Manual of determinative mineralogy : with an introduction on blow-pipe analysis

Brush, George Jarvis · 1875 · Historical

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Harvard University

Department Of

Geological Sciences

Library

Transferred to

Cabot Science Library

June 2005

Manual

Op

Determinative Mineralogy.

With An Introduction On

Blowpipe Analysis

By

George J. Brush,

Director of the Sheffield Scientific School of Tale University.

REVISED AND ENLARGED, WITH ENTIRELY NEW TABLES FOR THE IDENTIFICATION OF MINERALS,

By

Samuel L. Penfield,

Professor of Mineralogy in the Sheffield Scientific School

of Tale University.

)

Sixteenth Edition, He Vised. Fikst Thousand.

New York:

John Wiley & Sons.

London: CHAPMAN & HALL, Limited.

; v

Copyright, 1806,

Bt

8Amuel L. Penfield.

Robert Drummond. Elkctrotyprr And Printer, Nsw York.

Preface.

The present work is a complete revision of the " Manual of Determinative Mineralogy and Blowpipe Analysis ' by Prof. Geo. J. Brush, which has been very generally used since its first appear- ance in 1874, as shown by the fact that fourteen editions of it have appeared. In 1896 a revision of the introductory chapters devoted to blowpipe analysis and the chemical reactions of the elements was published, and there are now added a chapter on the physical properties of minerals, devoted chiefly to crystallography, and a new set of analytical tables for the identification of minerals.

In preparing the introductory chapters, great pains has been taken in the selection of the tests for the elements. Many of the experiments are performed by means of the blowpipe, but chem- ical tests in the wet way are recommended when it is believed that they are more decisive. All the tests have been carefully verified, and many of them have been devised especially for the present work. To make the book more convenient for reference, conspic- uous headlines and catch- words have been freely used. The tests for the rare elements, and those for the common ones which are only occasionally employed, are printed in small type. It is hoped that the plan adopted of giving full directions concerning the methods of manipulation and the quantities of materials to be taken in making many of the tests will be found useful.

It must be borne in mind constantly that accuracy is of the utmost importance in determinative mineralogy, and it is believed that no methods are so generally to be relied upon for giving deci- sive results as those based upon the identification of the chemical constituents of the minerals. Moreover, most minerals can be iden- tified by means of very simple tests, although some cannot be determined beyond question without resorting to the more elab-

Iv Preface.

orate methods of quantitative chemical analysis, or an exact deter- mination of their crystalline form.

The chapter on the physical properties of minerals is a new feature of the book which it is believed will add to its usefulness. The endeavor has been made to present the important subject of crystallography as simply as possible. Importance has been attached to the description of those forms which are most frequent in their occurrence, and, with few exceptions, the examples chosen to illustrate the different systems represent the development of the simple forms which prevail on specimens of common minerals. Rare and complex forms have been treated very briefly, and theo- retical considerations have been ]eft largely to the more elaborate treatises on crystallography. In describing the physical properties of crystals the idea has constantly been kept in mind that the book is to be used for the identification of minerals and, consequently, only those methods are included which are especially important as a means for identification. Optical methods have been omitted because they would increase the size of the volume to too great an extent, and, except as they are accompanied by accurate descrip- tions of the crystal forms, their application is limited.

The analytical tables for the identification of minerals are an outgrowth of the tables of von Kobell as modified by Professor Brush. The introduction, however, of a large number of new species since 1874 has necessitated a complete rearrangement of the minerals. The tables have been so developed that tests for characteristic chemical constituents furnish the chief means for identification. Thus, in identifying minerals, students may gain possession of important information concerning the chemical com- position of the compounds. The distribution of the minerals in the tables, and statements concerning their chemical and blowpipe characters, have been verified in almost all cases by experiments made upon well-authenticated specimens in the Brush collection at New Haven. In some cases, however, it has not been possible to locate rare minerals with certainty in the places where they prop- erly belong, because the original descriptions hate not been suffi- ciently complete. The author would be pleased to receive any information concerning the properties of minerals which could be incorporated in future editions, and thus render the tables more complete and accurate. The tables are intended to include all of the well-characterized mineral species known at the present time, and although nearly eight hundred species have been included, it is

Preface. T

believed that they are adapted to the use of beginners who desire especially to become acquainted with the common minerals. In order to accomplish this end the common minerals are printed conspicuously in capitals, and thus on opening any page of the tables they may be recognized at once by glancing down the column " Name of Species."

The author takes pleasure in expressing his obligations to his associates, Professors G. J. Brush, E. S. Dana, L. V. Pirsson, and H. L. Wells, for many valuable suggestions, and to the Misses L. P. and K. J. Bush of New Haven for services rendered in the preparation of the manuscript and in proof-reading. The wood- cuts were prepared by the skillful engraver, Mr. W. F. Hopson of New Haven.

New Haven, October 1, 1808.

Prefaces Of The Former

Editions Of This Work,

By George J. Brush.

Preface To The First Edition.

The material in this compilation was, for the greater part, prepared almost twenty years since, by Prof. S. W. Johnson and myself, as a text-book for the students in our laboratory. Circumstances prevented its publication at that time, but it has served as the basis of a course of lectures and practical exercises annually given in the Sheffield Laboratory.

The plan of instruction has been to have the student work through a course of Qualitative Blowpipe Analysis as introduc- tory to Determinative Mineralogy. For the latter subject, we have employed von Kobell's Tafeln znr Bestimmung der Mine- ralien, many of the students taking the work in the original, while others made use of either Erni's or Elderhorst's transla- tions. These " Tables " were translated by Prof. Johnson and my- self while we were students of Prof, von Kobell in 1853-4, at Munich, and it was after our suggestion, in 1860, to Prof. Elder- horst, that he introduced von KobelFs " Tables " into the second edition of his " Manual," although he did not avail himself of our translation, which was then offered to him for that purpose.

PREFACE TO THE FIRST EDITION". vii

The " Tables " as now presented are based on the tenth German edition of von Kobell's book. Additions of new species have been made, and in many cases, fuller details are given in re- gard to old species, and the whole material has been thrown into an entirely new shape, which it is believed will greatly facilitate the work of the student. The preparation of the tables in this form, the idea of which was suggested to me by Prof. W. T. Roepper, has been performed, under my supervision, by my as- sistant, Mr. George W. Hawes, who has also aided me greatly in revising the rest of the work, and in the reading of the proof- sheets.

The main authorities used in the original preparation and later revision of the chapters on Blowpipe Analysis were the works of Berzelius and Plattner. The third and fourth edi- tions of Plattner, the latter edited by Prof. Richter, have been chiefly consulted. The complete work of Plattner, with still later additions by Prof. Richter, has been made accessible to English- reading students through an excellent translation by Prof. H. B. Cornwall, and this cannot be too highly commended to those who desire to become fully acquainted with this important sub- ject.

In Determinative Mineralogy, besides the works of von Kobell, free use has been made of the treatises of Naumajstn and Dana, especially of the pyrognostic characters contributed by myself to the latter work. This constitutes, in accordance with the original plan of Professor Dana and myself, the Determina- tive Part of his System of Mineralogy. It is proposed at some future time to add to the volume methods for the determination of minerals by their physical characters.

In conclusion, I take great pleasure in acknowledging my in- debtedness to my colleague, Prof. S. W. Johnson, who has not only generously given me his share in the original work, but has constantly aided me by his advice in the revision here presented.

Sheffield Laboratory of Yale College, New Haven, December 15, 1874.

Pkeface To The Third And Later Editions.

This edition has been so far revised as to substitute for the old formulas for minerals, those based upon the atomic weights of the elements adopted by the so-called new chemistry. The formulas for the most part have been taken from Rammehberg's Minerahhemie (Leipzig, 1875), and are made to correspond as far as possible with those given in Dr. M. S. Dana's Textbook of Mineralogy (John Wiley & Sons, New York, 1877).

It should be stated here that as the main object of this book is the identification of. mineral species by a method largely based on the blowpipe characters of their elemental constituents, this point has been kept in view in writing their formulas. Instead of giving a symbol for a group of elements, as is usual in min- eralogical treatises, it has been necessary to give the elements in full, and in some instances, for want of space, a simple list of the constituents is substituted for the formulas. This has also been done in the case of minerals where no satisfactory formulas- have been deduced.

It has not been thought advisable to alter the old common names used for reagents and compounds, since the book is in- tended not only for students in colleges and schools, but for all the different classes of persons who are interested in the study of minerals.

A few changes and additions in the text of the tables are made, which, it is trusted, will facilitate the work of the student. My acknowledgments are again due to Mr. George W. Hawes for his cooperation in making these changes.

New Haven, May 1, 1878.

Table Of Contents.

Chapter L

Introduction And Chemical Principlbs.

The Mineral Kingdom: Minerals 1

Rocks: Chemistry 2

Chapter Ii.

APPARATUS AND REAGENTS, AND CHEMICAL PRINCIPLES IN- VOLVED IN THEIR USE.

Apparatus 10

Dry Reagents '. 24

Gaseous Reagents : Wet Reagents 27

The Nature and Use of Flames 81

Chapter Iii.

Reactions Op The Elements.

Aluminium 48

Other Elements follow ia Alphabetical Order.

Chapter Iv.

TABULATED ARRANGEMENT OF THE MORE IMPORTANT BLOWPIPE AND CHEMICAL REACTIONS.

Heating in the Platinum-pointed Forceps : Flame Coloration 135

Heating in the Closed Tube 137

Heating in the Open Tube 140

Heating on Charcoal 142

Treatment with Cobalt Nitrate 146

Fusion with the Fluxes on Platinum Wire 147

Treatment with Acids, and Reactions with the Common Elements. 151

Table Of Contents.

Chapter V.

PlOB

Physical Properties Op Minerals.

Crystallography . 155

Structure of Minerals 1 221

Cohesion Relations of Minerals 223

Properties depending upon Light 227

Properties depending upon Heat 280

Properties depending upon Weight : Specific Gravity 232

Chapter Vi.

TABLES FOR THE DETERMINATION OF MINERAL SPECIES BY MEANS OF SIMPLE CHEMICAL EXPERIMENTS IN THE WET AND DRY WAY AND BY THEIR PHYSICAL PROPERTIES.

Introduction to the Tables 239

Analytical Table for the Identification of Minerals : General Classification.. . 245 Tables 246

Index To Subjectmatter 308

Index To Minerals 807

Determinative Mineralogy And Blowpipe

Analysis,

Chapter L

Introduction And Chemical Principles.

The Mineral Kingdom. — Natural products are commonly divided into three kingdoms, — animal, vegetable, and mineral. The latter includes those substances constituting or found in the crust of the earth and not those made through the agency of life. They are, therefore, frequently called inorganic materials. Among these, two classes are recognized, which are known as minerals and i ocks.

Minerals. — These are definite chemical compounds occurring in the mineral kingdom. The following may serve as examples :

Pyrite, sulphide of iron, FeSt.

Quartz oxide of silicon, SiOt.

Orthoclasey silicate of potassium and aluminium, KAlSi,Oe.

Chemical formulae show the invariable composition of the minerals when pure, that of quartz, for example, indicating that 1 atom of silicon is in combination with 2 atoms of oxygen. It ought to be possible to express the composition of every mineral by a chemical formula, but there are some for which this cannot yet be done, owing to the fact that they have not been sufficiently investigated.

On examining minerals, it will be observed that they usually occur in definite geometrical shapes called crystals, when condi- tions favorable for the formation of crystals have prevailed.

2% Introduction And Chemical Principles.

Every distinct chemical compound occurring in inorganic nature, having a definite molecular structure or system of crystallization and well-defined physical properties, constitutes a mineral species. Up to the present time, between eight and nine hundred minerals, which deserve to rank as distinct species, have been recognized. Of these, however, only a few can be considered as common, and really important either as rock-forming minerals in making up the crust of the earth, or as ores of the useful metals, or its otherwise valuable in the arts. Each mineral species has received a name (usually ending in ite> signifying of the nature of J 'like'') by which it ia commonly known. In assigning these names no sys- tem has been followed, some being derived from chemical, phys- ical, or fanciful peculiarities, some from localities where the minerals were first found, while many are named after persons.

Rocks. — With the exception of a few glassy lavas, rocks are aggregates of mineral particles. The term rock is often used in a general way for designating any portion of the earth' s crust, but the kinds of rock to which geologists have assigned special names contain certain minerals in about the same proportion throughout. Thus, granite is one of the commonest rocks of the globe, and, on examination, a fragment of it will be found to be made up of different minerals. The most conspicuous is orthoclajse, KAlSi,0,r together with a corresponding soda mineral, albite, NaAlSi,Of% and quartz, SiO„ while a number of others may be present in small amounts. The proportion of these minerals differs in differ- ent kinds of granite, and it is therefore evident that the composition of this rock cannot be expressed by a definite chemical formula.

In a rock, the structure may be coarse-grained, so that the particles can be detected with the naked eye, or fine-grained, ren- dering a microscope necessary to distinguish the different com- ponents. Usually a rock is composed of different minerals, but it sometimes consists of only one. Thus, marble is an aggregate of particles of calcite, CaCO„ and quartzite of quartz, SiO,. The study of rocks, known as lithology or petrography, necessitates a previous knowledge of mineralogy.

Introduction And Chemical Principles. 3

Chemistry. — Mineralogy is chiefly a chemical science, and for a proper understanding of minerals, some knowledge of elementary chemistry is indispensable. A brief summary, therefore, of some important chemical principles will be first given. By a careful study of the experimental part of the following chapters, it is believed that much useful information concerning general element- ary chemistry may be gained.

Elements. — A substance which cannot be separated into sim- pler constituents is regarded as an element At the present time, about 70 elements are recognized. Of these, less than half are of common occurrence, while, from a consideration of a large num- ber of rock analyses, F. W. Clarke* has calculated that 99 per cent of the solid crust of the earth, for a depth of ten miles, is composed of the following eight elements :

Oxygen, 47. 3# Calcium, 3.8#

Silicon, 27.2 Magnesium, 2.7

Aluminium, 7.8 Sodium, 2.4

Iron, 5.4 Potassium, 2.4

Chemical Affinity, Atoms, and Molecules.— Elements manifest tendencies to unite with one another. This property is known as chemical affinity. It is usually strongest between metallic and non-metallic elements ; as sodium and chlorine in sodium chloride. The smallest particle of an element which enters into combination is called an atom, and the smallest particle of a chemical compound which is capable of existence is called a molecule.

Symbols. — For convenience, elements are designated by sym- bols, usually the initial letter of their names, or this with one other letter. Each symbol stands for one atom of the element ; as S for sulphur, Pb for lead (Latin plumbum). PbS is the chemical for- mula of, and represents a molecule of, lead sulphide.

Law of Definite Proportion. — Atoms unite with one another in

definite, though frequently in two or more different, proportions.

♦Phil. Soc. of Washington, Boll. IX., p. 138, 1889.

4 Introduction And Chemical Principles.

For example, carbon, sulphur, and arsenic, each f orm two distinct oxides, CO and CO,, SO, and SO,, As,0, and As,0§.

Valence. — This term is used to express the numerical propor- tion in which elements unite with or replace hydrogen. Chlorine is univalent and oxygen bivalent, because they unite with hydro- gen to form the molecules HC1 and H,0, respectively. The term valence is also applied to compounds. Thus, sulphuric acid being H,S04, the radical S04 is said to be bivalent.

Acids. — Compounds resulting from the union of non-metallic elements, with hydrogen or hydrogen and oxygen, in which the hydrogen atoms may be replaced by metals, are called acids. These usually possess a sharp, sour taste and have the property of turning blue litmus-paper red. The common mineral- forming acids are hydrochloric, HC1 ; nitric, HNO, ; hydrofluoric, HP ; hydrogen sulphide, H,S ; sulphuric, H,S04 ; carbonic. H,CO,; boric, H,BO, ; phosphoric, H,P04 ; arsenic, H,As04 ; orthosilicic H4Si04 ; metasilicic, H4Si,0„ and polysilicic, H4Si,Oa. In the fore- going formulae, the groups of elements with which the hydrogen atoms are united are often called acid radicals. Thus, S04 is the acid radical of sulphuric acid ; P04 of phosphoric ; Si04 of ortho- silicic, etc.

Bases. — Combinations of metals with oxygen and hydrogen (the hydroxides ; for example, NaOH, sodium hydroxide) are called bases. These have the property of neutralizing acids, and, if soluble in water, of turning red litmus-paper blue. The combinations of metals with oxygen are sometimes called basic oxides.

Salts.— Compounds formed by the combination of acids and bases, and resulting in the replacement of part or all of the hydro- gen adorns of the acid by metals, are called salts. The great majority of minerals are salts, and in a natural chemical classifica- tion they are subdivided into groups according to the acid radi- cals which they contain ; i.e., the sulphides, salts of hydrogen sulphide, iij one group ; the sulphates, salts of sulphuric acid, in another ; the silicates, salts of silicic acid, in a third, etc.

Introduction And Chemical Principles. 5

With a knowledge of the valence of a given metal, it is a sim- ple matter to write the normal salt of any known acid, as shown by the following table :

Hydrochloric, Sulphuric, Phosphoric, Orthosilicic, HC1. HtS04. HsP04. H4Si04.

Sodium, Na, univalent, NaCl Na,S04 Na.PO. Na4SiO

Calcium, Ca, bivalent, CaCl. CaSO, Ca.(P04)t Ca,Si04

Ferric iron, Fe, trivalent, FeClt Fe,(S04), FeP04 Fe4(Si04)

Chemical Equations. — When chemical substances react upon or unite with one another, definite transformations take place, which can be expressed in the form of equations. Thus, when calcite is dissolved in hydrochloric acid, or barite is fused with sodium carbonate, the results are shown as follows :

CaCO, + 2HC1 CaCl, + H,0 + CO,. BaS04 + Na, CO, BaCO, + Na, S04.

The practice of writing correct equations serves a useful pur- pose in affording a knowledge of the manner in which chemical reactions take place.

Atomic Weight. — It has been found that an atom of an element possesses a definite relative weight, known as its atomic weight. This is. based on an atom of hydrogen, the lightest of all elements, as a standard (the weight of the hydrogen atom being taken as 1). The atomic weights of the common elements have been very accurately determined and are generally given with their descriptions.

Molecular Weight. — The molecular weight of a substance is equal to the sum of the atomic weights of the elements constituting the molecule.' Thus, calcium, carbon, and oxygen, having the atomic weights 40, 12, and 16, respectively, CaCO, has a TaolecvZar weight of 40 + 12 + 48 100.

Relations between Chemical Formulae and Percentage Com- position.— With a knowledge of the chemical formula of a com- pound and of the atomic weights, the percentage composition of the different constituents can be readily calculated. For example, sphalerite is ZnS. The atomic weights are Zn 65. 4 and

Introduction And Chemical Principles,

S 32, hence the molecular weight of ZnS is 97.4. In 97.4 parts by weight of ZnS there are 65.4 parts of zinc, consequently the zinc in 100 parts may be readily calculated by a simple proportion,

thus : 97.4 : 65.4 100 : #, which gives 67.1 as the per cent of zinc.

It is often convenient to give the percentages of combinations of the elements, especially the oxides, instead of the elements them- selves. This is illustrated by the following examples, where the percentages are derived from the molecular weights by the propor- tion, Total Mol. Wt. : MoL Wt. of constituent 100 : x:

Andradite Garnet.

Ca.FeaSuOia 3CaO.Fe,0,.8SiO. AtWt. Mol.wt.

O.' 83 I x 3 180 85-4* Fei, 112 ( Ca, 40 O, 16

508 100.0

160 Fe,0., 81.5 I x 3 =168 CaO, 83.1

Dolomite. CaMg(C03)a CaCOs.MgCO,.

AuWt. Mol.Wt.

Ca, 40

O, 12}- 100 CaCO,, 54.3%

0„ 48

Mg, 24

C, 12}. 84 MgCO„ 45.7

O., 48

Quantitative Chemical Analyses. — The chemical composition of minerals is determined by means of quantitative analyses, and many of these will be found recorded in the larger treatises on mineralogy. Now, since a percentage analysis gives the weights of the different constituents in one hundred parts, and each constituent has its definite relative weight (atomic or molec- ular), therefore the relative number of atoms or molecules may be found by dividing the percentages by their atomic or molecular weights. The quotients indicate the ratio of the constituents, which is usually a simple one.

The following examples of actual analyses will illustrate this :

Sphalerite. Found. At.Wt. Ratio. S, 82.93 + 82 =1.029 Zn, 66.69 +65.4 1.019 Fe, .42

Andradite Garnet.

Found. MoLWt. Ratio. SiOtf 85.44+ 60 .591 Fe,0,, 31.85 + 160 .199 CaO, 32.85+ 56 .587 MgO, .20.

Introduction And Chemical Principles. 7

The ratios derived from these analyses are as follows :

S : Zn 1.029 : 1.019 1.00 : 0.99, or very nearly 1:1.

SiO, : Fe,0, : CaO .591 : .199 : .587 2.95 : 1.00 : 2.97, or nearly

The formula of sphalerite is, therefore, ZnS, and that of the garnet, 3CaO.Fe,0,.3SiO,, or Ca,Fe2SisOia. These analyses may be compared with the theoretical values calculated in the previous paragraphs.

Isomorphism (ivos, equal, + M°P<Pv form). — Substances which are analogous in chemical composition frequently show a simi- larity in crystallization. This is known as isomorphism. Thus, the alums, KAl(S04),.12HtO, and (NH4)Al(S04),.12HtO, are iso- morphous. They must have similarity in molecular arrangement, for they not only crystallize in the same shapes, but, from a solu- tion containing both salts, a crystal may be grown consisting partly of potash and partly of ammonia alum. This tendency of two salts to crystallize together constitutes the strongest proof of their isomorphism.

Isomorphism plays a very important part in mineralogy. Many species are mixtures of two or more isomorphous chemical molecules, and, owing to this fact, the physical properties (espe- cially color, specific gravity, and fusibility) are often found to vary widely. For example, sphalerite when it has the composi- tion ZnS is colorless or nearly so. It usually, however, contains isomorphous FeS, and the color becomes darker aa the percentage of iron sulphide increases. Columbite, FeNb,Oe , and the isomor- phous tantalite, FeTa,Oe, have the specific gravities 5.3 and 8.2, respectively; while intermediate mixtures of the two molecules have specific gravities ranging between these values.

Concerning isomorphous mixtures, it is often stated that one element replaces the other; i.e., sphalerite is ZnS, but part of the zinc may be replaced by iron. To express the composition of these mixed compounds, two methods are commonly employed ; either the isomorphous elements are designated by some symbol,

8 IffTBODUCTIOtf AKD CHEMICAL PRINCIPLES.

as R, or they are enclosed in parentheses. For example, sphaler- ite is said to have the composition RS, where R Zn and Fe, or (Zn,Fe)S, giving importance to the prevailing constituent by plac- ing it first, and often, also, by using larger type. By the latter formula, it is not meant that sphalerite contains one atom of zinc, ') one of iron, and one of sulphur, but that the zinc and iron taken together are equivalent to one atom of a bivalent metal.

The following examples will illustrate the methods of deriving formulae from analyses of isomorphous compounds :

I. n. in.

Brown Sphalerite. Black Sphalerite. Almandine Garnet.

Roxbury, Conn. Felsdbanya. Fort Wrangel, Alaska.

Found. At.Wt. Ratio. Found. At.Wt. Ratio. Found. Mol.Wt. Ratio.

8, 33.36 h- 32 =1.048 S, 83.25+ 32 =1.039 SiO*, 39.29+ 60 .655

Zn, 68.36 + 65.4= .969 Zn, 50.02 -i- 65.4= .756 AUO, 21.70 + 102 .213

Fe, 3.60 + 56 .064 Fe, 15.44 + 56 .276 FeO, 30.82+ 72 - .428

Od, .30 + 112 .003 MnO, 1.51+ 71 .021

100.88 Pb, 1.01 + 207 .005 MgO, 5.26+ 40 .131

CaO, 1.99 + 56 .036

In I, the ratio of S : Zn + Fe 1.043 : 1.033 1.00 : 0.99 or almost exactly 1 : 1. The formula is therefore (Zn,Fe)S. The ratio of Zn : Fe .969 : .064 or approximately 15 : 1, and the composition of the mineral may be regarded more exactly as 15ZnS + FeS.

In II, the ratio of S : Zn + Fe + Cd + Pb 1.039 : 1.040 or 1 : 1. The formula is therefore (Zn,Fe,Cd,Pb)S, or, since Zn : Fe .756 : .276 or nearly 11:4, the composition is more exactly HZnS + 4FeS + traces of CdS and PbS.

In III, FeO, MnO, MgO, and CaO are isomorphous and will be regarded as RO. The ratio of SiO, : Al,Ot : RO .655 : .213 : .616 3.07:1.00:2.89. TIip ratio nrwroxi mates to 3:1:3, and the formula is 3RO. Al,0,.3SiO, , or R,AlfSi,Olf, where R Fe, Mg, Ca, and Mn.

Dimorphism and Trimorphism. — Minerals which have the same percentage composition, but occur in two essentially differ-

Introduction And Chemical Principles. 9

ent crystalline forms, are said to be dimorphous. Thus, carbon crystallizes in the isometric system as diamond, which is hard and transparent, with specific gravity 3.52; and in the hexagonal system as graphite, which is soft and opaque, with Sp. Gr. =2.15. Calcium carbonate, CaCO,, crystallized in the hexagonal system, Sp. Gr. 2.71, is calcite ; and in the orthorhombic system, Sp. Gr. 2.94, it is aragonita Iron sulphide, FeS,, crystallized in the isometric system, Sp. Gr. =5.02, is pyrite, and in the orthorhom- bic system, Sp. Gr. 4.90, it is marcasite. Titanic oxide, TiO,, crystallizes in two entirely independent modifications in the tetragonal system, with Sp. Gr. 4.20, as rutile, and with Sp. Gr. 3.90, as octahedrite, and also in the orthorhombic system, Sp. Gr. 4.0, as brookite. The last case, where three independ- ent modifications of TiO, occur, is an example of trimorphism. Dimorphism and trimorphism may be due either to variations in the number of atoms, to variations in the arrangement of the latter in the chemical molecule, or to variations in the arrange- ment of the particles in the structure of the crystal. No exact means for determining the size of th* chemical molecule in solid substances exists at present. TiO,, for example, is the simple empirical formula for rutile, but its true composition is undoubt- edly some multiple of TiOt.

Chapter Ii.

Apparatus And Reagents, And The Principles Involved In

Their Use.

Part 1. Apparatus.

Although a great deal of blowpipe apparatus has been devised, only that will be described in the present work which is necessary or convenient for making the simple tests for the identification of the elements and the determination of minerals. In performing most of the experiments a simple and inexpensive outfit will suffice, which, if necessary, can be packed in small space, so as to be portable. Moreover, a little ingenuity will often enable one to supply the place of much apparatus.

The Mouth- Blowpipe.— This instrument, for centuries em- ployed only by artisans in soldering and in other operations re- quiring an intense heat, has been for a period of considerably over one hundred years an invaluable means of scientific research.* It is of the greatest service to the mineralogist and chemist for the identification of minerals and the detection of their ingredients, and may even be used for the quantitative separation of several metals from their ores.f

For a brief history of the use of the blowpipe, see Berzelius's work, Die Anwendung des IMhrohrs; or the translation by J. D. Whitney, Boston, 1845. A more complete history is found in Kopp's Gesehichte der Chemie, II, p. 44, Braunschweig, 1844, and also in von KobelPs Gesehichte der Mineralogie, Mil nchen, 1864.

t Quantitative blowpipe analysis is beyond the scope of the present .work. Those interested in Plattner's methods of assaying ores of gold, silver, copper, lead, cobalt, nickel, Iron, etc., by means of the blowpipe, are referred to bis work, Probirkunst mit dem IMhrohre; German edition, by Th. Richter; American translation, by H. B. Cornwall.

Apparatus.

With no other fuel than that furnished by a common lamp or candle, the blowpipe renders it possible to produce in a moment a most intense heat. In the blowpipe Uame, not only are many refractory bodies melted or volatilized, but entirely opposite chemical effects, oxidation and reduction, may be produced. Almost all chemical substances may be made to manifest some characteristic phenomena under its influence, either alone or in the presence of certain other substances known as reagents, and thus their nature may be detected.

The blowpipe is represented in its usual form in Fig. 1. The parts a and b fit into the chamber c with ground joints. Any moisture from the breath which condenses in a collects in c, and may be removed by disjointing the parts. The instrument is also furnished with a tip or jet (the most important part), which fits on b by means of a ground joint, and is shown at d in correct proportion and twice the natural size. The hole at the end of the tip should be slightly tapering and from 0.4 to 0.6 mm. in diameter. It should be bored in such a manner that its axis is in line with the axis of the tube b when the parts are fitted together. Very durable and inexpensive tips are made of brass. Those bored and turned out from solid platinum are expensive and scarcely better than brass, while light ones spun from platinum foil are unsatisfactory. Tips are very apt to become stopped with dust or foreign matter, and new ones often contain bits of metal turn- ings, . or need to be reamed out to the proper size and taper. Cleaning and adjusting can best be accomplished by means of a four-Bided, slightly tapering reamer, which may be made by filing down the sides of a large steel needle or pin. For the successful working of the blowpipe, it is also important that the

12 Apparatus.

hole through b should not be eccentric, and that there should be nothing to disturb the passage of air.

The instrument as shown in Pig. 1, but without the trumpet mouthpiece, is of the original form proposed in the last century by Gahn, and employed by Berzelius. Fatigue is apt to result in using it, as considerable effort is required to keep the lips closed about the tube for any length of time.

Fig. 1 represents the blowpipe provided with the trumpet mouthpiece, e, recommended by Plattner. This is made of horn or hard rubber, 36 mm. in its outer diameter, and should have such a curvature that, when placed against the lips, it does not give an unnecessary or unequal pressure.

A very good mouthpiece may be made from a piece of glass tubing 5 cm. long, and of such diameter as fits the blowpipe tube. It should first be strongly heated for half its length in the tiame of a lamp, and when quite soft flattened between two smooth me- tallic surfaces, to give it the form shown in Fig. 2. The other end should then be cemented into the blowpipe by means of sealing-wax. This kind of mouthpiece, when inserted between the lips, displaces them but slightly from their customary position, and causes very little fatigue.

The blowpipe is usually made of brass, or preferably of German silver. The length of the instrument should be measured by the visual distance of the operator, the ordi- FlQ- 2 nary length being from 20 to 22 cm., exclusive of the

mouthpiece.

The common, artisan's blowpipe, Fig. 3, consists of a tapering and curved tube of brass, terminating in an orifice as large as a small needle. When well constructed, this simple instrument answers most purposes, and is often made without the bulb near the bend, which is intended to collect the moisture condens- ing from the breath.

A great deal of ingenuity has been expended in devising different forms of blowpipes and mouthpieces, each supposed to have some special feature either of excellence or of cheapness to

Apparatus.

recommend it. However, if the blowpipe has a good tip, the form is of little importance, provided the operator is skil- ful and has become accustomed to the use of his in- strument.

Blowing.— In blowpipe operations it is often neces- sary to maintain an uninterrupted stream of air for several successive minutes. To be able to do this easily requires some practice. It is best learned by fully dis- tending the cheeks, closing the communication between the mouth-cavity and windpipe by means of the palate, and breathing through the nose. When one is accus- tomed to keeping the cheeks thus inflated, the mouth- piece of the blowpipe may be pressed against or inserted between the lips, and the same thing repeated without attempting to blow or do more than keep the cheeks distended. To the experienced operator, continuous blowing is hardly an effort.*

Fuel and Lamps.— The most convenient combustible is ordinary illuminating-gas burned in a Bunsen burner, Fig.T

Fig. 4. The gas issues from a small orifice near the lower end of the tube, and mixes with a large proportion of air which enters through holes at h. Usually the lamp is provided with a ring at k, fitting loosely over d, and by turning this the supply of air can be varied. The mixture of gas and air should be so regulated that the burner gives a non-luminous, blue flame, with a distinctly outlined inner cone about 5 cm. high. For use with the blowpipe, an additional

Fig. 4

Various mechanical contrivances have been devised where the air is supplied from bellows, but they are regarded as unnecessary. The strength of the blast needs to be often varied in order to bring about different effects, and with the breath this can be most readily accomplished. Only students showing enterprise and patience sufficient to master the use of ordinary instruments will be likely to make muoh progress in blowpipe analysis.

Apparatus.

tube, e, is supplied, which fits loosely inside of and goes down below the holes at A, thus cutting off the supply of air, and causing the gas to burn with a luminous flame. The tube is flat- tened at the top, and one side is made a little lower than the other, so that the blowpipe flame can be directed downward when necessary. A slightly raised notch at the upper side serves as a rest for the blowpipe tip.

