipe, which might occur in case of a break. The simplest form is a loaded flap-vaive of leather on the inside of the pipe, arranged to cover a hole from 1 to 4 inches in diameter. A very simple automatic valve is shown in Fig. 45, which consists of a small chamber above the pipe, in which hangs an inverted

88 PLACER AND HYDRAULIC MINING. g

bell or cylinder a, closed at the top. When simply air escaping, this cylinder will remain in the position shown the i 1 1 u 5 1 r a t i o owing to its Of weight, but as SOI as water rises in the chamber, air w be trapped unde the bell, causing to float up and sea against the top the chamber, tl closing the openinj FIG. M. /', and hence pre

venting the escape of the water. Should the flow of wate cease, the bell will immediately fall and air will entel through the opening b, thus protecting the pipe from collapse Pig. 46 shows a form of blow-off, or drain valve, low points along the pipe for emptying the same. Fig. 47 shows a combination auto- matic blow-off and vacuum valve, which is employed at high points in the pipe-line. The valve on the right is kept closed when the pipe is full and the valve immediately over the pipe open. The pressure in the horizontal tube will keep the central valve closed. In case any small amount of air does collect in the pipe, it can be easily discharged by opening the small valve at the right. Now, if a break should occit anywhere in the pipe-line and a vacuum result at the uppe point, the central valve would fall of its own weight, thui admitting air and preventing the collapse of the pipe.

§ 39 Placer And Hydraulic Mining. 89

refilling the pipe, this valve, being open, allows the air to escape, and when properly constructed will close upon being reached by the water. This latter effect may be accom- plished either by making the lower part of the valve so that it will trap some air and float up, or by shaping the upper disk properly, the escaping water will strike it and lift it high enough so that the current can catch and close it.

133. Laying PIpe-Dnes. — To preserve iron pipe, it should be laid in a trench and covered with earth to a depth of at least one foot. Wooden pipe should be painted on the outside with the same mixture that is used for covering the bands. Iron pipes should be covered inside and out with asphalt or coal-tar. Such pipes, well coated, have been found in good condition after 15 years of continuous ser- vice. The following are mixtures that have been found to give good results for this purpose:

Crude Asphalt 28

Coal-tar (free from oily matter) 72!

Or, Refined Asphalt n;.5

Coal-tar (free from oily matter) 83. S;*

To prepare either of these, the asphalt is broken into small pieces and heated with the coal-tar to a temperature of about 400° F. and well stirred. The pipe to be coated is dried and immersed in this mixture, where it should be allowed to remain until it acquires the temperature of the bath. When coated, it is removed and placed on trestles to drip and dry in the sun and air. For convenience in immersing, wrought-iron troughs of such a size that they will conveniently contain one section of pipe arc provided.

134. FllllitK Plpes.~Pipes should be filled in such a manner as to prevent as far as possible the admission of air, which will be drawn in with the water in surprising quantities unless care is taken. The best plan is to put a gate in the pipe below the intake, and thus regulate the flow and maintain a steady pressure. Where the pipes which convey water to the mines are supplied from flumes, some

PLACER AND HYDRAULIC MININGr

over a weir anil esuajn water in the pressure quiet to prevent air fn

kind of box is necessary. TKis is commonly called a pe stock or pressure box, and is illustrated in Fig. 48. A gl tiugoC barsshould so placed in the flm as to remove all di iir brush before water passes into ti penstock, and t surplus water shoi be allowed to do , its MiMivii III the illustration. TI box should be sufficiently deep a( m being carried into the pipe, accomplish this, the box is frequently made of two parts, tl water flowing from the flume into one and from it into tl other through a grating or partition provided with sma holes. As the water coming through ditches almost invi riably carries more or less sand with it, and as this would 6 liable to cut and scour the inside of the metal pipe, it is qu important that it should be settled out or separated hefoi the water enters the pipe. This is usually accomplished b means of a sand-box, which may be constructed in coi tion with the pressure box, or al a point in the flume s what above the pressure box. The sand-box is simply ai enlargement in the flume, so arranged that the velocity of th current is reduced and the sand allowed to settle on th bottom of the box, where it accumulates and from where j is occasionally flushed out by means of a gate near the hot torn of the box. Sometimes pressure boxes are made largri and provided with a chamber below the intake pipe, it beinj intended that the sand will accumulate in this chambel and that it can be removed from there periodically.

I3S. Supply or Feed Pipes. — Water is conveyed I iron pipes from the pressure box to the claim and dis tributed to the discharge-pipes by means of iron gates. Thi supply pipe is usually funnel-shaped where it connects witi the pressure box, and from there it is usually of a uniforii

S39

Placer And Hydraulic Mining.

diameter. Where pipes from 23 inches to 30 inches in diam- eter are employed, mela! lighter ihan No. 14 B. O. advisable. The main sup- ply pipe should descend into the diggings or mine by the most convenient and direct line pos.-ible- Sharp angles and rises fir depressions should In- avoided. Air-valves should be provided for the escape of the air when filling the pipe, and to prevent col- lapse in case of a break the pipes should be well braced and weighted at all turns or angles. In filling the supply pipe, water should be turned on gradually, for if this is not the case, the moment the pipe becomes tilled the sudden check in the flow of the water will result in a violent water-hammer, which may strain the pipe badly, or even burst it. Leakage in any of the joints may he stopped by running some sawdust into the supply pipe. Wherever it is necessary to join the supply pipe and one of the dis- tributing pipes, the present practice is to fork the main pipe by means of a Y joint and to provide each branch with a gate-valve similar to that shown in Fig. 49.

Examples Of Placers.

Alma Placer.

I3B. As an example of ordinary placer mining, we may take that of the Green Mountain Company at Alma, South Park, Colorado. In South Park, at an altitude of Ifl.iiOi) feet above the sea, is an extensive area of i))acer ground located on the banks of the South Platte River and extending from

n PLACER AND HYDRAULIC MIKING,

the base of Ht. Lincoln to Fairplay, a distance of of

30 mites. This area consists of rolling banks of pebbi boulders, grarel, and on both sides of stream, the surface bcii covered with grass and few spare trees, and d ping gently towards mountainside for an avi age width of about half mile. Portions of placer banks have worked at Alma and Fairplay, but the banl are far from being exhausted. The principal hydraul workings are at Alma, where the banks are thickest, owii to the convergence of the tributary streams at that poin A good supply of water can be obtained during the sumrai months, and hence the beds are worked continuously nigl and day during the season. The gravel and drift materii was undoubtedly first brought down by the glaciers, but hi subsequently been washed and worked over again by tl streams which flowed from the canons. Where a section the bank is exposed, as at Alma, it exhibits a structui from the grass roots down to bed-rock, similar to that show in Fig. 50, which may be described as follows: At the there is first a foot or two of black earth in which there little gold. Below this, a foot or two of clay with pebbll in it, and then a few feet of sandy layers irregularly beddc in streaks as if formed by eddies and currents, and lilo wise comparatively poor in gold. The remainder of ti deposit to bed-rock, 30 to 50 feet, is composed of subangiil) and rounded pebbles and boulders of all sizes, from a fra lion of an inch to a yard or more in diameter, the who being cemented together with sand, clay, and in places wil iron oxide, so that it forms a tolerably tough conglomerai which can be attacked only by means of a pick or with Giant having a good head of water. The banks contini

§ 39 Placer And Hydraulic Mining. 93

down both sides of the creek for several miles, but are thick- est at Alma opposite the outlet of the tributary canons — Buckskin and Mosquito. Here is the site of one of the oldest workings in Colorado. The banks have been cut back for a long distance from the river, presenting a ver- tical cliff, in some places 70 feet high and about a mile in length. This cliff is cut by narrow channels, ravines, or gashes, which have been made by the Giants or flume water- falls. Some of these cats are narrow gashes not penetra- ting far into the bank, while others lead through narrow ravines into wide open amphitheaters surrounded by high banks, the center being occupied by piles of large boulders which have been thrown out of the sluices and stacked up in the course of the work. Winding through this mass of debris may be seen the remains of the old abandoned gravel sluices.

The Alma placer is operated in this district, and it may be described as follows ; The sluices pass to the river- bottom through a narrow ravine, as shown in Fig. 51, and the ends of the sluices are divided into short curved tribu- s so as to distribute the tailings over the river-bottom.

In this mine there are two sluices coming from the amphi- theater out through the ravine, the ravine being over a thousand feet long and the amphitheater 200 feet wide and about 70 feet deep. Fig. 53 illustrates the amphi- theater at Che head of the sluices, and here the method of

Placer And Hydraulic Mining.

§39

carrying on the work may be seen. Water is allowed to flow over the bank as flume waterfalls, which can be seen at the far end of the illustration. The disintegration of the material left standing between the gulches cut by these waterfalls is effected by means of hydraulic Giants, and all the material is washed into the gravel sluices. The sluices are lined with block pavement similar to those which have already been described. The operations mav be

described as follows: After the washing has continued for some time, a greater or less number of large boulders accu- mulate at the feet of the waterfalls and above the sluices. When this occurs, the flume waterfalls are turned off and the Giants turned on to some other portion of the bank. Then men climb into the pathway of the refuse stream and pick out the larger boulders, some of which have to be blasted before they can be handled. These boulders, if small, are loaded on a stone-boat, which is hoisted out of the way by means of a large derrick seen in the center of the illustration. Large boulders are slung on to the derricks by means of chains and hoisted without the use of the stone-boat. The derrick is operated by a 10-foot Pelton water-wheel similar to that shown in Fig. 25. After the large boulders have been removed, the Giants are once more turned on, and the gravel and pebbles which had been held back by the boulders are washed into the flumes so as to c.tpose the sandstone

g 39 PLACER AND HYDRAULK

bed-rock. The bed-rock cleaners then dig up and shovel into the sluice the rotten surface of the sandstone to a depth of a foot or so, or to such a depth as experience has proved that the gold will occur. They examine a!l cracks in the rock and scrape out any gold there with knives or brush it out. After this the bed-rock cuts are advanced and the work of the flume waterfalls and Giants begins again as before. While the water is flowing down over the bank, men are at work with long-handled shovels ground-sluicing or helping along or removingout of the way of the stream any boulders, and keeping the water in as definite a channel as possible, so that its work may be effective. The ravine leading to this placer, which is 1,000 feet long, and the amphitheater, 200 feet wide by 70 feet deep, were both exca- vated within six months.

137. Preliminary Operations Kecessary.— Before

this particular enterprise was undertaken, the ground was prospected and the presence of gold in paying quantities assured by sinking shafts to the bed-rock and testing the gravel from them, and also by testing the material from the exposed faces by panning. The question of water- supply was considered and a reservoir constructed with an area of 6 acres and an average depth of 10 feet. The dam is made of gravel and brush and is provided with timber cribs and gates for the wasteway. The ditch from the dam to the mine is about 2 miles long and carries 2,000 miner's inches. It is 12 feet wide, 3 feet deep, and has a grade of 10 feet to the mile. At one place a flume 240 feet long was built and carried on trestles, the flume being () feet wide and 3 feet deep. At the end of the flume on trestles there is a flume resting on a rock and running at right angles to the main flume, and from this four ditches arc carried to the general workings. A penstock is placed at the end of one of these branch ditches, and from this point two pipe-lines are carried to the Giants. The pipes are 'ii inches in diameter at the penstock, but taper gradually to 10 inches in diameter at the Giants, the lines being

1)6 Placer And Hydraulic Mining.

each approsimately ."iOO feet long. There are two Giants of the size known as No. 2. The Giants use 3(Kl miner's inches each, and the ditch has a capacity of about 2.000 miner's inches, the remainder of the water being employed for o[jera- ting the derrick, or as a lluine waterfall. The two sluices arc each 3 feet wide by 4 feet high, or deep, but they are paved with wooden-block rlfSes 8 inches thick, which reduces the depth by that amount. The force of the water in the sluices is so great that boulders weighing 100 pounds are frequently carried entirely through the sluices. The grade of the sluices is i inches to li feet, or 33 inches to 100 feet. The sluice line is laid on bed-rock, which has been cut down in places to receive it. At curves the gravel sluices are raised on the outer side. The sluices are each 4,000 feet in length, but most of the gold collects in the first 400 feet of each sluice.

138. Cleaalns Up. — In this placer about 2 c quicksilver are supposed to be used for each ounce of gold to be caught. The clean-ups, which occur at regular inter- vals, are conducted as follows: The riffles arc first taken out in sections and everything washed clear. Tlie packing of small stones, which was located between the blocks, is then removed with 12-tined forks and the floor cleaned. The quicksilver is removed and washed clean from the black sand, after which it is strained, the amalgam retorted, and the bullion melted down, preparatory to being sent away, as described in Arts. 67 to 72.

Roscoe Placer.