A burner like the one shown in Fig. 5 is con- venient, but as it gives only a luminous flame it is not suitable for heating glass tubes, etc., and an additional Bunsen burner is necessary.

When gas is not at hand, olive- or rape-oil, burned in a lamp with a rectangular wick, 5 X 10 mm. in diameter, may be used. Fig. 6 represents the form of lamp proposed by Berzelius and G' R improved by Plattner. The openings for the

wick and for the admission of oil are provided with close-fitting screw-caps, and the apparatus q

can be taken apart and packed in small space for transportation.

Fig. 7 represents a lamp made by the Buffalo Dental Manur facturing Co., which gives satis- factory results.

A form of lamp adapted for portable blowpipe apparatus is represented in Fig. 8. Paraffin is used as fuel, and must be melted before lighting, but, when once ignited, the heat from the flame will keep a sufficient quantity of the paraffin in a liquid condition. Fig. 6.

When more convenient material is not at hand, candles of good quality will answer for most purposes. A large candle with a flat wick can be easily made, and is some improvement on the ordinary

Apparatus.

form. For heating glass tubes, boiling liquids in test-tubes, etc., it is desirable to have a dame which does not deposit soot, and if

Fio. 7. Fig. 8.

a Bunsen burner cannot be used, an alcohol lamp, Fig. 9, with a circular wick 10 to 15 mm. in diameter, ia needed. Such a lamp, however, is not adapted for use with the blowpipe, as the flame is not rich enough in carbon to give suitable re- duction effects.

Platinum-pointed Forceps. — These are in- dispensable for holding fragments of minerals which are to be heated before the blowpipe. Fig. 10 represents the usual form. They are p,,, e

made of steel, and should be nickel-plated. The platinum points are opened by pressure, and are rendered self-closing by means of a spring, which should not be too strong. The platinum needs occasional cleaning, which is best done by scouring with sea-sand.

Fig. 10. The steel ends are useful for picking up and handling fragments of minerals and for detaching pieces from specimens. The only precaution that is needed in the use of the forceps is never to allow minerals with metallic luster to fuse against the red-hot platinum, since the latter may form a fusible alloy with lead, arsenic,

16 Apparatus.

antimony, or other readily reducible elements. If the platinum 'does become alloyed, it is best to cut off the ends of the forceps, and reshape them with a file.

Platinum Wire. — This is used for supporting beads of fused borax, salt of phosphorus, or other fluxes, and for introducing powders into the flame. A kind about 0.4 mm. in diameter (weighing 0.247 grs. for every 10 cm.) is best.

Loops. — For the support of fluxes, loops, Fig, 11, are used, which are made by bending the platinum wire over a p conical point. As a rule, these loops should be from 3 to 4 mm. in diameter. The beads may generally be removed by straightening out the wire, or sometimes by dissolving them in acid.

The double loop is made by grasping the wire in the

I*IG' llm steel end of the platinum-pointed forceps, and making a

double turn about the latter. It is only recommended to serve as

an additional support when a considerable quantity of material is

to be fused with some flux.

Holders. — A contrivance like Fig. 12 is convenient for holding FlG* 12-

platinum wire. Short pieces of wire may also be fused into the end of a glass tube or rod.

Platinum Spoons.— These may be usefully employed in a few operations where fusions are to be made. Preferably the spoon, Fig. 13, should have a bowl 18 to 20 mm. in diameter, and need not weigh over 1.25 grams. It Fig. 13. js keld in the platinum forceps, and the fusions may be soaked out by digestion in a test-tube imi with water or acids. Spoons with long han- dies, Fig. 14, are often recommended, but FlG- 14-

they are necessarily heavier, and are not very serviceable if the bowls are small.

Charcoal.— This is used in many operations as a support for the assay, and, moreover, the carbon often assists in bringing about reductions. For most purposes, any piece of well-burned

Apparatus. 17

charcoal that does not snap nor become fissured in the flame will suffice. The kinds made from basswood, pine, or willow are recommended. It is a good plan to have the material sawed out into rectangular blocks of about 10 X 3 X 2 cm. Excellent charcoal, prepared especially for blowpipe work, can be procured from dealers.

Usually the assay is best heated on a smooth, flat surface, although occasionally a slight depression or cavity, which may be cut with a penknife, is needed.

A good piece of charcoal will last for some time, a clean sur- face being afforded by filing or cutting away the part that has been used.

For the uses of charcoal, see p. 39.

Gypsum Tablets. — These are prepared by making plaster of Paris into a thin paste with water, pouring this upon a sheet of glass, and spreading it out evenly until it is about 3 or 4 mm. thick. Before the plaster sets, its surface is ruled off by means of a knife into rectangular blocks about 4X8 cm. across, which are removed after the plaster hardens.

These tablets are admirably adapted for collecting sublimates, especially colored ones, and, as recommended by Haanel,* are used as follows:

The finely powdered material to be tested is placed near one end of the tablet, moistened with a few drops of hydriodic acid, and heated at the tip of a small oxidizing flame. The iodides, as they volatilize, condense on the white gypsum as coatings, some of which are very beautiful. White coatings may be collected on tablets which have been previously blackened by holding them over a sooty flame. As a substitute for hydriodic acid, Wheeler and Lnedekingf have found that ordinary tincture of iodine answers in most cases, and an iodide of sulphur, prepared by fusing 4 parts by weight of iodine and 6 of sulphur, is of still more general application. Moses X suggests using a flux prepared by mixing 2 parts of sulphur, 1 of potassium iodide, and 1 of potassium bisulphate.

Glass Tubing. — A supply of hard glass tnbing, varying from 3 to 6 mm. in internal diameter, is needed for making closed and open tubes.

Trans. Roy. Soc. Canada, Section III, p. 65, 1883.

t Trans. St. Louis Acad, of Sci., vol. iv, p. 676. 1886.

J School of Mines Quarterly, New York, vol. x, p. 320. 1889.

18 Apparatus.

Closed Tubes. — These are tubes closed at one end, Fig. 15,

and should be about 8 cm. long, and 3 to 4 mm. in inter- F|G- 15- nal diameter. They may read-

ily be made by heating a tube of twice the required length, at the middle, in a Bunsen-burner flame, and turning it slowly so that the glass will be uniformly heated. When the glass becomes quite soft, the tube is removed from the flame and pulled in two. The slender terminations are then removed by holding the end of the tube nearly through the flame, allowing the glass, where it has been pulled out and is quite thin, to fuse together, and then pull- ing away the termination.

These tubes are used for heating substances out of contact with, or with but limited access of, air. Substances are best intro- duced in the form of fragments, which drop to the bottom of the tube, leaving the walls perfectly clean.

The principal effects that may be observed, when substances are heated in closed tubes, are the distillation or giving off of volatile products (gases, liquids, or solids), which collect in the upper, cold part of the tube ; but any change which the material undergoes should be carefully noted.

For a list of the closed-tube reactions, see Chapter IV, p. 139.

Bulb Tubes. — Tubes with a bulb at one end, Pig. 16, are employed in a number of operations. They may be made by heating the end of a tube like that shown

in Fig. 15 over a blast-lamp until the glass becomes quite soft, and then blowing a bulb of the desired size. With a Bunsen- burner or alcohol flame, sufficient heat cannot be obtained to make these tubes from hard glass, but if one is not able to blow them, they can be procured from dealers. A good size for the bulb is from 12 to 18 mm. in diameter.

Open Tubes. — These are tubes, open at both ends, which are employed in heating or roasting substances in a current of air;

Apparatus. 19

and thus bringing about oxidation. The tubes should be from 5 to 7 mm. in internal diameter and 15 to 17 cm. long. The sub-' stance (best in the form of tine powder, so as to expose a maximum surface to the air) is placed about 4 cm. from one end. This may be readily accomplished by putting the powder upon a slip of paper, folded into a V-shaped trough, slipping this to the desired distance into the tube, and inverting. The tube, held in a slanting position (from 20° to 30°), with the powder in the lower end, is i?- then heated for some time, first just

above the substance to insure a draft of air, and finally directly under it. Straight tubes can be used for almost all experiments, but sometimes the powder has a tendency to fall out, and then a bent tube, Fig. 17, may be used. The powder is placed near the bend, and the flame applied somewhat above it so as to insure a draft of air.

For a list of the open-tube reactions, see Chapter IV, p. 141. Diamond Mortar. — The most convenient form is shown in Fig. 18. It is made from the very best tool-steel, and is almost

indispensable for pulverizing minerals. A small fragment, not over 6 mm. in diameter, is placed in the cavity; the pestle is then

Appabatu8.

inserted, and struck several sharp blows with a hammer. If the pestle, which should not fit too closely, is twisted so as to give a sort of milling motion, a very fine powder can be obtained. The mortar can be readily cleaned by grinding up bits of glass and wiping the cavity and pestle with a dry cloth.

Mortars made in three parts, Fig. 19, which are frequently recommended and kept in stock by dealers, are not as serviceable as the kind described in the foregoing paragraph.

Agate Mortar and Pestle.— These, Fig. 20, are used for reduc- ing minerals to a very fine powder. The mortar should be from 5 to 8 cm. in diameter. The mortar and pestle are used for grinding, neier for pounding hard bodies.

Fin 20

If a diamond or agate mortar is not at hand, mineral fragments may be pulverized by wrapping in several folds of thick paper, and hammering on an anvil. A cheap porcelain mortar will also serve for grinding all but very hard minerals.

Hammer. — A small, artisan's hammer will answer most pur- poses.

Anvil. — A small block of hardened steel, or any convenient flat steel surface (as the base of a diamond mortar) is suitable.

Pliers.— Cutting-pliers are very serviceable for detaching and breaking up small fragments of minerals. Those shaped like Fig. 21 are made especially for this purpose, but ordinary pliers, such as are used for cutting wire, are an excellent substitute.

File. — A small three-cornered file is used for cutting glass tubes. A notch is cut in one side of the tube, which is then half pulled, half broken in two.

Magnet. — A common horseshoe magnet, or a magnetized knife-blade, serves to recognize mag- netic bodies. A magnetic needle is sometimes useful for delicate determinations.

Lens. — A good magnif ying-glass will be found very useful.

Fig. 31.

Apparatus. 21

An achromatic triplet, of about 1 inch focal length, is best, but is expensive, and a cheaper form of lens will answer.

Watch-glasses — A number of these, from 3 to 4 cm. in diam- eter, will be found convenient for holding mineral fragments and powders. Small butter-plates or white porcelain India-ink slabs with three or I more depressions Berve the same purpose.

Metal Scoop.— This, Fig. 22, is well Fig. 82.

adapted for handling powders, and especially for transferring them to tubes.

Ivory Spoon and Spatula. — An ivory spoon, Pig. 23, with a bowl 5 X 10 mm. inner diameter, is useful for handling powders

thin and flat, serves as a spatula

Fig. 28. for handling and mixing reagents.

A knife-blade also makes an excellent spatula.

Test-tubes. — For making tests in the wet way, test-tubes are rery necessary. They should be from 15 to 20 mm. in diameter and about 16 cm. long. A large feather will be found very conven- ient for cleaning such tubes. A test-tube stand, Fig. 24, and some form of holder, for use when liquids are to be boiled, should be Fio. u.

obtained. One like Fig. 25 can Lie cut from a piece of pine.

Beakers and Flasks. — A few of these, of various sizes, will prove of much service. The largest ones need not have a capacity of over 150 cc.

Funnel and Filter-paper.— A glass funnel about 5 cm. in

22 Apparatus.

diameter and a supply of filter-papers are needed. It will be well to buy cut papers, 7 and 9 cm. in diameter, from dealers.

Filtering and Washing. — To make a filtration, a piece of paper is folded twice upon itself, thus forming a quadrant, and this is opened so as to form a conical cap, having three thick- nesses of paper on one side and one on the other. It is snugly inserted into a dry funnel, and moistened with water. The material to be filtered is then poured upon the paper, care being taken not to have it go above the top. When the liquid has all rnn out, water is added till even with the top of the paper, or dropped aroand the edge so as to moisten every part. By repeating this several times, the soluble materials are wholly

washed away from the insoluble

portions.

Porcelain Dishes.— Those with

handles, called casseroles, Fig._ 26,

are most convenient for boiling Fig. 36. liquids and making evaporations.

From 7 to 9 cm. in diameter is a good size.

Porcelain Crucibles. — These should be about 3 cm. in diameter, and are useful in a number of ways, especially for obtaining a small quantity of a precipitate "which has been collected upon a

Pig. 27. Pia. 28.

filter-paper and needs to be subsequently examined. For this purpose the paper is put into the crucible, and the latter, sup- ported on a triangle made of iron wire, Fig. 27, is heated over a

Apparatus.

lamp until the carbon of the paper has completely burned away, leaving the precipitate together with the trifling ash of the paper. Lamp-stand. — This may be purchased from dealers, or one like Fig. 27 may be easily made. By slightly bending the coil of wire which goes about the upright, the proper degree of tension may be obtained, so that the ring will move readily up and down, and yet stay fixed in any position.

Wash-bottle. — This, Fig. 28, can be made from a flask, or from any bottle having a neck wide enough to receive a doubly perforated stopper.

Dropping-bottles and bulbs. — A form like that shown in Fig. 29, about 35 mm. in diameter, is convenient for water, when only a small quantity is needed. If less than two thirds full, by closing the larger opening and inverting, the heat of the hand will expand the air and drive out the water drop by drop. Fig. 30 represents a form with a bulb 30 mm. in Fig. 29.

diameter, and is convenient for holding reagents which are to be used a drop at a time. In order to fill it, the bulb is warmed and the end dipped under the surface of the liquid, when, on cooling, a few drops of the latter will enter. This is then boiled to expel the air, and the tip again Fro. 30. brought quickly under the liquid, when the condensation of the steam will cause the liquid almost immediately to rush in. The bulb should not be more than two thirds full. A convenient form of dropping- Fie. 81. bottle with hollow stopper is shown in Fig. 31.

Pipette. — A glass tube of 5 mm. inner diameter, heated over

a lamp and drawn out to a capil- lary, Fig. 32, will serve as a Fl°- w- pipette, and will be found useful

for taking up small quantities of liquids and introducing them into tubes.

24 reagents.

. - . Part 2. Reagents,

Reagents are substances employed to produce changes in bodies, in order to test their composition. They are known as dry, gaseous, or wet, according as they are used in the solid, gaseous, or liquid form. Most of them can be obtained, suffi ciently pure, at drug stores or from dealers in chemicals. The solids and liquids should be carefully labeUed and kept in suitable, well-stoppered bottles. For greater convenience, however, it is well to have on hand a supply of some of the more common dry reagents in wooden or glass pill-boxes about 4 cm. in diameter.

Dry Reagents.

Sodium Carbonate, Na,COt. — Dry sodium carbonate may be purchased, or it may be made by heating the commercial bicar- bonate in a porcelain dish until it becomes anhydrous. Sodium carbonate is used for decomposing many substances, and owes its action to the tendency of sodium to unite with non-metallic or acid-forming elements. Thus, ZnS + NatCOt Na,S + ZnO -f- CO,. Fusions with sodium carbonate are frequently made in a loop on platinum wire, and in order to obtain a bead, it is recommended to make the material into a thick paste with water, to take this up in the loop, Fig. 11, and to fuse in an oxidizing flame. The bead should be clear when hot, but white and opaque when cold. If heated in the reducing flame, it will be brown, owing to the presence of carbon.

For a list of some of the reactions *with sodium carbonate, see Chapter IV, pp. 145 and 151.

Borax, or Sodium Tetraborate, JN*a,B4O7,10H,O.— The crys- tallized commercial salt is usually sufficiently pure, and is broken into coarse powder for use. Borax is generally fused into a bead on platinum wire, and to make this, the platinum loop, Fig. 11, is heated and touched to the salt, and the adhering material fused before the blowpipe until a clear glass is obtained. The bead should be lenticular in shape, and clear and colorless. To

Reagent8.

introduce the material to be tested into the bead, touch the latter when hot to a small particle of the substance, or to a little of the powder, and heat before the blowpipe. Borax dissolves various substances, especially the oxides of the metals, and with many of them gives characteristic colors.

For a list of the tests, see Chapter IV, p. 148.

Borax-glass.— This is needed for only a few experiments. A little at a time may be made by fusing borax in a rather large loop on platinum wire, and crushing the glass in a diamond mortar. It may also be purchased.

Phosphorous Salt, or Hydrogen Sodium Ammonium Phos- phate, HNaNH4P04.4H,0 ; sometimes called Microcosmic Salt— This is generally fused into a bead on platinum wire. The bead is made in the same way as the borax one, but the material becomes very liquid, and is apt to drop from the loop when first heated. This may be avoided, however, by heating gently at first, and holding the bead just above the flame, so that the escaping steam and the force of the blast may buoy up the liquid. The salt is changed by fusion to Sodium Metaphosphate, NaPO,. The reactions with sodium metaphosphate beads are mostly similar to those with borax, and a tabulated list of them will be found in Chapter IV, p. 149.

Test-papers. — Blue litmus- and yellow turmeric-paper may be purchased from the dealers. The former is turned red by acids, and the latter reddish-brown by alkalies. The turmeric-paper also serves for the recognition of boracic acid and zirconium. For use, these papers are conveniently cut into narrow strips.

Potassium Bisulphate, HKS04, and Potassium Pyrosulphate, K,StOt ; sometimes called Add Sulphate of Potash. — This can be made by heating crystallized potassium sulphate with half its weight of concentrated sulphuric acid (10 grams K,S04 and 3 cc. H,S04) in a porcelain dish until vigorous frothing ceases. The fusion solidifies to an opaque mass, which should be pulverized and preserved in a well-stoppered bottle. Heating changes HKS04 into pyrosulphate, K.8,0,, and finally to normal sulphate,

26 Bkageht8.

K,SO#. A variety of minerals are decomposed by fusion with potassium bisulphate, and such fusions may be made either in the platinum spoon, porcelain crucible, or often even in a test- tube.

Potassium Bisulphate and Fluorite. — The finely pulverized materials, mixed in the proportion of 3 parts of the former to 1 of the latter, are useful for detecting boron in some of its combina- tions, and it is well to have a small supply of the mixture on hand. The mixture when heated liberates hydrofluoric acid.

2HKS04 + CaF, K.SO, + CaS04 + 2HP.

Potassium Iodide and Sulphur. — The pulverized materials, mixed in equal proportions, are used for detecting bismuth and lead.

Oxide of Copper, CuO. — This is useful for detecting chlorine. A little of the oxide may be purchased, or made by dissolving copper in nitric acid, evaporating the solution to dryness, and igniting to redness in a porcelain dish. A little powdered cuprite or malachite will answer equally well.

Potassium Nitrate, KNO,. — This is used occasionally for fusing with minerals when an oxidation is required.

Bone-ash — This is needed for the silver assay. It will be best to purchase a small supply from a dealer.

Granulated Tin, Zinc, and Lead. — These may be purchased from the dealers. The first two are used, generally with acids, in making reductions, as they dissolve in acids with - evolution of hydrogen, and change many combinations from a higher to a lower valence. Thus, SFeCl, + Zn 2PeCl1 + ZnCl,, or possibly FeCl, + H FeCl, + HC1. Lead is used for the silver assay, and should be free from silver. This is commonly called test- lead.

Magnesium. — This may be useful for detecting phosphoric acid. It is best to have the magnesium ribbon.

Gaseous Reageht8.

Hydrogen Sulphide, H,S. — When a little of this reagent is needed it may be generated in the simple appa- ratus shown in Fig. 33. The bottle contains frag- ments of ferrous sulphide, FeS, and concentrated hydrochloric acid diluted with an equal volume of water is poured in through the thistle-tube, so as to give as nearly constant a flow of gas as pos- sible. FeS + 2HC1 H,S + FeCI,. By means of a glass tube and a rubber connection, the gas may be led into any liquid in order to bring about a precipitation.

Chlorine, CI. — This reagent is seldom needed, but a little of it may be prepared by warming powdered pyrolusite, MnO,, with concentrated hydrochloric acid (p. 101), and carrying oft the Flo. 88. chlorine by means of a bent glass tube running through a per- forated cork. Chlorine-water, or water saturated with chlorine gas, is sometimes used.

Wet Reagents.

Wet reagents, especially acids, should be kept in bottles with ground-glass stoppers, and should be handled carefully. Acids when boiled give off disagreeable and corrosive fumes, and it is quite essential that these should be carried off by a good draft, which may be accomplished by arranging a hood or small chamber connecting with a chimney-flue. If acids are spilled upon fabrics, the spots should be immediately moistened with ammonia to neutralize the acid, and then thoroughly washed with water.

Water. — Distilled water is best, but clean rain-water may be substituted. It is convenient to keep a supply of water iu a wash- bottle, Fig. 28.

Hydrochloric Acid, HC1.— This reagent is a solution of HCI gas in water. The pure concentrated acid of the dealers contains

28 Beagents.

about 40$ HC1, and for most operations it is best to use the acid diluted with an equal volume of water.

Nitric Acid, HNQ,. — This is useful for dissolving many min- erals, and in the concentrated form it is a strong oxidizing agent. The acid is exceedingly corrosive and needs to be handled very carefully.

Nitrohydrochloric Acid, or Aqua Regia. — This is prepared by mixing 1 part of nitric acid and 3 of hydrochloric. It is a power- ful solvent and oxidizing agent.

Sulphuric Acid, HaS04, or Oil of Vitriol. — This needs to be handled with much care. When added u water, a great deal of heat is generated, and when hot (boiling-point 338° C), water should never be added to it. For many tests it is well to employ a dilute acid, made by adding 1 volume of acid to 4 of water.

Hydriodic Acid, HI. — This is needed for only a few tests, and does not keep well, as it decomposes, with separation of free iodine. It may be prepared by suspending iodine in water, pass- ing hydrogen sulphide gas into the liquid until the solution becomes colorless, and then decanting from the separated sulphur. It is convenient to keep a supply of this in a dropping-bottle, Pig. 31.

Hydrochlorplatinic Acid, H,PtCl6; often called Platinic Chlo- ride.—This is useful for detecting potassium in presence of lithium and sodium. Its preparation is explained under platinum (Chapter III, p. 103).

Ammonium Hydroxide, NH4OH; commonly called Ammonia. — This reagent is a solution of ammonia-gas, NH, , in water. It is a strong alkali, and should not be added to acids unless the latter are cold and dilute.

Potassium Hydroxide, KOC— This is another strong alkali. Its solution does not keep well in glass, and it will be found more convenient to have the stick potash broken up and preserved in a well-stoppered bottle

Barium Hydroxide, BaOaH,. — A solution of this may be pre- pared by dissolving the crystallized salt in 30 parts of warm water,

Keagents. 29

cooling and filtering off the insoluble material, ivhich consists mostly of barium carbonate. Calcium hydroxide, lime-water, CaOJI,, may be substituted, and is prepared by shaking up a small quantity of quicklime with water, allowing this to stand for some hours, and then decanting off the clear liquid.

Ammonium Sulphide, (NH4),S. — This may be prepared by saturating a little ammonia with hydrogen sulphide, and then adding two thirds the volume of the same ammonia. On long standing it turns yellow, and then contains an excess of sulphur.

Ammonium Molybdate, (NH4),Mo04. — This is almost indis- pensable for the detection of phosphates. It may be prepared by dissolving molybdic oxide, MoO, , in ammonia, and pouring the solution into dilute nitric acid, being careful to have an excess of the latter. The solution is allowed to stand, and anything that may separate out is filtered off.

Cobalt Nitrate, Co(NOs),. — The crystallized salt is dissolved in 10 parts of water, and the solution kept most conveniently in a dropping-bulb, Fig. 30. It is used for moistening infusible substances, especially those containing aluminium and inc, which are afterwards intensely ignited before the blowpipe, and assume characteristic colors. Cobalt nitrate when ignited is decomposed, yielding a deposit of cobalt oxide upon the assay, (Cd(NO,), CoO + 2NO, + O), and this oxide unites with it, giving colored compounds of unknown composition. The reagent may be applied to a fragment of mineral held in the platinum forceps, but the reaction usually succeeds better if the finely powdered mineral is made into a thin paste with the cobalt nitrate solution, and a little of this, placed upon charcoal, is intensely ignited before the blowpipe. This latter method is especially recommended for hard and compact minerals.

Aqueous solutions of the following salts may be kept in glass- stoppered bottles, or, if they are te be used only occasionally, it is recommended to keep a supply of the pulverized dry salts on hand, and to dissolve a small quantity in a test-tube when needed.

Ammonium Carbonate, (NH4),CO,. — The commercial, dry salt

30 Reagents.

is a mixture of ammonium bicarbonate, HNH4COt , and ammonium carbamate, NH,NH CO,. Its solution in water, however, may be regarded as containing normal ammonium carbonate, (NH4),COs.

Ammonium Oxalate, (NH4)tC,04.2HtO.

Di-Sodium Hydrogen Phosphate, NatHP04.12HtO ; commonly called Sodium Phosphate.

Barium Chloride, BaCl,.2H,0.

Silver Nitrate, AgNO,.

Potassium Ferrocyanide, K4Fe(CN)..3H,0.

Potassium Ferricyanide, K,Fe,(CN)lt. — An aqueous solution of this salt does not keep well.

Ammonium Sulphocyanate, NH4CNS.

The list of reagents, both wet and dry, might be considerably enlarged, but the principal ones have been given, and those not in the list which are mentioned in subsequent chapters can be easily procured. Any reagents used in a well-equipped chemical labo* ratory may at times be found convenient.

Solution. — Of the foregoing reagents, water and the acids are commonly employed for dissolving substances. The appropriate solvent for a mineral can be learned only by experience or by a knowledge of the chemical composition of the material. As most minerals are insoluble in water, its use as a solvent is limited. Hydrochloric acid is most generally employed, and is preferred to other strong acids, as it is safer to handle. Nitric acid is needed when an oxidation is required, as when sulphides or arsenides are to be dissolved. It is seldom necessary to use sulphuric acid.

In order to dissolve a mineral it is best to treat some of the very finely powdered Tnaterial in a test-tube with from 5 to 10 cc. of the solvent (it may be necessary to try several solvents before the appropriate one is found), and, if the material does not dissolve in the cold liquid, the contents of the tube should be heated to boiling, which, in tjie majority of cases, greatly facili- tates solution.

Precipitation. — When insoluble compounds are formed by adding reagents to solutions, the process is called precipitation.

Nature Of Flames. 31

When solutions are mixed, precipitation will take place, provided an insoluble compound can be formed by the interchange of the chemical constituents. For example, when aqueous solutions of sodium chloride and silver nitrate are mixed, a white precipitate of silver chloride will be formed, because silver chloride is insol- uble in water. NaCl + AgNO, AgCl + NaNOt . Precipitation furnishes a means for detecting many elements, and it is also useful for separating substances, since the insoluble precipitates may be collected on filter-papers and thus removed from solutions.

Part 3. On the Nature and Uses of Flames.

Combustion. — This is ordinarily an oxidation process, and where a flame is produced, the latter results from the combination of carbon and hydrogen of different gases and vapors with the oxygen of the air, the final products of the oxidation being carbon dioxide, CO, , and water, H,0.

When a lamp or candle is burning, the oil or the melted material of the candle is carried up into the wick by capillary attraction, and is there converted by the heat of the flame into gas or vapor, which burns. Such gases, as well as ordinary illuminating-gas, are not definite chemical compounds, but mixtures, usually of different combinations of carbon and hydro- gen, and are known as hydrocarbons. Water-gas, with which many cities are now supplied, is made by blowing steam through glowing coals, when the following reaction takes place : H,0 +C 2H + CO. The resulting gas (a mixture of hydrogen and carbon monoxide), which burns with a non-luminous flame, has to be mixed with some volatile material rich in carbon, in order to make it luminous.

The Candle Flame. — This, Pig. 34, has been chosen as repre- senting a typical luminous flame, and may be regarded as containing three distinct parts, as follows :

(1) An outer part, a, where the gases are fully exposed to the oxygen of the air, and where the combustion is com-

82 Natuke Of Flames.

plete ; that is, where carbon is burned to CO, , and hydrogen to H.O. These gases form an invisible envelope about all /o\ ordinary flames.

(2) An inner zone, b, the luminous part of the Jlame, is characterized by an incomplete combustion, since only a limited supply of oxygen, which pene- trates the outer envelope, is available. Hence, carbon burns to its lower oxide, carbon monoxide, CO, while hydrogen forms H,0. Moreover, the heat of the flame decomposes some of the gas, with separation oifinely divided carbon. This being heated to incandescence Fio. m. renders the flame luminous, and will deposit as soot upon any cold substance held in the flame.

(3) Still further within the flame is the zone c, which contains the unhurried gases as they are first formed by the heat and rise up from "the wick.

The three zones, a, b, and c, naturally grade into one another, and are not separated by sharply defined boundaries.

The Bunsen-burner Flame.— This, Pig. 35, has three zones corresponding to a, b, and c, of the candle flame, except that sufficient air is allowed to mix with the gas to prevent the separation of carbon in 6. The flame, therefore, is non-luminous and depos- its no soot. The outer envelope, a, contain- ing CO, and H,0, is invisible; the zone b, containing CO, some CO., and H,0, is pale violet; and the inner zone, c, containing a mixture of unburned gas and air, is sharply outlined against ft by a pale blue border.

Special precautions should be taken that the flame does not snap down and burn at the base.

Uses Of Flakes. 33

The Blowpipe Flame — This is produced by placing the tip of the blowpipe into the gas or lamp flame, and blowing a mod- erately strong blast of air. If a gas flame is nsed, it should burn from the jet e, Fig. 4, p. 13, and should be from 3 to 4 cm.

The operator should be com- 0 fortably seated at the table, his arm resting upon its edge,

and the blowpipe grasped near FlQ- m-

the water-chamber, between the thumb and first and second fingers of the right hand. The blast should be so regulated that the flame will be deflected into a slightly tapering, dis- tinctly outlined, blue cone, Fig. 36, in which the zones a, b, and c, correspond exactly to those of the Bunsen-burner flame. The flame should not appear luminous, except, perhaps, a small portion just above the blowpipe tip, which is not carried along by the draft. If the hole in the tip is well bored, the flame will neither flutter nor show irregularities, even when the blast is strongest.

Heating and Fusion. — The hottest part of the blowpipe flame is at r, Fig. 36, just beyond the tip of the inner blue cone. At this point, minerals are heated to determine their fusibility or other phenomena which they may exhibit. Even platinum can be readily melted if in the form of fine wire (not over 0.2 mm. in diameter), so as not to radiate nor conduct away the heat too rapidly.

In testing minerals, the size and shape of the fragment to be used is a matter of considerable importance. If too large, it is difficult, often impossible, to heat it up to the desired tempera* tare, while, if too small, the reaction may not show with sufficient distinctness. Beginners almost invariably err in taking too large pieces. Usually the reaction succeeds best either with a splinter or a fragment with a thin edge, and a size about as large as a lead- pencil point (1 mm. in diameter and 4 mm. long) can be recom- mended. The fragment should be held in the forceps in such a

34 Uses Op Flames.

manner that the greater part of it projects free beyond the plati- num tips in order that heat may not be wasted in warming up the metal, and so that a point or edge of the mineral is turned in the ion of the name, Fig. 37. Any change i the mineral undergoes may be a help i identification, and should be care- noted ; e.g., whether fusible or infu- sible, and in the former ease the degree of fusibility and the manner in which the mineral fuses, whether quietly or with intumescence (swelling); whether to a clear, white, or vesicular (full of bubbles) glass; whether to a light- or dark-colored mass or slag, or to a magnetic or non-magnetic mass.

Decrepitation. — It frequently happens that a mineral, when introduced into the blowpipe flame, snaps or explodes, so that it is difficult and often impossible to secure a piece which can be held in the forceps and heated. This phenomenon, known as decrepitation, may be due to unequal expansion of the material. More often, however, it results from the presence in the mineral of minute cavities containing gases or liquids (commonly water, sometimes liquid carbon dioxide), the expansion of which causes the explosion.

At times a fragment of a decrepitating mineral may be heated in the forceps, if at first very carefully introdnced into the ordinary gas or lamp flame, so that it becomes slowly and uniformly heated before being subjected to the more intense heat of the blowpipe flame. Another wav is to heat sev- eral large pieces in a closed tube until decrepitation ceases, when, on - ing out the fragments, one may be selected of the right size and shape to he taken in the forceps and heated before the blowpipe. When the above methods fail, the following, suggested by Berzelius, may be resorted to: Grind the mineral to a very fine powder, make into a thin paste with water, then spread ont a drop of this upon a clean charcoal surface, and hent before the blowpipe, at first very gently, finally as intensely as possible. If fusion has not already been observed, a coherent cake will usually be obtained, which with care can be lifted in the forceps, and its edge intro- duced into the blowpipe flame.

Uses Of Flames. 35

Flame Coloration. — The heat of the blowpipe flame is so intense that many substances are volatilized, and several of the ele- ments in them may then be recognized by the colors they impart to the flame (compare table, Chapter IV, p. 136). The test may be made with a fragment held in the clean platinum forceps, as shown in Fig. 37, but usually it succeeds better when a minute quantity of the finely powdered material is taken upon a clean platinum wire and introduced into the Bunsen-burner or blowpipe flame. For the latter purpose, a wire may be cleaned by heating until it imparts no coloration to the flame, or, if there is much material adhering to it, it may be boiled in any strong acid, then washed with water and heated (compare Sodium, p.ll$ §1,6). The straight wire is next moistened with pure water, and its end touched to the powdered mineral so as to take up a minute quantity of the materia, which is then introduced into the flame. Often the merest trace that will adhere to a dry wire is sufficient to give a magnificent flame color. The tests are, as a rule, exceedingly delicate, and the essential condition to be fulfilled is that the material shall be heated hot enough to volatilize the element or compound which gives the color. Often a sufficient temperature cannot be obtained when a rather large fragment held in the forceps, or considerable material supported in a loop on plati- num wire, is heated before the blowpipe.

The colors are best seen in a dark room, but as this is usually not convenient a dark screen (book-cover) as a background will be found advantageous.

Oxidation. — By oxidation is meant the union of a substance with oxygen (compare Combustion, p. 31). Many substances -when heated before the blowpipe readily take on oxygen from the air and are oxidized. The flame then imparts nothing to them, but simply brings about conditions favorable for the taking up of oxygen. For example, pieces of wood or a copper wire under ordinary conditions may be kept almost indefinitely, but if they are intensely heated, with access of air, the former burns, or

36 Uses Of Flames.

oxidizes, and the latter is gradually converted into copper oxide, CuO.

Oxidizing Flame. — The flame represented in Pig. 36 is usually called the oxidizing flame, and the part favorable for oxidation, is at o, beyond the blue and violet cones, c and b, and especially where the air can and the carbon monoxide in b cannot have access to the substance.

Reduction. — Usually by the term reduction is meant the taking away of oxygen. In a more general sense, it may refer to the formation of a metal from any of its compounds, or to the change of some element in chemical combination from a higher to a lower valence. Thus, the conversion of CuO or Cu,S to metallic copper, or of Fed, to Fed, (ferric to ferrous chloride), would be spoken of as reductions.

Reducing Flame. — By means of the blowpipe flame, reductions are made by taking away oxygen, and this is accomplished by heating substances so that they are exposed to the action of car- bon monoTide. Carbon monoxide, CO, is a reducing gas, since it has a tendency to take on oxygen and become carbon dioxide,

Fig. 38.

CO,. Many oxides, therefore, when heated with CO give np their oxygen, and are reduced either to a metal or to a lower oxide. The following equations will illustrate this: CuO + CO Cu+CO„ and Fe,0, + CO 2FeO + CO,. The part of the flame most favorable for reduction is at r, Fig. 36, where the heat is intense and carbon monoxide predominates. When a substance is large, it is fre- quently impossible to make a satisfactory reduction in a flame like that shown in Fig. 36, for, while a portion is exposed to the action of carbon monoxide in the zone b, another portion most

Uses Of Flames. 37

project into the air and will there have a tendency to oxidize. In such cases, a broader flame, Fig. 38, should be used. This is made by deflecting the gas or lamp flame by a gentle blast, and regulating the latter so that the flame is slightly luminous, but still does not deposit soot upon the assay held at r.

Reductions are frequently made on charcoal, and the reducing action of the carbon monoxide is then augmented by that of the glowing carbon.

The following experiments will serve to illustrate the use and application of the blowpipe :

a. To prove that water, H,0, and carbon dioxide, C0t, are products of combustion, take a dry bottle and for a few seconds deflect a small blow- pipe flame down into it, Fig. 39. The water which condenses on the sides of the glass has resulted from the oxidation of the hydrogen in the gas. That the bottle also contains GO, may be proved by adding a little deal* barium hydroxide water, inserting the stopper, and shaking, when a white precipitate forms, which is barium car- bonate, BaCO,. CO.+BaO.HBaCO.+HO.

b. To show the intense heat of the blowpipe flame, and to acquire skill in the manipulation of FlG- 8&-

the instrument and in maintaining a continuous blast, fuse platinum wire and fragments of minerals used in the scale of fusibility (p. 230). The platinum wire should not be over 0.2 mm. in diameter, and it is best to bend it near the end and hold it end on toward the flame (compare Fig. 37).

c. To show that the inner portion of a flame contains a zone of unburned gas, make use of a Bunsen-burner flame, Fig. 35, and hold a glass tube across it at r until it becomes quite soft; then remove from the flame, and draw out to a narrow tube. Next, hold the narrow tube across the flame at s, and observe that it softens in two places where it passes through the edges of the flame, but the portion within the cone c neither fuses nor becomes red-hot. By holding one end of a rather narrow glass tube in c, a little of the unburned gas may be drawn off to one side, and burned at the other end of the tube.

d. To make a flame test, take a fragment of barite, BaS04, in the forceps, and heat before the blowpipe, as shown in Fig. 37, until a distinct color is obtained. Barium imparts a yellowish-green coloration to the outer part of the flame. Barite also fuses at about 3 in the scale of fusibil- ity, and Is very apt to decrepitate. Also test the flame coloration by taking

38 Uses Of Flames.

np powdered barite on platinum wire, as directed on p. 35, and heating both in the blowpipe and the Bunsen-burner flames. In the latter case, introduce the material into the edge of the flame, at about r, Fig. 35.

e. To test the reducing character of the blowpipe flame, make some experiments with hematite, FetOt (a splintery variety is best), which should not be magnetic before heating, but becomes so upon reduction to a lower oxide, FeO. Taking a fresh fragment for each experiment, hold it in the forceps, and heat before the blowpipe for several seconds at the points o, r, and 8, Fig. 36, and, after cooling, test with a magnet. If the fragments become at all magnetic, it shows that the reducing gas, carbon monoxide, was present in that part of the flame where they were heated. Fe,0, -f- CO 2FeO + CO,. The reduction is strongest at r, the tip of the blue cone, where the heat is most intense, and diminishes toward o, but it is impossible to make a general statement of just where reduction ceases, as this depends both upon the size of the flame and strength of the blast.

j. To illustrate reduction and oxidation, select a small splinter of hema- tite, make sure that it is not magnetic, and then heat for an instant only in the reducing flame, so as to form FeO sufficient to make the fragment only slightly magnetic. It should then be heated for a considerable time at a point o, Fig. 36 (beyond the point where carbon monoxide exists), until the FeO has taken up oxygen from the air, and become oxidized to Fe,Os, when the fragment will cease to be magnetic. Considerable care and skill are necessary for performing this experiment successfully. If the fragment becomes very magnetic, it will be best to start with a fresh one, for the oxidation goes on slowly, and it will require a long time for its completion. Further, if FeO has been fused on the splinter, it will be almost impossible to complete the oxidation with the blowpipe, since, although the outer surface may be converted into Fe,Oa, the air will not be able to reach the interior and make the oxidation complete.

g. To further illustrate oxidation and reduction, make a borax bead on platinum wire, as directed on p. 24; touch the bead when hot to a very small particle of pyrolusite, MnO„ and dissolve the latter in the borax by heating at about the point o, Fig. 36. If the experiment is successful, the bead should have a fine reddish- violet color, while if it is black or very dark, too much pyrolusite was added, and a new bead should be made. The color is due to an oxide of manganese higher than MnO, and if the bead is heated in the reducing flame, MnO will be formed, and the bead will become color- less. In order to make a reduction of this kind, the following suggestion is offered : Heat the bead very hot at r, Fig. 36, where reduction goes on, and then, without interruption, change the position of the blowpipe and the character of the blast in order to make a more bulky flame, Fig. 38, so that the bead may be completely protected from the oxidizing action of the air. If the colorless bead is further heated, so that the air has access to it,

Uses Of Flames. 39

the reddish- violet color, characteristic for manganese, will again appear (compare p. 93, § 2). In making both oxidations and reductions, it is a great; advantage to be able to heat the substances very hot.

The Uses of Charcoal. — Both reductions and oxidations are made on charcoal. For the former, the best results are obtained by inclining the charcoal, and directing the flame downward, so as to strike the assay a little beyond the tip of the blue cone, as shown in Fig. 40. The combined effect of the flame and the burn-

ing charcoal gives an intense heat, and the reducing action may be made very strong. Further, many elements are volatilized, and, passing into the air, take on oxygen and deposit character- istic coatings of oxide on the coal.

For a list of the coatings and the effects of heating on char- coal, see Chapter IV, p. 143.

Roasting. — This is a term which is often applied to the heat- ing of substances in contact with air. It generally results in oxidation, and is most conveniently done on charcoal. In order to roast a substance, the finely powdered material is spread out on the surface of the charcoal so as to allow free access of air, and is then heated with a small oxidizing flame, Fig. 41, at a consider- able distance beyond the tip of the blue cone.

The heat required for roasting is very moderate — scarcely a red heat. If possible, the material should not be allowed to fuse, as it then does not expose sufficient snrface to the air. When very fusible minerals are to be roasted, it is often best to mix them with about an equal volume of powdered charcoal, which prevents

40 Oses Of Flamb8.

the material from running together, and subsequently burns away. Another way is to fuse and continue to heat the material until the more volatile constituents are driven out, and then to

pulverize with a little charcoal, and roast carefully by means of a small oxidizing flame.

Roasting is a very important metallurgical process, especially in treating ores containing sulphur, arsenic, or antimony, as these elements are removed as volatile oxides, leaving oxides of the metals which are subsequently reduced.

The following experiments will serve to illustrate some of the effects which may be produced by heating od charcoal:

a. To illustrate the formation of a metal, take a very little powdered malachite (Cu.01I),CO, , and three times as much of a mixture of equal parts of sodium carbonate and borax as a flux, moisten to a paste with water, then heat intensely, as shown in Fig. 40, until the copper fuses and collects to a globule.

To illustrate the formation of a metal and a coating of oxide, take a little powdered cerussite, PbCO, , an equal volume of powdered charcoal and 3 volumes of sodium carbonate, moisten to a paste with water, then heat for some time, as shown in Fig. 40, until the lead unites to a globule and a considerable coating of yellow lead oxide collects on the charcoal.

c. To illustrate oxidation or roasting, place some finely powdered pyrite, FeS, , on a flat charcoal surface, spread the material out into a thin layer, and heat very gently witli a small oxidizing flame, as shown in Fig. 41. The pyrite is thus oxidized, yielding sulphurous anhydride gas, SO,, detected by its odor, and a residue of Fe,0, , or a mixture of Fe,0, with FeO. If the roasting is continued until the material no longer emits an odor of burning sulphur, the oxidation will be complete, or nearly so, and the resi- due will have the dark red color of ferric oxide.

Chapter Iil

Reactions Of The Elements.

For convenience of reference, the subject matter of this chapter has been arranged alphabetically. In studying the reactions of the common elements, however, it may be recommended to take them up in the following order, which has been chosen partly according to Mendeleeff s periodic system of the elements, and partly to bring together some of the elements which exhibit simi- larities in their analytical reactions

1. Hydrogen, p. 81. 4. Potassium, p. 105. 7. Strontium, p. 116. 10. Zinc, p. ISO.

2. Lithium, 90. 5. Magnesium, 91. 8. Barium, 52. 11. Copper, 71. 3 Sodium, 115. 6. Calcium, 58. 9. Aluminium, 4$. 12. Silver, US.

In the descriptions of tests and experiments, sizes and distances will be riven in millimeters and centimeters ; quantities of powders and dry reagents in term* of the ivory spoon; and the volume of liquids in cubic centimeters.

Inch Scab.

Centimeter Scale.

J

e

15

Fie. 42.— Inch and centimeter scales, ivory spoon, and end of a test-tube with cublo

centimeters indicated upon it. All natural size.

42 REACTIONS OF THE ELEMENTS. Aluminium

13. Lead, p. 87. 18. Cobalt, p 71. 23. Chlorine, p. 67. 28. Bismuth, p. 54.

14. Mercury, 98. 19. Nickel, 96. 24. Boron, ' 56. 29. Carbon, 67.

15. Chromium, 69. 20. Oxygen, 100. 25. Phosphorus, 101. 80. Silicon, 107.

16. Manganese, 92. 21. Sulphur, 118. 26. Arsenic, 47. 31. Titanium, 127.

17. Iron, 88. 22. Fluorine, 75. 27. Antimony, 43. 82. Tin, 125.

Aluminium, Al. — Trivalent. Atomic weight, 27.

Occurrence. — Next to oxygen and silicon, aluminium is prob- ably the most abundant element in the crust of the earth (p. 3). It is a metallic element, occurring most frequently in the group of silicates, while it is also found in a number of oxides, fluorides, phosphates, and sulphates. Kaolinite, H4Al,SisOt ; cyanite, Al,SiO, ; orthoclase, KAlSi,0, ; almandine garnet, Fe,Al$(Si04), ; corundum, A1,0, ; and cryolite, Na, A1F, , may serve as examples of its compounds. Aluminium also plays the part of a weak acid, and by some authors, spinel, MgAla04 MgO.Al,Ot, and a few similar compounds are regarded as aluminates. Aluminium is a constituent of most rocks, almost the only exceptions being the carbonates, sandstones, and quartzites.

Detection. — Igniting with cobalt nitrate is the only satisfac- tory blowpipe test for aluminium. For a test in the wet way, precipitation with ammonia is recommended. 1. Test with Cobalt Nitrate. — Infusible minerals containing aluminium, if moistened with cobalt nitrate and intensely ignited before the blowpipe, assume a fine blue color. Cobalt nitrate on ignition yields cobalt oxide, CoO, which is black, and this oxide unites in some inexplicable way with the alumina to give the characteristic blue color. In applying the test to very hard min- erals it is best to powder them, then moisten with cobalt nitrate and heat either on charcoal or on a small loop on platinum wire. The test is restricted to compounds which are light colored, or become so on ignition, and is not characteristic if applied to fusible minerals, as cobalt oxide may impart a blue color to any fused material or flux. Zinc silicates also give a blue color, p. 183.

Apply this test to fragments of cyanite, AltSiOt , held in the forceps, and to finely powdered corundum, AlO,.

2. Precipitation with Ammonia. — Ammonia, when added in

Antimony REACTIONS OF THE ELEMENTS. 43

slight excess to an acid solution containing aluminium, precipi- tates gelatinous aluminium hydroxide, A1(0H);. A great many other substances yield, with ammonia, gelatinous precipitates resembling aluminium hydroxide, and therefore it is necessary to make the following additional tests: Collect the precipitate on a filter-paper, wash with water, transfer some of it to a test- tube, and add potassium hydroxide, when the precipitate, if it is aluminium hydroxide, will go easily and completely into solution. Burn the paper containing the precipitate in a porcelain crucible (Fig. 27, p. 2*2), and test the residue with cobalt nitrate.

Dissolve an ivory spoonful of alum, KAl(S04)8.12HaO, in a test-tube in 5 cc. of hot water, add 2 cc. of hydrochloric acid, and then ammonia in slight excess; that is, until a distinct odor of ammonia is perceptible after the contents of the tube have been thoroughly mixed. Filter off the pre- cipitate, and test as recommended above.

3. For detecting aluminium in insoluble silicates, where the above methods cannot be directly applied, see p. 110, § 4.

Ammonium, NH4. — Univalent. Molecular weight, 18.

Occurrence. —The radical ammonium, NH4 , plays the part of a metal, and in its chemical relations is very similar to potassium. Minerals containing ajnmonium are of rather rare occurrence, and are generally soluble in water. Sal ammoniac, NTT4C1, and struv- ite, NH4MgP04.6HtO, are examples of its compounds.

Detection. — Compounds containing ammonium, when boiled with a solution of potassium hydroxide, or heated in a closed tube with lime (ignited calcite), yield the strong and very characteristic odor of ammonia.

Antimony, Sb.— Trivalent and pentavalent. Atomic weight,

Occurrence. — Antimony is found chiefly in combination with sulphur, either as stibnite, Sb,S,, or as sulphantimonites, which are salts of sulpTiantimoniotbs acids, H,SbtS4, H4Sb,S,, H,SbtS6, H,SbtSt* etc. The composition of the sulphantimonites is fre- quently expressed as a combination of Sb,Sa with sulphides of

44 REACTIONS OF THE ELEMENTS. Antimony

the metals, examples being, — zinkenite, PbSb,S4 PbS.SbtS, ; jamesonite, PbtSb,S, 2PbS.Sb1S, ; pyrargyrite, Ag.SbS, 3AgaS.Sb,S, ; and tetrahedrite, Cu8SbtS7 4CufS.Sb,S,. (See also the sulpharsenites (p. 47), with which the snlphantimonites are frequently isomorphous.) Antimony also occurs native, rarely in combination with metals as antimonides, breithanptite, NiSb, and occasionally in different combinations with oxygen, senarmontite, SbtO, , and cervantite, Sb,04.

Detection. — Antimony may usually be detected by the coat- ing of oxide formed by roasting on charcoal or in the open tube. The closed-tube reaction is also recommended for sulphide of antimony. v 1. Roasting on Charcoal: Coating of Oxide. — Most anti- mony compounds, when heated on charcoal in the oxidizing flame, yield a dense white sublimate of oxide of antimony, which de- posits quite near the heated part (compare Arsenic), and appears bluish if the coating is thin, so that the black of the charcoal shows through it. The coating is due to volatilization of the antimony and its oxidation in passing into the air. It is quite volatile when heated before the blowpipe either in the oxidizing or reducing flames, and may be driven about and made to change its place on the charcoal. The fumes have no distinctive odor (difference from arsenic). In the absence of other elements which give coatings on charcoal, this test serves as a very simple and characteristic one for the detection of antimony. Where other elements (especially lead and bismuth) interfere, the open-tube reaction will give confirmatory and decisive results.

Some oxides of antimony are not volatile in the oxidizing flame, and when these are to be tested it is necessary to heat them in a reducing flame to convert the antimony to the metallic state, so that it will volatilize and give the coating of oxide described above.

Test the foregoing with stibnite, SbaSf. Place about ivory spoonful of it on a flat charcoal surface, and heat with a small oxidizing flame (p. 40, Fig. 41) until the material is completely volatilized. Note that the sublimate

Antimony REACTIONS OF THE ELEMENTS. 45

deposits close to the heated part '(difference from arsenic), and test its volatility in both the oxidizing and reducing flames. The odor which may be observed is due, not to the antimony, but to sulphur (p. 119, § 2).

2. Roasting in the Open Tube: Sublimate of Oxide. — When metallic antimony and its compounds with sulphur are heated in the open tube, oxides of antimony are formed and deposit as sub- limates on the walls of the tube, but the products vary somewhat with the conditions. If sulphur is present, the oxide usually appears as a dense white smoke, and most of it settles for a considerable distance along the under side of the tube, while some of it condenses as a ring rather near the heated part. The ring is Sb,0, , and when examined with a lens will frequently be found to consist of two kinds of crystals, octahedrons and prisms, corre- sponding to senarmontite and valentinite, two forms of Sb,0, found in nature. When heated, this part of the sublimate is completely volatile, and may be driven up and out of the tube, although much more slowly than oxide of arsenic. Th6 white sublimate which condenses along the bottom of the tube is prob- ably antimonate of antimony, SbSb04. It is non-volatile, in- fusible, and becomes straw-yellow when hot, but white again when cold. In the absence of sulphur and in some compounds containing it (apparently those that oxidize slowly), only the vol- atile Sb,0, forms. Just why the presence of sulphur causes the formation of the higher oxide is not known, but probably its oxide acts in some way as a means for transferring oxygen, changing Sb,08 to Sb904.

Test the above with stibnite, SbaS, , using about £ of an ivory spoonful, and heating very carefully, as directed on p. 19. Test also the volatility of the sublimate, and compare the reaction carefully with the correspond- ing one for arsenic (p. 48, § 2). To obtain the wholly volatile sublimate of Sb90, , heat a little metallic antimony in the open tube.

3. Heating in the Closed Tube. — Sulphide of antimony and many sulphantimonites, when heated in a closed tube, yield a characteristic looking sublimate of oxy sulphide of antimony,

46 REACTIONS OF THE ELEMENTS Antimony

Sb,S,0. This requires a rather intense heat for its production. It is volatilized with difficulty, and appears black when hot, but changes on cooling to a rich reddish-brown.

Metallic antimony cannot be volatilized in a closed glass tube, except at a very high temperature, where hard glass softens. Owing to this behavior, arsenic and antimony, which frequently occur together, especially in sulpharsenites and sulphantimonites, may sometimes be conveniently separated and identified, since arsenic and its sulphides volatilize readily. After driving the sublimate a short way up the tube, cut off the latter a little below it, and test for the arsenic by the open-tube method (p. 48, § 2). After removing the residue from the tube, test it for antimony, either before the blowpipe on charcoal, or in the open tube. To test for arsenic in presence of antimony, see also p. 49, § 4.

Take a small fragment of stibnite in a closed tube, and heat it at a high temperature and for a considerable time. The small quantity of air in the tube is all that is necessary to bring about the reaction shown by the following equation : Sb,St + 0 Sb,S,0 + S. A slight ring of sulphur deposits beyond the antimony sublimate. This is one of the few closed- tube reactions where the air in the tube plays an important part.

4. Test with Hydriodic Acid on a Gypsum Tablet. — Antimony compounds, when treated according to directions given on p. 17, yield a beautiful red coating of iodide of antimony, which disap- pears when held over strong ammonia.

5. Flcme Test.— When antimony compounds are heated before the blowpipe in the reducing flame, antimony volatilizes and im- parts to the flame a pale greenish color. The precautions against alloying the forceps, mentioned on p. 15, should be observed.

6. Oxidation with Nitric Acid. — When antimony or its sul- phides are treated with concentrated nitric acid, the antimony is oxidized to metantimonic acid, SbO,OH (?), which is a white sub- stance, very insoluble in water and in nitric acid. By diluting with water and filtering, quite a satisfactory separation of anti- mony may be obtained from other substances with which it is apt to occur in combination. The material on the filter-paper may be

Aroanlc KE ACTION 8 OF THE ELEMENTS. 47

examined for antimony by heating before the blowpipe on char- coal, and the different metals in the filtrate may be precipitated by appropriate reagents. This treatment will frequently be found convenient, especially for detecting a small quantity of antimony in presence of arsenic.

Arsenic, As. — Trivalent and pentavalent. Atomic weight, 75.

Occurrence. — Arsenic usually plays the part of a non metallic element, and forms three important classes of compounds, — the arsenides, the sulpharsenites, and the arsenates. In arsenides, the metals are united directly with arsenic ; as nicolite, NiAs, and smaltite, CoAs,. These compounds are analogous to the sulphides and are often isomorphous with them. Several compounds are known which are combinations of arsenide and sulphide; as the commonest of the arsenic minerals, arsenopyrite, FeAsS FeAs, + FeS,. The sulpharsenites may be regarded as salts of sidpharsenious acids, H9As9S4, H4As,S,, H,AsaS,, H8As,S,, etc. Examples of these compounds are sartorite, PbAs9S4 PbSAstS,; dufrenoysite, Pb,As,S,=2PbS.As,St; proustite, Ag,AsSt =3Ag,S.AssS,; and tennantite, Cu8As,St=4CutS.AstS,. The num- ber of Sulphantimonites, is quite large, but they are of rather rare occurrence (compare sulphantimonites, p. 43). Enargite, Cu,AsS4 3Cu,S. AsJ3,, is a svlphar senate or salt of sulpharsenic acid, H, AsS4 , but other salts of this acid are exceedingly rare. The arsenates, salts of arsenic acid, HtAs04, are analogous to the phosphates, and although a great many of them are known, they are of rather rare occurrence. Examples are mimetite, Pb4(PbClXP04),; olivenite, Cu(CuOH)As04 ; and scorodite, PeAs04. 2H,0. In addition to the foregoing classes of compounds, the ele- ment occurs as native arsenic, as the sulphides, realgar, AsS, and orpiment, As,S, , and sparingly as the oxide, As9Of.

Detection. — The method that should be used for the detec- tion of arsenic depends upon whether or not the mineral contains oxygen. With those compounds containing no oxygen, it is best to employ an oxidation process, such as roasting on charcoal er in

48 jiEACTli/Sb OF THE ELEMENTS. Arsenic

the open tube. Heating in a closed tube is a good method for some compounds. With arsenates it is necessary to employ a reduction process.

Tests for Arsenic in Minerals containing No Oxygen.

1. Boasting on Charcoal: Coating of Oxide : Arsenical Odor. — When arsenic, its sulphide, or an arsenide, is heated before the blowpipe on charcoal, volatile products are given off, and the arsenic unites with the oxygen of the air to form As„0, , a white, volatile substance, which condenses on the charcoal at a consid- erable distance from the assay. The fumes that are given off when the assay is heated in the reducing flame have a disagree- able, garlic-like odor with which one soon becomes familiar, and which serves as a characteristic test for the identification of the element. The odor is perhaps due to the formation of a little arseniuretted hydrogen AsH,. It does not come from As,Oa , for this, when volatilized without reduction, gives no odor.

The tests mentioned above may be very well observed by heating either the powder or fragments of arsenopyrite, FeAsS, on a flat charcoal surface. Note carefully that the sublimate deposits at a considerable distance from the assay, and test its volatility by heating with a blowpipe flame (com- pare Antimony, p. 44, § I). In addition to the garlic odor of the arsenic, the sulphur, especially after the assay has been heated for some time, yields a strong pungent odor of SO, (p. 119, § 2), which is entirely different from that of the arsenic, and must not be mistaken for it.

2. Roasting in the Open Tube. — When arsenic, an arsenide, or a sulphide of arsenic, is heated in an open tube, a sublimate of white crystalline arsenious oxide, As,0, , is formed, and condenses as a ring on the sides of the glass. The sublimate is further char- acterized by being volatile, so that it can be readily driven up and out of the tube by heating. The crystals of AstO, develop best where the glass is rather warm, and by breaking the tube and examining them with a microscope it will be found that they are usually simple, but occasionally twinned, octahedrons.

Heat from to of an ivory spoonful of powdered arsenopyrite, FeAsS, in an open tube, and observe the reactions mentioned above.

nlo BEACTIONS OF THE ELEMENTS* 49

2FeAsS + 10 0 Fe.O, + 2S0, + As.O,. If a yellow deposit of sulphide of arsenic forms, or a black one of arsenic, it indicates that the oxidation has not been made properly; either the substance was heated too rapidly, or there was not a sufficient draft of air passing up the tube to bring about the oxidation (see p. 19).

3. Heating in the Closed Tube : Arsenical Mirror. — When arsenic and some arsenides are heated in the closed tube, arsenic volatilizes and condenses on the cold walls of the tube. When very little deposits, the sublimate appears brilliant black (arseni- cal mirror) ; but if much of it is driven off, that which is nearest to the heated end crystallizes and appears gray. If the tube is broken just below the sublimate and heated so that the arsenic volatilizes, the characteristic garlic odor may be observed very distinctly, perhaps better in this way than in any other, and a very little arsenic is sufficient to give it.

Test the above with arsenopyrite, FeAsS. At first, perhaps, a little yellow sulphide of arsenic may be driven off, but the arsenical mirror soon makes its appearance. Owing to the greater affinity of iron for sulphur than for arsenic, the change which the mineral undergoes is essentially as follows : PeAsS FeS -r As.

The sulphides of arsenic, realgar, AsS, and orpiment, As9SB, when heated in the closed tube, are completely volatilized, condensing at first as a reddish-yellow sublimate, changing to dark red or almost black when hot, and to reddish-yellow when cold.

4. {Special Test for Oxide of Arsenic. — An exceedingly deli- cate test, proposed by Berzelius, may be made by placing a little oxide of arsenic at the bottom of a closed tube drawn out as in Pig. 43, and above it, a splinter of charcoal. Heat is first applied at the upper end of the charcoal, until Fig.. 43.

the latter becomes red hot, and then at the lower end, when the oxide of arsenic volatilizes, becomes reduced in passing the red-hot charcoal, and condenses above as an arsenical mirror. This method will be found very convenient for testing coatings of oxides, obtained by heating before the blowpipe on charcoal, when there is any doubt as to whether they contain arsenious oxide.

60 REACTIONS OF THE ELEMENTS Amnio

It will also be especially useful when it is desired to detect arsenic in the presence of antimony, for the two elements frequently occur together, and both give volatile white coatings on charcoal, but antimony oxide gives no mirror when treated as above. It is to be noted, however, that when a considerable quantity of antimony is taken, a trifling dark deposit of some antimony compound may form near the charcoal, but this should not be mistaken for the characteristic arsenical mirror, which forms a considerable distance up the tube. In order to make the test, it is only necessary to scrape up a little of the coating which is farthest away from the assay (a little charcoal powder with it does no harm), and heat in the tube as directed above.

5. Test with Eydr iodic Acid on a Gypsum Tablet. — Arsenic compounds, when treated according to directions given on p. 17, yield a very volatile orange to yellow coating of iodide of arsenic.

6. Flame Test. — If arsenic is volatilized from a mineral by heat- ing before the blowpipe in the reducing flame, it imparts to the latter a violet tinge. The color may also be obtained when either arsenic or its sublimate of oxide in a tube is volatilized, so that it passes from the end of the tube into the reducing part of a Bunsen-burner flame.

7. Oxidation with Nitric Acid. — Compounds of arsenic, when boiled with concentrated nitric acid, are, with few exceptions, oxidized and dissolved, with formation of arsenic acid, H,As04. To detect arsenic in the solution, the methods given beyond under arsenates (§ 9, b) may be employed.

Arsenates.

Detection. — The reduction of arsenates in the closed tube, with the formation of an arsenical mirror, furnishes the best means of detection. The oxidation and roasting processes used for the detection of arsenic in arsenides and other compounds containing no oxygen cannot be applied to arsenates, as they are already oxidized.

nlo REACTIONS OF THE ELEMENTS. 51

1. Reduction in the Closed Tube: Arsenical Mirror. — a. With few exceptions the arsenates are readily fusible, and for all such the following decisive test may be applied : In a narrow closed tube place a few splinters of charcoal and a fragment of the arsenate, and heat intensely with a blowpipe flame, so that the fused mineral comes in contact with the charcoal. Under these conditions the arsenate is reduced, and the arsenic volatilizes and forms an arsenical mirror.

b. Provided the arsenate is infusible in the closed tube, and in the absence of easily reducible metals, such as lead, copper, or iron, proceed as follows: Mix a little of the finely powdered mineral with 4 volumes of dry sodium* carbonate and i little powdered charcoal, transfer to a closed tube, warm gently at first, and then heat intensely in a Bunsen-burner or blowpipe flame. Under these conditions the arsenic, resulting from the reducing action of the charcoal, will volatilize, and condense on the glass as an arsenical mirror.

c. When the foregoing tests cannot be applied, mix the pow- dered mineral with about 6 volumes of sodium carbonate, and fuse either in a platinum spoon or on a flat charcoal surface, using an oxidizing flame. The fused material is transferred to a test-tube, boiled for a minute with about 6 cc. of water, in order to dissolve the sodium arsenate resulting from the fusion, and then filtered. To the filtrate hydrochloric acid is added in excess, then an excess of ammonia, which may cause the precipitation of some arsenate, and lastly a little magnesium sulphate solution, in order to precip- itate the arsenic as ammonium magnesium arsenate, NH4MgAs04. Filter off the precipitate, dry it by pressing between blotting. paper, mix a little of it with sodium carbonate and charcoal powder, and heat in a closed tube as directed in § b. Provided the precipitate is small, place the filter-paper containing it in a porcelain crucible, char the paper by very gentle ignition, and test the charred material, mixed with a little sodium carbonate and charcoal powder, in a closed tube.

52 BBACTIONS OF THE ELEMENTS. Barton*

Barium, Ba. — Bivalent. Atomic weight, 137.

Occurrence. — Barium is an alkali-earth metal, which is found quite abundantly in barite, BaS04, and in some regions in witherite, BaCO, , but other combinations containing it are seldom met with. It occurs in only a few silicates (hyalophane, harmotome, brewsterite), and sparingly in the igneous rocks of some regions.

Detection. — Usually barium may be readily detected by the flame coloration, alkaline reaction, and precipitation as barium sulphate.

1. Flame Test— Barium gives a yellowish-green coloration to the flame, which may sometimes be intensified by moistening the assay with hydrochloric acid. The color cannot be obtained directly from silicates, and must not be mistaken for that of boron and phosphorus.