1 39. As an example of a placer which has been exposed

by means of a wing-dam, the Roscoe placer may be described. This is situated in the cafion of Clear Creek, Colorado. Clear Creek Cafion is one of the steepest and grandest in the front range. It is cut through granite rock for a distance of some 40 miles to an average depth of 1,000 feet. About 13 miles from its outlet on the plain the creek forks, one

§ 39 Placer And Hydraulicmining. 97

branch leading up to the gold-mining region of Central and the other to the gold-mining region of Idaho Springs. The main creek receives the drainage of two gold-bearing dis- tricts. Ac Central, in addition to the gold derived from the veins and rocks direct, the creek brings down a great deal of flour gold and fine amalgam in the tailings from the old stamp-mills, which, by their crude methods, lost in the past upwards of 40 per cent, of the gold in the ore, together with a good deal of amalgam. This refuse matter from the mills had been accumulating for 30 years, and was in addition to all that the placer formerly contained. Miners and prospectors in the past obtained a good deal of gold from the shallow or surface washings, but the deep, underlying bed-rock was out of their reach. At one point the caiion is crossed by several hard quartz and feldspar veins. These formed a natural dam, which was finally broken through by the creek as its ca3on was being eroded : but the miners confined it to narrow limits at this point. At some comparatively recent time some huge masses of rock have fallen into the creek at this point in such a manner as to practically dam it and form a waterfall about 30 feet high. Above this natural dam there is a large expanse of ground, consisting of placer matei'ial and old tailings. The Roscoe placerwas opened to work this deposit. The fall of water over the natural dam gave a good dumping -ground for the tailings, and the flat area above made it convenient to construct a large flume along one bank of the creek, into which the stream was turned by means of a wing-dam, thus exposing the bed of the creek with its placer ground and accumulation of tailings.

1 40. Preliminary 'ork. — Before commencing oper- ations, the ground wasirospected by sinking shafts to bed- rock, and the presence of gold assured. In general, the work was carried out as follows; First, a flume was con- structed on the south bank of the stream capable of carry- ing all the water of the creek. This flume was 10 feet wide, tj feet deep, and 3,400 feel long. The flooring of the

98 Placer And Hydraulic Mining.

flume was 4 inches thick and the sides 2 inches. The grade on curves was H inches to 16 feet and in the straight portions J inch to 10 feet. Tlie flume was not straight, but followed the course of the stream, the outside edge of the flume being elevated on curves so as to prevent the water from splash- ing. The water was turned into the flume by means of a wing-dam, which was first constructed with the aid of sand-bags, as shown in Fig, 34. and subsequently backed up by means of a bank of earth and a substantial wooden frame- work composed of triangular bents. The whole was then backed up with stone and gravel, and the down-stream face riprapped with boulders taken from the drift material. By this means the entire creek bed above the natural dam was exposed for work. To provide a water-supply for the opera- tion of the Giants and hydraulic elevators, a dam was con- structed about 3 miles up stream and an intake flume 800 feet long built to a combination penstock and sand-bos. This penstock was provided with a grating which removed the brush, leaves, etc., and was made large and deep enough to serve as a sand-box, the surplus water escaping over a weir and flowing back to the river. The penstock was 8 feet square and 16 feet deep. Part way down, one side of the penstock was connected to a 48-inch wooden-stave pipe made of pine boards banded with round steel hoops, like that shown in Fig. 42. After leaving the penstock, the pipe was buried for a distance of about 300 feet under a stone embankment and then passed under the railroad track by means of an arch. The wooden pipe diminished gradually from a diameter uf 48 inches at the penstock to 22 inches where it joined the metal pipe. The wooden pipe extended to within about of a mile from the mine, where it was joined to a metal pipe, which gradually diminished from 22 inches to 16 inches in diameter. For the last mile there were 2 metal pipes, one 16 inches and the other 12 inches in diameter, which ran parallel. One of these pipes supplied the water for the Giant nozzle and the other for the hydraulic elevator. The pressure on the pipes at the nozzle was 87 pounds per square inch, and the Giant would throw a coluig

§ 39 Placer And Hydr

of water 4 inches in diameter for a distance of 165 feet If the pipes were closed at the end, the pressure would be

189 pounds per sq. in. In addition to the construction of thi.' flume and wing-dam for diverting the stream and the

Placer And Hydraulic Mining.

pipe-lines for supplying water, it was necessary to consti sluices to supply water for washing the gravel, and for undercurrents whii.h tre.iied the fine material. The main iravel sluice was 308 feet long, 4 feet wide, and 3 feet deep, and was paved with square W')oden-blocfc riffles. At the end of this sluice there was a grizzly which removed all material over inch in diameter and passed it tt the waterfall, the fine portion going to the first undercurrent, which was 13 feet wide, 24 feet long, and set on a grade of 6 inches in 24 feet. Tliis box was lined with riffles made by nailing narrow wooden slats across the bottom and securing pieces of J flat strap iron to the top, so j that the edges of the strap iron " projected over the slats on both sides. This formed riffles very much like the angle-iron rif- fles illustrated in Fig. 15. The material which passed over the first undercurrent was taken up by a second sluice and carried to a second undercurrent, which was 24 feet wide, feet long, and covered with burlap or sacking iplHSHIH material. The burlap carpets r 1 were occasionally drawn off on to ' wliKyMlM" wooden rollers and carried to wooden tanks, where they were carefully washed. The material caught by this undercurrent consisted largely of flour gold and pyrites, which had accu- mulated from the tailings of the mills above. Before the

nain

Placer And Hydraulic Mining.

material passed on to the second undercurrent, it passed over a perforated plate, which removed everything over one-half inch in diameter,

141. Method of Operation. — After the flumes and pipe-lines were constructed, operations were started as follows: A pit was sunk at the upper end of the sluice line with the aid of the hydraulic Giants and hydraulic elevator. The elevator used was of the Ludlum ty[.>e, as illustrated in Fig, 23. Fig. 53 gives a general view of the placer, show- ing the railroad track on the north bank, the main flume for deflecting the course of the stream on the south bank, and the pit in which operations were carried on in the fore- ground. To the left of the pit can be seen the gravel sluices, and below them the two undercurrents. Fig. 64 is a general view showing the entire valley from the point at which water for the pipe-line was taken from the stream down to below the last undercurrent. Fig. 55 shows the pit

or excavation at the lower end of the workings. In tliis illustration it will he noticed that water for some of the work was taken directly from the large flume which deflected the stream, while the water for operating one of the Giants and the hydraulic clcvatcirs was conveyed down by the pi]>e-

loa

Placer And Hydraulic Mining.

line. Of the two pipes at the back of the illustration, ascend from the pit into the gravel sluices, one is a gravef elevator and the other a water elevator. The cleaning-up, preparing', retorting of the amalgam, and melting of the bullion were carried on in the manner already described.

WORKINO PLACERS BY DREDOBS. 142. General Conslileradoo. — Where streams i not be diverted from their course by Humes and wing-dam so as to expose the bed, or in cases where bench placers do not have sufficient water for hydraulicking, it becomes neces- sary to introduce some other method for e.ncavating and.i handling the material. Such deposits are commonly workei by means of dredges. Dredges may be divided into tw classes, those which excavate the material by means of i line of buckets on an endless chain, and those of the dippi type, which are provided with a single bucket, like a steai shovel.

IIUCKET DRCncnS.

143. General Description uf Plant.— This dredges is usually employed in operating placers in tfatti beds of streams or where a sufficient quantity of wi be obtained to use a flatboat, on which the machinery placed. The plant consists of a series of buckets on chains, which excavate the material and lift it on to the dredg-eJ There are also sets of centrifugal pumps for furnishin water to the sluices and handling tailings, and for similai purposes, and usually an elevator for raising the taiUti and depositing them behind the dredge. After the mate- rial is excavated, it always takes up considerably mort space than in the bank, and hence the tailings pile always higher than the bank from which it is extractedt'l As the material comes from the buckets, it is usually pass through a trommel to remove the larger stones, which pas

U

§ 39 Placer And Hydraulic Mining. 103

at once to the tailings discharge or through a chute, which drops them in ihe rear of the dredge. The material which passed through the trommel is conveyed over s%ts of riffles — tables covered with burlap, matting, or other fibrous material — and sometimes over amalgamated copper plates. Frequently several trommels or screens are introduced into the line of apparatus so as to remove portions of J:he mate- rial at different points; as, for instance, the first trommel may allow anything that will pass through a 1-inch opening to go over the first riffles; the second may remove all above inch in diameter and be situated above the last riffles or the tables; and where copper plates are employed a screen is frequently introduced which removes everything above inch in diameter, so that the plates will not be subject to an excessive scouring action.

144. Dispoaltion of Tailings. — Tailings are elevated and discharged in the rear of the dredge. This may be accomplished by means of a bucket elevator and discharge

sluice, or they may be collected in a well- or sump and forced to the rear by means of the centrifugal pump.

145. CleanloK of the Bed-Hock.— The gold which is situated on bed-rock may be obtained by a number of devices. Sometimes the suction of a powerful centrifugal pump is passed over the surface of the bed-rock for the purpose of drawing up any particles of gold, black sand, or other material which may be deposited upon the bed-rock; but it is probable that this device would not be able to handle any nuggets, and it is certain that it would not obtain the gold from deep crevices in the bed-rock.

Where the bed-rock is soft, 3 or 3 feet of it may be taken up by means of the buckets of the dredge and run through the sluices in the ordinary manner.

If the material on bed-rock is very rich and the bed-rock hard and uneven, diving-bells may be employed and men sent down to the bottom to clean the bed-rock by hand.

In working placers which are not situated in the bed of a river, and esjwcially when working placers located on

Placer And Hydraulic Mining.

high benches, the dredge Is sometimes operated when fioat>>a ing in water which has been pumped into the pit. In thiftj case, it may be possible to pump the pit dry and clean up the- bcd-rock by hand, the dredge being supported upuu special 1 piles or legs while this operation is in progress. The water J necessary for use in the sluices while working the material I cleaned from bed-rock is obtained either by pumping the J water which flows into the opening through the centrifugal 1 pump, or the water pumped from the pit may be retained I in a reservoir or dam adjoining the pit, and the centrifugal J pump draw its supply from this source.

146. WattlilnK Plant Located on Sbore. — It also been proposed to employ dredges located in the stream, and to convey the material to washing plants on the shore, 1 which would be provided with ordinary sluices, under- 1 currents, etc. ; but this device has the disadvantage that it J requires the disposition of the tailings at some distance from j the point where active operations are being carried on, and that the tailings are liable to bank up and necessitate the ' removal of the permanent works.

Dipper Dredges.

147. General Description of Plant. — Dipper

dredges are practically steam shovels, which are fitted up for operating in gravel banks, and are provided with some form of gravel elevator for removing the tailings and stack- ing them to one side of or behind the machine. They also have a set of trommels, pumps, sluice boxes, tables, amal- gamating plates, etc. The water for use in the trommels and on the tables is frequently supplied hy a small pumping plant which draws its supply from a reservoir near the plant, and the water which drains out of the tailings is allowed to flow into the same reservoir, so that it is used over and over.

14S. General Application. — These dipper dredges are employed where there is not water enough to use a boat, and hence the other form of machine is not practi-

§ 39 Placer And Hydraulic Mining. 105

cable. In some cases there is not even water enough to sluice the material over the riffles, and hence some form of dry-placer washing machine has to be introduced. These dry-placer washers work on the principle of the fanning mill or pneumatic jig, the material being screened to a comparatively uniform size and the lighter sand blown away, leaving the gold collected behind the riffles, where it is sometimes held as amalgam by means of quicksilver.

General Remarks Concerning Dredges.

1 49. As a rule, moving or handling material by mechan- ical means is always more expensive than hydraulicking, but it becomes necessary when a sufficient head and volume of water can not be obtained. As a rule, it is always best to employ one of the dredges which operates in water, as their capacity is usually greater and the wear and tear on the machine less. Dredges of this class have been employed for raising and working the tailings from old concentration mills.

Placer dredging is a comparatively new method of opera- tion, but it has certainly been very successful in many cases, and it is undoubtedly not only the best but the only economical method to work certain classes of deposits.

"1 I

"I-

M I

, f

f

(

't

A Series

Op

Questions And Examples

Relating to the Subjects Treated of in this Volume.

It will be noticed that the various Question Papers that follow have been given the same section numbers as the Instruction Papers to which they refer. No attempt should be made to answer any of the questions or to solve any of the examples until the Instruction Paper having the same section number as the Question Paper in which the questions or examples occur has been carefully studied.

r

;W

Blowpiping.

(1) What is a chemical element f

(2) Name the gaseous elements; the liquid elements; the non-metallic elements.

(3) Define molecule; atom.

(4) Define atomic weight ; molecular weight.

(5) Give the chemical . symbols for lead, copper, iron, sulphur, arsenic, and antimony. What is the advantage of the use of chemical symbols ?

(6) Express, as a proper chemical formula, a compound containing two parts (by volume) of aluminum, and six each of oxygen and hydrogen, combined as the hydrate radical {OH), Give the formula for chromic sulphate (chromium sesquisulphate).

(7) What is chemical affinity f

(8) Name and illustrate by equations the three classes of chemical reactions.

(9) What is the valence of an element ?

(10) What are subscripts, and how are they used ?

(11) What is a radical?

(12) What are coefficients, and how are they used ?

(13) How does a coefficient or subscript, immediately out- side of brackets enclosing a chemical expression, affect the expression within the brackets ?

(14) Define acid ; anhydride.

(15) Define base ; salt.

§34

9 Blowpiping. § 34

(16) Describe the characteristic reactions produced by &uljjecting carbonates, sulphides, and silicates to the action of the common mineral acids.

(IT) Mention some mineral substances not affected by these acids.

(18) State clearly how the blowpipe should be ustid, and tell what precautions the beginner should observe.