Make the experiment with barite or witherite, holding fragments in the forceps and heating before the blowpipe. Make the test also by heating some of the powder on a platinum wire, as directed on p. 35.

2. Alkaline Reaction. — With the exception of the silicates and phosphates, barium minerals become alkaline upon intense ignition before the blowpipe. A similar reaction is obtained with other minerals containing alkalies and alkaline earths.

Heat fragments of barite or witherite, and place them upon moistened turmeric-paper. For the cause of the alkaline reaction, see Calcium

(P. 58, § 1).

3. Precipitation as Barium Sulphate. — Barium sulphate, BaS0o is very insoluble in water and dilute acids, and will be pre- cipitated, therefore, from solutions containing barium, upon the addition of a few drops of dilute sulphuric acid. The test is a very delicate one, and will always serve to distinguish compounds containing barium from those containing boron and phosphorus, which may give green flame colorations. It will also serve for the detection of barium in silicates and other compounds.

Beryllium REACTIONS OF t&E ELEMENTS. 55

a. Dissolve i ivory spoonful of witherite in 3 cc. of dilute hydro- chloric acid, warm if necessary, dilute with from 10 to 15 cc. of water, and add dilute sulphuric acid, when a white precipitate will form, which is barium sulphate. This should be collected on a filter-paper, washed with water, and tested on platinum wire, as directed under § 1.

b. To apply this test to silicates, dissolve in hydrochloric acid (after previous fusion with sodium carbonate, if the mineral should happen to be insoluble, see p. 110, § 4), separate the silica, precipitate barium sulphate with sulphuric acid, collect on a small filter, and make a flame test on platinum wire. If both barium and strontium are* present, a mixed flame will be obtained, and, after moistening with hydrochloric acid, often the red of strontium will appear strongest at first, while later the green of barium may be seen. In order to obtain decisive results, it may be necessary to make use of a spectroscope.

4. Specific Gravity. — On account of the high atomic weight of barium, minerals containing it are characterized by high specific gravities, considerably greater than those of the corresponding strontium or calcium compounds (see p. 118, § 4).

Beryllium, Be. — Bivalent. Atomic weight, 9.

Occurrence. — Although usually regarded as a rare element, beryllium, sometimes called glucinum, Gl, is found in the common mineral beryl, BesAl,(Si01)t and in a number of others which are not very rare; as chrysoberyl, phenacite, leucophanite, helvite, euclase, gadolinite, beryl! onite, and herderite.

Detection, — There are no satisfactory blowpipe reactions for beryllium, and tests must be made, therefore, in the wet way, which requires some skill in manipulation.

a. If the mineral is a silicate, treat it according to directions given on p. 110, § 4, for the solution of the mineral and separation of silicic acid; then heat the filtrate from the silica to boiling, and precipitate the beryllium with ammonia, which will also cause precipitation of iron, aluminium, and possibly other elements, if present. Ammonia precipitates beryllium hydroxide, which resembles aluminium hydroxide in appearance. This is filtered and washed well with water, transferred together with the paper to some vessel, and warmed with dilute hydrochloric acid in order to dis- solve it. The paper is filtered off, and the filtrate evaporated carefully (best in a casserole) until only a drop or two of the acid is left. After cool- ing, a few drops of water are added to obtain everything in solution, and then a little potassium hydroxide solution, a drop at a time, and just suffi- cient to dissolve the precipitate of beryllium hydroxide which forms at

54 REACTIONS OF THE ELEMENTS. Bismuth

first. The solution is then dilated with cold water to a volume of at least' 50 cc, any precipitate of ferric hydroxide or other material filtered off, and the filtrate boiled for a short time, when, if beryllium is present, a pre- cipitate of beryllium hydroxide will appear. The precipitate, if collected on a filter-paper and iguiied, yields beryllium oxide, and this when ignited with cobalt nitrate assumes a not very decisive lavender color.

b. If the mineral is a phosphate, special treatment is needed.. The powdered mineral is dissolved in hydrochloric acid (after fusion with sodium carbonate, if necessary); when cold, ammonia is added until a per- manent precipitate forms, and then hydrochloric acid, a drop at a time, until the solution becomes clear. To the now nearly neutral, cold, and not too concentrated solution, sodium acetate is. added, and the precipitated beryllium phosphate, which may also contain ferric and aluminium phos- phates, is filtered and washed. The precipitate is next ignited in a crucible until the carbon of the paper is destroyed, and is then fused in platinum with sodium carbonate, by which treatment sodium phosphate and beryllium oxide are formed. The fusion is then treated with hot water to dissolve the spdium phosphate, the beryllium oxide is collected on a filter-paper and washed, and it is afterwards dissolved in hydrochloric acid and tested with potassium hydroxide, as described under a. If it is known that the alkali-earth metals are absent, the mineral may be fused directly with sodium carbonate, and treated like the above sodium carbonate fusion.

Bismuth, Bi — Trivalent. Atomic weight, 208.

Occurrence. — Bismuth plays the part of a weak basic element and also that of an acid- forming one, and is of rather rare occur- rence in minerals. It is found native and as sulphide, selenide, telluride, oxide, silicate, and carbonate. The combinations of its sulphide with sulphides of the metals, the svlphobismvihites are analogous to the sulphantimonites and sulpharsenites,

Detection. — Usually bismuth may be readily detected by its reactions on charcoal and by the iodine tests.

1. Reduction on Charcoal to Metallic BismtUh, and Formation of a Coating of Bismuth Oxide. — Usually bismuth can be readily reduced from its compounds by mixing ivory spoonful of the powdered mineral with about 3 volumes of sodium carbonate and heating on charcoal in the reducing flame. The globules of the metal thus obtained are readily fusible and are bright when in the flame, but become covered with a coating of oxide when exposed

bismuth REACTIONS OF THE ELEMENTS. 55

to the air. They are brittle, and, if removed from the charcoal and hammered on an anvil, they may flatten to some extent at first, bat cannot be beaten into a thin sheet like lead. Heated before the blowpipe, bismuth is somewhat volatile, and its vapor passing into the air becomes oxidized, and settles on the coal as a lemon- to orange-yellow coating of bismuth oxide, which is white at a dis- tance from the assay. The coating may be volatilized by heating in both the oxidizing and reducing flames without imparting any color to them. The reactions are quite similar to those of lead, but may be distinguished by the iodine tests.

Make the test by heating any simple bismnth mineral, or the commer- cial oxide of bismuth, as directed above. A somewhat better idea of the bismnth coating may be obtained by removing a globule of the metal and heating it alone before the blowpipe on a fresh piece of charcoal.

2. Iodine Tests. — An excellent test proposed by von Kobell consists in adding to a small portion of the powdered mineral 3 or 4 times its volume of a mixture of potassium iodide and sulphur (p. 26), and heating before the blowpipe on charcoal with a small oxidizing flame, when a coating is produced which is yellow near the assay, and bordered on the outer edges by a brilliant red.

The test on a gypsum plate, made as directed on p. 17, yields a chocolate-brown coating of bismuth iodide, which is changed to a brilliant red by exposing for a short time to the fumes of strong, ammonia.

3. Tests in the Wet Way. — If the mineral is soluble in hydro- chloric acid, evaporate the solution until only a few drops remain, and then pour it into a test-tube about one third full of water, when a white precipitate of bismuth oxychloride, BiOCl, will form, which may be collected on a filter and tested, as in § 1. If the mineral is not soluble in hydrochloric acid, dissolve in nitric, then add excess of hydrochloric acid, concentrate to a small volume and pour into water, as directed above. If the presence of lead is suspected, dissolve in nitric and 2 or 3 cc. of concentrated sulphuric acid, evaporate in a casserole until the nitric acid is all expelled,. and,,

5(> REACTIONS OF THE ELEMENTS. Boron

after cooling, digest with water and filter off the insoluble lead sulphate, which may be tested according to p. 87, § 1. To the filtrate, add ammonia to precipitate bismuth hydroxide, and this,, when collected on a filter, may be tested according to § 1.

Boron, B. — Trivalent. Atomic weight, 11.

Occurrence. — Boron is the characteristic, non-metallic ele- ment of boric acid, HtBO„ and its salts, the borates. The latter are not very common, borax, NaaB4Ot.10HaO, being the most im- portant. Boron is also found as a constituent of a number of sili- cates; as tourmaline, axinite, datolite, and danburite. Boron minerals have usually been formed by the action of vapors given off during igneous activity.

Detection. — Boron may be detected by the flame coloration and the test with turmeric-paper.

J 1. Flame Test. — Many boron minerals when heated before the blowpipe impart a green color to the flame. The color is a rather bright one, inclining somewhat to yellow (siskin-green), aw must not be confounded with that of barium, from which it may readily be distinguished by other tests.

Minerals which do not give the boron flame when heated alone usually show it when their powder is mixed intimately with about 3 volumes of the potassium bisulphate and fluorite mixture (p. 26), and heated rather gently before the blowpipe or in a Bun- sen-burner flame. The mixture is most conveniently introduced into the flame by taking up a little of it on the end of a hot plati- num wire or in a small loop. The hydrofluoric acid liberated by the mixture attacks the mineral, forming boron fluoride, BF„ and this gives a green flame coloration, which is usually of only mo mentary duration.

Tests may be made with datolite, Ca(BOH)Si04, or danburite, CaB,(Si04)„ which give a green flame color when heated alone, and also with tourmaline, in which case it is necessary to make use of the potassium bisulphate and fluorite mixture.

2. Test with Turmeric-paper. — If turmeric-paper is moistened with a dilute hydrochloric acid solution of a mineral containing

Cadmium REACTIONS OF THE ELEMENTS. 57

boron, and then dried at 100° C. (on the outside of a test-tube con- taining boiling water), it assumes a reddish-brown color, and this is changed to inky-black by moistening with ammonia. The test is very delicate and satisfactory, and may be applied to all boron minerals, for, if insoluble in acids, they may be dissolved after fusion with sodium carbonate, as directed on p. 110, §§ 3 and 4.

Bromine, Br. — Univalent. Atomic weight, 80.

Occurrence. — This non-metallic element is found very rarely in min- erals, the only ones of importance being the silver ores, embolite, AgCl with AgBr, and bromyrite, AgBr. The bromides, salts of hydrobromic acid, are mostly soluble in water.

Detection. — Many of the reactions of bromine are similar to those of chlorine and iodine. Silver nitrate precipitates silver bromide, AgBr. When a bromide is heated in a bulb tnbe with potassium bisulphate and pyrolnsite, bromine is liberated, and may be distinguished by the red color of its vapor, and the formation of liquid bromine if the reaction is strong. (Chlorides and iodides when similarly treated yield chlorine gas and iodine, respectively.) Silver bromide, when heated in a closed tube with galena, yields a sublimate of lead bromide, which is sulphur-yellow when hot, and

white when cold.

For the detection of bromine in presence of iodine, see p. 69.

Cadmium, Cd.— Bivalent. Atomic weight, 112.

Occurrence. — Cadmium is a rather rare element, and is mostly found „ associated with zinc in some varieties of sphalerite and smithsonite. Only one cadmium mineral is known, greenockite, CdS.

Detection. — If minerals containing cadmium are mixed with sodium carbonate and heated before the blowpipe on a flat charcoal surface in the reducing flame, metallic dadmium is readily formed and volatilized. The element unites with the oxygen of the air, and the resulting oxide collects on the charcoal as a reddish-brown coating, which is yellow distant from the assay, and usually iridescent if only a little of it forms.

In the presence of zinc, the foregoing method may sometimes be em- ployed, since, owing to the ease with which cadmium is reduced and vola- tilized, its coating will appear before that of zinc. It is better, however, to proceed as follows : Dissolve from 4 to 6 ivory spoonfuls of the mineral in nitric acid, add 1 or 2 cc. of concentrated sulphuric acid, and evaporate in a casserole until the nitric acid is removed. On cooling, add about 100 cc. of water and 10 cc. of hydrochloric acid, filter, and pass hydrogen sulphide gas through the filtrate for half an hour, then filter off the precipitated

58 REACTIONS OF THE ELEMENTS. Oamlum

cadmium sulphide, and wash with water. Place the paper containing the precipitate upon a piece of charcoal, add sodium carbonate, and heat before the blowpipe, first with a small oxidizing flame until the paper is burned, and then in a reducing flame to obtain the coating of cadmium oxide.

Caesium, Cs. — Univalent Atomic weight, 133.

Occurrence. — This very rare alkali metal has been found in pollucite, H,Cs4 Al4(SiO,)f , and in small quantities in some varieties of lepidolite and beryl. Rubidium is often found with caesium.

Detection. — Caesium is similar to potassium, and may be precipitated as caesium platinic chloride, CsvPtGl6 (see p. 106, § 3). The precipitate is much more insoluble than the corresponding potassium compound, sepa- rates in a finer condition, and has a paler color. To make sure of its iden-

tity, it is best to heat some of the precipitate on a platinum wire, and examine the flame with a spectroscope.

Calcium, Ca. — Bivalent. Atomic weight, 40.

Occurrence. — This alkali-earth metal is found very abun- dantly in nature (see p. 3). It is a constituent of many silicates and of most rocks, while its combinations with hydrofluoric, car- bonic, sulphuric, phosphoric, and other acids are very common. Examples of important calcium minerals are calcite, CaCO,; fluorite, CaP, ; gypsum, CaS04.2H,0; pyroxene, CaMg(SiO.),; and apatite, Ca4(CaF)(P04)f.

Detection. — Usually, the best methods to apply are the alka- line reaction after heating, and the precipitation as calcium sul- phate, carbonate, or oxalate.

1. Alkaline Reaction. — Calcium minerals become alkaline upon ignition before the blowpipe, with the exception of the silicates, phosphates, borates, and the salts of a few rare acids. A similar reaction is obtained with other minerals containing alkalies and alkaline earths.

a. Heat a fragment of calcite before the blowpipe, and place it upon a piece of moistened turmeric-paper. In this experiment, the heat drives out CO, from the calcite, leaving lime, CaO, which dissolves to some extent in the water and gives the alkaline reaction.

b. Heat a fragment of fluorite, and place it upon moistened turmeric- paper. In this experiment, water (one of the products of combustion) reacts to some extent upon the fluorite, as follows* OaFt + HtO OaO + 2HF.

telotom REACTIONS OF THE KLEMENT8. 59

Fluorite, if heated in a closed tube, would not decompose nor become alkaline.

c. Heat a fragment of gypsum and test on turmeric-paper. In this ex- periment, the intense heat of the blowpipe flame is perhaps sufficient to drive out SO, from CaS04, although the water resulting from combustion undoubtedly assists very much in bringing about the decomposition (com* pare p. 81, § 1, where only neutral water is given off by heating gypsum in a closed tube).

2. Flame Test — A few calcium compounds when heated before the blowpipe volatilize to some extent and give a yellowish-red coloration to the flame. The color is often weak, and in testing most calcium minerals it does not appear at all. Since calcium chloride is volatile, the color may often be observed when the assay is heated, after moistening with hydrochloric acid. The flame must not be mistaken for the much redder one of strontium (see p. 116, § 1).

Heat a fragment of calcite in the platinum forceps, and observe that it gives only a very little or no color to the flame ; then touch it to a drop of hydrochloric acid and heat again. Better still, mix powdered calcite with a drop of hydrochloric acid, then touch the end of a clean platinum wire to the mixture, and introduce it into a Bunsen-burner or blowpipe flame.

3. Precipitation as Calcium Sulphate {Gypsum). — As gypsum, QaSO.2HtO, is rather insoluble in water, and sparingly so in di- lute hydrochloric acid, it may be precipitated from a solution containing calcium upon the addition of a few drops of dilute mlphurie acid, provided the solution is neither too dilute nor too strongly acid. If the test is carried out according to the details given below, it will be found a very convenient one for the detec- tion of calcium.

Dissolve 2 ivory spoonfuls of calcite in a test-tube in 3 cc. of hydro- chloric acid, divide the solution into 2 parts, dilute one with about 10 times its volume of water, and then add a few drops of dilute sulphuric acid to each. The precipitate which forms in the concentrated solution is calcium sulphate, and this will dissolve readily upon addition of water and warming (difference from strontium and barium). No precipitate forms in the dilute solution, owing to the solubility of the calcium sulphate.

60 REACTIONS OF THE ELEMENTS. Calcium

4. Behavior toward Ammonia. — Calcium is not precipitated from solutions upon addition of ammonia, except when carbonic, phosphoric, silicic, boric, or other acids are present with which calcium forms insoluble compounds. This behavior is very im- portant, for often other elements which are present with calcium in a solution may be precipitated by means of ammonia, separated by filtration, and the calcium detected in the filtrate by the tests given beyond.

a. Dissolve an ivory spoonful of calcite in a test-tube in 3 cc. of dilute hydrochloric acid, boil for a few seconds to expel 00,, dilute with about 10 cc. of water, and add an excess of ammonia; i.e., until the solution smells of ammonia, or shows a blue color with litmus-paper. If the calcite should be impure, traces of foreign substances may be precipitated, but no calcium will be thrown down. Save the solution for experiments under §§ 5 and 6.

b. Dissolve an ivory spoonful of apatite, calcium phosphate, in a test' tube, in 3 cc. of hydrochloric acid, dilute with water, and add ammonia in excess. In this experiment, the precipitate which forms is calcium phos- phate, and this, although soluble in acids, is insoluble in neutral or alkaline solutions.

5. Precipitation as Calcium Carbonate. — Ammonium carbon- ate added to a solution made strongly alkaline with ammonia precipitates calcium carbonate, CaCO,. If made from a boiling solution, the precipitation is practically complete, and the calcium c*tn be removed by filtering.

/ 6. Precipitation as Calcium Oxalate. -Ammonium oxalate added to an alkaline or even slightly acid solution precipitates calcium oxalate, CaC,04. The test is very delicate, and the sep- aration complete, but the precipitate comes down in a very finely divided condition, and is apt to run through a filter-paper. It may almost always, however, be readily filtered if the precipita- tion is made in a hot solution, and then allowed to stand for an hour before filtering.

The following method may sometimes be found convenient for the de- tection of calcium in phosphates: Dissolve an ivory spoonful of the pow- dered mineral in a test-tube in 3 cc. of hydrochloric acid, add ammonia until a precipitate forms, and then hydrochloric acid, a drop at a time,

Carbon REACTIONS OF THE ELEMENTS. 61

until the solution becomes clear. Dilute now with about 10 cc. of water, and add ammonium oxalate, when, if calcium is present, it will be precipi- tated from the slightly acid solution as oxalate. The above may be tested with apatite.

7. For the detection of calcium in silicates and complex bodies, see p. 110, § 4.

Carbon, C. — Tetravalent. Atomic weight, 12.

OccukrjgeJH almond and graphite are crystallized forms of carbon, and anthracite coal is also nearly pure carbon. Bitumi- nous coal, asphalt, paraffin, mineral oils, and many natural gases are different forms of hydrocarbons ; i.e., combinations of carbon and hydrogen, for which usually no definite chemical formulae can be given, and which cannot, therefore, be classed as definite mineral species. The carbonates, salts of carbonic acid, H,CO„ form a very important class of minerals, including such common ones as calcite and aragonite, CaCO, ; dolomite, CaMg(COa)a; siderite, FfeCO, , and many others.

Detection. — The burning of carbon with formation of carbon dioxide, and the closed-tube reactions serve for the detection of the different forms of coal, hydrocarbons, and organic substances. For carbonates, effervescence with acids is usually a sufficient test.

Carbon, Anthracite and Bituminous Coals, Hydrocarbons, and

Organic Matter.

Closed-tube Reactions. — Hydrocarbons, bituminous coals, and organic matter, when heated in a closed tube, usually suffer destructive distillation. Tar-like substances, oils, water, and gas are given off, and condense in the tube, while a strong empyreuma t jc odor may usually be observed. The residue, if any is left, is gen- erally nearly pure carbon. Anthracite coal and the different forms of nearly pure carbon suffer no change when heated in a closed tube, except that perhaps a little water is driven off.

a. To show the effect of organic matter, heat a small fragment of wood in a closed tube.

62 BEACTIONS OF THE ELEMENTS. Oarbon

h. Partly fill a bulb tube or a large closed tube with bituminous coal,

draw out the upper end, as in Fig. 44,

then apply heat to the bulb, and set fire

to the escaping gas. If the residue left

„ , in the tube forms a hard, coherent, vesi-

cular mass it would indicate a coking coal, while if soft and pulverulent, it would indicate a non-coking coal.

c. Partly fill a bulb tube or a large closed tube with pyrolusite, MnOt 9 carefully shove a piece of anthracite coal to a position near the pyrolusite, a, Fig. 45, and apply heat, first to the coal until it becomes red hot, then to the pyrolusite. As oxygen is driven a from the pyrolusite, the coal will burn, Fl°-

and continue to glow as long as the supply of oxygen lasts or any of the coal remains (compare p. 100, § 1).

Graphite is a form of carbon which burns with great difficulty, and cannot be tested as above, while diamond burns quite readily, provided that part of the glass where the diamond is located is heated intensely so as to start the combustion.

Carbonates.

t, 1. Iffiertescence with Acids.— When carbonates are dissolved in acids, carbon dioxide gas, CO, , is given off with effervescence? The carbonates are salts of a weak acid, and when treated with a strong acid they are decomposed, yielding salts of the stronger, arid setting the weaker acid free. Theoretical carbonic acid is HfiOt , but when liberated it splits up into H,0 and CO,. There- fore, the reaction between calcium carbonate and hydrochloric acid may be represented as follows: CaCO, + 2HC1 CaCl, + H,0 + CO,. Any strong acid (hydrochloric, nitric, or sulphuric) may be used to liberate carbon dioxide, by strong be- ing meant one with strong chemical affinity, not a concentrated acid. The reaction usually succeeds best when dilute hydro- chloric acid is used, and it may take place in the cold, although sometimes it is necessary to apply heat. When heat has to be applied, care must be taken not to mistake boiling and escaping- bubbles of steam for carbon dioxide. Carbon dioxide is charac- terized by being a heavy, colorless, and odorless gas, which is not apt to be confounded with other gases. It does not support com-

Carbon REACTIONS OF THE ELEMENTS. 63

bustion, and, when brought in contact with clear barium hydrox- ide solution, it gives a white precipitate of barium carbonate. CO, + BaO.H, BaCO, + H.O.

a. Take 2 ivory spoonfuls of powdered calcite in a test-tube, add a little water and an equal quantity of hydrochloric acid, when an efferves- cence will be observed, and the air will soon be displaced by the heavier carbon dioxide, if the tube is held vertically. A burning match, if thrust into the tube, will be immediately extinguished. Pour a little barium hydroxide solution into a second test-tube, and, holding the two tubes mouth to mouth, incline the one containing the carbon dioxide, so that the heavy gas can pour down into the one containing the barium hydroxide, when, on shaking the latter, a white precipitate of barium carbonate will appear. It is evident that the test with barium hydroxide, made as suggested above, can be used only when carbon dioxide is abundantly given off and the tube is filled with the gas.

A more delicate method of testing with barium hydroxide is to make use of a tube like the one shown in Fig. 46. Fragments of the carbonate

Fig. 46.

to be tested are placed in the lower bulb, and, by means of a pipette, dilute acid is introduced, care being taken not to allow any of it to get into the upper bulb, or on the sides of the tube above the latter. The tube being held nearly horizontal, barium hydroxide is then introduced into the upper bulb, where a precipitate of barium carbonate will be formed by the escap- ing carbon dioxide.

Effervescence may be detected in a minute particle of mineral by bring- ing the latter in contact with a drop of acid on a watch-glass or in a test* tube.

b. Take some dolomite, CaMg(GOB)s, and treat it exactly as described under a, and it will be observed that only a very slight or no effervescence takes place in the cold, but, on warming, carbon dioxide is abundantly given off. In testing carbonates which are soluble only in hot acids, it is best to have the mineral finely pulverized. Care must always be taken not to mistake boiling for effervescence.

c. The mistake is sometimes made of testing carbonates with acids which are too concentrated, as illustrated by the following experiments: In dry

64 REACTIONS OF THE ELEMENTS. Oarbon

test-tabes treat fragments of witherite, BaCO, , with concentrated hydro- chloric acid, and cerussite, PbCO,, with concentrated nitric acid, and, in both cases, there will be only a very trifling or no effervescence, owing to the insolubility of barium chloride and lead nitrate in the respective acids. On dilution with 2 of 3 volumes of water, however, effervescence will commence, because the salts which form on# the outside of the fragments dissolve, and thus fresh surfaces of the carbonates are constantly exposed to the action of the acids.

d. In order to show that there is sometimes danger of overlooking a small quantity of a carbonate, test as follows : Dissolve from i to £ of an ivory spoonful of sodium carbonate in 5 cc. of cold water, and add a little hydrochloric acid, when no or only a slight effervescence will be visible, owing to the fact that carbon dioxide is soluble to some extent, and remains dissolved in the liquid. On heating, the gas makes its appearance.

2. Decomposition by Heating: Closed-tube Reaction. — Car- bonates when heated are usually decomposed, carbon dioxide going off and oxides of the metals being left. An exceedingly- delicate test may be made by heating a small particle of a carbon- ate in a closed tube, and testing for the presence of carbon dioxide, by bringing a little barium hydroxide solution into the upper end of the tube by means of a capillary pipette.

The ease with which carbonates decompose depends upon the character of the metals with which the carbonic acid radical is in combination. Carbonates of the metals with strong chemical affinity, such as potassium or sodium, are not decomposed at a red heat, while those with weak chemical affinity, like iron or zinc, decompose at a moderate temperature. Calcium occupies an inter- mediate position, and calcite, or limestone, CaCO, , is not decom- posed at a low red heat, but is wholly converted by intense ignition into CaO, as illustrated by the familiar example of burn- ing lime. CaCO, CaO + CO,.

Make the experiment by heating a small fragment of siderite, FeCO,, in a closed tube, and observe that the brown, non-magnetic mineral is changed to black magnetic oxide of iron, while the carbon dioxide in the tube may be detected by means of barium hydroxide.

Cerium, Ce. — Usually trivalent, but tetravalent in eerie com- pounds. Atomic weight, 140.

Cr(iim REACTIONS OF THE ELEMENT8. 65

In connection with cerium it will be well to consider a number of other elements, known as the Rare Earth Metals. The more important of these are lanthanum, La; didymium, Di; yttrium, Y; erbium, Er; and thorium, Th. This group, however, has been further subdivided, so that it now includes gadolinium, neodymium, praseodymium, samarium, scandium, ter- bium, thulium, and ytterbium, but the reactions for these rare substances are so obscure and difficult that no attempt will be made to give them in the present work.

Occurrence. — The rare earths are usually found associated with one another, and minerals containing essentially the cerium group (Ce, La, and Di) are cerite, allanite, monazite, fergusonite, samarskite, tysonite, parisite, and bastnaesite. The yttrium earths (Y and Er) are found especially in gadolinite, xenotime, yttrotautalite, euxenite, polycrase, aud sipylite. Tho- rium is found in thorite, monazite, aeschynite, polymignite, and thoro- gummite.

Detection. — The rare earths are all precipitated as hydroxides from acid solutions by means of ammonium or potassium hydroxides, but this precipitation may be often omitted when it is known that calcium is absent. The precipitate when filtered and washed is dissolved in hydro- chloric acid, the excess of acid removed by evaporation, the residue dissolved in water, and oxalic acid added, when a precipitate of oxalates of the earths will be thrown down, which is insoluble in oxalic acid. The precipitate when filtered, washed, and ignited, yields oxides of the earths. ,

In order to detect thorium, the oxides are dissolved by boiling with a few cc. of dilute sulphuric acid, the solution evaporated, transferred finally to a crucible, and heated carefully until the excess of sulphuric acid is wholly driven off, thus converting the earths into normal sulphates. The sulphuric acid must be driven off in a good draft, for the fumes are very irritating, and in order to regulate the heat it is best to place the crucible containing the sulphates inside a porcelain one, thus leaving an air space between, and to adjust the heat so that the outer crucible is not heated above faint red- ness. The crucible should be covered toward the end of the operation, and the heating continued until no white fumes appear when the cover is raised. If the sulphates have been properly heated, they should be wholly .soluble in cold water, and thorium may then be precipitated from the dilute solution by adding sodium thiosulphate, Na,3,0,, and boiling. The pre- cipitate, when collected on a filter-paper, washed, and ignited, yields tho- rium oxide, ThO,. Zirconium, if present, will precipitate with thorium, and, from solutions which are too concentrated, cerium may also be precipi- tated. To make certain, therefore, of the identity of the thorium, it will be best to convert the ignited material again into sulphate, and to repeat the precipitation with sodium thiosulphate.

66 REACTIONS OF THE ELEMENTS. Genunt

In order to detect the remaining groups, the earths contained in the filtrate from the thorium are precipitated by means of oxalic acid, and converted into sulphates, as directed above. The sulphates are then dissolved in a little cold water, and about 2 volumes of a boiling, saturated solution of potassium sulphate are added, which precipitates Ce, La, and Di completely, as double potassium sulphates, Cet(S04)t -f 3KtS04, while Y and Er remain in solution. After standing a few hours in the cold, the precipitate may be filtered, and washed with a cold saturated solution of potassium sulphate. From the filtrate, Y and Er may be then precipitated by means of ammonium oxalate, while the precipitate containing Ge, La, and Di, may be dissolved in hot hydrochloric acid, and the earths precipitated by addition of ammonium oxalate and am- monia. The detection of the separate elements in the two groups is a difficult matter, and is usually not very important. Ge, La, and Di almost invariably occur together, while Y and Er are usually associated with one another.

In the cerium group, pure ignited oxide of cerium, GeO„ is nearly white, as are also the oxides of lanthanum, La,Os, and didymium, Di,0„ but a mixture of cerium oxide with the latter always has a brown color. If the solution of the ignited oxides in sulphuric acid is yellow, it indicates cerium, and is due to eerie sulphate, Ce(S04),. After ignit- ing the sulphates, however, cerous sulphate, Ce,(S04),, is formed, which gives a colorless solutitin. If the oxides are dissolved in a borax bead in the oxidizing fltfme a brownish-red or yellow. bead, fading to yellow on cooling, indicates cerium. In the reducing flame, the bead becomes colorless or nearly so. With phosphorus salt, the colors for cerium in the oxidizing flame are yellow when hot, fading to colorless when cold, and in the reducing flame, colorless both when hot and cold. When cerium does not interfere, didymium may be detected by means of the borax or salt of phosphorus beads, for when a considerable quantity is die- solved it imparts to them a pale rose color in both the oxidizing and reducing flames. Didymium also imparts to solutions a pale rose color, which may be seen when they are concentrated. If a solution is held before the slit of a spectroscope directed toward a strong light, or if the oxalate precipitate is held in a strong light and examined with a spectro- scope, dark bands may be seen interrupting the continuous spectrum, which are known as absorption bands, and indicate the presence of the didymium group among the elements precipitated by potassium sulphate. A prominent band is located in the yellow, and another about the middle of the green.

Yttrium gives no absorption spectrum, but erbium and the rare earths related to it give a series of strong absorption bands.

Chlorine REACTIONS OP THE ELEMENTS. 67

Chlorine, CI. — Univalent. Atomic weight, 35.5.

Occurrence. — Chlorine is the characteristic non-metallic ele- ment of hydrochloric acid, HC1, and the chlorides. With the exception of silver, lead, and mercurous chlorides, the simple chlorides of the metals are soluble in water, and their occurrence, therefore, as minerals is rather restricted, since they cannot occur where water is abundant. Of the soluble chlorides, halite, NaCl ; sylvite, KC1; and carnalite, KMgCl,.6H,0; and of the insoluble ones, cerargyrite, AgCl, are the most important minerals. A number of combinations of chlorides with oxides or hydroxides of the metals, called oxy chlorides, are known, and chlorine is fre- quently found in combination with other acids, especially silicic and phosphoric, and is then often isomorphous with fluorine and hydroxyl. Examples are atacamite, CuaCl(OH)t or CuCl, + 3Cu(OH), ; sodalite, Na4(AlCl)Al9(Si04)8 ; and pyromorphite, Pb4(PbCl)(P04)f.

Detection. — The most satisfactory tests for chlorine are pre- cipitation as silver chloride, or the formation of chlorine gas.

1. Precipitation as Silver Chloride. — Silver chloride, AgCl, is very insoluble in water and dilute nitric acid. A very delicate test may therefore be made by dissolving a chloride in water or dilute nitric acid, and precipitating silver chloride by adding a few drops of a solution of silver nitrate. Bromine and iodine give similar reactions. If much chlorine is present, a white, curdy precipitate forms, or, if a trace is present, there is at first only a bluish-white opalescence. On exposure to light, the pre- cipitate soon acquires a violet color.

In order to apply this test to minerals which are insoluble in acids, first fuse with sodium carbonate, as directed under silicates (p. 110, § 4), soak out the fusion with water and dilute nitric acid, filter if necessary, and then add silver nitrate.

To illustrate this test, dissolve ivory spoonful of halite (common salt) in a few cc. of water, and then add a few drops of nitric acid and of silver nitrate. NaCl + AgNO, AgCl + NaNO,, Test the solubility of the precipitate in an excess of ammonia.

68 REACTIONS OF THE ELEMENTS. Chlorine

2. Evolution of Chlorine. — A very satisfactory test in the dry way may be made by mixing the powdered chloride with about 4 times its volume of potassium bisulphate and a little pow- dered pyrolusite, MnO, , and heating the mixture either in a bulb tube or a small test-tube, when chlorine gas will be given off, and may be recognized by its pungent odor or its bleaching action on a strip of moistened litmus-paper held inside the tube (compare p. 101, § 2).

Insoluble compounds, such as silver chloride or a silicate, should first be fused with sodium carbonate, the fusion pul- verized, and then treated as above.

3. Flame Test. — Chloride of copper is volatile before the blow- pipe, giving an azure-blue and sometimes a green coloration to the flame (compare Copper, p. 72, § 1). To use this behavior for the detection of chlorine, Berzelius recommended the following treatment : To a small salt of phosphorus bead add copper oxide until the bead is dark and opaque, then touch it while hot to the substance to be tested, and heat before the blowpipe in an oxidiz- ing flame, when chloride of copper will volatilize and impart a blue color to the flame- The test answers very well for most chlorides, but is not sufficiently delicate for the detection of small quantities of chlorine in minerals. Bromine gives a similar reac - tion.

4. To distinguish silver chloride, silver bromide, and silver iodide from one another, the following method will be found very convenient : Heat a fragment of the mineral and a little pure, pul- verized galena together in a closed tube, and observe the color of the sublimate formed. . Silver chloride yields lead chloride, and this fuses on the hot glass to colorless globules which become white when cold. Silver bromide yields lead bromide, which is sulphur-yellow when hot and white when cold. Silver iodide yields lead iodide, which is dark orange-red when hot and lemon- yellow when cold. If iodine is detected by the foregoing test, bromine and chlorine may also be present, and, if iodine is absent, the reaction for bromine will obscure that of chlorine.

Ohfomlum REACTIONS OF THE ELEMENTS. . 69

5. The detection of chlorine in the presence of bromine and iodine is not a simple matter. If combined with silver, place the material in a test- tube with some granulated zinc, add dilute sulphuric acid, allow the reduc- tion to proceed for some minutes, and then filter or decant the solution of zinc salts from the insoluble silver. Take a few drops of the solution in a test-tube, add some starch paste (a little starch boiled up with considerable water), and then a little, red, fuming nitric acid, when, if iodine is present, it will impart a deep blue color to the starch. To the blue solution add chlorine water drop by drop, which at first sets iodine free, but, when added in excess, combines with it to form a colorless compound. Continue, there- fore, to add the chlorine water until the color of iodine disappears, when, if bromine is absent, the solution will be colorless, but, if present, it will be yellowish-red, owing to liberated bromine. This color shows more dis- tinctly when the liquid is agitated with carbon disulphide, which dissolves the bromine.

For the detection of chlorine, provided bromine and iodine are present, take another portion of the solution, add silver nitrate and a little nitric acid, and then filter off and wash the precipitate, which may contain AgCl, AgBr, and Agl. Transfer this to a beaker, treat with ammonia to dissolve AgCl and AgBr, filter from the insoluble Agl, then precipitate the silver salts from the filtrate by addition of nitric acid, and collect them on a filter. Mix the moist precipitate on charcoal with a little more than its volume of sodium carbonate, fuse before the blowpipe, cut away the fusion, treat it with hot water, filter the soluble sodium chlo- ride and bromide from the silver, and evaporate the filtrate to dryness in a dish or casserole. Grind the dried residue with an equal volume of potassium di- chromate, transfer to a tubulated test-tube, Fig. 47, add a little concentrated sulphuric acid, close with a stopper, and warm, when, if chlorine is present, it forms with the chromium a red gas, CrCl,0, , which condenses to a liquid of the same color, while bromine forms red vapors of bromine. If some of the red vapors are distilled over into a second test-tube, and nG' 7"

are then treated with a little ammonia, the bromine will be converted wholly into colorless compounds, while the OCl,Ot will yield ammonium chromate, which is yellow. The yellow color of ammonium chromate in the second test-tube is, therefore, a proof that chlorine was present.

Chromium, Cr. — Trivalent and sexivalent. Atomic weight, 52.5,

Occurrence. — Chromium is not a very abundant element, and the mineral from which nearly all its commercial compounds are

70 REACTIONS OF THE ELEMENTS. Chrcmlum

made is chromite, FeCr04 FeO.Cr/V The element is found, in small quantities, in some varieties of spinel, garnet, muscovite, beryl, clinochlore, and other minerals where Cr.O, is isomorphous with Al,Ot or FeaO,. Of the chromates, crocoite, PbCr04, is the commonest.

Detection. — The colors which chromium imparts to the fluxes usually serve for its detection.

1. Test with a Borax Bead. — If a very little oxide of chromium is dissolved before the blowpipe in a borax bead in the oxidizing flame, the bead will be decided yellow when hot, changing to yel- lowish-green when cold. With more of the oxide, the colors are deeper, red when hot, changing through yellow to a fine yellowish- green when cold. After heating in the reducing flame, as soon as the bead cools below a red heat, it assumes a fine green color, and shows none of the yellow which is so prominent after heating in the oxidizing flame. It is probable that the color produced in the oxidizing flame depends upon the presence of OO, , the anhydride of chromic acid, salts of which are yellow or red ; while in the reducing flame the basic oxide CraO, is formed, which usually imparts an intense green color to solutions. i 2. Test with Salt of Phosphorus. — The colors which are ob- tained in the oxidizing flame with this flux are dirty green when hot, changing to fine green when cold. After reduction, the colors are about the same as in the oxidizing flame, but not so decided.

Chromium must not be confounded with vanadium, which gives in the reducing flame almost identical reactions with the flaxes, but in the oxidizing flame differs in yielding a yellow bead with salt of phosphorus, which flux never acquires other than a green color with chromium.

3. Special Tests for Small Quantities of CJiromium when Associated with other Substances which Color the Fluxes.— If the mineral is a silicate, fuse it in a platinum spoon with about 4 volumes of sodium carbonate and 2 of potassium nitrate, by which means an alkali chromate, soluble in water, will be formed. Soak out the fusion in a test-tube with about 5 cc. of water, filter, and, if chromium is present, the filtrate will have a yellow color. Make the filtrate slightly acid with acetic acid, filter again if neces-

Copper REACTIONS OF THE ELEMENTS. 71

sary, and add a little lead acetate, when a yellow precipitate of lead chro- mate will form, which may be collected on a filter, washed with water, and tested with the fluxes (compare Vanadium, p. 130, § 2). If the precipitate is very small, it will be best to burn the paper in a porcelain crucible and test the residue.

If the mineral is an oxide difficult to decompose, as some kinds of spinel or chromite, dissolve as much as possible of the very finely powdered mineral before the blowpipe in a borax bead, remove the latter from the wire, crush it in a diamond mortar, then mix with 2 or 3 volumes of sodium carbonate and 1 of potassium nitrate, fuse in a platinum spoon, and proceed exactly as described in the previous paragraph.

Cobalt, Co. — Bivalent. Atomic weight, 59.

Occurrence. — Cobalt is a comparatively rare element, found usually in combination with sulphur or arsenic, and generally associated with nickel and iron, with which it is isomorphous. A few of its more important compounds are linnaeite, Co, S4 ; smaltite, Co As, ; cobaltite, CoSAs ; and erythrite, Coi(As04),.8H10.

Detection. — The blue color which cobalt oxide imparts to the fluxes serves as a very simple and delicate means for its detection. .. - 1. Test with the Fluxes. — Oxide of cobalt is soluble before the blowpipe both in the borax and salt of phosphorus beads, imparting to them a fine blue color, which remains the same in both the oxidizing and reducing flames. The test is so delicate that cobalt can be detected in the presence of a considerable quantity of iron and nickel.

When copper or nickel interferes with the test for cobalt, remove the bead from the wire, and fuse it on charcoal with a granule of tin in a strong reducing flame, until the copper and nickel are reduced to the metallic state, when the flux will show the blue color of cobalt.

See also the special method . for treating minerals containing cobalt, nickel, iron, and copper (p. 97, § 4).

Columbium, Cb. — See Niobium.

Copper, Cu. — Bivalent in cupric and univalent in cuprous com- pounds. Atomic weight, 63.4.

Occurrence. — Copper is widely distributed in nature and is

72 REACTIONS OF THE ELEMENTS. Copper

found in a great many minerals. A few of its most important compounds are chalcopyrite, CiiFeS, ; chalcocite, CuS ; bornite, Cu8FeS8; tetrahedrite, essentially Cu8SbaST ; malachite, (CuOH)tC08; and cuprite, CufO. Copper also occurs in the native state abun- dantly in a few localities.

Detection.— The flame coloration, the formation of globules of metallic copper, and the colors imparted to fluxes and to solu- tions make the detection of copper a very easy matter. I 1. Flame Tests. — If finely divided oxide of copper is intro- duced into a colorless flame, it imparts to it an emerald-green color, which may sometimes be observed on heating minerals before the blowpipe, but often no color is obtained because no volatile com- pound of copper is present. If the assay is moistened with hydro- chloric acid, however, copper chloride, which is volatile, will be formed, and this gives a strong azure-blue color to the flame, tinged usually on the outer edges with emerald-green, due to the decom- position of the chloride and formation of copper oxide. The flame test for copper after moistening with hydrochloric acid is very delicate, but if the mineral is a sulphide, it should be fused in the oxidizing flame or roasted before applying the acid.

a. Take a piece of chalcopyrite in the platinum forceps, heat it before the blowpipe in the oxidizing flame, then touch it to a drop of hydrochloric acid, and heat again. The copper chloride soon volatilizes, but the flame may be repeatedly obtained by renewed applications of acid.

The test may also be made on platinum wire, according to directions given on p. 35.

b. Boast a little powdered chalcopyrite on charcoal, as directed on p. 39, then moisten the product with a drop of hydrochloric acid, and heat before the blowpipe in the reducing flame. In this experiment, the azure-bine flame of copper chloride is obtained in great perfection, and the surface of the charcoal near the assay will show the copper reaction if touched with the reducing flame. A beautiful emerald-green flame is obtained if the assay is moistened with hydriodic instead of hydrochloric acid, and heated before the blowpipe.

c. In order to show the green flame color given by oxide of copper, take a little malachite or cuprite in a diamond mortar, and pulverize it by striking with a hammer in close proximity to a Bunsen-burner flame, so that the fine dust from the mortar will pass into the flame.

Ooppr REACTIONS OF THE ELEMENT8. 73

2. Reduction on Charcoal to Metallic Copper. — From copper oxides and minerals containing oxide of copper, the metal may be readily reduced and obtained as fused globules by heating intensely in a reducing flame, with a flux, on charcoal. Copper globules are bright when covered with the reducing flame, but acquire a coating of black oxide on exposure to the air. They are malleable, can be flattened by hammering on an anvil, and show the red color characteristic of copper. The best flux to use is a mix- ture of equal parts of sodium carbonate and borax : This serves to keep iron and other difficultly reducible metals in solution, as in a slag, while copper may easily be reduced and fused to a globule. Minerals containing sulphur, arsenic, or antimony should first be carefully roasted, according to directions given on p. 39, then mixed with the appropriate flux, and reduced. It is evident that, when other readily reducible metals are present, a globule will be obtained which is not pure copper.

As beginners usually have some difficulty in fusing copper before the blowpipe on charcoal, it is best to use only a small quan- tity of the mineral and flux. About to ± ivory spoonful of the mineral and two or three times as much flux will be found to be a suitable quantity.

Obtain globules of copper from malachite, using a mixture of sodium carbonate and borax as a flux, and from chalcopyrite, which must first be roasted and afterwards fluxed with a mixture of sodium carbonate and borax

3. Reactions with the Fluxes. — Copper oxide dissolves readily both in the borax and salt of phosphorus beads on platinum wire. In the oxidizing flame, the colors are green when hot, but change to blue when cold. The color is due to the presence of cupric oxide, CuO, and the test is very delicate. In the reducing flame, the colors are paler, almost colorless, with little copper ; while if much is present, there is a separation of cuprous oxide, CuaO, when the fluxes solidify, which renders the beads opaque and red by reflected light. A still better way to show this reduction is to remove the bead from the wire, and, placing it on charcoal with a small grain of tin, to fuse the two together in a reducing flame. The t>ead

74 BEACTI0N8 OF THE ELEMENTS. Copper

will then be clear and nearly colorless when hot, but opaque and red on solidifying. The action of the tin is to take oxygen from the cupric oxide, changing it to cuprous oxide. The reaction suc- ceeds best with the salt of phosphorus bead, and the heating on charcoal in either case must not be too hot nor continued too long a time, as the copper may thus be reduced to the metallic state. 4. Color \of Solutions : Test with Ammonia. — If a mineral con- taining copper is dissolved in an acid (usually nitric or hydrochloric is best), the solution will be colored blue or green. On dilution with water and addition of ammonia in excess, the color becomes deep blue, owing to the formation of a complex cuproammonium salt. The test is a very good one for copper, but the color must not be confounded with the similar but much fainter blue given by solutions containing nickel when similarly treated.

a. To make this test, dissolve i ivory spoonful of malachite in a test- tube, in 3 cc. of hydrochloric acid, dilute with 10 cc. of water, and add excess of ammonia.

b. Dissolve i ivory spoonful of powdered chalcopyrite in a test-tube, in 3 cc. of nitric acid, boil until red fumes cease to appear, dilute with 10 cc. of water, and add ammonia in excess. In this experiment, the formation of a precipitate of ferric hydroxide (p 87, § 5) may at first prevent the blue color from being seen, but by allowing the precipitate to settle, or better by filtering it off, the color shows distinctly.

5. Cuprous Compounds. — Besides the sulphides and the closely related arsenides, tellurides, and selenides, there are very few min- erals which are cuprous compounds, cuprite, Cu,0, being the only common one.

A quantitative analysis id the only means available for proving that, in combinations with sulphur, copper exists in the cuprous condition. If it is demonstrated, for example, that the atomic ratio of copper to sulphur is 2:1 (see p. 6), the compound must be CutS, or cuprous sulphide.

To illustrate the reactions of cuprous oxide, dissolve an ivory spoon- ful of powdered cuprite in 3 cc. of h<Jt hydrochloric acid. Observe that the solution is nearly colorless or brown, and not blue, as with cupric com- pounds. Cool the liquid, and then add a large excess of cold water, when

Fluorine REACTIONS OF THE ELEMENTS. 75

a white precipitate of cuprous chloride, CuCl, will be thrown down, which is only sparingly soluble in water and dilute acids. The precipitate is soluble in excess of ammonia, and, if oxidation has been avoided, the intense blue color characteristic of cupric compounds (§ 4) will not be obtained, although some of the copper may have become changed to the cupric condition, owing to the oxidizing action of the air.

Didymium, Di. — Trivalent. Atomic weight, 142.

Erbium, Er. — Trivalent. Atomic weight, 166.

The reactions of these rare earth -metals are given under Cerium.

Fluorine, F. — Univalent. Atomic weight, 19.

Occurrence. — Fluorine is the characteristic non-metallic ele- ment of hydrofluoric acid, HF, and the fluorides. The number of fluorides that have been identified as minerals is not very- large, fluorite, CaF,; and cryolite, Na,AlFe, being the most important. Fluorine is found frequently as a constituent of silicates and phosphates, as in topaz, (AlF)„Si04 ; chondrodite, Mg,[Mg(F.OH)]9(Si04),; apatite, Ca4(CaF)(P04)8 ; and amblygonite, Ii(AlF)P04 , and, in such compounds, hydroxyl and occasionally chlorine are isomorphous with, and partially replace, the fluorine.

Detection. — The etching of glass and the formation of volatile compounds with silicon furnish the best methods for the detection of fluorine.

1. Etching of Glass. — This test is applicable only to. com- pounds, other than silicates, which are decomposed by sulphuric acid. If without a platinum crucible, prepare some small paste- board trays or box-covers by placing them in melted paraffin and allowing them to remain until the paper is thoroughly permeated; then, leaving several drops of paraffin in the bottom of each, place them to one side on a sheet of paper to cool. At the same time some pieces of window glass, larger than the tops of the boxes, may be coated with paraffin by dipping them in the melted material and allowing them to cool. To make a test for fluorine, in a platinum crucible or one of the prepared trays put an ivory spoonf ul of the finely powdered mineral and 3 or 4 drops of concen- trated sulphuric acid, mix the two together and cover with one of

76 REACTIONS OF THE ELEMENTS. Fluorine

the prepared glass plates on the under side of which lines have been traced through the paraffin with some pointed instrument. The action of sulphuric acid on the fluoride liberates hydrofluoric acid, HF, which attacks the silica, SiO, , of the glass wherever it is not protected by the paraffin; thus, 4HF + SiO, SiF4+ 2H,0. For a successful experiment the etching should be allowed to pro- ceed for at least one half hour, or longer if the amount of fluorine is small. The presence of fluorine is revealed by a distinct etch- ing of the glass, seen best after warming the plate and cleaning off the paraffin with a bit of paper or cloth.

Make the experiment with fluorite, CaF, , when the decomposition with sulphuric acid may be expressed as follows : CaFt + HtS04 CaS04 + 21IF.

U' 2. Test with Potassium Bisulphate. — This test is applicable only to compounds which are decomposed by fusion with the reagent Mix some finely powdered fluoride with an equal volume of powdered glass and 2 or 3 volumes of potassium bisulphate, then put not over £ ivory spoonful of this mixture in a closed tube of 6 mm. internal diameter and heat gently. The hydrofluoric acid liberated by the reaction attacks the glass, 4HF + SiO, SiF4 -f 2H,0, and at the place where the water condenses a second decom- position occurs, as follows : 3SiF4 + 2H,0 2H,SiF§ (hydrofluo- silicic acid) + SiO,. The separated silica, SiO, , forms a white ring in the tube, which is volatile as long as hydrofluosilicic acid is present, but on breaking the tube just above the fusion and wash- ing away the hydrofluosilicic acid from the upper portion with water, and then drying, the silica will no longer be volatile. The etching of the tube is not a conspicuous feature of this test, but the ring of silica is very characteristic, especially its behavior before and after washing with water.

3. Test with Sodium Metaphosphate. — This test will often be found convenient, since it can be applied to minerals which are not decomposed by sulphuric add. If the finely powdered mineral is mixed with from 4 to 6 parts of sodium metaphosphate, transferred to a bulb tube (which should not be more than one quarter full) and heated very hot, hydrofluoric acid will be given off, which etches the glass, and deposits a ring of silica exactly as described.

fluorine ABACTIONS OF THE ELKMENT8. 77

in § 2. The test is excellent for silicates when the proportion of fluorine is not too small (less than 5 per cent), but when very small quantities are to be detected the method given in § 4 is preferable.

Sodium metaphosphate may be prepared by heating phosphorus salt in a platinum dish until ammonia and water are expelled, or a sufficient quantity for an experiment may be quickly made by fusing beads of phos- phorus salt on platinum wire, and crushing them in a diamond mortar. To make the experiment, test for fluorine in topaz. The reaction with topaz cannot be expressed by a definite equation, but in order to illustrate the chemical principle involved, the simpler case of calcium fluoride, CaF, , may be chosen. CaF, + NaPO, + H,0 CaNaP04 + 2HF. It is evident that water or hydroxyl must be present in order to form HF, and this may come either from, hydroxyl in the mineral or from a trace of water that was not wholly driven out from the sodium metaphosphate.

4. Precipitation as Calcium Fluoride. —This test is especially applicable for detecting small quantities of fluorine in silicates. The mineral is first fused with sodium carbonate, exactly as described under silicates (p. 110, § 4). The fusion is then pulverized, treated in a test-tube with 5 cc. of boiling water, filtered and washed, by which means sodium fluoride is obtained in solu- tion. The filtrate is acidified with hydrochloric acid, boiled for a short time to expel carbon dioxide, a little calcium chloride added (some calcite dissolved in hydrochloric acid will answer), and then ammonia in excess. The precipitate will contain calcium fluoride, but a precipitate is not a proof that fluorine is present, for other compounds may be thrown down at this point. The precipitate must be collected on a filter-paper, washed well with water, and ignited in a crucible until the paper is completely destroyed, when the resi- due is tested according to § 2. It is not safe to test according to §1, for sometimes considerable silica is precipitated with the calcium fluoride, and in that case the hydrofluoric acid will derive silica from the precipitate instead of etching the glass.

5. Acid Water in a Closed Tube. — Most minerals containing fluorine and hydroxyl yield acid water in the closed tube, which reddens blue litmus-paper, and when the reaction is strong the glass is distinctly etched. Unless the glass is etched, however,

73 KEACT10N8 OF TAB ELEMENTS. ' °°w

a proof of the presence of fluorine must be obtained by testing according to some of the foregoing methods. In cases where fluorine is isomorphous with hydroxyl, hydrofluoric acid will sometimes be given off instead of water. The acid then etches the glass, forms a deposit of silica, and gives a strong pungent smell at the end of the tube. Prom Brazilian topaz, for example, which on analysis yields 2.5 per cent of water, the hydrogen is mostly expelled as hydrofluoric acid, and there is scarcely any indication of water, but, if freshly ignited lime or magnesia is mixed with the mineral in the closed tube, the fluorine will be retained and water driven off.

Gallium, Ga.— Trivalent. Atomic weight, 69.8.

Occurrence. — This exceedingly rare metal has been found in traces in sphalerite from a few localities. It is best detected by means of the spark spectrum.

Germanium, Gte. — Tetravalent. Atomic weight, 72.3.

Occurrence. — This very rare element has been found in argyrodite, Aga6eS6; canfieldite, Agg(SnGe)S#, in which tin and germanium are isomorphous, and in small quantity in the rare mineral euxenite.

Detection. — When argyrodite is heated before the blowpipe on char- coal, germanium volatilizes, and gives at first a pure white coating of oxide near the assay, which on prolonged heating moves farther out and assumes a greenish to brownish but mainly lemon-yellow color. When examined with a lens, the coating presents a glazed or enamel-like surface, while scattered about on the charcoal near the assay, fused, transparent to milk- white globules of germanium oxide may be detected.

In the closed tube, heated intensely before the blowpipe, a slight sublimate of germanium oxide forms, pale yellow when hot, becoming lighter on cooling, which with a lens may be seen to consist of numerous colorless to pale yellow globules.

Germanium gives no reaction in the open tube. It also imparts no characteristic color to the flame, to the fluxes, or to its solution in acids.

Glucinum, G. — See Beryllium.

m

Gold, An. — Univalent and trivalent. Atomic weight, 197.3.

Occurrence. — Gold occurs usually in the free state, that is, as native gold,, which always contains some silver and sometimes traces of copper and

Gold REACTIONS OF THE ELEMENTS. 79

iron. Native gold from California generally contains about 88 per cent of the pare metal. Gold is found disseminated in small quantity in the rocks of some regions, especially the crystalline schists. It is often concentrated in veins, where it is usually associated with quartz and pyrite, and it collects in the sands and gravels which have resulted from the disintegra- tion of rocks and mountain masses that have contained gold. Owing to its weak chemical affinity it does not form very stable compounds, and the only element vith which it is found in chemical combination in nature is tellurium. Petzite, sylvanite, krennerite, and calaverite are tell u rides of gold and silver, and nagyagite is a telluride and sulphide of lead and gold.

Detection. — The color, fusibility, malleability, high specific gravity, and insolubility in any one acid are characters which serve for the ready detection of native gold.

As gold is worth $20.67 a troy ounce, only a small percentage of the metal is needed to make an ore very valuable. One per cent would be equal to 291.66 troy ounces a ton, worth $6028. An ore containing per cent of gold would be a rich one, and under favorable conditions, by hydraulic mining, gravels are washed which do not carry over ten cents worth of gold a ton, or less than 1 0 0*0 0 0 of one per cent of the pure metal.

Washing and Collecting in Mercury. — When gold is present in very small quantity, even less than yjVff of one per cent, it may be usually detected with great ease by washing or panning. This process consists in washing away with water the lighter rock constituents (for the most part less than 3 in specific gravity) from the gold, which varies from 15 to 19.3 in specific gravity, according to the proportion of silver it contains. In order to make the test, select a sample of the ore weighing at least a pound, pulverize it, and sift the material through a fine sieve. At the end of the operation, care must be taken to look for particles of gold on the sieve, for, being malleable, the particles are not pulverized. The powder, and the metal left on the sieve, if there is any, are put in a metal pan, £ cc. of mercury is added, and the pan is immersed in water and agitated for some time with a rocking and twisting motion, by which means the heavy gold goes rapidly to the bottom, while the lighter constituents arrange themselves above according to differences in specific gravity. From time to time the pan is inclined, and by a little motion a ripple of water is made to pass over the contents of the pan, and carry off some of the lighter material from the top. By continuing this process, the material is finally concentrated so that the gold is contained in a very small volume, and is taken up by the mercury at the bottom of the pan. To get rid of the last of the rock material, the contents of the pan are transferred to a mortar, and ground in a stieam of water, by which treatment the fine particles are rapidly carried away, and finally only the mercury, with which the gold has amalgamated, is left. In order to obtain the gold, the mercury contain- ing it is dried with blotting-paper, transferred to a shallow cavity on char-

Reactions Of Tse Elements.

coal, and volatilized by heating with a small blowpipe flame. The residual gold may be fused to a globule, using a little borax or sodium carbonate when necessary. In order that no ill effects may result from the poisonous

Pm. 48. mercury vapors, a piece of wet blotting-paper should be placed on the char- coal, care being taken not to wet the cavity, and another piece arched over it (Fig. 48), thus furnishing a large cooling surface upon which the mer- cury will condense.

When tellurides are to be tested, the powdered ore should be roasted and then washed jib directed above. The roasting may be accomplished by putting the ore in an iron pan (a piece of sheet iron with the edges turned np) and heating it to faint redness in a Btove for some time. It is w-ll to stir the powder occasionally with an iron wire.

Gold may he washed or panned without the use of mercury. After washing away the lighter material the particles of gold may often be seen on the bottom of the pan aa a "color." The metallic particles may be collected in mercury and treated as directed in the foregoing paragraph, or the concentrated material may be fused with test load and borax, and treated as directed under the silver assay,{p. 114, § 3).

The gold globules obtained by the foregoing processes will always contain some sliver. In order to obtain the pure gold, the metal should be fused with about 3 times its weight of pure silver, and then treated in a porcelain dish or capsule with a little warm nitric acid, which dissolves the silver and leaves the gold as a brownish-black powder or dark coherent mass. This process of separating gold from silver is called parting. The finely divided gold may be washed and finally collected and fused into a globule on charcoal.

In exceptional cases, platinum or some of the metals of the platinum group may be found with the gold.

Helium, He. — Atomic weight, 4?,

Occurrence. — This element has been recently discovered, and it seems to be present only in minerals containing uranium, tho- rium, and yttrium. It is given off as a gas when minerals con- taining it are heated or are dissolved in sulphuric acid. It is detected by means of the spark spectrum.

Hydrogen REACTIONS OF THE ELEMENTS. 81

Hydrogen, H. Univalent. Atomic weight, 1.

Occurrence. — Hydrogen is found abundantly in nature in combination with oxygen as water, and in combination with carbon in hydrocarbons (p. 61). There are many minerals which crystallize with a definite quantity of water, known as water of crystallization. This water constitutes a part of the chemical molecule, and is always expressed in the formula. Thus, gypsum is CaS04.2HtO, and it contains 21 per cent of H,0; natron is NasCOs.10HtO, and it contains 63 per cent of HtO. Such min- erals are called hydrous, while those containing no water are anhydrous. It is characteristic of water of crystallization that it is expelled from a mineral by very gentle ignition, always at a temperature far below a red heat and frequently below 100° C. Again, there are minerals containing the univalent radical 7iy- droxyl, OH, which are known as hydroxides. For example, brucite is magnesium hydroxide, Mg(OH), or MgO,H, , and limon- ite is a ferric hydroxide, Fe408(OH)e. Hydroxides when heated yield water. Thus, brucite, Mg(OH)a MgO + HaO, and limon- ite, Fe408(OH)e 2Fe,08 + 3HaO, but it is characteristic for hy- droxides that they must be strongly heated, sometimes to a white heat, before they are decomposed and water is given off. They thus differ from compounds containing water of crystallization.

Water of Crystallization and Hydroxyl.

Detection. — Water is readily detected by means of the closed- tub reaction.

1. Closed-tube Reaction. — Minerals containing either water of crystallization or hydroxyl, when heated in the closed tube, yield water, which collects on the cold walls of the tube. . The test is very delicate, and usually pure distilled water is obtained "which is neutral to teskpapers.

a. To illustrate this reaction, heat gypsum or brucite in a closed tube, using fragments about 2 to 4 mm. in diameter, and also make one experi- ment with a minute fragment, in order to show the small quantity of water which may be detected by this means.

82 REACTIONS OF THE ELEMENTS. toawi*

b. To illustrate the difference between water of crystallization and hydroxyl, take two closed tubes of equal size, place some gypsum in one and brucite in the other, and then, holding the tubes side by side, pass them back and forth through a small flame so as to heat the ends slowly and equally. In the tube containing gypsum, water is driven off when the temperature is scarcely above 100° C, while brucite does not yield water until the temperature is much higher.

2. Add Water in the Closed Tube. — Hydrous compounds of the weak basic elements, such as iron, aluminium, copper, and zinc, with volatile acids, are decomposed on strong ignition, yield- ing acid water (compare the tests for Fluorine, p. 77, § 5, and for a sulphate, p. 123, § 3).

An excellent closed-tube experiment may be made with copperas, FeSO%. 7H,0, which it is well to compare with that of gypsum. By heating very gently, only neutral water is driven off at first, but on stronger ignition the FeS04 is decomposed into FeO and SO,. A secondary reaction also sets in, giving SOt, which may be detected by its odor. 2FeO -+- SO, Fe.O, + SO,. Both SO, and SO,, the anhydrides of sulphuric and sulphurous acids, render the water in the tube strongly acid. The strong basic elements, such as sodium, potassium, calcium, strontium, and barium, form stable sulphates; that is, sulphates which are not decomposed except by intense ignition, and which do not part with their acid constituents in a closed tube.

3. Alkaline Water in the Closed Tube. — Minerals which yield alkaline water are of rare occurrence, but it is sometimes obtained from those containing ammonia.

Indium, In. — Trivalent. Atomic weight, 113.3.

Occurrence. — This exceedingly rare metal has been found in small quantity in sphalerite from a few localities. Its presence is revealed by the blue color it imparts to non-luminous flames, and these when examined with the spectroscope show an intense indigo-blue and a less intense violet line. .

Iodine, I. — Univalent. Atomic weight, 127.

Occurrence. — Iodine is rarely met with, and the only known minerals containing it are iodyrite, Agl; marshite, Cul; and lautarite, Ca(IO,),.

Detection. — The reactions of iodine are similar to those of chlorine and bromine (see p. 67). Silver nitrate precipitates silver iodide, Agl, which differs from silver chloride and silver bromide in being almost inaol*

Iron BBACTIOK8 OF THE ELEMENTS. 83

able in ammonia. With potassium bisulphate in a bulb tube, either with or without pyrolusite, iodine is liberated, and may be recognized by its violet Tapors, or, if the reaction is strong, by its crystallization in the tube. Silver iodide when heated in a closed tube with galena yields a sublimate of lead iodide, which is dark orange-red when hot, changing to lemon- yellow when cold.

Iridium, Ir. — Trivalent and tetravalent. Atomic weight, 193. Iridium is one of the rare metals occurring with platinum (see p. 104).

Iron, Fe. — Bivalent in ferrous and trivalent in ferric com pounds. Atomic weight, 56.

Occurrence. — Iron is found very abundantly in minerals (p. 3), and those from which most of the metal of commerce is made are magnetite, Fe,04 ; hematite, Fe,0, ; limonite, Fe408(OH)e ; and siderite, FeCO,. Iron is found in a great variety of combinations with sulphur (pyrite, FeSt ; pyrrhotite, FenS„ ; and chalcopyrite, CuFeS,), and among the salts of most of the mineral acids, sili- cates, phosphates, etc. It is important to distinguish between two classes of compounds, the ferrous containing bivalent, and the ferric containing trivalent, iron. Examples of ferrous com- pounds are :

/

siderite, Pe<Q>C O; almandine garnet, Si ;and

JA-Ok triphylite, Fe<07P 0*'

and at ferric compounds:

hematite, >o; andradite garnet, Si ; and Fe=0 O OFe

scotodite, Fe£ O-7AS 0.2H.O.