(19) In what particulars is the Bunsen burner superior to the spirit lamp or candle for blowpipiog ?

(2U) Define oxidation.

(21) Define reduction.

(22) What wet tests are employed in connection with the blowpipe ?

(23) Give Platlner's scheme for the examination of sub- stances B. B,

(34) Name the elements whose compounds give charac- teristic reactions in the closed tube and in the open tube; also state what is the chemical difference in the reactions in the two tubes.

(25) Give the reactions for arsenic and antimony in both open and closed tubes.

(2G) How is selenium recognized both in the open and the closed tube tests ?

(27) Give reactions for tellurium in both tubes.

(38) Describe the method of heating on charcoal, and state what precautions must be observed in the case of materials which decrepitate or tend to blow or fly away,

(29) To what principle is the oxidizing action of the O. F. due, and to what principle is the reducing action of the R. F. due ?

(30) Give the reactions on charcoal for bismuth, cad- mium, and zinc.

(31) Describe in detail the operation of roasting. Why

Blowpiping.

is it necessary to roast substances containing sulphur and arsenic before treating them in the beads ?

(33) Give Von Kobell's scale of fusibility. How would yon test the fusibility of a mineral that decrepitates or flies to pieces when heated ?

(33) What characteristic reactions do each of the follow- ing elements give when tried with a colorless flame : sodium ; barium; copper; and calcium?

(34) To what class of substances is the test with cobalt solution applicable? In the case of what elements is it to be relied upon ?

(35) Describe clearly and briefly the method of testing substances in the borax and salt of phosphorus beads. What is flaming?

(3G) Give the reactions with borax bead in both flames for iron; manganese; zinc; nickel; copper; cobalt; and chromium.

(37) Give the reactions with salt of phosphorus bead in both flames for the elements named in the preceding ques- tion.

(38) What metals are reducible from their compounds on charcoal with soda ? What other fluxes are of advantage in the case of difficultly reducible substances ?

(30) Give the characteristic tests for fluorine, chlorine, and bromine.

(40) Give the characteristic reactions for zinc; (/') mercury.

(41) How is the presence of water detected in minerals ?

(42) How is the presence of sulphur detected when it is in the form of a sulphate ?

Test each of the minerals named in questions 43-50, and, as your answer to each question, describe the reactions obtained, stating what element each indicates; and also state your inference as to the composition of the minerals,

referring, if you desire to do so, to Instruction Paper, sun

t Mineralogy (or to any other convenient source), for ttt

J position, as a check on your work ;

Chalcopyrite. J

(45)

(48)

(49)

(60)

Mineralogy.

(1) What is a mineral ?

(2) In examining a mineral, what physical characteristics should be observed ?

(3) What is the difference between cleavage and fracture ?

(4) What is meant by conchoidal fracture ?

(5) What is meant by the streak of a mineral ? How is it best obtained ?

(6) What is meant by brittle ; flexible ; malleable ; ductile ; clastic ?

(7) Define splendent luster ; vitreous luster.

(8) Give Mohs' scale of hardness, and describe how it is used in determining the hardness of a mineral.

(9) Give a general scheme for the examination of min- eral specimens.

(10) What is the specific gravity of a substance ? How may it be determined ?

(11) What is meant by columnar structure ; granular structure ?

(12) Name the crystal systems, and give the principal characteristics of each.

(13) De fi ne sjm me try plane ; sym me try axis.

(14) What are hcmihedral forms ?

(15) What is basal cleavage ?

(16) What is ttvinning?

(17) Are perfect crystals common in nature ?

(18) How may distorted crystals be identified ?

§35

Mineralogy.

(10) How does gold occur in nature ?

(iO) What tests distinguish gold from substances a >>imilar appearance ?

(21) Name the principal iron minerals,

(32) What arc the general characteristics of the minerals ?

(2:)) Give the color and streak of each of the prim iron minerals.

(34) What are the distinguishing characteristica pyrite ?

(25) How is siderite distinguished from mineral! similar appearance ?

(3f>) What are the general characteristics of the minerals ?

(37) What valuable impurity do the lead minerals contain ?

(38) What are the principal zinc ores 7

(29) What tests distinguish franklinite from sJml minerals, notably magnetite ?

(30) Give the general characteristics of the sih minerals.

(31) Describe the mineral cerargyrite.

(32) What are the general characteristics of the copi minerals ?

(33) How is malachite distinguished from chrysocolla

(34) Describe the mineral cuprite.

(35) How may chalcopyrite be distinguished from pyrit

(36) Describe the mineral garnierite, and give its bio pipe and other characteristics.

(37) What is stibnite, and how is it distinguished ?

(38) Describe the mineral sphalerite, and give its che ical composition.

(311) What are the principal varieties of coal ?

§ 35 Mineralogy. 3

(40) What difference in composition is particularly noticeable in the different varieties of coal ?

(41) How may calcite be distinguished from fluorite ?

(42) Give the general characteristics of the manganese minerals.

(43) Describe the mineral cinnabar, and give its blow- pipe reactions.

(44) How may dolomite be distinguished from cclcite ?

(45) Describe the mineral opal.

(4G) What makes a mineral a precious stone ?

(47) What varieties of corundum are precious stones ? Give the color of each.

(48) How is the corundum (oriental) ruby distinguished from the spinel ruby ?

(49) How is a garnet distinguished from a (oriental) ruby?

(50) What is gypsum ? Give its composition and charac- teristics.

(51) Of what value are pyrite and chalcopyrite ?

(52) For what purposes is zinc used ?

(53) Name four of the principal gangue minerals and give a description of each.

.: 113' i

" ;: i.f ;fi;

flilf.:

Assaying.

(1) {a) What is quantitative analysis ? {d) What is usually understood by the term assay " ?

(2) What is assaying ?

(3) To what may fire assaying be compared in its opera- tions ?

(4) Describe the crucible method of assaying as conducted in a muffle furnace.

(5) (a) Describe the sampling and assaying of base bul- lion, (i) How are the results of a base-bullion assay reported ?

(6) (a) What precautions must be taken when setting up balances ? (d) How may balances be prevented from rusting ?

(7) {a) What are the advantages of the muffle furnace ? (b) For what are wind furnaces chiefly used ?

(8) From duplicate -A.-T. charges of an ore, two gold- silver buttons are obtained weighing 15.76 mg. and 15.74 mg., respectively; and after parting, the gold from the two buttons is found to weigh 1.98 mg. In weighing, a 1-mg. rider is used, and each division of the balance beam corre- sponds to -j*y mg. (a) Describe the complete operation of weighing the buttons, before and after parting," naming the weights used, giving number of divisions on balance beam indicated by rider, etc. (b) Report the assay of the ore in ounces of gold and silver per ton of ore.

(9) (a) How is fine bullion sampled ? {b) For what purpose is the preliminary assay " of fine bullion made? (r) How are the results of a fine-bullion assay reported ?

§36

9 Assaying.

(10) (a) By what three methods may ferru: chloride be reduced to ferrous chloride in the solution obtained in the bichromate method for the determination of iron in ores? (i) Describe the reduction of ferric chloride to ferrous chloride by means of test iead.

(11) What method of analysis is generally used for the determination of copper in its ores ?

(12) What is meant (a) by volumetric analysis ? (A) by gravimetric analysis? (In answering, state briefly the principles involved in making volumetric and gravimetric analyses. )

(13) (rt) What is a "rider" and how is it used? What are the advantages of a rider ?

(14) (rt) What are fluxes and their uses ? (d) Nametfiti principal fluxes and reducing agents.

(15) Teil how you would assay a sample of concentrates — consisting principally of iron pyrites — by the crucible method of assaying; {Jj) by the scorification method of assaying. (Give fluxes to be used and amounts of each.)

(16) If from a preliminary assay of 600 mg, of fine bul- lion we obtain 300 mg, of silver, and analysis shows the bullion to contain 15 per cent, copper, how would the "proof" assay be made up?

(17) Volumtiric determination of iron in ore. Duplicate 1-g. ore charges. Titrations of the solutions of iron con- sumed 48.3 and 48.2 c. c, respectively, of the standard solu- tion. Standard of solution is 0.00995 (1 c. c. 0.00995 g. of iron). What per cent, of iron does the ore contain 7

(18) (i?) What metals are commonly determined by the fire assay ? (b) What metals can be most accurately deter- mined by the fire assay ? (c) Why should we use the fir assay for any other metals ?

(10) (rt) What weights should the assayerhave, and how should they be handled ? (A) Why are metric weights used iii analytical chemical work ?

J

§ 36 Assaying.

(20) (a) For what is litharge used in the crucible assay ? Why should each new lot of litharge be assayed before the litharge is used in assaying ores ? (c) How would you make a litharge assay ?

(21) (rt) Describe the operation of "parting" the gold- silver buttons from ore assays. (_6) What is " inquarting " ?

(23) The standard of a potassium-permanganate solution for iron is 0.01. In a volumetric analysis of a mangaHese ore in which 1 gram of ore was used, 30.5 c. c. of the stand- ard solution were consumed. What per cent, of manga- nese does the ore contain ?

(33) Describe the volumetric method of determining copper in its ores by means of a standard solution of cyanide of potassium.

(34) {a) When determining the value of an ore, what, in addition to its gold and silver contents, should be taken into consideration ? Mention the principal ingredients of ores, besides gold and silver, for which the smelters pay a bonus, and also mention the ingredients for which the smelters make an extra charge.

(25) (ii) What furnace tools are required for assaying ? (b) For what are iron molds used ?

(20) If from 3 A. T. of litharge we obtain a silvt-r button weighing 1.5 mg., and in a subsequent crucible assay of an ore in which 1 A. T. of ore and 1 A. T. of litharge are used, we obtain a button of silver weighing 5.75 mg., how many ounces of silver does a ton of the orf contain ?

(37) How does the determination of copper in fine bullion differ from the determination of copper in ores ?

(28) If, after making all corrections for loss of silver in a fine-bullion assay, we find that 500 mg, of bullion contains 308. fi mg. of silver and 16 rag. of gold, how would the results of the assay be reported ?

(39) The standard of a potassium-permanganate solution for iron is 0.01. In a volumetric analysis of an ore for

r

4 Assaying.

lime {CaO),' 3QA c. c, of the standard solution were Kumcd. {a) What per cent, of iitmr does the ore conl {6) What per cent, of calcium (Ca) does the ore contali

(30) In the phiisjihorous determination, if arsenic is ktM to lie present, what precaution in regard to the tempera) of the ore solution must be taken at the lime the inoly solution is added ?

(31) (a) What is an "assay ton"? (fi) Show how assay ton is derived, giving proportion expressing the tion between an assay ton and a ton of 3,000 pounds

pois.

(32) If from 45 g. of test lead we obtain a button of! Vfr weighing .3 mg., and in !i subsequent scorification of iin ore in which .1 A. T. of ore and 45 g. of test lea< used, we obtain a button of silver weighing 32.5 rag., many ounces of silver does the ere contain per ton ?

('.]3) {a) Describe the fire assay for lead with ox Ores. How does this assay differ from the assay of phide lead ores ?

(34) (fl) What is "insoluble matter"? How is determined in an ore ?

(35) (n) What apparatus is required for crushing a otherwise preparing samples for assay previous to weighi charges ? (6) What is a tin sampler ?

(30) ((7) Name the different kinds of crucibles used in i assaying, melting bullion, etc. What qualities shoi good crucibles and scorifiers possess ?

(37) Scoicification assay. Ore charges ly A. T. 1 gold-silver buttons weigh 3.45 mg. and 3.47 mg., respe ively, and the gold from both buttons weighs 3.12 n {a) How many ounces of gold and silver does the ore c( tain per ton ? {b) With gold at $20.07 per ounce and sih at t.GO per ounce, what is the value of the ore per ton ?

(38) Lead fire assay. Duplicate 5-g. ore charges a used. Weights of lead buttons are 3.35 g. and 3.87 )

§36

AssAvme.

respectively, (a) What per cent, of lead does the ore con- tain ? Had we taken lO-g. charges of ore instead of 5-g. charges, and the buttons weighed 3.25 g. and 3.27 g., respectively, what per cent, of lead would the ore have con- tained ?

(39) What forms the basis of the separation of silica from other insoluble matter?

(40) If an ore contains 15 per cent, of copper, how many c. c. of a solution of cyanide of potassium having a stand- ard of 0.005 will be consumed in titrating a solution when 1 g. of the ore is used ?

(41) Describe in detail the operation of pulverizing a sample by means of the bucking board and muller.

(42) Give rule for the calculation of the number of ounces of gold and silver per ton of ore (without metallic scales), and state same in the shape of a formula.

(43) (a) What is "lead flux " ? (A) Give the parts (by weight) of the constituent chemicals of a good lead flux.

(44) Crucible assay. Ore charges J- A. T. Weight of gold-silver buttons 4.76 mg. and 4.75 mg., respectively. Gold from both buttons weighs 0,75 mg. (a) How many ounces of gold and silver does the ore contain per ton ? {b) What is the value of the ore per ton, with gold and silver worth ♦20.07 and t.59 per ounce, respectively ?

(45) {a) What two volumetric methods are commonly used for the determination of iron in its ores ? (#) In what are these two methods similar? (f) Mention the principal chemical change that takes place in the iron solution during titration in each method. (In answering {c) give the condi- tion in which the iron exists at start as well as at end of titration. )

(40) How would you prepare and standardize an approx- imately half-normal solution of cyanide of potassium for the volumetric determination of copper in its ores? (Give each step in standardizing.)

8 Assaying.

used \-g. charges of ore. A solution of potassium perman- ganate having an iron standard of 0.01 was used to determine the iron and the lime, and in the iron tttralion, 25 c. c. of ihe standard solution were consumed, and in the /inu titration, \HA c. c. of the standard solution were consumed. In the copper determination. 26.3 c. c. of a solution of potassium cyanide having a standard of 0.0049 were con- sumed; in the zinc determination, 4.5 c c. of a solution of potassium ferrocyanide having a standard of 0. 0099 were consumed; and from a 1-g. charge of the ore the silica weighed 0.135 g. How many ounces of gold and silver did the ore contain per ton, and what were the percentages of iron, lime, copper, zinc, and silica in the ore '

Geology.

(1) What is geology ?

(2) Into what three divisions does the subject of geology seem to naturally divide itself ?

(3) What are the constituents of the atmosphere, and which of them are effective in changing the form of the earth, and why ?

(4) What are boulders of disintegration, and how are they formed ?

(5) How do such rocks as granite, gneiss, etc., become disintegrated ?

(6) What effect has frost upon rocks ?

(7) What is talus, or slide rock ?

(8) How are waterfalls formed ?

(9) What is the relation between the carrying power and the eroding power of water ? Describe fully.

(10) Wtrart is meant by the sorting power of water, and what effect has it upon deposits made from running water ? Answer fully.

(11) Explain why a river has a winding course.

(12) What is the flood-plain of a river, and of what two parts is it composed when a river empties into a tideless sea or lake ?

(13) What is an estuary, and what deposits may form in an estuary ?

(14) What is a glacier, and what effect have glaciers in changing the surface of the earth ?

(15) What is the origin of springs? Explain and illus- trate with a sketch.

§37

S GEOLOGY. g

(111) WTiat is the cause of artesian wells ?

(17) Explain the manner in which deposits are formed at springs, and state why it is that if the material can be in solution before the water comes to the surface, it becomes deposited after the water reaches the surface.

(IS) What is the general effect of all the aqueous and atmospheric agencies in their action upon the earth, and what is the general effect of igneous agencies ?

(19) If one were to descend into the earth, what changes in temperature would be noted as the depth below the sun face increased ?

(20) What is a volcano

(1) What are dikes, and how are they formed {'i'i) Is the surface of the land stationary, or are certain

changes going on ?

(23) From what is the coal formed ?

(24) What effect does carbonaceous matter have in the depositing of iron and other metals ?

(3o) What is the origin of limestone '

(26) What is meant by the crust of the earth ?

(27) What is meant by the term "rock " as it is com- monly employed in geology ?

(28) Define the following terms: "Dip," "anticline," "conformity," and "strike."

(2U) What are fossils ?

(30) Why is it that vegetable life has to precede animal life on the earth ?

(31) Name the different eras or ages as they would occur in a complete geological section, and give the characteristic form of life for each period.

(32) What is the distinction between stratified and unstratified rocks ?

{'3'i) Give the characteristics of the plutonic or massive rocks, and name one of the forms belonging to this class. (34) What is porphyry f

)

§ 37 Geology. 3

(35) Give the general characteristics of the volcanic or eruptive rocks, and name one of the rocks belonging to this class.

(36) What is the distinction between acid and basic rocks ?

(37) What is a dike ?

(38) How can the relative age of igneous rocks be deter- mined ?

(39) What is volcanic conglomerate or breccia ?

(40) What is meant by amygdaloidal structure in lava ?

(41) How may general metamorphism of the rocks be effected ?

(42) Define metamorphism.

(43) What is the probable origin of granite ?

(44) What is the distinction between joints and fissures in rock formations ?

(45) What is a fault ?

(46) Give the common law of slip in faults.

(47) What is a reverse fault ?

(48) What is the distinction between a mineral vein and a dike ?

(49) What is a horse in a vein ?

(50) What are the common gangue minerals ?

(51) How can the age of a rock deposit be judged ?

(52) What changes occur near the surface of veins ?

(53) What are placer deposits ?

(54) Has the wall rock any effect upon the contents of the vein ?

(55) What evidence is there that the material in veins was deposited from hot solutions ?

(56) Does depth have any effect upon the richness of mineral deposits ?

(57) What fossils occur in the Archean rocks ?

(5S) In what age did fishes first appear in any consider- able abundance ?

4 GEOLOGY. g 87

(59) Why is the Carboniferous period frequently spoken of as the Coal period ?

(CO) What are pay chutes or chimneys ?

(fil) How does gold occur in nature ?

((ja) How does silver occur in nature ?

(fi;)) What are the requirements for a good iron ore ?

((14) How does iron ore occur ?

((i5) What two general classes of copper ores are there ?

((iH) What are the uses for manganese ores ?

(G7) What can you say in regard to the occurrence of nickel and cobalt f

(68) What are the impurities which occur in coal, and what effect have they upon the value of the coal ?

(69) What are the essential qualificaliona for a good building stone?

(70) Define pigments, and name two materials which are commonly classed under this head,

(71) What is another name for graphite?

(72) Por what is corundum used ?

Prospecting.

(1) Define the term **ore."

(2) How docs the outcrop of a vein differ from the deeper parts and the surrounding country rock ?

(3) What is float," and how does the prospector follow it up ?

(4) How is the outcrop of a vein sampled ? Describe quartering."

(5) What is booming"?

(()) What are the dimensions of individual lode claims (a) in the United States ? (d) in Canada ?

(7) What is the discovery shaft," and how deep should it be for a valid location in the United States ? How does the Canadian practice differ in this respect ?

(8) Show by diagram how a lode claim is staked (a) in the United States; (b) in Canada.

(9) Give distinction between apex and outcrop of a vein.

(10) How are the locator's rights limited (a) if the apex of the vein crosses one side line of a claim ? (d) if the apex crosses both side lines ? (r) if the apex departs from one side line twice ? Give diagrams.

(11) What assessment work is necessary to hold a lode claim ?

(1'2) Does a lode claim have to be rectangular ? Make a sketch of a lode claim and describe it.

(13) What are placer deposits, and how are they formed ?

(14) How are placer deposits prospected? Describe panning.

§38

Prospecting.

(15) What are the dimensions of placer claims for indj-j viduals (ii) in the United States ? in Canada ?

(10) How are placer claims located and recorded {a) ii the United States ? (i) in Canada ?

(IT) Is the discovertr allowed to stake out a claim eastern or southern United States?

(18) Prom what formations are gems obtained ?

(10) Describe an outfit suitable for a prospector search- ing for gems.

{W) How can you search for a lost vein underground! (a) when pinched out ? when cut by a fault ?

i'il) Why does one diamond-drill hole give no indicatitai'] as to the dip of the formation passed through ? Illustrate with a sketch.

(!2) Sketch an irregular ore-body and show a good arrangement of diamond-drill holes for prospecting the same.

(S3) What is magnetic prospecting, and how should it be carried on ?

(34) What are the two classes of mill sites ? Describe each.

(25) What are the dimensions of a tunnel site ?

(26) How is a tunnel site staked, and where is the loca- tion notice placed ?

(27) What are the rights of the locator of a tunnel site ?

(28) How is steel hardened ? What is tempering ?

(29) What conditions determine the temper of tools ?

(30) What are the geological formations and prevailing ores of Arizona and California ?

(31) What are the main geological features (a) of Nevada? (i) of Utah?

(32) What are the general geological features of the Black Hills of South Dakota, and what are the ores found there ?

Placer and Hydraulic Mining.

(1) Describe the method of formation of placer deposits.

(2) What is the character of the country in which the most favorable conditions for the formation of placer depos- its occur ?

(3) How are placer deposits worked ?

(4) What is hydraulicking ? Describe the operation.

(5) How may slight leaks in pipes be stopped ?

(6) How are iron pipes made and put together ?

(7) What is an inverted siphon, and when is it employed ?

(8) How is gold usually distributed in placer deposits ?

(9) What are deep or ancient placers ?

(10) Why can flumes be given a steeper grade than ditches ?

(11) Describe booming.

(12) How are deposits in frozen ground worked ?

(13) Describe drifting and state under what conditions it is resorted to.

(14) In hydraulic mining, how is the earth broken down and removed ?

(15) How is a placer deposit prospected ?

(16) In selecting a reservoir site, what points should be observed ? What should be the character of the ground ?

(17) For what purposes are dams employed ?

(18) Why are masonry dams not employed extensively in placer mining ?

(19) Under what circumstances are earthen dams used ?

(20) What are wasteways ?

§39

2 PLACER AND HYDRAULIC MINING. g 39 j

{'il) How is flowing water measured ?

(23) What is the miner's inch ?

(23) What points should be observed in constructing a j ditch line?

(34) What is the smallest cross-section of a ditch for a given discharge ? What is the "hydraulic depth " ?

(a.5) In digging a ditch on a hillside, what re caul ion should be observed ?

i'iG) What precaution should be observed in carrying a flume along a hillside ?

(27) How are flumes constructed ? Mention special points to be observed in laying curves.

(as) How may flumes be carried along the face of a cliff ?

(SO) Under what conditions are wooden and iron pipes, respectively, used ?

(30) What precautions are to be observed in filling pi pes ?

(3t) How are iron pipes treated to prevent rusting ?

(3'2) For what purpose are air-valves employed ?

(:j;t) Describe the " Hydraulic Giant " and the action of the deflecting nozzle.

(34) What is a batea f

(35) Describethe "Cradle or Rocker."

(36) Describe the "Tom."

(37) What are the conditions affecting the length and grade of sluices ?

(38) When dredges are employed for working placer deposits, by what different methods may the bed-rock be cleaned ?

(39) Name and describe the different kinds of riffles used in box sluicing.

(40) What are undercurrents, and for what are they used ?

(41) Describe an undercurrent, including the grizzly in the main sluice.

§ 39 Placer And Hydraulic Mining. 8

(42) Describe the method of blasting cement gravel banks.

(43) For what purposes are tunnels used in placer mining ?

(44) Describe the method of charging sluices.

(45) Describe the operation of cleaning up a sluice and the preparation of amalgam for retorting.

(46) Describe the retorting of amalgam, giving the pre- cautions which must be observed during the process.

(47) State how banks are caved, giving the precautions which must be observed during the process.

(48) For what class of deposits are dredges employed ?

(49) Describe the Ludlum hydraulic gravel elevator.

(50) What form of joint is used at the junction of the supply pipe and one of the distributing pipes ?

'1

*ir::n "III:

A Key

To All The

Questions And Examples

included in the Question Papers in this Volume.

It will be noticed that the Keys have been given the same section numbers as the Question Papers to which they refer. All article references refer to the Instruction Paper bearing the same section number as the Key in which it occurs, unless the title of some other Instruction Paper is given in connection with the article number.

J

Blowpiping

(1)

See Art. 2.

(2)

See Arts. 3 and 4.

(3)

See Arts. 6 and 7.

(4)

See Arts. 8 and 9.

See Art. lO.

(6)

Al, {0/f),'. Cr, {SOX

(7)

See Art. 1 5.

(8)

See Arts. 1 6 to 1 9.

(9)

See Art. 22.

(lO]

) See Art. 1 2.

(11]

) See Art. 1 3.

(12]

) See Art. 1 4.

(13]

1 See Art. 1 3.

(14]

1 See Art. 31.

(is:

) See Arts. 33 and 34.

(16]

1 See Arts. 44 to 46.

(17]

) See Art. 48.

(18]

) See Arts. 49 to S3.

(19]

) See Art. 54.

(2o;

) See Art. 36.

(21]

1 See Art. 37.

(22]

1 See Arts. 41 to 43*

(23]

1 See Art. 94.

§34

(24: (25; (26;

(27

(28; (29; (3o:

(31

(32; (33;

(34; (3s:

(36)

(37: (38; (39;

(4o;

(41

(42;

(43-50)

Blowpiping.

Arts. 96 to 98. Arts. 96 and 98. Arts. 96 and 98. Arts. 96 and 98. Arts. 99 and lOO. Arts. 58 and 59. Art. lOO.

Arts. 105 and 106. Arts. lOl and 102. Art. 103. Art. 104. Arts 107 to 111. Tables III and IV. Tables V and VI. Arts 112 to 114r Art. lis. Table VII. Art. 96. Art. 117. No Key.

)

d

Mineralogy

(1)

See Art. 1.

(2)

See Art. 2.

(3)

See Arts. 9 and lO.

(4)

See Art. lO.

See Art. 4.

(6)

See Art. 12.

(7)

See Arts. 5 and

(8)

See Art. 11.

(9)

See Arts. 1 to 1 7.

(10]

I See Arts. 14 to 16.

(11]

► See Art. 8.

(12;

1 See Arts. 18 and 19,

(13]

) See Art. 1 9.

(14]

1 See Art. 21.

(15]

) See Art. 22.

(16]

) See Art. 29.

(17]

I See Art. 36.

(18]

1 See Art. 36.

(19]

) See Art. 80.

(20]

1 See Art. 81.

(21]

1 See Arts. 39 to 45.

(22]

) See Art 38.