84 REACTIONS OP THE ELEMENTS. Iron

Many minerals contain both ferrous and ferric iron, as magnet- ite, Fe,04 PeO + FetOt. Ferrous iron is very often isomor- phous with the bivalent metals, magnesium, manganese, zinc, cobalt, and nickel; and ferric iron, with the trivalent metal aluminium.

Detection. — The magnet will usually serve for the detection of iron, while more delicate tests can be made with the fluxes or in the wet way with potassium ferri- and ferrocyanides. 1. Test with a Magnet — Only a few of the minerals contain- ing iron (magnetite and pyrrhotite) are attracted by the ordinary magnet,* but many of them, especially the sulphides, oxides, and carbonates, become magnetic after being heated before the blow- pipe in the reducing flame, either on charcoal or in the f orceps. - When thus heated, silicates and phosphates become magnetic only when they contain a rather large percentage of iron, but the test is rendered more delicate if the powdered mineral is fused on charcoal with about twice its volume of sodium carbonate, and the resulting slag tested with a magnet.

A magnet will not attract a piece of red-hot iron, and frag- ments of minerals that have been heated will not be attracted until they have become cold.

a. Illustrate the above by testing fragments of pyrite and hematite with a magnet, both before and after heating in the reducing flame (compare experiments e and / on p. 38).

b. Test almandine garnet with a magnet, after fusing before the blow- pipe, and also test the slag made by fusing the powdered mineral with sodium carbonate on charcoal.

2. Test with the Borax Bead. — The oxides of iron are soluble in borax, and give colors which depend upon the amount of material in solution and the state of oxidation of the iron. la tlie oxidizing flame, the bead contains FetO, , and with little oxide it is yellow (amber-colored) when hot, fading to nearly colorless

An electromagnet, arranged with its poles close together so as to give & con- centrated field, attracts all minerals containing iron, unless the percentage of the metal is small.

Iron BEACTIONS OF THE ELEMENTS. 85

when cold, while with more oxide it is brownish-red when hot and yellow when cold. In the reducing flame, the bead contains FeO, or PeO with PetOt , and the colors are not so intense, with little oxide, being pale green when hot, colorless when cold; and with more oxide, bottle-green when hot, changing to a paler shade oa cooling.

3. Test with the Salt of Phosphorus Bead. — In the oxidizing flame with little oxide, the color is yellow when hot, changing to colorless when cold, and with more oxide, brownish - red,

. changing through yellow to nearly colorless. In the reducing

; flame with little oxide, the color is pale yellow when hot, fading

through pale green to colorless, and with more oxide, brownish-red

when hot, changing on cooling to yellowish-green, and finally to

nearly colorless or, if much oxide was used, to a very pale violet.

4. Special Tests for Ferrous and Ferric Iron. — With the exception of the sulphides and a few rare combinations, if minerals are dissolved in hydrochloric or sulphuric acid, the solution will contain the iron in the same state of oxidation as it existed in the original substance. For example, siderite, ferrous carbonate; and hematite, ferric oxide, when dissolved in hydro- chloric acid, yield ferrous and ferric chlorides, respectively. FeCO, + 2HC1 FeCl, + HfO + COw and Fe,08 + 6HC1 2FeCl, + 3H,0.

Ferrous Iron. — This may be detected by adding potassium ferricyanide to the cold, dilute, acid solution, when a deep blue precipitate of ferrous ferricyanide will be formed, which does not differ in color from Prussian blue. SFeCl, + KtPei(CN)lt Fe.Fe.CCN),, + 6KC1.

In solutions containing ferrous salts, potassium ferrooyanide produces a pale bluish-white precipitate of K,Fet(CN)§ , which by absorption of oxygen from the air speedily acquires a blue color. Ammonium sulpho- cyanate causes no coloration in solutions of ferrous salts, provided they are entirely free from ferric compounds.

Ferric Iron. — This may be detected by adding potassium ferro* cyanide, to the cold, dilute, acid solution, when a deep blue

86 REACTIONS OF THK ELEMENTS. Iron

precipitate of ferric ferrocyanide, or Prussian blue, will be formed. 4FeCl, + 3K4Fe(CN), Fe.PeCN),. + 12KC1.

Addition of ammonium sulphocyanate, NH4CNS, produces, even in dilute solutions of ferric salts, an intense blood-red color, but no precipitate.

Potassium ferri cyanide deepens the color of solutions containing ferric salts, but fails to produce a precipitate.

Conversion of Iron from One State of Oxidation to the Other. — a. Ferrous iron may be converted to ferric by boiling the hydro- chloric acid solution with a few drops of nitric acid. The reaction is a rather complicated one, but in principle it is simple. Nitric acid furnishes oxygen, and the change may be indicated as follows : 2FeCls + 2HC1 + O 2FeCl, + H,0.

b. Ferric iron may be changed to ferrous by boiling the hydro- chloric acid solution with metallic tin or zinc until the yellow color entirely disappears (see p. 26).

Prepare a solution containing ferrous iron by dissolving £ ivory spoonful of powdered siderite in 5 cc. of boiling hydrochloric acid.

a. To illustrate the reaction for ferrous iron, take a few drops of the solution in a clean test-tube, dilute with cold water, and add a little of a freshly prepared solution of potassium ferricyanide, but avoid using a large excess of the reagent, for in this case, owing to the yellow color of the solution, the precipitate, when suspended in it, will appear green instead of blue.

b. To show the conversion of ferrous to ferric iron, boil the remainder of the solution with a few drops of nitric acid, and note the change in color.

c. To illustrate the reactions for ferric iron, take a few drops of the solution, oxidized as directed in the foregoing paragraph, dilute with water, and add a little potassium ferrocyanide, or test a similar dilute solution with ammonium sulphocyanate. Save the remainder of the solution for the experiment under § 5.

The tests with potassium ferricyanide for ferrous iron and with pot*s- sium ferrocyanide for ferric iron are exceedingly delicate, and a very good way of applying them is to take drops of each reagent on a clean porcelain plate, and by means of a glass rod or tube to bring in contact with Chein drops of the solution to be tested.

Detection of Ferrous and Ferric Iron in Insoluble MtTveraZs especially Silicates. — Most minerals which are insoluble in acids

Uad REACTIONS OF THE ELEMENTS. 87

may be dissolved after they have been decomposed by fusion with borax. To make the test, take about J ivory spoonful of the finely powdered mineral and three times its volume of powdered borax- glass in a rather large closed tube, and fuse in a Bunsen-burner flame. While hot, crack the glass about the fusion by touching drops of water to it, break off the end, transfer to a test-tube con- taining 3 cc. of hydrochloric acid and boil for about a minute, then dilute with 5 cc. of water. Divide the solution into two irts and test one for ferrons iron with potassium ferricyanide, the other for ferric iron either with ammonium sulphocyanate or potassium ferrocyanide. The tests are very decisive, and oxida- tion resulting from contact with the air and reduction during fusion, which can not be wholly avoided, are so trifling that practically they may be disregarded.

f 5. Precipitation of Ferric Iron with Ammonia. — Ammonia added in excess to a solution containing ferric iron precipi- tates the latter completely as brownish-red ferric hydroxide. FeCl, + 3NH4OH Fe(OH), + 3NH4C1. The precipitate ' can be readily filtered, and thus iron can be wholly removed from a solution. Ferrous iron is partially thrown down by ammonia as a dirty green precipitate, which slowly acquires a brown color, owing to the absorption of oxygen from the air.

Lanthanum, La. — Trivalent. Atomic weight, 138. The reactions of this rare earth-metal are given under Cerium.

Lead, Pb. — Bivalent and tetravalent. Atomic weight, 207.

Occurrence. — Lead is very widely distributed in nature and is found most abundantly in galena, PbS. Among various other combinations, the commonest are cerussite, PbCO, ; anglesite, PbSO, ; pyromorphite, Pb4(PbCl)(P04). ; and wulfenite, PbMo04. It is worthy of note that silicates of lead are exceedingly rare.

Detection. — The formation of metallic globules and a coating of the oxide on charcoal are usually sufficient for the detection of lead.

1. Reduction on Charcoal to Metallic Lead and Formation of a Coating of Lead Oxide. — Lead is readily reduced from its

88 REACTIONS OF THE ELEMENTS. LeaH

compounds, and one of the best methods for its detection is to mix ivory spoonful of the powdered mineral with an equal volume of charcoal-dust and about 3 volumes of sodium carbonate, moisten to a paste with water, transfer to a flat charcoal surface or a shal- low cavity, and heat before the blowpipe in a moderately strong reducing flame. By a little manipulation of the blast, ilw particles of lead may be made to move about and unite into a single globule, which appears bright when covered with the reducing flame, but on cooling becomes dull, owing to a coating of oxide. Lead is, moreover, somewhat volatile, and that portion which passes off as vapor unites with the oxygen of the air, and deposits on the charcoal as a coating of oxide, which is sulphur- yellow near, and bluish- white distant from the assay. The coating is volatile when heated in either the oxidizing or reducing flame. The lead globule is soft and malleable, and may be cut with a knife or flattened by hammering on an anvil.

The test may be made with cerussite or other lead compound, and it will be well to make a good-sized lead globule for use in future experiments. The best idea of the coating of lead oxide may be obtained by removing the globule to a shallow cavity in a fresh piece of charcoal, and heating for a short time before the blowpipe at the tip of the blue cone.

From the foregoing reaction on charcoal, the identity of lead is seldom doubtful, but the test is sometimes modified by the presence of other elements, while bismuth gives reactions which in appearance are very similar to those of lead.

When galena is roasted alone on charcoal at a rather high temperature, an abundant white sublimate is formed, resembling oxide of antimony, and consisting chiefly of some volatile com- bination of PbO and SO,. If roasted carefully, however (p. 39, Fig. 41), at a very low temperature, SO, is given off, and a globule of lead formed, accompanied by the yellow coating of lead oxide, but without much of the white coating just mentioned.

In the presence of sulphide of antimony, it is recommended to roast the powdered mineral on charcoal with a very small oxidizing flame, until the antimony is mostly volatilized, and then to add

Lead REACTIONS OF THE ELEMENTS. 89

sodium carbonate to the residue, and heat in the reducing flame so as to form globules of metallic lead, which, however, will still contain some antimony.

2. Iodine Test. — When a coating of lead oxide on charcoal is moistened with a few drops of hydriodic acid and heated with a small flame, a volatile and very conspicuous chrome-yellow deposit of lead iodide is formed, which appears greenish-yellow when there is only a thin coating of it on the coal. A similar coating may be obtained by adding to the powdered mineral from 2 to 4 volumes of a mixture of potassium iodide and sulphur (p. 26;, and heat- ing on charcoal in a small oxidizing flame, or by heating on a gypsum tablet as described on p. 17.

3. Flame Colwation. — Lead compounds, when heated in a. re- ducing flame before the blowpipe, may impart a pale azure-blue color to the flame, showing a greenish tinge in the outer parts. If the experiment is made in the forceps, special care must be taken not to alloy the platinum.

4. Solution and Precipitation of Lead. — It is best to use dilute nitric acid (1 part HNO, to 2 of water) for the solution of lead minerals. Concentrated nitric acid will not answer, owing to the insolubility of lead nitrate in it. From solutions containing lead, sulphuric and hydrochloric acids throw down lead sulphate, PbS04, and lead chloride, PbCl, , respectively, as heavy white precipitates. The chloride is quite soluble in hot water and sparingly so in cold, therefore it will not be formed in solutions which are hot or too dilute. It is frequently convenient to dissolve a lead mineral in rather dilute boiling hydrochloric acid, when, on cooling, most of the lead will crystallize out as lead chloride.

Tests may be made by dissolving the lead globule from § 1 in about 3 cc. of dilute nitric acid, dividing into 2 parts, and adding to one a few drops of dilute sulphuric and to the other a few drops of hydrochloric acid. They may also be made with the solution obtained by dissolving some lead min- eral (cerussite or pyromorphite) in dilute nitric acid.

In some minerals, it may be found advantageous to test for lead as follows: Decompose from 3 to 5 ivory spoonfuls of the fine

90 REACTIONS OF THE ELEMENTS. Lithium

powder in a casserole with nitric acid, add 2 cc. of concentrated sulphuric acid, and evaporate until the nitric acid is removed, and white, choking fumes of sulphuric acid commence to come off. When the dish becomes cold, add water, stir for some time, then filter off the insoluble lead sulphate, and test some of it according to § 1.

Lithium, Ii. — Univalent. Atomic weight, 7.

Occurrence. — This alkali metal is found only in the silicates

and phosphates, but is not of very rare occurrence. The commonest minerals containing it are lepidolite, LiK[Al(F.OH)JAl(SiO,), ; spodumene, IaAl(SiO,)t ; triphylite, LiFePO, ; lithiophilite, IiMnP04 ; amblygonite, Li[Al(F.OH)]P04 ; and some varieties of tourmaline and mica.

Detection. — The crimson color which lithium imparts to a flame will usually serve for its detection. The test may be made according to directions given on p. 35. The color of a pure lithium flame is nearly monochromatic, showing, when examined with the spectroscope, one bright crimson and one very faint yellowish-red band. In testing minerals, it will be found that the appearance of the flame is somewhat modified by the presence of other substances, especially sodium, which is apt to occur in small quantities with lithium, but usually its disturbing influence may be overcome by the fact that lithium is more volatile than sodium. When, therefore, the assay is first introduced into the flame, the red of lithium will show before the yellow of sodium, and when the flame is strongest, if the position of the assay is changed to where the heat is less intense, the yellow will disappear first, and finally the red of lithium will be distinctly seen. Where the pro- portion of sodium is large, however, the spectroscope must be fresorted to. In testing silicates, it will often be found advan- tageous to mix the assay with powdered gypsum, and to heat as directed under potassium (p. 105, § 1, c). Colored glasses do not assist very much in the analysis of mixed flames containing lithium.

Magnesium REACTIONS OF THE ELEMENTS. 91

The crimson flame of lithium must not be mistaken for that of strontium, which it resembles very closely (p. 116, § 1).

Magnesium, Mg. — Bivalent. Atomic weight, 24.

Occurrence. — Magnesium is a very common element (p. 3), being found in a great many silicates, several of which are important rock-making minerals; as pyroxene, amphibole, biotite, enstatite, olivine, and serpentine. It occurs also in a variety of other combinations, such as brucite, MgOtH, ; magnesite, MgCO, ; dolomite, MgCaCO,), ; spinel, MgAlt04 , etc. In the majority of its compounds, some ferrous iron is isomorphous with the magnesium.

Detection. — There are no satisfactory blowpipe tests for mag- nesium, and it is best detected in the wet way by precipitation as ammonium magnesium phosphate.

1 . Precipitation as Ammonium Magnesium Phosphate. — From a solution made strongly alkaline with ammonia, sodium phos- phate causes the formation of a white crystalline precipitate of ammonium magnesium phosphate, NH4MgP04.6HsO. Before making the test for magnesium, however, it must be ascertained that substances precipitated by ammonia, ammonium sulphide and ammonium carbonate or oxalate, have been removed from the solution, as otherwise a phosphate of some other element might be thrown down and mistaken for magnesium; while magnesium will not be precipitated by the above-mentioned reagents, provided (a) that the solution is sufficiently dilute, (ft) that it contains some free mineral acid, such as hydrochloric or nitric, and (fc) that it does not contain an acid with which magnesium forms an insoluble combination (phosphoric, for example). The manner in which the test is applied may be illustrated by the following experiments:

a. Dissolve ± ivory spoonful of brucite, MgO,Hf , in 3 cc. of hydro- chloric acid, warm if necessary, dilate with from 5 to 10 cc. of water, add ammonia in excess, and finally a few drops of a solution of sodium phosphate.

b. Dissolve 4 ivory spoonful of dolomite, CaMg(COt), (with probably a trace of FeCO,), in 3 cc. of boiling hydrochloric acid, add a drop of nitric

92 REACTIONS OF THE ELEMENTS. ManganeM

acid to oxidize the iron, then 5 cc. of water, heat to boiling, add ammonia in excess, and filter, provided a precipitate of ferric hydroxide has formed (p. 87, § 5). To the filtrate containing calcium and magnesium chlorides add ammonium carbonate or oxalate, which precipitate calcium (p. 60, §§ 5 and 6), filter, and test the filtrate with sodium phosphate.

For the detection of magnesium in silicates and complex bodies, see p. 110, § 4. 2. Alkaline Reaction. — A few magnesium minerals become alkaline after ignition, but the test, which is made by placing the ignited material upon moistened turmeric-paper, is not very de- cisive nor satisfactory.

3. Test with Cobalt Nitrate. — Some of the white or colorless magnesium compounds, when moistened with cobalt nitrate and ignited before the blowpipe, assume a faint pink color, but the test is neither very general in its application nor very satisfactory.

Manganese, Mn. — In minerals, usually bivalent, but sometimes trivalent and tetravalent. Atomic weight, 55.

Occurrence. — Manganese is very widely distributed in na- ture, small quantities of it, usually a fraction of 1 per cent, being found in many minerals and in most of the silicate rocks. Some of the common manganese minerals are pyrolusite, MnOt ; mangan- ite, MnO(OH) ; braunite, Mn,0, ; hausmannite, Mns04; rhodochro- site, MnCO, ; rhodonite, MnSiO, ; tephroite, MntSi04 ; and lithi- ophilite, LiMnP04. It occurs rarely as sulphide (alabandite, MnS, and hauerite, MnSt).

Detection. — Manganese can be readily detected by means of the sodium carbonate and borax beads.

, 1. Test with a Sodium Carbonate Bead. — Oxide of manganese dissolves in a sodium carbonate bead, when heated before the . blowpipe in the oxidizing flame, with the formation of sodium manganate, Na,Mn04. The bead thus formed is green when hot and bluish-green when cold. The test is a very delicate one, and other substances are not apt to interfere with it. In the reducing flame, the manganese is reduced to MnO and the bead loses its color.

Mercury REACTIONS OF TUE ELEMENTS. 93

The experiment can be made by dissolving a very little pyrolusite, or other mineral containing manganese, in a sodium carbonate bead made according to directions given on p. 24.

A similar test may be made by fusing some of the finely powdered mineral on platinum-foil or in a spoon with sodium carbonate, to which a little potassium nitrate has been added in order to bring about the oxidation. By this means a very small quantity of oxide of manganese, 0.10 per cent, may be detected by the bluish-green color of the fusion.

>£2. Test with a' Borax Bead. — Oxide of manganese dissolves in boraXj giving in the oxidizing flame a bead which is opaque while hot, but on cooling becomes transparent and has a fine, reddish- violet or amethystine color, due to the presence of a higher oxide of manganese. It takes only a very little manganese to give this test, and if too much is added, the color of the bead is so intense that it appears black. If the bead is not too strongly colored, it will speedily become transparent while held in the reducing flame The manganese is thus reduced to a lower oxide, MnO, and the bead is colorless. If the bead containing MnO is again heatBn the oxidizing flame, clouds, which indicate the presence 01 a, higher oxide of manganese soon make their appearance, and, on cooling, the bead is reddish-violet. Other substances which giv4 colors to borax may, of course, interfere with this test.

3. The Salt of Phosphorus Bead. — This assumes an amethys- tine color with manganese if heated in the oxidizing flame, but the test is not so delicate nor satisfactory as with borax.

4. The Higher Oxides of Manganese — There are a number of these containing more oxygen than MnO. They dissolve in hydrochloric acid with evolution of chlorine gas, and some of them, when heated, give oxygen gas (compare Oxygen, p. 100, §§ 1 and 2).

Mercury, Hg. — Bivalent in mercuric, and univalent in mercu- rous, compounds. Atomic weight, 200.

Occurrence. — Mercury is not widely disseminated in nature and is found in only a few minerals, the one which furnishes most

94 RBACTT0N8 OF THE ELEMENTS. Ntorourf

of the metal of commerce being cinnabar, HgS. The following are all of rather rare occurrence : native mercury ; amalgam, Ag with Hg ; tiemannite, HgSe '; onof rite, HgSe with HgS ; calomel, HgCl, and the varieties of tetrahedrite containing mercury.

Detection. — The formatioi\ of metallic mercury, by heating with sodium carbonate in a closed tube, is usually the most satis- factory test.

1. Closed-tube Tests. — If the pulverized mineral is intimately mixed with about 4 volumes of dry sodium carbonate, transferred to a closed tube, covered with an additional layer of sodium car- bonate about i cm. long, and heated in a Bunsen-burner flame, at first rather cautiously, the mineral will be decomposed and metal- lie mercury will distil off and condense as globules on the walls of the tube. If only a little mercury is formed, it will appear as a gray sublimate composed of minute globules which may be made to unite by rubbing with a platinum wire or slip of paper.

Mercury compounds, when heated alone in a closed tube,

usually volatilize without decomposition.

Vr. To make the test, take about ivory spoonful of cinnabar and 2 of dry sodium carbonate, mix them intimately by trituration in an agate mor- tar, and proceed as directed above. Dry sodium carbonate may be had by heating some of the ordinary material below redness either in a porcelain crucible or on any clean metal surface. The reaction is as follows : HgS + NCO, Hg + 0 + CO, 4- Na,S. On breaking the tube and placing some of the residue containing Na,S on silver along with a drop of water, a test for the sulphur may be obtained (p. 120, § 5).

b. Heat some cinnabar alone m a closed tube, and observe the black sublimate of HgS. which resembles the arsenical mirror. Also observe that no metallic mercury is formed.

2. Open-tube Reaction, — A convenient way of testing sulphide of mercury is to roast a little of the mineral in a rather large open tube, when the products formed are essentially metallic mercury and SOt. For success in this experiment, the tube is at first heated very hot just above the substance, and then the latter is heated nery carqfvlly and gradually so as not to drive off any black, unoxidized sublimate of HgS. Often a slight non-metallic sublimate forms, possibly some combination of oxide of mercury

Molybdenum REACTI0N8 OF THE ELEMENTS. 95

and SO, , but if this is driven up the tube by heat, it is for the most part decomposed, and the resulting gray sublimate will be found to consist of minute globules of mercury, which may be united by rubbing with a wire or slip of paper.

3. Precipitation upon Copper.— li a bit of clean copper is placed in a solution containing mercury, the mercury will deposit in the metallic state upon the copper, and the latter will then appear as if it had been silver-plated.

Boil a mixture of powdered cinnabar and pyrolusite for a short time with hydrochloric acid, dilute with water, and introduce into the cold solu- tion a copper coin or strip previously cleaned by dipping it into strong nitric acid and washing with water. The action of the pyrolusite is to liberate chlorine (p. 101, § 2), which is essential for the solution of the cinnabar. The deposition of mercury upon the copper is due to a simple interchange of the metals. HgCl, + Ou Hg + CuCl,.

Molybdenum, Mo. — Tejfcravalent and sexivalent. Atomic weight, 96.

Occurrence. — Molybdenum is found sparingly in nature, and mostlup molybdenite, MoS, , and wulfenite, PbMo04.

Detection. — The character of the test for molybdenum depends upon whether the element occurs as sulphide or in an oxidized condition. For the former, an oxidation, and for the latter, a reduction test is recommended.

,1. Roasting on Charcoal — If a fragment of molybdenite is heated on v. a flat charcoal surface for a considerable time in the oxidizing flame, there results, at a short distance from the assay, a coating of molybdic oxide, MoOt. This is pale yellow when hot, almost white when cold, and often consists of delicate crystals. Still nearer to the assay, the charcoal is covered with a very thin, tarnished, copper-colored coating of MoO,, which is seen best when cold and by reflected light. The MoO, coating is volatile in the oxidizing flame, and, if touched for an instant with a moder- ately hot reducing flame, it assumes a beautiful ultramarine- blue color (very characteristic), due probably to a combination of MoO, and MoO,.

2. Roasting in the Open Tube. — If thin shavings of molybdenite are heated at a high temperature in an open tube, a yellow sublimate of MoO, deposits a little above the assay, and frequently forms a mass of delicate crystals.

3. Flame Test. — A fragment of molybdenite, held in the forceps and heated before the blowpipe at the tip of the blue cone, imparts a pale yellowish-green color to the flame.

96 REACTIONS OF THE ELEMENTS. Nlokel

4. Reduction Test. — In a test-tube take about i ivory spoonful of finely powdered molybdate (wulfenite, PbMo04) and a scrap of paper not over 1 mm. square, add from 3 to 6 drops of water and an equal quantity of con- centrated sulphuric acid and heat until copious fumes of the acid begin to come off, then, after allowing the tube to become cold, add water a drop at a time. Theaddition of the first few drops of water gives rise to a magni- ficent deep-blue color, which quickly disappears when the quantity of water added amounts to a few cubic centimeters. The exact nature of this reaction is not well understood, but it is due presumably to a slight reducing action caused by the presence of the paper. It generally does not succeed well when only a very minute quantity of mineral is tested.

5. Reactions with the Fluxes. — The salt of phosphorus bead is best. If a small quantity of the oxide is dissolved in the bead in the oxidizing flame, the glass is yellowish-green when hot, changing to almost colorless when cold. In the reducing flame it becomes dirty green when hot, changing to a fine green on cooling. The tests with borax are neither very satisfactory nor decisive.

Nickel, Ni. — Bivalent. Atomic weight, 59.

Occurrence. — Nickel is a comparatively rare element, occur-

j ring most often as a sulphide or arsenide, and associated usually y mth cobalt and iron. Some of its important compounds are

millerite, NiS ; niccolite, NiAs ; chloanthite, NiAs, ; gersdorfite, NiSAs ; penthandite, NiS with PeS ; and genthite, a hydrous sili- cate of nickel and magnesium. Nickel is found with cobalt in most of the sulphides and arsenides mentioned under the latter element, and much of the metal of commerce is obtained from nickeliferous pyrrhotite, essentially FeS, but containing from 1 to 5 per cent of Ni isomorphous with the Fe.

Detection. — The element is usually detected by the color its oxide imparts to the borax bead in the oxidizing flame.

1. Test with a Borax Bead. — Oxide of nickel dissolves in the borax bead, and in the oxidizing flame yields a violet color when hot, not unlike the color given by manganese, but changing to reddish-brown on cooling. By rather long heating in a strong reducing flame, the bead becomes opaque, owing to the separation of metallic nickel, and if the bead is removed from the wire and fused on charcoal in the reducing flame together with a granule of

fllckel REACTIONS OF THE ELEMENTS. 97

metallic tin, an alloy of tin and nickel is formed, and the glass finally becomes colorless or nearly so. A small* percentage of cobalt will completely obscure the color of nickel, while a trace of cobalt in the presence of much nickel may be detected, as described on p. 71, § 1.

2. Test with a Salt of Phosphorus Bead. — This test for nickel is not very satisfactory. In the oxidizing flame, with little oxide, the bead is reddish when hot, and becomes pale yellow on cooling, while with much oxide it is brownish-red when hot, becoming reddish-yellow on cooling. In the reducing flame on platinum wire, the color of the bead is unchanged, but if heated for a long time on charcoal with a granule of tin, metallic nickel is formed, which alloys with the tin, and the glass becomes colorless.

3. Test with Ammonia. — This reagent, when added to a solu- tion containing nickel, may cause a slight precipitate at first, but the precipitate speedily dissolves and imparts a pale blue color to the solution, which must not be confounded with the much deeper color given by copper when its solutions are treated in a similar way.

4 Special Tests for Nickel and Cobalt when they Occur with Other Substances.— Treat some of the powdered mineral in a casserole with acid (nitric is best if the mineral is a sulphide or arsenide), and boil until solu- tion is effected and only about 5 cc. of acid remain. Then dilute with water, boil, add ammonia in considerable excess, and filter, when the nickel and cobalt, or at least the greater part of them, will be found in the filtrate free from iron. Boil the filtrate in a casserole, add caustic potash, and continue the boiling until the ammonia salts are decomposed, and addi- tion of more potash does not produce any additional smell of ammonia. By this treatment, nickel and cobalt are precipitated as hydroxides. These should be collected on a filter and washed once or twice with hot water. Test some of the precipitate with a borax bead in the oxidizing flame, and if it shows the color of nickel, cobalt is absent, or present only in very small quantity (compare p. 71, § 1). If, on the other hand, the bead is blue, indicating cobalt, nickel is possibly present, and may be tested for as

follows :

Ignite the paper with the precipitate in a porcelain crucible until the carbon is burned away, or, if there is a large quantity of the precipitate, some of it may be placed on charcoal and dried out with a blowpipe flame.

98 REACTIONS OF THE ELBMENT8. Niobium

The dried material is then ground in a mortar with about twice its volume of metallic arsenic and a very little fused borax, transferred to a closed tube, and heated gently at first, and finally intensely, before the blowpipe, until the nickel and cobalt, which have now united with the arsenic to form arsenides, fuse into a single globule. The glass is then cracked, and the metallic globule freed as completely as possible from slag. It is next placed upon charcoal together with a bit of borax glass, and heated at first in the reducing flame and then continuously in the oxidizing flame, by which treatment the cobalt is slowly oxidized and imparts to the borax its- characteristic color. Sometimes the color is not seen distinctly until some of the fused borax is taken up in the forceps and drawn out into a thread. If the quantity of cobalt is considerable, it may be necessary to remove the globule from the slag (best done by taking the globule in the forceps and plunging it while hot into cold water), and fuse it with a fresh portion of borax. As long as cobalt is present, nickel will not oxidize, and the surface of the bead remains bright while hot, but when the cobalt has all been re- moved, the nickel commences to oxidize, and its oxide forms a crust over the surface of the bead, which is not as readily dissolved by the borax as the oxide of cobalt. The appearance of the bead, therefore, indicates that cobalt is no longer present, and if the bead is removed and fused against a fresh portion of borax, it imparts to the latter the brown color char- acteristic for nickel. Considerable experience in the use of the blowpipe is needed to carry out this operation successfully. Sometimes a mineral may be fused directly in the reducing flame, to a globule of sulphide or arsenide, and then treated in the oxidizing flame with borax on charcoal as described above. If iron is present, it oxidizes before the cobalt. Copper, which does not interfere with the test, oxidizes only after the nickel has all been re- moved.

For the detection of small quantities of nickel in pyrrhotite, the test as given above may be recommended.

Niobium, Nb. — Pentavalent. Atomic weight, 94.

Oocurbenoe. — Niobium, called also columbium, Cb, is almost invari- ably associated with tantalum, and together they constitute the acid-form- ing elements of a group of minerals known as the niobates and tantalates. The two elements are isomorphous with one another, and their compounds are characterized by being unusually heavy. Some of the more common minerals containing them are columbite, tantalite, pyrochlore, microlite, fergusonite, samarskite, euxenite, and polycrase. Niobium is, moreover, occasionally found in silicates, as wohlerite.

Detection. — Niobium is best detected by boiling an acid solution con- taining it with metallic tin, and obtaining a blue color which is due to reduction.

*ftrosn REACTIONS OF THE BLEHENT8. 99

1. Reduction Test. — As the niobates are usually very insoluble in acids, they must first be decomposed, which may be accomplished most conven- iently as follows: Mix the finely powdered mineral with about 5 times its bulk of borax, moisten to a paste with water, take up some of the mixture in a loop on platinum wire, and fuse at a high temperature before the blow- pipe. Make two or three of these beads, remove them from the wire, crush in a diamond mortar, and boil the powder with 5 cc. of hydrochloric acid, which should yield a clear or nearly clear solution. On adding some gran- ulated tin, and boiling, the blue color of niobium will appear, which is not readily changed to brown by continued boiling, and which rapidly disap- pears upon addition of water. The blue color is due to reduction, but the composition of the compound which causes it is not definitely known. If titanium is present, the violet color due to the reduction of that element appears before the blue of niobium. An acid solution containing niobium, if treated in a similar manner with metallic zinc, becomes sometimes mo- mentarily blue, but the color soon changes to brown, owing to reduction to NbCl,. Tungsten gives similar reduction tests, but may be readily dis- tinguished from niobium by a number of reactions mentioned under that element.

2. Decomposition with Potassium Bisulphate. — A method that is very generally adopted for the decomposition of niobates and tantalates is to fuse the finely powdered mineral with from 8 to 10 parts of potassium bisul- phate. The fusion is ordinarily done in a crucible, but it may also be made in a test-tube, since the heat which is required need not exceed faint red- ness and the glass is not attacked. When the decomposition is complete, as shown by the disappearance of dark particles, the tube may be inclined and turned while cooling, causing the fusion to solidify as a thin crust on its sides, so that it may be more readily dissolved on subsequent treatment. It is digested with cold water, which requires considerable time (the application of heat is not recommended), and there is left an insoluble white residue consisting of niobic and tantalic oxides, while the bases are in solution. The insoluble oxides are collected on a filter and washed, and if a portion of them is treated in a test-tube with hot concentrated hydrochloric acid, and boiled with granulated tin, the blue color due to niobium may be obtained.

For the separation of small quantities of tungsten and tin from the in- soluble niobic and tantalic oxides, see p. 126, § 3.

3. Oxide of niobium gives no satisfactory reactions with the fluxes.

Nitrogen, N. — Trivalent and pentavalent. , Atomic "weight, 14.

Occurrence. — Nitrogen is the characteristic non-metallic ele- ment of nitric acid, HNOs , and of the nitrates. The simple ni- trates of the metals are soluble in water, and are not found as

100 REACTIONS OF THE ELEMENTS. Oxygen

numerals in regions where there is a considerable rainfall. In arid regions, however, they may accumulate and be of great commer- cial importance, as the sodium nitrate deposits of Chili and Peru. The ammonium compounds also contain nitrogen, and have already been mentioned on p. 43.

Detection of Nitrates.— When heated in a closed tube, or, better, in a bulb tube, with potassium bisulphate, nitrates are decomposed and yield NO, gas, which may be detected by its red color (seen best by looking into the tube lengthwise), and also by its odor. Potassium bisulphate may be omitted in testing nitrates of the heavy metals, for they are so readily decomposed that NO# gas is given off even on moderate ignition.

Osmium, Os. — See the platinum metals, p. 104. Oxygen, O. — Bivalent. Atomic weight, 16.

Occurrence. — Oxygen is the most abundant element in the crust of the earth (p. 3). With the exception of the native ele- ments, the sulphides, fluorides, and halogen salts, oxygen is present in all minerals. Many elements unite with oxygen in varying proportions; those containing the smallest quantity of oxygen are called lower oxides, or ous compounds (PeO ferrous oxide), and those with more oxygen, higher oxides, or ic com- pounds (Fe.O, ferric oxide).

Detection. — Usually no direct test is made for oxygen, but if a mineral is determined to be a salt of some oxygen acid, as car- bonic or silicic, which may be readily done, it must contain oxygen ; while, on the other hand, if it is a sulphide or chloride, it probably will not contain oxygen. However, oxysulphides, oxychlorides, and oxyfluorides, although rare, are known, as are also chlorides

and fluorides containing water of crystallization. For some of the

higher oxides, the closed-tube test, or the liberation of chlorine when dissolved in hydrochloric acid, may be applied.

1. Closed-tube Reaction. — Some of the higher oxides, when heated in a closed tube, yield oxygen gas, which is colorless and

Phosphorus BE ACTION 8 OF THE ELEMENT8. 101

odorless, bat may be detected by burning a piece of charcoal in the tube.

Place some fragments of pyrolusite, MnO, , in the bottom of a closed tube, and a little above, a sliver of charcoal (compare Fig. 45, p. 62) ; then heat the charcoal alone, and observe that although it gets red hot, it does not burn, owing to the limited supply of air in the tube. Keeping the charcoal hot, apply heat to the pyrolusite, and as soon as oxygen com- mences to be given off, the charcoal will burn brightly, and continue to do so as long as oxygen is supplied by the mineral. The reaction is 3MnO, Mn,04 + 20.

2. Liberation of Chlorine. — When some of the higher oxides are dissolved in hydrochloric acid, chlorine gas is liberated, which may be recognized by its peculiar odor and bleaching action, while ordinary oxides when similarly treated do not set chlorine free. These differences are illustrated by the following equations:

MnOt + 4HC1 MnCl, + 2H.0 + 2C1.

Fe.O, + 6HC1 2FeCl, + 3H.O.

Whether chlorine is liberated or not depends upon the charac- ter of the metal. The oxygen of the oxide and hydrogen of the acid unite to form water, and if the chlorine thus available is more than sufficient to satisfy the valence of the metal, the excess will be liberated.

/ Treat one ivory spoonful of finely powdered pyrolusite, MnO„ in a test- tube with 5 cc. of hot hydrochloric acid. Observe the odor of the escaping gas, and also bleach a piece of moistened litmus-paper by holding it for a short time within the test-tube.

Palladium, Pd. — See the platinum metals, p. 104.

Phosphorus, P. — Pentavalent (usually). Atomic weight, 31.

Occurrence. — Phosphorus is the characteristic non-metallic element of phosphoric acid, H,P04, and its salts, the phosphates. Although a great many phosphates are known, the majority of them are rare minerals, and many of them are isomorphous with arsenates and vanadates. The following will serve as illustrations :

102 BE ACTIONS OF THE ELEMENTS. Phosphorus

apatite, Ca4(CaF)(P04), ; triphylite, Ii(Fe,Mn)P04; and vivianite, Fe,(P04),.8H,0.

Detection. — Ammonium molybdate is the best reagent for the detection of phosphates, but the "flame coloration or the reduction test with magnesium may be used.

1. Test with Ammonium Molybdate. — When a nitric acid solution of a phosphate is added to a solution of ammonium mo* lybdate, according to the directions given beyond, a yellow precipitate of ammonium phosphomolybdate, approximately MoI0(NH4),POM.liH,O, is thrown down, and furnishes an exceedingly delicate test. Only a little of the phosphate solu- tion should be added to the ammonium molybdate at first, since the precipitate may not form if an excess of phosphoric acid is present. The precipitation should take place in a cold or only slightly warmed solution, for if heated to boiling, other things, especially a corresponding arsenic compound might be thrown down and mistaken for the phosphate precipitate. If the mineral is insoluble in nitric acid, it may be first fused in a sodium carbonate bead and then dissolved in this acid. An acid other than nitric may be used for dissolving the mineral, but in that case it is best to nearly neutralize the excess of free acid with ammonia, before adding the solution to the ammonium molybdate. When applying this test, it is recommended to follow quite closely the details of the experiment as given below.

Dissolve i ivory spoonful of apatite in about 3 cc. of warm nitric acid, and pour a few drops of the solution into another test-tube containing about 5 cc. of ammonium molybdate, when, after standing a few minutes in the cold, the yellow precipitate will make its appearance.

2. Flame Test. — Many phosphates when heated before the blowpipe impart a pale bluish-green color to the flame, while others often show the reaction if moistened with concentrated sulphuric acid and then heated. The color, although not very marked, is often sufficient for the identification of a phosphate (compare p. 136).

Platinum REACTIONS OF THE ELEMENTS. 103

The experiment may be made with fragments of wavellite, AleP4019. 12H,0, or apatite. In case the latter mineral is used, it is necessary to moisten the fragment with sulphuric acid, and then the color is distinct for only a short time.

3. Reduction with Metallic Magnesium. — Phosphates of the alkalies and alkaline earths, when strongly ignited in a closed tube with magnesium, are reduced, with the formation of a phosphide. This, when moistened with water, gives the disagree- able odor of phosphuretted hydrogen, PHS, somewhat like the garlic odor of arsenic. When phosphates of aluminium and the heavy metals are to be tested, it is best to fuse the powdered mineral with 2 parts of sodium carbonate on charcoal, to remove and grind up the fused mass, and then to ignite the powder with magnesium.

The experiment may be made with apatite or wavellite. In the latter case, however, the mineral should first be (used with sodium carbonate.

Take a piece of magnesium ribbon about 25 mm. long, roll or fold it up into a compact mass, and drop it into a closed glass tube. Next add the finely powdered phosphate, tap the tube so as to bring the powder as much as possible in contact with the magnesium, and ignite very strongly with a blowpipe flame, being careful to hold the tube in such a manner that, if an explosion should occur, the contents would not be shot out into the face. Crack off the end of the tube by dropping water upon it while it is siill hot, moisten the contents with a few drops of water, and observe the odor of the phosphuretted hydrogen; or, after allowing the tube to become cold, introduce a drop or two of water, and observe the odor at the end of the tube.

Platinum, Pt. — Bivalent and tetravalent. Atomic weight, 195.

Occurrence. — Platinum is found native, but it then always contains some iron and traces of other metals belonging to the platinum group. The only mineral containing platinum in chemical combination is sperrylite, PtAs,.

Detection. — The color, high specific gravity, infusibility, and insolu- bility in any single acid, are properties which serve for the identification of platinum. When the metal occurs in 'sand, it may be concentrated by washing as described under gold, but without lifting mercury. For a more definite test for platinum, it is recommended to fuse the metal in a cavity on charcoal with some test-lead, using borax, if necessary, to take tip

104 REACTIONS OF THE ELEMENTS. Platinum

impurities., The metallic globule, freed from slag by hammering, is then treated with dilute nitric acid (1HNO, : 2H,0), which dissolves everything but the platinum metals and gold, and these are then collected upon a filter-paper, washed, and ignited. The finely divided platinum thus obtained dissolves readily in aqua regia, giving a reddish-yellow solution containing hydrochlorplatinic acid, HsPtCl„ which should be evaporated nearly to dryness, at a moderate heat, treated with hydrochloric acid, and again evaporated. It should be finally taken up with a little water, filtered if necessary, and added to a concentrated solution of ammonium chloride,, when a yellow precipitate of ammonium platinic chloride, (NH4)sPtCldr will be thrown down. The precipitate, if collected upon a filter, washed with alcohol, and ignited, yields a gray platinum sponge, containing often some other metals of the platinum group. Gold, if present, will be in the filtrate.

The Rarer Metals of the Platinum Group.

Ruthenium, Ru.— Atomic weight, 101.5. Rhodium, Rh. — Atomic weight, 103. Palladium, Pd. — Atomic weight, 106.5. Osmium, Os. — Atomic weight, 190.8. Iridium, Ir. — Atomic weight, 193.1.

Occurrence. — All the above metals are found in small quantity in native platinum. Iridium and palladium, containing some platinum and traces 'of the other platinum metals, are found native. Iridosmine is a mix- ture consisting chiefly of iridium and osmium. La u rite is essentially RuSt.

Detection. — The analysis of the platinum metals is one of the difficult problems of analytical chemistry for which advanced works on the subject should be consulted. A few special tests, however, will be given.

Osmium is characterized by a volatile oxide, Os04, which has an exceedingly penetrating and disagreeable odor, somewhat resembling bro- mine. The vapors are poisonous and should not be breathed too freely. The odor may be obtained by heating the powdered mineral in an open tube, and a very characteristic test may be made by bringing the upper end of the tube within a Bunsen-burner flame, so that the osmic oxide will pass into the latter, which will become luminous, owing to the reduction of the osmic oxide and to the glowing of the finely divided metallic osmium. The odor of osmium is also obtained when the finely divided mineral is oxidized by fusing in a bulb tube with sodium or potassium nitrate.

Iridium And: iridosmine are characterized by their hardness (6-7) and insolubility in acids, even aqua regia failing to dissolve them. Iridium is partially oxidized by fusion with sodium nitrate (this may be done in a

Potassium REACTIONS OF THE ELEMENTS. 105

bulb tube), and the fused mass when boiled with aqua regia yields a deep red to reddish-black solution.

Native palladium exhibits a bluish tarnish, which is lost by heating in the reducing flame, the color becoming like that of platinum, but is regained by heating moderately in the air (best in an open tube). When a piece is flattened on an anvil to expose a maximum surface, and fused with potassium bisulphate, the metal is oxidized and dissolved to some extent. On soaking out the fusion in water, and adding a very small crystal of potassium iodide, a black precipitate of palladous iodide is formed, which dissolves in a large excess of potassium iodide, giving a deep wine-red color.

Potassium, K. — Univalent. Atomic weight, 39.1.

Occurrence. — Potassium is a very abundant element, and, although its simple salts are soluble in water, it occurs in insoluble combinations in many silicates. Orthoclase, KAlSitO, , is one* of the most abundant minerals in the crust of the earth. The most important minerals for the production of potassium compounds are certain soluble chlorides (sylvite, carnalite), which are found in connection with deposits of rock salt.

Detection. — Flame coloration furnishes the most convenient means of testing for potassium, and, where this test cannot be applied, precipitation as potassium platinic chloride may be resorted to.

Sj£ 1. Maine Test. — Volatile potassium compounds color the flame pale violet, and the test may be made by introducing the sub- stance, held in the forceps or in a loop on platinum wire, into the hottest part of the Bunsen-burner or blowpipe flame. The flame color is not very strong and is easily obscured by other elements, especially sodium, but by viewing it through blue glass of suffi- cient thickness, the disturbing colors may be absorbed, and the potash flame will be distinctly seen of a violet or purplish-red color, depending upon the depth of color of the glass.

a. Take up some sylvite, KC1, in a small loop on platinum wife, intro- duce it into a Bunsen-burner flame, and observe the color. Also examine the flame through various thicknesses of blue glass.

h. Add a little sodium chloride to the potassium chloride, and repeat the foregoing experiment.

c. In testing silicates from which, under ordinary conditions, the potas-

100 REACTIONS OF THE ELEMENTS. Potassium

sium is not readily volatilized, the following method will be found very useful: Mix the finely powdered mineral with an equal volume of powdered gypsum, and having heated a platinum wire until it gives no color to the flame, touch the end of it to a drop of water and then to the mixture, so as to take up a little of the latter. Introduce this carefully into the hottest part of a Bunsen-burner flame, and observe the color, making use of blue glass to absorb the yellow resulting from sodium, which is almost sure to be present, in traces at least, with potassium. Gypsum, when fused with the mineral, forms calcium silicate and potassium sulphate, and the latter, when it volatilizes, imparts the color to the flame. Instead of a straight wire, a small loop may be used for taking up the mixture, but it is necessary to have a heat sufficiently intense to fuse the minerals together and liberate the potassium sulphate. The test is quite delicate.

2. Alkaline Reaction. — With the exception of the silicates, phosphates, borates, and salts of a few rare acids, the potassium compounds become alkaline upon intense ignition before the blowpipe. The test is not so satisfactory as that made with minerals containing other alkalies and alkaline earths.

3. Precipitation as Potassium Platinic Chloride. — If hydro- chlorplatinic acid, HtPtCl, , is added to a rather concentrated, neutral, or slightly acid solution containing potassium, a yellow crystalline precipitate of potassium platinic chloride, KfPtCl,, will be formed, which furnishes an excellent means for detecting potassium. The precipitate is sparingly soluble in water, and almost absolutely insoluble in alcohol. Ammonium compounds yield a similar precipitate, (NH.PtCl,.

a. In order to make the test, dissolve a little sylvite, EC1, in a few drops of water, and then add a few drops of hydrochlorplatinic acid.

h. To adapt the test to insoluble silicates, proceed as follows: Fuse the powdered mineral with sodium carbonate, as described in detail under silicates (p. 110, § 4). Pulverize the fused mass, treat it in a test-tube with a little hydrochloric acid, evaporate to dryness, and after cooling add about 2 cc. of water and boil. Next add an equal volume of alcohol, filter through a small paper, and add a few drops of the hydrochlorplatinic acid solution to the filtrate in order to precipitate the potassium.

Rhodium, Rh. — See the rare metals of the platinum group, p. 104. Rubidium, Rb. — Univalent. Atomic weight, 86.5.

Occurrence. — This rare alkali metal is found very sparingly together with caesium in some varieties of lepidolite.

Silicon REACTIONS OF THE ELEMENTS. 107

Detection. — Rubidium is very similar to potassium, and forms an insoluble platinic chloride, Rb,PtCle. Examination with a spectroscope is needed for its identification.

Selenium, Se. — Bivalent and sexivalent. Atomic weight, 79.

Occurrence. — This rare element is found usually in combination with the metals, as selenides; clausthalite, PbSe; tiemannite, HgSe, etc., which are analogous to sulphides.

Detection. — When a substance containing selenium is heated before the blowpipe on charcoal, a curious odor may be observed which is de- scribed by Berzelius as similar to that of radishes and also of decaying radishes. It is impossible to describe this odor, but only a few trials are necessary to render it familiar, and it is so pronounced and characteristic ' that a very minute quantity of selenium may be detected by means of it. If the selenium is present in considerable quantity, it volatilizes as a brown- ish smoke, and some of it deposits at a little distance from the assay as a silvery coating of oxide, SeO,, which may have an outer border of red, owing to admixture of finely divided selenium. If the coating is touched with the reducing flame, the selenium volatilizes, and imparts a magnificent azure-blue color to the flame. This is an extremely delicate and character- istic test.

In the open tube, selenium yields a white oxide, Se09, which usually crystallizes in radiating prisms on the sides of the glass, and is reddened by an admixture of finely divided selenium. The sublimate is volatile, and, if driven up the tube, it may be made to give a beautiful blue color if the tube is held so that the vapors at the end pass into the reducing part of a Bunsen-burner flame.

In the closed tube, selenium volatilizes from some of its compounds, and condenses as black globules fused against the glass, but where the globules are, very minute, they transmit some light and cause the thinnest part of the sublimate to appear red or brown. Owing to the air in the tube, a little oxide, SeO, , may form, which crystallizes on the glass above

the selenium.

Silicon, Si. — Tetravalent. Atomic weight, 28.

Occurrence. — Next to oxygen, silicon is the most abundant element in the minerals which constitute the crust of the earth (p. 3). In combination with oxygen, it forms the very common mineral, quartz, SiO,, and it is the characteristic non-metallic element in the silicates, or salts of silicic acid. Silicates are very numerous, and salts of several kinds or types of silicic acids are recognized, the most important of which are as follows:

108 REACTIONS OF THE ELEMENTS. Silicon

Orthosilicic acid, H4Si04.

Metasilicic acid, H4Si,0, 211,810,.

Trisilicic acid, H4Si,08.

Tetrasilicic acid, H4Si401# 2H,Sit06. The acids, written as above in a progressive series, differ from one another by addition of SiOt. There are no methods for deter- mining just what kind of silicic acid is contained in any given silicate except quantitative chemical analyses from which the ratio between the silica and the metals may be calculated (p. 6). For example, in forsterite, Mg : Si 2 : 1, and, Mg being biva- lent, the formula must be Mg,Si04, a salt of orthosilicic acid. In orthoclase, K : Al : Si 1 : 1 : 3, and potassium being univalent and aluminium trivalent, the formula is KAlSisO„. In the major- ity of cases, the empirical formulae of the silicates have been determined with a fair degree of accuracy, and most of them have been found to correspond to the few types of acids already men- tioned, the orthosilicates and metasilicates being the commonest. The formulae of some silicates, however, and among them a few of the common ones, are uncertain. The true constitution of the silicates, that is, their structural formulae or the manner in which the atoms are united to one another, is uncertain, and largely a matter of conjecture. It has been found that the metals sodium, potassium, calcium, magnesium, ferrous and ferric iron, and aluminium, are of very common occurrence in the silicates, and that orthosilicates are more soluble in acids than metasilicates and polysilicates.

Detection. — The surest method for the identification of a silicate is to get the mineral in solution in an acid, and obtain gelatinous silica by evaporation. The residue or skeleton of silica obtained in the salt of phosphorus bead furnishes a simple but not very delicate test.

1. Formation of a Jelly. — When a silicate is dissolved in acid the solution may be regarded as containing free silicic acid, possibly H4Si04, and, upon evaporation, there comes a point when the latter can no longer remain in solution, but yields a

*llloon REACTIONS OF THE ELEMENTS. 109

gelatinous mass. If the evaporation is continued until the mass becomes dry, and the latter is then moistened with strong acid and digested with water, the bases will go into solution, while the silica remains insoluble and may be separated by filtering. Comparative tests have shown that gelatinization is more readily obtained with nitric than with hydrochloric acid, although in many cases either will answer. As most silicates are insoluble in acids, a previous decomposition, by fusion with sodium carbon- ate, is usually necessary before applying the test (compare § 4).

To illustrate the foregoing, in the case of soluble silicates, take about 2 ivory spoonfuls of finely powdered calamine (ZnOH),SiOs, or nepheline, essentially NaAlSi04, mix in a test-tube with about 1 cc. of water, then add 3 cc. of nitric or hydrochloric acid, warm, and observe that the mineral yields a perfectly clear solution. Boil the solution, and it will soon become thick from the separation of gelatinous silica. The gelatinous silica is insoluble in water and acids, and, if thoroughly washed with water and dried over sulphuric acid, has essentially the composition H,SiOs. The reason for adding the water at the beginning of this experiment ia to thoroughly mix the mineral with the acid. If omitted, the acid when it first comes in contact with the dry material will often form a layer of gelatinous silica over the powder and prevent a portion of it from going into solution.

2. Separation of Silica without Gelatinization. — Some sili- cates are completely decomposed by boiling with acids, the bases going into solution, while the silica is left in an insoluble condi- tion, but without any formation of a jelly. From the appearance of the test it is sometimes rather difficult to tell whether a mineral has been decomposed or not, but the separated silica, having a low index of refraction, makes the liquid in which it is suspended appear translucent and almost clear, while the fine, suspended powder of an insoluble mineral causes the liquid to appear white and milky. A sure test is to filter, and evaporate a drop of the solution on a piece of glass or platinum, when, if a considerable residue is left, it indicates that a decomposition has taken place, and the bases have gone into solution.

An experiment to illustrate the above may be made by boiling 2 ivory spoonfuls of finely powdered serpentine or stilbite with 5 cc. of hydrochloric acid.

HO - REACTIONS OF THE ELEMENTS. Silicon

3. Fusion with Sodium Carbonate. — When quartz SiO,, or a silicate is fused with sodium, carbonate, a. sodium silicate is formed. Moreover, the fused mass will be soluble in acids, and, upon evapo- ration of the solution, gelatinous silica separates, as in § 1. Fusion with sodium carbonate is indispensable for the solution and subsequent analysis of insoluble silicates (compare § 4).

To illustrate the foregoing paragraph, take some very finely powdered quartz, SiO, , and an equal volume of sodium carbonate (rather less sodium carbonate than more), make into a paste with water, then support some of the mixture on a small loop on platinum wire and heat with an intense blowpipe flame. Instead of fusing on a platinum loop, the experiment suc- ceeds beautifully when a minute quantity of the mixture is heated intensely on a clean charcoal surf ace. If successful, a transparent bead should result, and the experiment illustrates the process of glass-making. The sodium carbonate brings about a decomposition of the quartz, the anhydride of silicic acid, with the formation of sodium silicate and evolution of carbon dioxide gas, the reaction being somewhat as follows : 2NasC0e + SiO,

Na4Si04+2C0t.

4. Special Treatment for the Detection of the Common Ele- ments in Silicates. — The methods to be described are for the detec- tion of aluminium, iron, calcium, and magnesium, which are very commonly present in silicates, but to devise a scheme applicable to all possible cases would require the elaborate methods of qualita- tive chemical analysis, which are* beyond the scope of the present work The scheme has been made as simple as possible, and the tests can be performed upon a small quantity of material and in a short time, but the beginner will find it necessary to follow the details quite closely.

If a silicate is insoluble in acids, it may be decomposed readily by fusion with sodium carbonate and then dissolved. For a test, mix a scant ivory spoonful of the finely powdered silicate with 3 parts of sodium carbonate, make into a paste with a drop of water and then take up a portion of the material on a loop on platinum wire and fuse before the blowpipe. Make two or three beads, if necessary, rather than attempt to fuse all of the material at once. In almost all cases there results after fusion an opaque mass, the presence of various oxides contained in the mineral, mixed with

Silicon REACTIONS OF THE ELEMENTS. Ill

the sodium silicate and excess of sodium carbonate, preventing the formation of a clear glass as in § 3. The several beads, after removal from the platinum wire, are pulverized in a diamond mortar, transferred to a test-tube, treated with about 1 cc. of water and an equal volume of nitric acid, and evaporated to dryness, being careful toward the end of the operation not to allow the tube to become very hot. After cooling, moisten the contents of the tube with about 3 cc. of hydrochloric acid, boil for a few seconds, so as to decompose any basic salts formed during the evaporation, then add 5 cc. of water, heat to boiling, and remove the insoluble silica by filtering. The silica separated at this point should be white, and may be tested as follows : Wash well on the paper with water, but do not add the washings to the first filtrate, puncture the paper, and, by means of a jet of water, wash the silica into a clean test-tube, then add a little potassium hydroxide and boil, when the silica, if pure, will go wholly into solution.

The filtrate from the silica contains the bases, with the iron in the ferric condition, owing to the use of nitric acid. The solution is heated to boiling, and ammonia is added in slight excess to pre- - cipitate aluminium and ferric hydroxides (p. 42, § 2, and p. 87 § 5), which are collected on a filter and washed with water. If the pre- cipitate is light-colored, iron is absent, or present only in small quantity ; if it is reddish-brown, indicating iron, aluminium may be also present, and must be specially tested for, as follows : By means of a knife-blade or spatula scrape off the precipitate from the filter, and with the aid of a jet of watei transfer it to a clean test- tube, or fold up the paper with the precipitate, and drop it into the test-tube. Have about 5 cc. of water present, then add some potassium hydroxide (a piece of stick potash 5 mm. long), and boil, by which treatment aluminium hydroxide is dissolved, and may be separated from the iron by filtering. The solution is made acid with hydrochloric acid, boiled, and ammonia added in excess, when aluminium, if present, will be precipitated. Whether fer- rous or ferric iron is contained in the mineral must be determined by special tests (p. 85, § 4).

The filtrate from the iron and aluminium may contain calcium

112 BE ACTIONS OF THE ELEMENTS. C.'Iloon

and magnesium (if much magnesium is present, some of it may have been precipitated by ammonia along with the iron and alumin ium). It is heated to boiling, and a little ammonium oxalate added in order to precipitate the calcium (p. 60, § 6). Calcium oxalate is precipitated in a very finely divided condition, and is liable to run through filter-paper. It is best, therefore, to let the precipitate stand for about ten minutes before filtering, and then, if the filtrate is turbid, to pass it a second or third time through the same filter until the pores of the paper become stopped, and clear filtrate is obtained. To the filtrate, a little ammonium oxalate is added to make sure of the complete precipitation of the calcium, and, if no precipitate forms, some sodium phosphate and strong ammonia are added to precipitate the magnesium (p. 91, § 1). If a precipitate does not form immediately, however, it must not be considered that magnesium is absent, for, if only a small quantity is present, and especially if the solution is warm, the precipitate may not appear until after standing some time in the cold. For alkalies, the tests given under sodium (p. 116, § 1, c) and potassium (p. 105, § 1, c) are recommended.

5. Test with the Salt of Phosphorus Bead. — Oxide of silicon dissolves with difficulty in a salt of phosphorus bead ; therefore, when some powdered silicate is fused in the bead, the silica, SiO, , is left as an insoluble skeleton or translucent mass, while the bases go into solution. The test may be recommended on account of its simplicity, but it is not delicate.

In order to test the above, touch the phosphorus bead when hot to any powdered silicate, so as to take up a quantity which before heating does not quite cover one half the surface of the bead, and then heat before the blowpipe, in the hottest part of the flame. As the bases dissolve in the hot glass, the silica moves about and collects together, and, when examined with a lens, it appears as a translucent mass, usually occupying a position in about the center of the bead, and is quite different in appearance from any undissolved mineral. Sometimes it is better to heat a fragment of the mineral in the bead, and after igniting for some time, the translucent silica skeleton may be seen surrounding a particle of the still undecomposed mineral.

6. Decomposition with Borax. — Silicates are quite soluble in a borax bead, and it may be sometimes found convenient to sub-

Silver REACTIONS OF THE ELEMENTS. 113

stitute this treatment for fusion with sodium carbonate in order to decompose a silicate.

Silver, Ag. — Univalent. Atomic weight, 108.

Occurrence. — Some silver is found native and as chloride or bromide, but by far the greater part of the metal of commerce is obtained from its compounds with sulphur. A few of the most important silver minerals are argentite, Ag.S ; stromeyerite, AgCuS; pyrargyrite, 3Ag9S.Sb„St ; proustite, 3Ag9S.As,S,; stephanite, SAg.S.SbJS,; polybasite, essentially 9Ag,S.Sb,St; cerargyrite, AgCl ; and emboli te, AgCl with AgBr. Silver is found, in sev- eral combinations with tellurium, and in small quantity in many sulphides ; as in galena, sphalerite, chalcocite, bornite, and tetra- hedrite, which are then called argentiferous. Owing to the value xA silver, it is profitable to extract it from ores which con- tain only a small percentage of the metal. An ore, for example, having one per cent of silver would yield 291 troy ounces of the metal per ton, and, under favorable conditions, ores containing less than one tenth of the above amount may be profitably worked.

Detection. —The metal is usually detected by reduction to the metallic state or by precipitation as silver chloride. 1. Reduction to Metallic Silver. — From pure silver minerals, the metal may be readily obtained on charcoal by fusion before the blowpipe with about 3 volumes of sodium carbonate. The metal easily fuses to a globule, and this is bright both while in the flame and after cooling, for the metal does not tend to oxidize. The silver globule is malleable, can be flattened by hammering on an anvil, and may be further tested according to § 3. When other readily reducible metals are present, the globule obtained by the above treatment will not be pure silver, and fusion with test-lead and cupellation on bone-ash (§ 2) may then be resorted to. Often fusion on a clean charcoal surface in the oxidizing flame with bo- rax is sufficient to free the metal from impurities, since the foreign substances oxidize, dissolve in the borax, and leave finally a globule of pure silver. When in combination with only volatile elements

114 REACTI0N8 OF THE ELEMENTS. Silver

(sulphur, arsenic, antimony), a silver globule may be obtained by heating some of the mineral alone on charcoal in the oxidizing flame. Silver is volatile to a slight degree, but alone on charcoal it gives no characteristic coating. When silver is associated with lead and antimony, however, the coatings which these latter ele- ments give on charcoal assume a reddish to deep lilac tint, which serves as a very certain indication of the presence of silver.

2. Cupellation on Bone-ash and Detection of Small Quantities of Silver. — A method well adapted for the detection of even very small quanti- ties of silver in minerals or ores is to mix an ivory spoonful of the finely pow- dered material with an equal volume each of borax glass and test-lead, transfer to a rather deep, funnel-shaped cavity in a compact piece of char- coal, and fuse before the blowpipe for some time in a reducing flame until the lead, which takes up all the silver, has united into one globule, while the impurities dissolve in the borax. Later an oxidizing flame may be used in order to form lead oxide, which dissolves in the borax and assists iu taking up the impurities. After cooling, the lead is removed from the charcoal, and freed from adhering slag by hammering on an anvil. A cupel is next pre- pared by filling a cavity on charcoal with bone-ash, and pressing the latter down firmly by means of an agate pestle or other smooth rounded surface, such as the back of the metal scoop (Fig. 22), so as to form a shallow de- pression about 1 5 mm. in diameter. Loose particles of bone-ash are removed by inverting and gently tapping the charcoal, and the cupel is heated in- tensely before the blowpipe in order to expel moisture. The lead button is then placed carefully upon the cupel, so as not to disturb the surface of the bone-ash, and fused before the blowpipe, first in the reducing flame until a bright metallic surface is obtained, and then in a small oxidizing flame (Fig. 41). It is necessary to heat in the oxidizing flame for several minutes in order to oxidize the lead, during which time the surface of the button shows a play of rainbow colors, due to a thin film of lead oxide, which con- stantly flows to the sides, and is absorbed by the bone-ash. Finally, when the last of the lead is oxidized, the play of color ceases, the globule is said to " blick," and the operation is completed. Frequently the amount of lead oxide formed is so great that it cannot all be absorbed by one cupel. The button then becomes surrounded by, and seems to float upon, the fused lead oxide, and when this happens, it is best to interrupt the operation and oxidize the last of the lead upon a fresh cupel.

Considerable practice is needed in order to make the silver assay easily

and quickly, but when the necessary skill has been acquired, the operation

. may be performed in less than fifteen minutes, and by assaying samples of

known value and saving the silver beads for comparison, one can soon learn

Sodium REACTIONS OF THE ELEMENTS. 115

to judge of the relative values of ores. By starting with weighed quantities of material, and especially by making use of the special apparatus men* tioned in Planner's elaborate treatise/ very good quantitative determina- tions of silver may be made by means of the blowpipe assay.

3. Precipitation as Silver Chloride.— Silver chloride, AgCl, is very insoluble in water and dilute nitric acid. A white precipitate of silver chloride will therefore form if silver is dissolved in di- lute nitric acid (1HNO, : 2H40) and a few drops of hydrochloric acid are added to the solution. If the quantity of the precipitiate is small it appears as a turbidity, while if a is considerable it col- lects as a curdy mass. It darkens on exposure to light and is readily soluble in ammonia. A globule of silver from one of the foregoing experiments may be tested in this way. It is also often convenient to test for silver by dissolving a mineral in hot, concen- trated, nitric acid, and, after dilution, and filtering if necessary, to precipitate the silver with hydrochloric acid. The precipitate, if collected on a filter, may be tested according to § 1.