(23]

1 See Arts. 39 to 45.

(24]

1 See Art. 44.

S36

Mineralogy.

)

(25

See Art. 42.

(26

See Art. 50.

(27

See Art. 60.

(28

See Arts. 65 to 71.

(29

See Art. 70.

(30

See Art. 72.

(31

See Art. 78.

(32

See Art. 47.

(33

See Art. 55.

(34

See Art. 53.

(35

See Art. 40.

(3

See Table I.

(37

See Table I.

(38

See Art. 66.

(39

See Art. 85.

(40)

See Arts. 85 to 90.

(41

See Table II and Arts. lOl and 104.

(42)

See Art. 92.

(43)

See Table 1 and Art. 94.

(44

See Table II and Arts. 101 and 102.

(45)

See Art. 98.

(46)

See Art. 08.

(47)

See Art. 98.

(48)

See Art. 98.

(40)

See Art. 98.

(50)

See Table II.

(51)

See Arts. 44 and 49.

(52)

See Art. 64.

(53)

See Arts. 00 to 104.

Assaying.

(1)

(fl) See Art. 1. (i) See Art. 3.

(2) See Art. 2.

(3) See Art. 6.

(4) See Arts. lOZtolH.

(5) (a) See Arts. 134 to 135. {6) See Art. 138.

(6) See Art. 26. See Art. 28.

(7) (a) See Art. 36. {6) See Art. 36.

(8) {a) In weighing the first button, place the button on one pan and it will be found that a 10-nig. and a 5-mg. weight in the other pan will not quite balance the button, while the addition of a 1-mg. weight will overbalance it; remove the l-mg. weight, close the scale case, and move the rider along the beam until the button is balanced. This will occur with the rider 38 divisions from the center of the beam on the side opposite to that in which the button is placed; hence, the weight of the button will be

10+5 + .38X 2=15.76 mg. Now remove the button which has been weighed, leaving the weights in the scale-pan and the rider in its position. Place the other button in the scale-pan and it will be found that the weights slightly overbalance the button. By removing the rider 1 division of a beam towards the center, §3G

8

it will be found that a balance is second button weighs

lO + S + .BTx a

15.74 mg.

Of course, the weight of the second button could be obtained by simply subtracting the amount the rider was moved from the first reading, or. as it was moved 1 division, it would represent .02 mg.

In weighing the gold, place the gold in one pan and il: will be found that the 2-mg. weight slightly overbalances, while a 1-mg. weight does not nearly balance it. It may be weighed by leaving the 1-mg. weight in place and moving the rider out 49 divisions ti) the side opposite to that on which the gold has been placed; hence, the weight will be

1 + .49 X 2 l.i

Img.

"J

This weight may also be obtained by leaving the 2-mg. weight on the side opposite the gold and carrying the rider across to the side on which the gold is being weighed. In this case, a balance will be established when the rider has been moved 1 division towards the pan containing the gold, and the weight will be

2 — .01 X 2 1.98 mg. (For detailed description of weighing see Art. 32.)

As i A. T. was taken, adding the two weights will give the amount contained in 1 A. T. ; hence,

31.50 mg. combined weight of gold and silver, or the total number of ounces per ton of precious metals contained in the ore- the weight of the gold equals the number of ounces per ton of gold in the ore, and

1.98 mg., or the number of ounces of gold per ton. 29.53 mg., or the number of ounces of silver per ton.

§ 36 Assaying. 3

(9) {a) See Art. 140. See Art. 141. {c) See Art. 1 44.

(10) {a) See Art. 181. (d) See Art. 1 82.

(11) See Art. 229.

(12) (a) and See Art. 4.

(13) {a) and See Art. 24.

( 1 4) (a) See Art. 60.

{If) See Arts. 64 to 76.

(15) (a) See Table I. {d) See Table III.

(16) From Table IV, by looking in the first column we

find 300, and opposite in the second column, 305 to 310 as the

number of milligrams of silver to be used in the proof assay

when 300 mg. were obtained from the preliminary assay.

As there is 15 copper in the bullion, we turn to the fourth

column of Table IV, and opposite 15 find in the fifth

column 75 mg. as the amount of c. p. copper to be added

to the proof assay. The sum of the weights of the silver

and the copper contained in the preliminary assay is as

follows:

375 and

125 mg.,

or the amount of test lead which must be used in making up the proof assay. In column 3 of Table IV, opposite 300 in the first column we find 15 as the number of milligrams of

A ASSAYING. g 36

c, p, lead foil to be used for wrapping the proof assay; hence, the proof assay will consist of

305 to 310 mg. of silver, 75 mg. of copper,

12S mg. of test lead,

all to be wrapped in 15 mg. of c. p. lead foil.

(17) In order to obtain the average of 2 titrations, add the results from both and divide the sum by 2.

2)9n.5 48.25 average number of c. c. As the standard of the iron solution is 0.00996, we must multiply the average number of c. c. by it.

48.25 X 0. 001195 .48008, or practically 48.0l5fi of iron.

(18) (a), {6), and (c) See Art. 6.

(19) (a) See Arts. 29 to 31. See Art. 29.

(20) and {c) See Art. 69.

(21) See Arts. lOO to 103. See Art. 105.

(22) As the standard for iron is normal and would read directly into per cent, of iron, it is simply necessary to multiply the number of c. c. used by the factor for man- ganese, or

20.5 X .2940 6.039, or practically 6.04!< manganese.

(23) See Arts. 232 to 235.

(24) (a) See Art. 8.

See Arts. 8 and 9.

(25) (a) See Arts. 40 to 43. See Art. 44.

§3

Assaying.

(26) As 3 A.T. of litharge were employed when testing the iitharge, it will be necessary to divide the result by 3 to obtain the amount of silver contained in 1 A. T. ; hence, 1.5 2 .7o mg.. or the amount of silver in 1 assay ton of litharge; and as 5.75 mg. were obtained as the total weight of silver, the weight of silver in the ore can be found by subtracting the amount of silver in the litharge from this, or 5.75 mg. — .75 — 5.0 mg. the number of ounces of silver per ton in the ore.

(27) See Arts. 229 to 236.

(28) As 600 mg. of fine bullion were used, it will be necessary to multiply the results by 2; hence, 398.5 X 2 797.0, or the number of milligrams of silver in 1,000 mg. of bullion, and 16x2 32, or the number of milligrams of gold in 1,000 mg. of bullion; hence, the bullion would be reported as 797.0 fine in silver and 32.0 fine in gold, or, as the bar would be stamped.

Silver 797,

Gold 032,

omitting the word fine.

(29) (i) As the iron solution is normal and as the results in CaO are just of those in iron, we will simply have to divide the number of c. c. obtained by 2, or 30.4 -r- 3 15.3, the percentage of CaO in the ore.

(6) As C<70 contains 71.43 of Ca, the percentage con- tained in the ore will be found by multiplying 15.2 by this factor, or 15.2 X .7143 .10857, or practically lO.Sti-t Ca.

(30) See Art. 213.

(31) (rt) and (d) See Art. 30.

(32) As the same amount of test lead was employed in the assay and in obtaining the amount of silver in the test lead, we will have simply to subtract the amount obtained

Assaying.

i'

from the results of the assay, or 38.5 — .33S.2 tog.\ As thenuniberoffntlligranis of silver contained in ,1 A.T. of I ore and as .1 of ore was employed, the results must be multiplied by 10 to obtain the amount contained in 1 A.T. ' Hence, 32.2 X 10= 32 mg., or the number of ounces of 1 silver per ton contained in the ore.

(33)

(34) (35)

(36)

(a) See Arts. 145 to 147.

(S) See Art. 148.

and See Art. 22S.

(a) See An.. 11 to 13.

See Art. 14.

(a) See Arts. 50 to 52.

See Art. 56.

(37) (a) First, adding the two weights so as to obtaim] the average, we have

6.92 total number mg. from -J A.T.

2.12 number of mg. of gold from A.T.

4.80 number of mg. of silver from A. T.

On account of the fact that only A. T. has been taken

for obtaining the results in milligrams, it will be necessary to

multiply by 5, or

2.12 X 5 10.6 ounces of gold per ton, 4.80 X 6 24.00 ounces of silver per ton. (6) The value of the precious metals is obtained by multi- plying the number of ounces of each by its value per ton, or 10,6 X 30. 67 $219. 10 24.00 X .60= 14.40 Total, 233.50

(38) (a) Owing to the fact that two 6-gram charges of

§ 36 Assaying. 7

ore were taken, the amount in one 10-gram charge can be obtained by adding the two results, or

0.52 g. of lead in 10 g. of ore; hence,

6.52 -4- 10 .652, or the ore contains 65.2 lead.

(6) If 10-gram charges had been taken in place of 6, and the same amount of lead obtained from each charge, the ore would have contained just half the amount of lead given above, or

.652 -r- 2 .326, or 32.6.

(39) See Art. 226.

(40) As the potassium-cyanide solution is a normal solution, it will take 2 c. c. of it to equal of copper when 1 gram of ore is employed, and hence 1 gram of ore con- taining 15 of copper would require 15 X 2 or 30 c. c. of the standard solution to titrate the copper.

(41) See Art. 13.

(42) See Art. 120.

(43) (a) and (6) See Art. 78.

(44) (a) As A. T. charges of ore were taken, the number of milligrams of the precious metal per A. T. will be found by adding the two results, or

9.51 mg. ounces precious metals per ton.

.75 mg. ounces gold per ton.

8.76 mg. ounces silver per ton.

(d) .75 X 20.67 $15.50, value of gold per ton. 8.76 X .59 5.17, value of silver per ton.

$20. 67, total value per ton.

Assaying.

(45) (a). and (c) See Art. 17a

(46) Sec Arts. 230 and 231.

(47) See Arts. 16 and 17.

(48) See Arts. 32 and 33.

(49) and See Art. 83.

(50) See Arts. 8S to 89.

(51) See Art. 128. See Art. 129.

(52) If 1 A. T. of #10. 00 ore had been taken, the weight ] of the button obtained from the assay would be 10,00-v ' 20.07 .48379, or practically .4838. As A. T. was taken, the weight of the button would be of this amount, or

.48382 .3419 mg.

n balances would not ili

(53) (") and {d) See Art. 104.

(54) and (c) See Arts. 11 and 18.

(55) (fl) See Art. 56. (i) See Art. 55.

(56) {a) and See Art. 89.

(57)

A r + 29.16G D

ounces per ton.

A+B

{6) As i A. T. was taken for the determination of gold and silver in pulp, the results from 1 A, T. can be obtained as follows:

197.04= mg. from 1 A. T.

1.75 mg. gold in the A. T. oz. per ton. 195.39 mg. silver in the A. T, oz. per ton.

§36 Assaying. 9

Now, substituting these factors in the equation, we obtain for silver

The value of gold per ton is obtained by substituting as follows :

248.5 X 1.75 + 29.166 X 5.62 , , 2.39 oz. gold per ton.

(c) The total value of the ore is as follows:

2.39 X 20.67 $ 49.4013, value of gold. 293.129 X .60 175.8774, value of silver.

$225.2787, or $225.28, total value per ton.

(58) See Arts. 172 and 175 to ISO.

(59) {a) and (6) See Art. 95.

(60) (a) See Art. 22. (6) See Art. 23.

(61) To obtain the weight of the barium sulphate, sub- tract the weight of the filter ash from the total weight obtained, or

This multiplied by .13734 .057545, or practically 5.7 5fl sulphur.

(62) (a) See Arts. 90 to 96. (t) See Art. 90.

(c) See Art. 94.

(63) {a), and {c) See Art. 133.

(64) As the piano wire contains only 99.7j< iron, it will be necessary to determine the amount of iron in the samples used, and

Assaying.

§36

0.1O5 X .997 ,104685, or the number of grams of iron in the first sample, and

0.112 X -997 .111664, or the number of grams of iron in the second sample.

Dividing each weight of iron by the number of c. c of solution which it required to titrate it. wc will obtain the standard for each case, or

0.I0468S -s- 20.9 .006008, for the first standard, and 0.111664 -i- 22.4 .004985, for the second standard. Adding these two, we obtain .009993, and dividing the result by 2, we have .0U499G g. , equals the amount of iron in grams which each c. c. of the standard solution is equal to, or the standard of the solution in iron.

(65) For the gold and silver determination, as i A, T, charges were taken; hence, it will be necessary to add the combined weight of the buttons to obtain the amount in 1 A. T., or

17.25 mg. weight of gold and silver. 2.35 mg. ounces of gold per ton. 14.90 mg. ounces of silver per ton. As 25 c. c. of the normal solution was employed in the iron determination and 1 gram of ore was taken, each c. c. of the solution will be equal to lj< iron, or the sample will contain 25 iron.

As the same solution was employed in titrating l gram of the ore in the determination of CaO, and as the standard for CaO is just that of iron, the result will be

18.4 2 9.2 the percentage of CaO in the sample. For obtaining the percentage of copper, we multiply the number of c. c. employed by the factor for the solution, or

26.3 X .0049 .12887, or practically 12.89 per cent, of copper.

"I

§ 36 Assaying, 11

In like manner, in the determination of zinc, we multiply the number of c. c. employed by the factor for the solution, or

4.5 X .0099 .04455, or practically 4.46j< zinc.

For the determination of silica in soluble matter, we would simply divide the weight obtained by the weight taken, or

.125 -T- 1.00 .125 n.5fl silica.

Hence the ore contains

2.35 ounces gold per ton,

14.9 ounces silver per ton,

25 iron,

9.2fl CaO,

12.89jit copper,

4.46 zinc,

12.5 silica.

Geology.

(1)

See Art. 1.

(2)

See Art. 2.

(3)

See Art. 4.

(4)

See Art. 1 3.

(5)

See Art. 8.

(6)

See Art. 14.

(7)

See Art. 14.

(8)

See Art. 21.

(9)

See Art. 23.

(lo;

1 See Art. 26.

(11]

I See Art. 27.

(12!

) See Arts. 28 to 30.

(13;

I See Arts. 31 and 32.

(14]

I See Art. 35.

(15]

I See Art. 38.

(16]

I See Art. 40.

(17]

1 See Art. 42.

(18]

1 See Art. 45.

(19]

1 See Art. 46.

(20]

I See Art. 48.

(21]

1 See Art. 49.

(22]

) See Art. 50.

(23]

I See Art. 62.

§37

(241 (2S]

(26;

(27 (28;

(3o;

(33;

(34; (35; (36; (37;

See Arts. S3 and S4.

Sec Arls. 73 to 80.

See Arts. 82 to 89. See Arts. 79 and 82.

See Art. 92.

(38

See Art. 94.

(39

See Art. 98.

(40

See Art. 99.

(41

See Art.. 109to 113.

(42

See Art. 116.

(43

See Art. 1 1 8.

(44

See Arts. 121 to 124.

(4S

See Art. 124.

(46

See Art. 1 27.

(47

See Arts. 128 and 129.

(48

See Art. 132.

(49

See Art. 140.

(So

See Art. 141.

(51

See Art. 147.

(52

See Arts. 148 and 149.

J

§ 87 Geology.

(53]

I See Art. 152.

(54)

1 See Art. 1 56.

1 See Art. 1 60.

(56)

1 See Art. 1 69.

(57)

1 See Art. 171,

(58]

1 See Art. 174.

(59)

1 See Art. 175.

(60)

See Art. 1 54.

(61)

See Arts. 181 and 182

(62)

1 See Arts. 1 86 and 1 87

(63)

1 See Art. 1 89.

(64)

1 See Arts. 190to 192.

(65)

1 See Art. 1 95.

(66]

1 See Arts. 203 to 207.

(67]

1 See Arts. 208 and 209.

(68)

1 See Arts. 216 to 218.

(69]

1 See Art. 227.

(70)

1 See Arts. 244 to 249.

(71]

1 See Art. 250.

(72]

1 See Art. 260.

mn

lit'ntj

r

5'

Prospecting

(1) See Art. 82.

(2) See Art. 81.

(3) See Arts. 35 and 36.

(4) See Arts. 37 to 39.

(5) See Art. 40.

(6) (a) See Art. 41. (6) See Art. 55.

(7) See Arts. 42 and 56.

(8) {a) See Art. 45. {6) See Art. 57.

(9) See Art. 47.

(10) {a) See Art. 48. (6) See Art. 49. (c) See Art. 50.

(11) See Arts. 53 to 60.

(12) See Art. 51.

( 1 3) See Art. 1 3.

(14) See Arts. 12 to 16.

(15) {a) See Arts. 18 and 19, See Art. 27.

(16) {a) See Art. 21. {6) See Art. 33.

§38

i PROSPECTING.

(17) Sec Art. H4.

(18) See ArL 73. (10) See Art. 73.

(20) See Art. 88. (A) See Art. 87.

(21) See Art. 93.

(22) Sec Arts. to 9.

(23) See Art. 9.

(24) See Arts. 67 and 68.

(25) See Arts. 61 and 62.

(26) See Arts. 64 and 65.

(27) See Arts. 61 lo 63.

(28) See Arts. 123 to 125.

(29) See Arts. 1 23 to 1 25.

(30) See Arts. 1 1 2 and 1 14.

(31) (a) See Art. 1 1 1. See Art. 110.

(32) See Art. 107.

d

Placer and Hydraulic Mining.

[3

:5

[6

[7

lO

Is

[Zz

See Arts. 1 to 4. See Arts. 4 to 8. See Arts. 1 5 to 24 and Art. 1 42.

See Arts. 41 to 50.

See Art. 1 28.

See Arts. 1 28 to 1 30.

See Art. 1 28.

See Arts. 13 and 74.

See Art. 14.

See Arts. 118 and 119.

See Art. 37.

See Art. 65.

See Art. 61.

See Art. 41.

See Art. 74.

See Art. 76.

See Art. 78.

See Art. 85.

See Arts. 86 and 87.

See Art. 83.

See Arts. 91 to 93.

See Arts. 108 to 1 10.

§89

PLACER AND HYDRACLIc'mININO.

(23)

Ste An. 112.

Se Art. IIS.

J

(28)

Sec Art. US.

See Ana. IZOtoIZZ.

(27)

See Art.. IZOa.id 121.

(28)

See Art. 12S.

See Ant. IZSMdlZS.

(30)

See An. 134.

(31)

See An. 133.

(32)

See Art. 132.

(33)

See Arts. 47 and 49.

(34)

See An. 1 7.

(35)

See Art. 21.

(36)

See Art. 22.

(37)

See Arts. 25 and 36.

J

Index.

Note.— All items in this index refer first to the section (see preface. Vol. I) and then to the pase of the section. Thus, '*Acids 84 18'* means that acids will be found on paflfe 18 of section 84.

A. Sec. Page.

Abandonment of lode claim in

British Columbia 88

Abandonment of placer claim

in British Columbia 88

Absorption and evaporation ... 89 Abutments and discharge

Rates 89

Accessory apparatus for blow-

piping . 84

Acicular structure 85

Acid, Hydriodic 34

" tests M

Acids 84

Acre, Area of 88

Actinolite 35

Adamantine luster 85

AflRnity, Chemical 34

Agate mortar 81

Agencies, Aqueous 87

Atmospheric 87

Chemical 87

Igneous 87

Organic 87

Age of ore deposits 87

Air and blow-off valves 80

Alabaster 37

Albertito Vi

Albite 83

Alkaline earth metals 84

solationa in vein for- mation 37

Alkalies 84

Alma placer 89

Alum 87

Aluminum 85

Amalgam, Cleaning of 89

kettles 89

Retorting of 89

Sec. Pagrt,

tt

Amalgamation

Amalgamation, Copper plates

for

Amethyst, Oriental

Amygdaloidal structure of lava

Analysis,

, Determinat i on

of lime in lime- stone or ores

lie

Electric method for

copper

tt

Ferrocyanide solu-

tion for determina-

tion of lead

It

Gravimetric

Gravimetric ipethod

for determining

phosphorus

Methods for the

determination of

zinc

tt

Method of determin-

ing sulphur

tt

of copper ores

t'

" iron ores contain-

ing organic

matter

" manganese ores. .

tt

Qualitative

Special method of.

t.

for iron ores. . .'. . Standard ores for

use m

Treatment of copper

ores in

t-

Treatment of iron

ores in

tt

Treatment of lead

ores in

Volumetric method

for phosphorus . . .

Iz

Aiialysi*. Volumui

Wet dc [or Ici

AniilylicBl balimcB Aocient plscer "

Andesltc . i

AiKleiilte )

Anhrdridei... ., )

Annealing cups . !

AddukI liLbor required to lode cUinu In the Vnlicil

SUtOB I

AnlhrkcfCe 1

AnUvllM !

Antimony 1

!

oncharcoal I

Apn and outcrap of cUimi ... t AppiirBtua, Acceiaorr, for

blowplpinB I

In placer mining t

placermining ... 1

(orblowpiping,,.. S

" el atBayiDg .. S

Aptoni for dams — I

Aqnooui agencies 3

Area and stiape at placer claims

iD United State It 3

Arenaceoui or sand rocks ... . 3

Argentite S

Arid regiuna. Placers in 3

Ariiona as prospecting re- gion a

Arsenic iD closed tube 3

" open tube B

oncharcoal... S

Arsenopyrite S

Artesian wells. Cause of S

Asbestos 3

Ashfromfuels 3

Asphal lie coal S

Asphalium and bitumen X

Asuy, Battery, for copper a

Index.

S€C.

Battery assay for copper 86

Bauxite SS

Beads, Borax S4

Beads, Borax, Colors imparted

to, by various oxides in O. F. S4 Beads, Borax, Colors imparted

to, by various oxides in R. P. Beads, Gold and silver, Parting

of S4

Salt OL phosphorus 3 1

Salt of phosphorus. Col- ors imparted to, by

various oxides in O. P. 34 Salt of phosphorus. Col- ors imparted to, by

variousoxidesinR. P. SI

Beakers 36

Bed and joints for flumes 89

rock, Cleaning up of, when

dredging 89

Beds, Minerals found in . . ... 87

" or sheets of lava 37

Beryl 85

.. . 35

Bicarbonate of soda 34

Bichromate solution for iron. . 36 solution for iron,

Standardizing of 36

Bmary compounds 34

Bismuth flux 34

in open tube 84

on charcoal 81

Bisulphate of potash 34

Bitumen and asphaltum 37

Bituminous coal 35

Black copper ore 35

Blacksraithing 38

Black tellurium 85

zinc ore 35

Blast, The blowpipe ai

Blasting gravel banks 89

Block riffles 89

Hlow-oif valves 89

Blowpipe lamps and fuels S4

outfit. Table of min-

erals sent with 35

reagents 34

Scheme for examin- ing substance be- fore 34

The JM

Blowpiping 34

Blow-ups .39

Blue copper carbonate STi

Board, Cupel 36

Bog iron ore 35

Page.

ro

!M

Sec.

Bone-ash 34

Booming 38

Borax 34

" 37

Page. Borax bead.s, Colors imparted

to, by various oxides in R. P. 34 60 Borax beads. Colors imparted

to, by various oxides in O. P. 34 58

Borax, Pusion with 34 49

" Glass 86 36

Bomite 85 87

Botryoidal structure 85 5

Bottles, Wash 36 91

Boulders of disintegration 87 6

Box, Reagent 84 86

Boxes, Puddling 89 12

Bracket flumes 89 83

Brazil-wood paper S4 86

Breccia, Volcanic 87 57

British Columbia, Free miners'

privileges in 88 18

British Columbia, Mill sites in 88 80 British Columbian practice in

regard to lode claims... 88 21

British Columbian practice in

regard to placer claims. 38 11

Brittle silver 85 54

Bromine, Test for 34 52

Brown clay ironstone 85 80

'' coal or lignite 35 62

hematite 35 80

or limonite ... 85 29

ocher 85 80

Brush dams 89 86

Bucket dredges 39 102

Bucking board 36 6

Building .stone 37 118

Bullion assays 86 75

Silver, Determination

of copper in 86 128

Bunsen burner ... 34 24

burners 36 98

Burette and filter stands 86 90

Burettes 86 88

Button balance 86 12

pincers 36 58

tongs 86 27

Buttons 86 19

Parting of 36 66

Weighing of 30 58

C. Sec. Page.

Cadmium on charcoal 31 44

Caking coals 35 62

Calamine 85 50

tt

kt

Index.

Sfc, Combining weights of the ele- ments 84

Compass, Miner's or dipping

needle 88

Composition of the atmosphere 37

Compounds, Binary 84

Conchoidal fracture 85

Concretionary or nodulai;

structure 87

Condition of the interior of the

earth 87

Conformable strata 87

Conglomerate, Volcanic 87

Connection of flume with ditch 39

Construction of flumes 39

Contact deposits 87

Continents, Origin of the first. 87

Contractions, Weir with end.. 89 Control assay. General method

of conducting 86

assays 86

Color of minerals 85

Colors imparted to the flame

by various minerals 84

Colorado as a prospecting re- gion 88

or lead-assay cruci- bles 86

Coloration of the flame . . 34

Columnar structure 85

of lava 87

Copper 85

Battery assay for 36

" Carbonate blue 85

" determination... 36

Determination of, in

silver bullion 36

determination. Solu- tion for standardi- zing cyanide in 86

" Electrolytic deter- mination of 86

Green carbonate of . . 85

minerals 85

Native 85

ore. Black 85

Red 85

" ores, Treatment of, in

analysis 86

oxide 34

" Peacock 85

plates for amalgama- tion 89

" pyrites 35

veins, Surface

changes in 87

Pasre.

Sec. Page, Correction or proof assay of

fine bullion 36 79

Corundum 86 70

♦' 35 80

Covering for pipes 89 89

Cradle or rocker 39 18

Creek claims in British Co- lumbia 88 11

Crest of weir 39 66

Cretaceous 87 43

" period 87 48

Cross-section of a ditch 39 78

Crown grant 88 80

Crucible assay 86 60

" " Charge for ... . 36 61 " charges for gold and

silver ores 86 42

for fusion assay 86 45

furnace 86 20

tongs 36 25

Crucibles . 36 28

" 36 90

Crushers, Laboratory 36 6

Cryolite 35 69

Crystals, Definition of 35 8

Twinned 85 21

Crystalline form 85 8

Crystallography 35 11

Cube. The 85 13

Cupel board 38 27

" capacity for absorbing

litharge 86 52

" mold and stand 84 31

tongs 86 26

Cupelling 36 50

" Temperature of muf- fle during 36 51

Cupels 86 29

Mold for 80 29

Cuprite 85 89

Cups, Annealing 36 31

Currents, Effects produced by,

in large bodies of water 37 17

Curves on flumes 39 81

Cyanide and ferrocyanide of

potassium 36 88

Cyanide of potassium as a

flux M 52

Cyanide of Potassium, Poison-

\nz with. Antidote for 36 1 28

D. Sec. Page,

Dam, Masonry core for 89 61

Dams 89 55

Aprons for 89 56

PVundatloD*

Deflnitlon of m DeflMling noi

ofcoppet W IM

copper in ril-

ver bullion. M gold BBd sil- ver in ..res, 34 M

" lewl Sd 181

" plioaphorni,. X 118

ilUFanhuliidrilleil

Dictiroiioope tor detenniDinK

son" i

Diotntar I

Dike* t

" ]

DllH, Vein tiKiiied In 1

Diorite )

Dipper dredge* 1

DIpplos needle 1

Direcl union or BTnihesis 1

DiKhargc gate* tor daml t

ofwelm J

Discovery ot lode claim by open cut, Adit, Tunnel or

DiEcovery ot vein for lode cUini in Columbia... 3

Discovery or knowledge of

Discovery shaft for lode claim

in the United States i

DIspoBitlon of tailings 3

dredges. t

DibiDIegration, Boulders of . . . !

rock* 1

Displacement... 1

U{91ortiDn In cryiCals 1

DistHbuMon ot goM In placer

" " goldlnslnlces. !

Ditch, ConnectioQ ot, with

Hume J

" Crofis-secliun of 1

SisBot !

Ditches and ilumcs !

Rules for the conairuc-

" Surveyinga linefor., 1

Dodecahedron, The 1

Dolomite J

Drags .

Dredge, with washing plant

Dredges, Bucket

Dipper

" Disposition ot tail- ings from

Index.

Src. Page. Dredging, Cleaning up of bed- rock when 89 108

Drift gravel mines 80 40

A study of. 87 89

" sets 89 41

Drifting in placer mining 89 40

Drill, Diamond, Prospecting

with 88 88

Drills for prospecting 88 M

Percussive or churn, for

prospecting 88 48

" Sharpening of 88 55

Drilling, Hand augers for 38 41

Dry ores or milling ores 85 58

Dry-stone dams 89 59

Dynamic geology 87 1

E. Sec. Page. Earth, Condition of the inte- rior of 37 36

" dams 39 60

Economic geology 87 1

Effect of frost 87 6

" " and erosion by

water 89 2

Bffectsofice 87 18

produced by currents and waves in large

bodies of water 87 17

of wind. 87 6

Elbows for iron pipes 89 87

Electrolytic determination f>f

copper , — 86 188

Elements, Chemical &I 1

" Table of chemical.. 84 5 Elevation, Changes of, in the

surface of the earth . 87 89

Elevator, Evans 39 87

Ludlum 89 86

Elevators, Hydraulic 89 86

Emerald 35 81

(aquamarine ; beryl) 85 81

Oriental 85 80

Eocene 87 48

Equations, Chemical 84 4

Equivalence or valence IM 11

Eroding action of a spring 87 80

power of water 37 10

Erosion by water. Effect of ... 89 8

Eruption, Modes of 37 58

Eruptive rocks. General char- acteristics of 37 51

Estuaries 37

Evans elevator 30 .T7

Evaporation and absorption. . . 8.> 54

Sec, Page.

Evolution of the "Giant" 89 80

Examination of a mineral 85 10

Examination of a substance

before the blowpipe 84 96

Examination with cobalt solu- tion S4 47

" with reagents 84 87

" without reagents &4 86 Examples for practice in figur- ing iron determinations 36 104

Examples for practice in lead

assaying 86 85

Examples in assaying given

for practice 86 71

'' of placers 80 91

prospecting re- gions 38 45

Excavating material, Methods

of 39 88

Exchange 84 8

" or substitution 84 10

Exposures available for geo- logical observations 37 82

F. Sec. Page. Fan holes drilled with a

diamond drill 88 37

Faulted veins 87 84

Faults, Law of slip in 87 68

Normal, Cause of 87 71

Reverse 87 69

Cause of 37 70

" Throw of 37 68

Feed-pipes 3D 90

Feel of a mineral 35 4

Felsite 37 50

Ferrocyanide of potassium. ... 86 88 " solution for lead

determination 86 131

Fibrous structure 35 4

File 84 31

Filiform or capillary structure 35 5

Filling of pipes 89 89

Filter and burette stands 86 90

" paper 86 90

Fine bullion assay 30 7M

" Reporting of assay

results from 36 81

Fire assay 36 8

" assaying 36 5

" clay crucibles 36 88

Fissure veins 37 74

Fissures 37 67

Cause of 37 67

Flagstone cleavage 37 39

Flagstones 87 119

FLkme, ColoraUtia of LhB i

Colon Imparled lo, by

varioiu mloeniU i

Thecharutcrof,. .,. I

I'lamlng )

Fluki )

PliHid-plafnotariw I

Piom ot water, WMUDramtDl nf I

PlBorine. TbM tor. . ..." 3

PJuurapikT 9

Flume.ConoectiDDDf.wlUidiech

" wBirrfaUi 1

Bedsandjoinliifur... i

" CoMtruetinn of . 8

Curveaon I

vB.dltchM 8

Gradeof S

PI m. Bismuth S

" Neutral oialatc of po-

tasa as 1

Plunes a

Gold and silvercrucible 3

" Uad a

" Mixed 3

PluKinKsndreducingreageiits a

Foil, Platinum 3

Foliated tellurium 3

Pooragold (see Iron pyrites).. 3

Porcep"

Forge for prospeiiors S

Forms o( placer deposits 3

Fossils 3

and charecleriaticB of

Iheperi.Kla H

Condition and use of.. 3

Foundations (or dams S

Fracture 3

Franklinite 3

Free milling ores S

Free miners' certificates for

British Columbia 3

Free miners' prlvilegeaiu Brit.

Index.

Sec. Page.

Giant,Little 89 Si

Glacialpenod 87 43

Glaciers 87 18

" Work of 89

Glass, Magnifying 84 82

" Silica for 87 128

tubes 84 89

Glasses, Watch 84 S2

Glimmering luster 86 8

Glistening or sheeny luster ... ffi 8

Globe monitor 89 80

Gneiss 87 80

Gold 85 67

adhering to stones in

placer deposits 89 15

and silver assay 86 45

crucible fluxes 86 40 " ores. Crucible

charges for. . 86 48

Parting of 84 S6

deposits. Surface changes

in 87 88

Determination of, in ores 84 58

Distribution of, in sluices 89 51

minerals 86 57

Mode of occurrence of, in

placers 89 6

Placer, Origin of 89 8

placers. Origin of 89 1

saving table 89 86

Goose-neck 89 80

Gouge or selvage 87 74

Grade of flumes 89 80

Graduates 86 90

Granite 87 48

" as a building rtone 87 119

" Origin of 87 65

Granular structure 85 4

Graphic tellurium 85 58

Graphite 85 78

or plumbago crucibl#s 86 28 Gravel, Handling and treating

of 39 41

Gravimetric analysis 86 1

Gravimetric method for deter- mining phosphorus.. 36 113

Greasy luster 85 8

Green carbonate of copper 85 40 Grizzly or grating for under- currents 30 24

Ground sluicing 39 28

Guano 37 121

Gypsum 85 77

" 87 117

H. Sec. Page.

Halite 85 74

Hammer 84 81

for beating out lead

buttons 86 27

Hand augers for drilling 88 41

Handling and treating the

gravel 89 41

Hardening and tempering 88 57

Hardness fracture 85 6

Heating in a closed tube 84 88

open tubes 84 40

on charcoal 84 48

Heavy spar 8S 89

Hematite 86 88

Brown 85 89

Hemihedral forms of the hex- agonal system.. 85 84 forms of the iso- metric system.. 85 18 forms of the tet- ragonal system of crystalliza- tion TSb 16

Hessian or sand crucibles 86 88

Hexagonal system of crystalli- zation 85 18

Hexagonal system of crystalli- zation 85 88

Hexoctahedron, The 85 18

Hill digging in British Colum- bia 88 11

Historic and structural geol- ogy 87 1

Hook gauge 89 68

Horn silver 85 56

Horn spoons 89 18

Horses 87 75

Hot solutions as depositing agents in the formation of

veins 87 H6

Hydraulic elevators or blow- ups 89 86

chief 89 80

giant 89 88

mines. Tunnels as

outlets for 89 48

nozzles. General re-

niarksconcerning 89 33

Hydraulicking 89 89

Hydriodic acid 84 85

I. Sec. Page

Icebergs 37 19

Ice, Effects of 37 18

Idaho as a prospecting region . . 38 50

Igneous agencies 37 25

Effect of 87 85

iDnpentube !

" ore*. Tretnient of. in

AnBlraiB i

" occi. White

Life Development ..

Llghling placer nitne i

Ughl mby silver :

Lfgnile 1

LlUle Giant. 1

Llmeslone ;

u buildins alone 1

Lime or calcueoiii locks i

LimoniiB . J

Liquid eleinenU 1

LllhargB 1

Litmus paper I

Local metamorphlsm i

LooHdi! aoil rEcordlnK of mill

sues in Brttish Columbia ... 1 Locating and recording: of mill

BiiesmilieXTnltedStatss..,. ) Location notice tor lode clkim

in the United Suies i

claim m United Sutes t

Location o( tode claims i

- plaeerclalms i

Lode claim. British Columbia.

Praelico In rcKard to !

Lode claim. United Stales,

Proclico in regard to t

Lodes ot veins. Prospectlne ttt t

Longitudinal nfflel ]

Long Tom I

Lodlumelevator

Lusler of minerals. i

M. S.

pliotua determinations a

Magnet i

Magnclio prospoeting 11

Uiutn It ving -glass S

Malavhila

Uammillary structure 3

Manffsme ,. . . ., i

Manganese

Manganese determi nations St

Manganous sulpbate solution, Preparation of. for use in iron nalysis H

material IS

Maps. Use of geological and

Marble K

Uarking of samples K

MartllB SB

Masonry core for dam

dami X

Massive or plutonio rocks ST

rocks. Origin of K

Material, Arrangement of, in

veins 37

Method* of excava-

ilng W

Matler. Constilulion of M

Matrasses M

Measurement of the flow of water W

Measures and weights, Tables of W

Mechanical elTecU of aqueous

Melaconite St

Mercuric chloride oliillon. Preparation of. lor Iron an-

alyiis as

Ifercory ... 3fi

U

Xt

inboltle m

Mesosoic S7

Metallic luster K

portance 8E

" Orlginot 37

elides. Reaction of the most eharaeteriiitic.. Si oxides. Reduction of,

with soda

" scales. Ores with, As- say ot M

Kffect of carbonaceous

NomBiiclature, Chemlcsl S4 14

Non- coal Ss Ss

N<>tdli,GauKlDg water by . ... 30 U Notice, Liiicatlon, for lode clkim

in the United Suisa 38 18

Soirle. Deflecting 3S m

NoiilcB. Hydraulic. Gsneral

re markB concern lug SB 3S

Numbering 11 [ umiilM ait BS

O. Sfc. Pagl.

Occurrence oE gold 117 101

Ocher 37 la!

" BtowQ 3S 30

Red an M

OctulieilrDn, The 8G 13

Oiliindipiiltlitnips 31

Opal ffi 87

ofminerals 3& 9

Open tube, Hming In S4 40

Ore 87 li

" and mineral depoalta 37 71

" depuBits. AKe of 37 79

" Surface chaoKeB

glau(MaKnirylng-KlaaB). . M

-' Peculiar occurrencelol... 37

ler. Analysiiinf lOR

MHUganeiie, Trealment

of M 111

' Metallic, of Mcondarylm-

purtance 3S a

Originof 37 87

" StaDdard Iron, for uie In

analysis 33 109

aayof SO gs

" Zinc, TrealtnenCoI, In an.

alyals 30 181

Orgaoic afcencles 37 80

Organic matter In iron ores,

Kffect r, on analyiii. 3fl ]0I

Origin df drift oiplaoerKDlil.. SO 3

" KOldplacer* 3U I

" hydraulli: mining. ,. 3U iW igneoua or eruptive

melaltlc orei 37 87

Origin of tlie first qontinenu. . 37

Oriiioclase

Onhnrhambic lyBCem of crys-

tallliation 3S

Uillution K

Outcrop ST

OutHl, Prospector's 83

Oxiklaie iiF poussa. Neutral . .. 3t

Oxidation anil reduction S4

Oxides, Action of, wilh acids.. 34 Uetailic, Cbaracter- iitic reactions of the

mostcammon 34

Uelallic, Redaction o(,

of. in analysis K

Oxiditing flame 31

P. Stc i

PalBoEoic 17

Pan for washing gold 8S

Panning S3

Paper. Braiil- wood 34

Filler 88

Turmeric 31

Parallel voina XI

Parting of gold and silver S4

" Strength uf reagents

for 38

Testing o( reagents

" the button 81

Pay chutes urchlnineys 37

Peacock copper SS

Pearly luster lb

Peatbogs , 87

Penstocic or prBSsnrc boa 38

Percolating waters. GITecI of.

in metninoTpllism 87

Percussive or churn drills for

prospecting 88

Pericds. PossItsBDdcharacter-

IsticBof 87

Permangnnatesoluiionturtron 88 PennBQganato solution foriron

analysis 88

Permanganate solution f or inm,

Standardising of 88

Prrmlan 87

period 87

Psroilde ol hydrogaa. Anti- dote tor potasilum cyanid*

>lM\lnt, IKMiah

poos and bmx caps m

pMuta and lad* Mil* K nt

BlialpluiE of M B

PtrlnHa, Ntalnloialauof ... M Putnailum Mid MdiDm carboB-

and [en

M St

cyanldg q|. . pBtMilBM cyaaMi, niiiilit

, AntlMtalor U

pulnailuoi cyanide lelutioo

[iir tripper detenniaatlaoi.. . W VH

I'liwpr. CornblDiDK M 10

l'ril..i.r.iitone K W

Index.

xxin

t4

Sec. Page. Preliminary investigation of

placers 89 51

Preparation needed for pros- pecting 88 1

Preparation of reagents 86 187

Preparation of standard solu- tions for iron determination 80 94

Preparing the sample 86 5

Pressure box or penstock 80 90

Effect of horizontal,

on rocks 87 64

Process of disintegration in

rocks 87 8

Proof, or correction assay of

fine bullion 86 79

Prospecting 88 1

Drills for .. 88 54

for gems and pre- cious stones.. 88 81 " placer deposits 88 6 General remarks

concerning 88 84

lodes for veins 88 13

Magnetic 88 48

Percussive or

churn drills for.. 88 48

Picks for 88 58

Underground 88 85

regions. Examples

of 88 45

with a diamond

drill 88 86

Prospector's forge 88 67

outfit 88 5

tools 88 62

Proustite 85 55

Psilomelane 85 64

Puddle wall of clay for dam... 89 60

Puddling boxes 39 12

Pulp balance 86 11

Pyrargyrite 85 55

Pyrite 85 82

Pyrites, Copper 35 86

Iron 35 82

'' Magnetic iron 85 84

Tin 85 68

Pyrolusite 85 64

Pyromorphite 35 46

Pyrrhotite 85 84

Q. Sec. Page.

Qualitative analysis 86 1

Quartering 86 7

Quartz 35 79

" 35 88

ti

Sec. Page.

Quaternary period 87 48

Quicksilver, Amount of, in bot- tle 89 28

(see Mercury) 37 112

R. Sec. Page.

Radiated structure 36 4

Radical 84 6

Railroad iron riffles 89 SI

Rapids, Cause of 87 9

Reagent box 84 86

Reagents, Blowpipe 84 82

" Examination with.. 84 87 " with-

out.. 84 86 Fluxing and redu- cing 86 84

" Preparation of 86 137

Red copper ore 85 89

" ocher 85 29

" zincore 85 50

Reducing agents. Reducing

power of 36 45

and fluxing re- agents 36 84

flame 84 26

power of reducing

agents 86 45

" reagents 86 39

Reduction 81 18

of metallic oxides

with soda 84 51

Refractory iron ores. Treat- ment of, in analysis 86 106

Refractory ores 35 58

Regions of glaciation and

placer formation 89 4

Relation between carrying power and eroding power of

water 87 10

Reniform structure 85 5

Requisites for a good iron ore. 87 103

Reservoirs 89 54

Resinous luster 35 8

Reticulated structure 85 4

Retorting amalgam 89 49

Retorts for amalgam 39 49

Reverse faults 37 69

Rhodochrosite 85 65

hodonite SS 64

Rhyolite 87 52

Richness of veins. Some fact.s

concerning 87 81

with depth 37 90

Rider, for balances 86 13

Riffles 89 17

Rifflrvlllock W

KHTdinK .. W

Zjgukg M

Righinnglid V-oMeli, Gsiv-

River. Flood plain K

Hiytn, Cau of winding

countol K

UeoliiuiicBl eBeet* ot

Klvcriwump X!

Rwwlog M

disliM

Roclr. Effect o[ wall, on can-

(colsDCveiD .. .. K

" HeantDsaf UiB term ;r7

" Slide.or lalus K

Ranks, ArenkceouB ar und ... K " ConocciioD belween

lnwntary 117

Erupiire, Speclnl tonaa

Igneous, ClasaificaticiQ

or eruptive, Origin of.. 87

Lima or calcareous ... 87

Massive. Origin of SI

Metaainrpliic 37

" Process ot ilisinlBgrn-

SlrailfietJ S7

" Strocture eoniinon to

" Unalralifled or igiic-

oua ST

Volcanic ot eruptive... X

Rocln, SUrnnK W

RoBcoi placer 30

RnHy, Oriental S6

Saddle rMfi 37

Salt a:

of phosphonu M

-' pbospborn* beads. Col- on) imparted to, bjr

tarlon>>oudE>tiiO.F. S4

phosphorus bcada. Col- on liDpaneti la. br

" phmpbanw, FuaioD

with M

Sattl M

" fiodaudpotub .. n

Sample, Preparinc at

Sampler. Tin or riflb fg

unplea, MarkiDK ot m

tfombcTiag: o( a,

Sampling A

base bull jon ff.

nf control aaaays ... . St

posft m

Snad or Hessian crucibles

KHndsloneasabnilding-stone.

Sapphire

S

S™iEof fuidblllly J4

" hardnMS, Uoh'a ... s

SchwE gj

tongs M

Scorification assay. SQ

" H

Scorlfle™ 3s

Screens and scmningr m

Sea. CbEOlcal depoBJia in

the ,..

Section, Geological j7

Segregation. Veins of gj

Seieniam in cloted tube 31

onchareoal gj

Selvage or gouge g-

Serpenline gg

sr

" as a buildiOR Mone S!

SeU, Drift gg

Shaft. Discover}-, tor lode elaJm

in the United States M

Shallow placers gg

Sharpening drills n

Index.

Side lines of claims, Apex

crossing of 88

Siderite 85

Sienna 87

Silica 86

" and insoluble matter, De- termination of 86

Determination of 86

for glass 37

Silicates, Action of, with acids 84

Silkyluster 85

Silurian 87

" period 87

Silver 35

and gold assay .. 86

" crucible fluxes 86

" Brittle 35

Determination of, in

ores 81

" glance 85

Horn 85

" Ligiit ruby 85

minerals 85

Native 85

" on charcoal 84

" ores, Crucible charges

" Ruby 86

Slate 87

Slaty cleavage 87

Slop- jar 86

Sluices 89

" Charging of 89

" Distribution of gold

in 89

" Grade of 89

Sluicing, Ground 39

Smaltite 85

Smithsonite 35

Soda 84

and potash salts 87

Reduction of metallic

oxides with 84

Sodium and potassium bicar-

bonates 86

" potassium car- bonates 86

" chloride 86

Sodium hydrate solution f<ir

phosphorus determination... 86

Soil, Formation of 87

Solid elements 34

Solution, Bichromate for iron.

Standardizing of .. 36

" Cobalt 81

Pasr. Sec. Page.

Solution, Cyanide, for copper 22 determinations ... 86 124

80 Manganous sulphate,

128 for u.se in iron an-

86 alysis 86 108

Magnesia mixture for

120 phosphorus deter-

121 mination 83 115

122 " Mercuric chloride,for

. 21 use in iron analysis 86 108

8 Molybdate, for phos-

48 phorus 86 115

92 Permanganate, for

52 iron analysis 86 108

102 " Permanganate, for

45 iron. Standardizing

40 of 86 96

64 " Sodium hydrate, for

phosphorus deter-

53 mination 86 116

54 Standard acid, for 56 phosphorus deter-

55 mination 86 117

53 Standard ferro-

54 cyanide, for the de-

44 termination of zinc 86 132

" Standard, for lead 42 determination 85 181

56 Stannous chloride, 120 for use in iron de-

39 terminations S6 106

93 Solutions, Alkaline, in vein for-

16 mations 87 86

27 " Hot, in vein forma-

tions 37 86

61 Sorting power of water 87 12

26 Source of water supply 89 53

28 Spatulas 86 7

67 Special occurrence of gold 87 101

49 Specific gravity 85 9

88 Specimens, Mineral, Examina-

126 tionof 85 10

Specular iron ore 35 29

51 Sphalerite 35 48

Spinel 86 80

85 Spirit and oil lamps 84 26

Spoons, Horn 80 12

85 Spot-plate 86 80

86 Springs, Deposits from 87 23

" Eroding action of 87 £0

116 Originof 87 20

2 Square-work mining 39 41

2 Staking a placer claim in Brit- ish Columbia 38 11

99 of lode claim in British

Columbia 88 24

1l.f-'.n.mK*Ski

*r:

T.nir:..fT

/' '

(t

.rtr''-"

#

f

T

J

t

-.iir'..'yit.

4!

Sec. Temperature, Increase of, with

depth 37

of muffle during

cupelling 86

Tempering and hardening 88

Test lead 84

Tests of fusibility M

" Wet 84

Tenacity 86

Tertiary period 87

Tetragonal system of crystal- lization 85

system of crystal- lization 85

Tetrahedrite 86

Tetrahexahedron, The 85

Testlead 86

" tubes 84

Tests, Acid 84

Theories of vein formation — 37

Throw of faults 37

Timbering for drift mines. ... S9

Tin 84

" 85

" 87

on charcoal 84

pyrites 85

Titrating dishes 86

Titration 86

Tom, Long 89

Tools, Furnace 86

Miscellaneous, for as- saying 86

Prospector's 88

Topaz 85

Oriental 85

Tongs, Button 86

" Crucible 86

Cupel 86

Scorifier 86

Trachyte 87

Transparency of minerals 85

Trapezohedron, The 85

Trappean Rocks 87

Translucent 85

Triassic period 87

Triclinic system of crystalliza- tion 86

" " crystalliza- tion 86

TrisocUhedron, The 85

Trommels — 80

Troy weight, Table of 86

Tube, Closed, Heating in 84

INDEX. xxvii

Paf. Sec. Page,

Tube, Open, Heating in 84 40

35 Tubes,Closed 84 80

Glass 84 29

51 Matrass 84 80

57 " Open 84 29

84 Test 84 80

45 Tunnel, Advantage of having

19 sluices in 80 48

7 sites in the United

48 States 88 26

Tunnels as outlets for hydrau-

11 lie mines 89 48

" Wooden linings for. .. 39 88

15 Turmeric paper 84 85

38 Turquoise 85 81

18 " 85 86

89 Twinned crystals 85 81

20 U Sec, Page.

86 Umber 87 128

68 Unconformable strata 37 88

41 Undercurrents 89 2S

85 Underground prospecting. ... 88 85 68 Union, Direct, or synthesis 34 8 65 United States, Mill sites in 88 28

111 United States practice in re-

44 gard to lode claims 88 17

68 United States practice in re-

90 gard to placer claims 88 9

2 United States, Tunnel sites in 88 26

14 Unstratified or igneous rocks.. 37 46

25 Utah as a prospecting region. . 88 50

27 V. Sec.

fiS Valence or equivalence 84

81 Value of a coal deposit 87

83 Valves 89

80 Blow-off 89

27 Vein formation, Theories of . . . 37

25 formed in a dike 87

26 Veins 37

26 Action of alkaline solu-

51 lions in the formation

2 of 87

18 Action of hot solutions

60 in the formation of . . . 37

2 Arrangement of ma-

43 terialin 37

Copper, Surface changes

12 in 87

Effect of wall-rock on . . . 87

18 " Fissure 87

35 Minerals found in 37

142 of infiltration 37

88 or lodes. Prospecting of. 38

Page,

J. Page.

Valiii of (efcrcgatiim 37 ?3

" Panllallsm or 87 l4

" RichneHof.witb depth, 17 DO " Some (act* cnaccmlng (he occurrence and

ricbnesBOf 97 W

Vdocl If at approach W IW

Vitreous lusler SB R

Volcanic conglomeralo and

breccia K! Sf

" or eruptive tocIeh , , . A7

VolBDietHc HnaIy*I> or Ktni-

lion 1

Von Kobell's acalo of Iiiil-

bllily U M

Vugs . - --, 17 90

W. Sec. Pag!'- Wall-rock, BITect o(. on ma-

Waab-bottle M U

WuhiDK trouEh H 10

WMte-Katei In flume* H H

Waatewarn fur damn SI aa

Watch-Rloiees . M HI

M ffl

Water, Chemical eirerlHor 37 SI Water, EffceiB produced by- currents in large bodies of.. 37 17 Water gauging by notch. ... S9 fifl

HowoC SB as

Relation between car- rying power ond ero- ding power of... 37 10

Sorllng power of 87 K

supply 89 M

TeMfnr M M

WaterfalU, Cauae of 87 S

Hlume 38 M

Water-wheels ., 80 38

Waves, Bflrecla produced by. in

large bod ien of water 37 IT

Weighing 36 10

and furnace work,

Orderof 86 fi3

Method.C 36 17

thebntlons M 68

Weight, Adjusting of, to the standard solutions used in

iron analysis M no

WeiKhl, Atomic 31 1

Wire, Platinur

lininjr* for

:. Pmg*.

n

s

'0)y) oy) y oy my)

Sunrord unMnffir UbrrtM

liliMyii

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