Sodium, Na. — Univalent. Atomic weight, 23.

Occurrence. — Sodium is a very abundant element, and al- though its simple salts are all soluble in water and are not ordi- narily found as nfinerals in wet regions, they often accumulate in desert or dry places, and form deposits of great commercial value. The most important compound is halite, NaCl, which is found both as rock salt and in solution in the water of the oceans. Double salts containing sodium, which are insoluble in water and often also in acids (for example, albite, NaAlSisOj, are very common, especially in the group of silicates.

Detection. — Sodium is usually detected by means of the flame /tjqloration and alkaline reaction.

'fcl. Flame Test. — Volatile sodium compounds color the flame yellow, and the test is exceedingly delicate. The color is monochro- matic, and therefore shows only a single band in the spectroscope. The flame color cannot be seen through moderately dark blue glass, as the yellow rays are wholly absorbed (see Potassium, p. 105, § 1).

♦ Probirkunst mit dem Ldthrohre. American translation by Cornwall.

116 REACTIONS OF THE ELEMENTS. Sodium

a. To illustrate the above, fuse in the forceps some halite or cryolite before the blowpipe, or, still better, fuse some of the material into a loop on platinum wire and introduce it into a Bunsen-burner flame at about the point r, Fig. 35, p. 32.

b. To illustrate the great delicacy of the reaction, heat a platinum wire until it gives no color to the flame, then draw it through the fingers, heat again, and observe the yellow color which results from the minute trace of sodium derived from contact with the fingers. The flame test is so exceed- ingly delicate that a great deal of judgment must be exercised in making use of it. A mineral should be regarded as containing sodium only when it gives an intense and prolonged yellow coloration, as in the previous test.

c. Silicates from which sodium is not readily volatilized may be fused with gypsum, as directed under potassium (p. 105, § 1, c).

2. Alkaline Reaction.— With the exception of the silicates, phosphates, borates, and the salts of a few rare acids, sodium com- pounds become alkaline upon ignition before the blowpipe. A similar reaction is obtained from other minerals containing the al- kalies and alkaline earths.

a. Make a loop about 3 mm. in diameter on platinum wire, fuse some halite in it, and continue to heat for some time, but not long enough to volatilize all the material. In order to test the alkaline reaction, bring the fused mass in contact with a piece of moistened turmeric-paper on a clean glazed surface. In this experiment, water (one of the products of combustion) acting at a high temperature brings abouff a partial decomposi- tion of the material, as follows: NaCl + H,0 NaOH + HC1.

b. If a fragment of cryolite, NasAlF#, is fused in a loop on platinum wire and heated before the blowpipe, the hydrofluoric acid which is driven off may be readily detected by its pungent odor, or by the reddening of a moistened blue litmus-paper held at a little distance beyond the flame, while the residue will impart an alkaline reaction to moistened turmeric-paper.

Strontium, Sr. — Bivalent. Atomic weight, 87.5.

Occurrence. — Strontium is found quite abundantly as celes- tite, SrS04 , and strontianite, SrCO, , but other combinations are rare (brewsterite).

Detection. — Strontium is usually detected by the flame color- ation, alkaline reaction after heating, and by precipitation as sul- phate.

1. Flame Test. — Strontium compounds when heated before the blowpipe impart a crimson color to the flame, and this may be ob-

Strontium REACTIONS OF THE ELEMENTS. 117

tained by igniting fragments held in the platinum-pointed forceps, or often still better by taking up some of the powdered mineral on platinum wire, as directed on p. 35, and heating before the blow- pipe or in the Bunsen-burner flame. Often the coloration can be made more intense by moistening the material with hydrochloric acid. The crimson flame- must not be mistaken for lithium, or, in case hydrochloric acid is used, for the yellowish-red of calcium (p. 59, § 2) , which, however, is not as persistent on prolonged heat- ing as the crimson of strontium. A spectroscope can be used to advantage.

2. Alkaline Reaction. — Strontium compounds become alkaline upon ignition before the blowpipe, with the exception of the sili- cates and phosphates (compare Calcium, p. 58, § 1). A similar re- action is obtained from other minerals containing the alkalies and alkaline earths. There are no lithium minerals known which yield an alkaline reaction after ignition, and therefore a crimson flame in connection with alkaline reaction is an almost certain proof of the presence of strontium.

, 3. Precipitation as Strontium Sulphate. — Strontium sulphate, SrS04, is very insoluble in water and dilute acids, and may be precipitated by adding a few drops of dilute sulphuric acid to solutions, provided the latter are not very dilute and do not con- tain too tfluch acid. The test will be found convenient in distin- guishing strontium from lithium and calcium, and for the detec- tion of strontium in silicates and phosphates which do not yield a flame coloration or alkaline reaction (compare Barium, p. 53, § 3, b).

Dissolve an ivory spoonful of strontianite in 3 cc. of warm hydrochloric acid, divide the solution into 2 parts, dilute one with about 5, and the other with 15 cc. of water, and add a few drops of dilute sulphuric acid to each. In the more concentrated solution, the precipitate forms almost immedi- ately, but in the other, only after standing for several minutes, while an ex- periment made in exactly the same manner with calcite, CaCO,, would not yield a precipitate of CaS04 in either solution (see p. 59, § 3) . In order to precipitate strontium completely as sulphate, it is necessary to add an equal volume of alcohol to the liquid.

118 REACTIONS OF THE ELEMENTS. Sulphur

4. Specific Gravity. — Strontium compounds are heavy, and their specific gravities lie between those of the corresponding cal- cium and barium salts, as the following examples show :

Specific Gravity. Specific Gravity.

Aragonite, CaCO, 2.95 Anhydrite, CaS04 , 2.98

Strontianite, SrCO, , 3.70 Celestite, SrS04 , 3.96

Witherite, BaCJO,, 4.35 Barite, BaS04, 4.48

Sulphur, S. — Bivalent and sexivalent. Atomic weight, 32.

Occurrence. — In addition to being found native, sulphur also occurs in two very important classes of compounds, the sulphides and sulphates. The sulphides may be generally regarded as salts of the weak acid, hydrogen sulphide, H,S, and the common ores of many of the valuable metals are of this class ; as argentite, Ag,S ; galena, PbS; sphalerite, ZnS; cinnabar, HgS, etc. The sulphates are salts of sulphuric acid, H,S04 , and the metals calcium, strontium, barium, and lead, form insoluble sulphates, which occur abundantly in nature. Soluble sulphates, especially those of the alkali metals, may accumulate in arid regions, and a number of double salts and basic sulphates are known. Sulphur is found rarely in combina- tion with a silicate ; as in helvite, MnMiSJBeXSiOJ, and noseite, Na4(NaS04Al)AUSi04)t.

Sulphides.

Detection. — Sulphides may be most conveniently detected by an oxidizing process, such as roasting in the open tube or on char- coal.

1. Oxidation or Roasting in the Open Tube. — An exceedingly delicate test for a sulphide is to heat some of the finely powdered mineral in an open tube, when sulphur dioxide, SO,, and usually an oxide of the metal are formed. Sulphur dioxide, the anhydride of sulphurous acid, is a colorless gas, which may be readily detected by its sharp, pungent odor and the acid reaction which it imparts to a piece of moistened litmus-paper placed at the end of the tube.

According to the directions given on p. 19, heat about of an ivory spoonful of finely powdered galena in an open tube until the odor of sulphur dioxide (burning sulphur) ceases, and the dark lead sulphide has changed

Sulphur REACTIONS OF THE ELEMENTS, 119

wholly to light-colored lead oxide. The reaction is essentially as follows : PbS + 30 PbO + SO,. Lead oxide and sulphur dioxide combine to form a rather volatile product, and a trace of this will usually be found as a white sub- limate a little above the lead oxide. The open- tube test is so delicate that when a minute particle of a sulphide is used, an acid reaction will be imparted to test-paper and usually even the odor of SO, will not escape detection.

When sulphides of iron, copper, and some other metals are roasted in the open tube, the oxides of the metals which are formed during the opera- tion act as oxidizing agents, &n& convert some SO, to SO,, the anhydride of sulphuric acid : Fe,0, + SO, 2PeO + SO,. The formation of SO, is indicated by white fumes passing up the tube, and some of the SO, derives sufficient moisture from the atmosphere to form a little H,S04 which con- denses as a liquid in the tube.

2. Oxidation or Roasting on Charcoal. — An excellent method for detecting sulphur, but not so delicate as the one just given, is to roast the finely powdered sulphide on charcoal according to the di- rections given on p. 39, and observe the odor of SOt. This test is especially recommended for sulphides which contain a great deal of sulphur.

3. Roasting in the Platinum Forceps. — Some sulphides oxidize so readily that, when held in the forceps and heated before the blowpipe, they take fire and continue to burn for some time, giving a strong odor of SO,. Pyrite, FeS, , and chalcopyrite, CuFeS, ,can be tested in this way.

4. Heating in a Closed Tube. — Many sulphides suffer no de- composition when heated in a closed tube, while others part with a portion of their sulphur, which condenses on the walls of the tube as a fused sublimate; having a dark amber color when hot, changing to pale yellow and becoming crystalline when cold. A sulphide of the metal always remains in the tube, and the test, although admirable for some sulphides, is not applicable in all cases. Owing to the air in the tube, there will always be some oxidation and formation of a little SO, , but necessarily this must be trifling in amount, since there is no free circulation of the air and only about one fifth of it is oxygen.

Excellent experiments for illustrating the behavior of different sulphides may be made by heating fragments of pyrite, FeS, , and galena, PbS, in

120 BEACTIONb OF THE ELEMENTS. Sulphur

separate tubes. The first gives an abundant sublimate of sulphur, but sulphide of iron, PeS, is left in the tube, as inay be proved by removing some of the material and roasting on charcoal or in the open tube. The galena, on the other hand, gives no sublimate, as there is no excess of sulphur above the normal sulphide, PbS.

5. Test on Silver after Fusion with Sodium Carbonate. — Whei a powdered sulphide is mixed with about 3 parts of sodium carbon- ate and fused before the blowpipe on charcoal, sodium sulphide will be formed, owing to the strong chemical affinity of sodium for sul- phur. If some of the fused mass or of the charcoal into which it has been absorbed is placed with a drop of water on a clean silver surface, a black stain of silver sulphide will be formed. The test is so delicate that, if sodium carbonate is heated alone on charcoal before the blowpipe for a long time with a gas flame, and then placed upon moistened silver, a slight discoloration may result from the traces of sulphur contained in the gas and charcoal, but it is not necessary to mistake this slight discoloration for the strong reaction given by sulphides. If selenium and tellurium are pres- ent, the test cannot be relied upon.

6. Oxidation ajid Solution by Means of Nitric Acid. — Nitric acid, owing to its strong oxidizing action, serves as the best solvent for sulphides. If hot, concentrated acid is used, there are two pro- cesses to be considered, which go on simultaneously ; (1) oxidation, and (2) solution of the products of oxidation. The final products may be generally regarded as sulphuric acid and nitrates of the metals. For example, pyrite, PeS, , is oxidized to sulphuric an- hydride, SO, , and ferric oxide, Fe,Ot , and the first of these com- bines with water to form sulphuric acid, H,SO , while the sec- ond dissolves in the nitric acid to form ferric nitrate, Fe(NOB)$. Since the metals oxidize more readily than sulphur, it frequently happens that a portion of the latter separates in a free state as a spongy mass. This separated sulphur oxidizes very slowly, and is yellow if pure, but is frequently black, owing to some undecom- posed sulphide, which is held mechanically in the sulphur and is thus protected from the action of the acid. When a sulphide is decomposed with concentrated nitric acid, no volatile sulphur com-

ulphur REACTIONS OF THE ELEMENTS. 121

pounds are formed, but all the sulphur remains either oxidized to sulphuric acid or partly separated in the free slate.

While oxidation is going on, the nitric acid must suffer decom- position, but this may take place in different ways ; for example, 2HNO,= O + 2NO.+ H,0, or 2HNO, 30 +2N0 + H.O. In either case, red vapors of NO, will be visible, for, provided the decomposi- tion takes place according to the last equations, the colorless gas, NO, takes on oxygen as soon as it comes in contact with the air, and changes to NOt. Since in the solution of sulphides in nitric acid th'ere is no certainty regarding the exact manner in which the acid will break up in order to bring about the oxidation, it is scarcely practical to express the reaction by means of equations, but when red fumes of NO, gas are abundantly given off, it is a sure indica- cation that oxidation is going on.

a. In order to illustrate this, treat about J ivory spoonful of powdered pyrite in a dry test-tube with 3 cc. of concentrated nitric acid, and boil until the evolution of red fumes ceases. The red fumes indicate that an oxi- dation is going on, and, if the experiment is successful, the mineral should be completely dissolved. Dilute the solution with 10 cc. of water, mix thor- oughly, and test the greater part of it in a separate test-tube with a little ba- rium chloride, when a white precipitate of barium sulphate will be thrown down (p. 122, § 1), indicating that sulphuric acid was formed. Dilute the remainder of the solution still further with water, divide into 2 portions, and test for ferric and ferrous iron according to p. 85, § 4. By this means it may be proved that the metal, as well as the sulphur, has been converted into the higher state of oxidation.

b. To illustrate the separation of free sulphur, and how this is dependent upon the character of the minerals, decompose equal portions of pyrite, FeS, (53.4£ S), and pyrrhotite, Fe.S,, (38.4# S), in separate test-tubes with nitric acid, and make the conditions of the experiments as nearly alike as possible. Observe that the pyrrhotite with the least sulphur is the most difficult to dissolve completely, and that by its decomposition sulphur is separated, while the pyrite with the most sulphur dissolves completely. A possible explanation of this is that pyrrhotite, which is easily soluble in non-oxidizing acids (hydrochloric, for example), with evolution of H,S, is at first decomposed by the nitric acid, giving H,S, which is instantly oxidized to Hs0 + S; while pyrite, which is insoluble in non-oxidizing acids, is oxi- dized by the concentrated acid without any intermediate formation of IIaS.

7. Solution in Hydrochloric Acid.— Most sulphides are either insoluble or difficultly soluble in hydrochloric acid, but those which

122 REACTIONS OF THE ELEMENTS. Sulphur

dissolve always give hydrogen sulphide gas, H,S. The reaction is usually a simple one. FeS + 2HC1 FeCl, + H,S. Hydrogen sul- phide is readily recognized by its offensive odor.

Treat some finely powdered pyrrhotite, FenSif (almost FeS), in a test- tube with 3 cc. of hydrochloric acid, and observe that a gas is evolved which has a disagreeable odor.

8Ulphate8.

Detection.— Either the barium chloride test, or the one on sil- ver after a sulphide has been formed by reduction, may be used for the detection of sulphates. The oxidation and roasting proc- esses used for the detection of sulphur in sulphides cannot be applied to sulphates, as they are already oxidized.

1. Test with Barium Chloride. — If barium chloride is added to a dilute hydrochloric acid solution of a sulphate, a white precip- itate of barium sulphate, BaS04, will form, which is almost abso- lutely insoluble in water and dilute acids, and serves therefore as a very delicate test for sulphates.

If the sulphate proves to be an insoluble one, test according to § 2, or fuse some of it in a platinum spoon with 6 parts of sodium carbonate, soak out the fusion with water, filter, make the filtrate slightly acid with hydrochloric acid, boil, and then test with barium chloride.

Illustrate the foregoing test by dissolving i ivory spoonful of gypsum, CaS04.2H90, in warm, dilute hydrochloric acid, and test the solution with a little barium chloride.

It is always best to dilute the acids before testing for a sulphate, for if barium chloride is added to concentrated hydrochloric or nitric acid, barium chloride or nitrate, both of which are insoluble in concentrated acids, might be thrown down, and mistaken for barium sulphate. They differ from the latter, however, in that they dissolve readily upon addition of water*

2. Test on Silver after Reduction to Sulphide. — If a powdered sulphate, mixed with an equal volume of charcoal powder and 2 of sodium carbonate, is made into a paste with water and fused on

Tantalum REACTIONS OF THE ELEMENTS. 123

platinum wire before the blowpipe until effervescence ceases, the

sulphate will undergo decomposition and reduction, and sodium

sulphide, Na,S, will be formed. That reduction has taken place

may be told by removing the bead from the wire, crushing it, and

placing the material with a drop of water on a clean silver surface.

Sodium sulphide will thus react with the silver and make a black

stain of silver sulphide, as follows : Na,S + 2Ag + H,0 + O

Ag,S + 2NaOH. The test is exceedingly delicate (see p. 120, § 5),

and, although it proves the presence of sulphur in a compound, it

is not necessarily a test for a sulphate, unless it has been proved

by a previous oxidizing experiment or by other means that the

mineral is not a sulphide.

As an experiment, test barite, BaS04 , as directed above. The reaction which goes on during fusion is as follows: BaS04 + NatCOt -f- 20 Na,S -f- BaCO, + 2C0t. Besides testing on silver, take some of the crushed prod- uct, resulting from fusion with sodium carbonate and charcoal, and digest it in a test-tube with a few drops of water, then add a few drops of hydro-, chloric acid, and observe the odor of the escaping hydrogen sulphide gas, which will serve as a certain proof that the sulphate has been reduced to a sulphide.

3. Closed-Tube Reactions. — The common sulphates, those of the alkalies, alkali earths, and lead, suffer no decomposition when heated in a closed tube, while sulphates of the less basic elements, such as aluminium, iron, and copper, are more or less decomposed, yielding sulphuric anhydride, SO, , or sulphurous anhydride,. SO,, or both. As water of crystallization is usually present in the latter compounds, it is also driven off and is made strongly acid by the oxides of sulphur (compare p. 82, § 2).

Tantalum, Ta. — Pentavalent. Atomic weight, 182.6.

Occurrence. — Tantalum is associated with niobium in the group of minerals known as the tantalates and niobates (see Niobium, p. 98).

Detection.— There are no simple tests for the detection of tantalum, but if niobium is found in any compound, it is almost certain that tantalum is also present. Tantalates are characterized by high specific gravities, greater than those of the corresponding niobium compounds.

In order to make a definite test for tantalum, separate the mixed tantalio and niobic oxides by fusion with potassium bisulphate, and treatment as

124 REACTIONS OF THE ELEMENTS. Tellurium

directed on p. 99, § 2. Treat the oxides in a platinum dish with a little pure hydrofluoric acid, filter if necessary, and add a little potassium fluoride. Evaporate the solution in a water-bath nearly, but not quite, to dryness, dis- solve the residue in the smallest possible quantity of boiling water, and al- low the solution to become cold, when, if tantalum is present, a very char- acteristic double salt, K,TaFt, crystallizes out in fine needles. The crystals, if collected on a filter-paper and dried, have the appearance of wool. It is necessary that the hydrofluoric acid should be free from hydrofluosilicic acid (alone it should give no precipitate. with potassium fluoride), and platinum or silver vessels must be used.

Tellurium, Te. — Usually bivalent in minerals. Atomic weight,

Occurrence. — Tellurium is found as the native element, but more often it is combined with the metals in tellurides, and it occurs rarely as tellurous oxide and salts of tellurous arid telluric acids. The tellurides are analogous to the sulphides, and some of the more important ones are tetrad- ymite, Bi,Tes; hessite, Ag/fe; altaite, PbTe; sylvanite, (Au,Ag)Te,; and calaverite, AuTe,. Tellurium is the only element with which gold has been found in minerals, in chemical combination.

Detection. — A very delicate test for tellurium or tellurides may be made by heating a little of the finely powdered mineral in a test-tube with about 5 cc. of concentrated sulphuric acid, when the latter assumes a beauti- ful reddish-violet color. After cooling, addition of water will cause the color to disappear/and a grayish-black precipitate of tellurium will be thrown down.

Another test, applicable to all compounds containing tellurium, is to heat a mixttire of the finely powdered substance with sodium carbonate and a little charcoal dust, in a rather large closed glass tube, by which means so- dium telluride is formed, and after cooling and addition of water, the solu- tion will assume a red dish- violet color. If a few drops of the solution are transferred to a porcelain plate or watch-glass by means of a pipette, the color soons disappears, and a gray precipitate of tellurium forms, owing to the oxidizing action of the air. The color disappears still more quickly if air is blown through some of the solution.

By heating in the open tube, tellurium and the tellurides are oxidized, and yield TeO,, which passes up the tube as a white smoke, but mostly con- denses near the heated part as a white sublimate. On heating the latter, it volatilizes very slowly, and fuses into globules, which are yellow when hot. and white or colorless when cold.

Heated in the closed tube, tellurium volatilizes and condenses on the hot glass as fused globules having a metallic luster. Accompanying the tellu-

Tin BEACTI0N8 OF THE ELEMKNTU. i~5

rium are white or colorless globules of the oxide, TeOa, formed from the oxidation, due to the air in the tube.

Heated before the blowpipe on charcoal, tellurium is volatilized, and con- denses near the heated part as a white sublimate of TeOa, somewhat resem- bling antimony oxide. Some tellurium may escape oxidation, and condense as a slight brownish coating distant from the assay. The sublimates volatil- ize when heated before the blowpipe and impart a pale greenish color to the reducing flame.

Thallium; Tl. — Univalent and trivalent. Atomic weight, 203. 6.

Occurkence. — Thallium is a very rare element, and thus far only two minerals containing it in considerable quantity have been observed, crookes- ite, (Cu,Tl,Ag)tSe, and lorandite, TlAsSf, both of which are exceedingly rare.

Detection. — Thallium and its salts are quite volatile when heated be- fore the blowpipe, and impart an intense green color to the flame. When the thallium flame is examined with the spectroscope, it shows only one bright green band. Heated before the blowpipe on charcoal in the reducing flamo, thallium compounds yield a slight white coating of thallium oxide. Heated on charcoal in the oxidizing flame, with potassium iodide and sulphur, a yellowish-green coating, resembling lead iodide, is obtained, but this may be readily distinguished from the latter by the flame coloration.

Thorium, Th. — Tetravalent. Atomic weight, 233. The reactions for this rare element are given under Cerium.

Tin, Sn. — Tetravalent in minerals. Atomic weight, 119.

Occurrence.— Tin is found chiefly as the oxide cassiterite, SnO,. Its combinations with sulphur and sulphides of the metals, the sulphostannaies (stannite, Cu,FeSnS, , and canfieldite, Ag.SnS,), are rare. Nordenskioldine is, perhaps, a basic stannate, Ca(BO),SnO. Traces of tin are found in many columbates and tantalates.

Detection. — Tin is usually detected by the formation of metal- lic globules by reduction on charcoal.

fp.. Reduction on Charcoal. — If ± ivory spoonful of finely pow dered tin oxide is mixed with an equal volume of powdered char- coal and 2 of sodium carbonate, made into a paste with water, and then heated on charcoal in the reducing flame, the tin will be read*

126 REACTION OF THE ELEMENTS. Tin

ily reduced, and collect into globules, which are bright when cov- ered with the reducing flame, but become coated with a film of ox- ide on exposure to the air. If heated intensely before the blow- pipe, and for a considerable time, sufficient tin may volatilize to give a rather conspicuous white coating of oxide, SnO,, on the charcoal. Tin globules are readily fusible, malleable, and, if cut, they show a white metallic color. If treated with a little, moder- ately concentrated, warm, nitric acid, they do not dissolve, but are oxidized to a white hydroxide (metastannic acid). Tin must not be confounded with other elements which give metallic globules on charcoal. V may be distinguished from lead and bismuth by the absence of a yellow coating of oxide on the charcoal, and from silver by the coating of oxide which forms both on the charcoal and over the surface of the globules.

Sodium carbonate and oxide of tin, when heated together with- out the addition of charcoal powder, usually form an infusible mass which is very difficult to reduce.

2. Oxidation with Nitric Acid. — The action of nitric acid upon metallic tin was mentioned in the previous paragraph. Sulphides of tin (the sul- phostannatee), if pulverized and treated with nitric acid, yield the insoluble metastannic acid, and after evaporating off most of the nitric acid and dilut- ing with water, tfiis may be collected on a filter, washed with water, and tested according to § 1.

3. Detection of Small Quantities of Tin. — Mix 1 or 2 ivory spoonfuls of the finely powdered mineral with 6 volumes each of sodium carbonate and of sulphur, transfer the mixture to a porcelain crucible, cover, and heat gently at first, finally for five or ten minutes at a red heat. On cooling, treat the fused mass with warm water, which dissolves sodium sulphostannate, while most other substances which are apt to be present will be insoluble. Filter, and by adding sulphuric acid to the filtrate, precipitate the tin as sulphide, which will be accompanied by much free sulphur. Collect the precipitate on a filter, wash several times with water, ignite in a crucible to get rid of the free sulphur and the paper, and test the residue before the blowpipe on charcoal, according to § 1. If a porcelain crucible is not at hand, the fusion with sodium carbonate and sulphur may be made in a large bulb tube or even in a test-tube.

When niobates and tantalates are fused with potassium bisulphate and treated as directed on p. 99, § 2, the oxides of tin and tungsten remain with

Titanium REACTIONS OF THE ELEMENTS. 127

the niobic and tantalic oxides, and these may be separated either by the sodium carbonate and sulphur fusion, or by digestion of the moist oxides with ammonium sulphide. After filtering, precipitate the tin and tungsten by addition of sulphuric acid, collect the precipitate on a filter, wash, ignite, and test for tin, as directed in § 1.

Titanium, Ti.— Tetravalent and trivalent. Atomic weight, 48.

Occurrence.— Although usually classed among the rare ele- ments, titanium is quite common, and is always found in combina- tion with oxygen. Rutile, octahedrite, and brookite, which are dif- ferent crystalline forms of TiO, ; ilmenite, or titanic iron (a com- bination of the oxides of iron and titanium); and titanite, CaTiSiO, , are the commonest titanium minerals. Some titanium, either in the form of ilmenite, titanitie, or rutile, is present in most igneous rocks.

Detection.— Titanium may be detected by the salt of phos- phorus bead, the reduction with metallic tin, or oxidation with hydrogen peroxide.

, 1. Test with Salt of Phosphorus.— Oxide of titanium, if dis- solved in a salt of phosphorus bead in the oxidizing flame, gives a glass which is yellow when hot, and colorless when cold, while in the reducing flame the glass is yellow while hot, but on cooling assumes a delicate violet color, due to the presence of Ti,Ot. Since the color is never very intense, and the presence of other sub- stances which color the bead interferes with it, one of the tests given beyond will nsnally be found more satisfactory.

No decisive test can be made with borax. i 2. Reduction with Tin. — Most titanium minerals are very in- soluble in acids, but after fusion with sodium carbonate, they go readily into solution in hydrochloric acid, and the solution con- tains TiCl4. If this acid solution is boiled with a little granulated tin, the titanium is reduced to TiClt, which causes the solution to assume a delicate violet color. Other substances with which tita- nium is apt to occur do not interfere, and the test is quite delicate, but if a substance is supposed to contain less than 3 per cent of T30., the test with hydrogen peroxide is to be preferred.

128 REACTIONS OF THE ELEMENTS. Tltanluni

To illustrate this test, mix ± ivory spoonful of the finely powdered min- eral (rutile or ilmenite) with ti volumes of sodium carbonate, make into a paste with water, and fuse before the blowpipe either on platinum wire or charcoal. Oxide of titanium, which is an acid anhydride, is decomposed readily by sodium carbonate, with formation of sodium *titanate, TiO, -f- 2Na,C'0, Na4'iiw4 ~COrj, and the latter is easily dissolved by hydro- chloric acid. Na4Ti04+ 8HC1 TiCl4+ 4NaCl + 4H,0. Treat the fusion in a test-tube with about 5 cc. of strong hydrochloric acid, boil until a solution is obtained, filter if necessary, then add a little granulated tin, and boil until the violet color makes its appearance. If the quantity of titanium is small, it is necessary to boil the liquid away until only 1 or 2 cc. are left. The color is seen best when the acid becomes cold, and the evolution of hydrogen ceases. If much titanium is present, sometimes on boiling, a portion of it will precipitate as oxide, but enough will always remain in solution to give the violet color.

In testing niobates and tantalates for titanium, it is best to fuse the material with borax, as directed on p. 98, § 1, and on dissolving the fusion in hydrochloric acid and boiling with tin, the violet color of titanium will appear before the blue of niobium.

3. Test with Hydrogen Peroxide. — For this exceedingly deli- cate test, the mineral must be dissolved in sulphuric acid, which may be accomplished by first fusing with sodium carbonat-e, as previously directed, treating the fusion in a test-tube with 1 cc. of concentrated sulphuric acid and 1 cc. of water, and heating until the solution becomes clear. When cold, water is added, then some hydrogen peroxide, and if titanium is present, the solution becomes reddish- yellow to deep amber, depending upon the quantity of the titanium in the solution.

Tungsten, W.— Sexivalent. Atomic weight, 185.

Occurrence. —Tungsten is the acid-forming element in a group of min- erals known as the tungstates, the most important of which are wolframite, (Fe,Mn)W04; hftbnerite, MnW04; and scheelite, CaW04. The element is found in small quantity in a number of the niobates and tantalates.

Detection. — 1. When a tungstate is decomposed by boiling with hydro- chloric acid, an insoluble, canary-yellow, tungstic oxide, WO, , is obtained, and if after the addition of a little granulated tin, the boiling is continued, a blue color is at first obtained (2WO, + W08), and this by further reduction finally changes to brown (WOt). Another very good way to test, after having decomposed the mineral with hydrochloric acid, is to collect the

Uranium ENACTIONS OF THE ELEMENTS. 129

WO, on a filter,- dissolve some of it in ammonia, acidify with hydrochloric acid, which usually causes a white or yellowish turbidity, and then boil with granulated tin. When a blue color has been obtained, dilute with water, when it will be found that the color does not disappear (compare Nio- bium), and that it is due to an insoluble compound suspended in the liquid.

2. If the tungstate is insoluble or difficultly soluble in hydrochloric acid (wolframite), mix the fine powder with 6 volumes of sodium carbonate, make into a paste with water, fuse in a loop on platinum wire, pulverize, and dis- solve in a test-tube in a little water. The sodium tungstate formed during fusion is soluble in water (difference from niobium); it may be separated from the bases by filtering, and, on acidifying the filtrate with hydrochloric acid and boiling with tin, the blue reduction test may be obtained.

3. In the salt of phosphorus bead in the oxidizing flame, oxide of tung- sten gives no color, but in the reducing flame, the bead becomes fine blue; The reactions with borax are not satisfactory.

4. In order to detect the small quantity of tungsten in niohates and tantalates, treat the oxides obtained by the potassium bisulphate fusion (p. 99, § 2) either with ammonium sulphide or a sodium carbonate and sulphur fusion, separate the tungsten exactly as described for tin (p. 126, § 3), and then test by the foregoing methods.

Uranium, U. — Tetravalent and sexivalent. Atomic weight,

Occurrence. — This rare element is found as an essential constituent in only a few minerals (uranite, gum mite, uranosphaerite, torbernite, autun- ite), while it occurs sparingly in a number of others, especially those con- taining the rare elements niobium, tantalum, thorium, zirconium, cerium, lanthanum, didyxnium, yttrium, and erbium; as fergusohite, samarskite, euxenite, and polycrase.

Detection. — 1. The reactions with the salt of phosphorus bead usually serve for the detection of uranium. In the oxidizing flame, the oxide is sol- uble to a clear yellow glass, which becomes yellowish -green on cooling, while after heating in the reducing flame, the bead assumes a fine green color. With borax, the colors are not so decisive, and are nearly like those of iron, being in the oxidizing flame reddish-yellow when hot, fading to yellow when cold, and in the reducing flame, very pale green, fading to almost color- less.

2. In the presence of other elements which impart color to the fluxes, and for the detection of small quantities of uranium in minerals, it is best to proceed as follows : Make a solution in hydrochloric acid (after fusion with sodium carbonate, if necessary, as directed under silicates, p. 110, § 4, or with borax, as directed under njobates, p. 98, § 1), nearly neutralize the excess of acid with ammonia, add solid ammonium carbonate, shake

130 REACTIONS OF THE ELEMENTS. Vanadium

vigorously, and allow the liquid to stand for a few minutes. The uranium is at first precipitated, but is soluble in an excess of the ammonium carbon- ate, and by filtering may be separated from a great many elements which are precipitated by that reagent. Sometimes there is difficulty in obtaining a clear filtrate, and, if so, a few drops of ammonium sulphide may be added with the ammonium carbonate. Make the filtrate containing the uranium acid, boil to expel carbon dioxide, add ammonia in excess, collect the precip- itate containing uranium on a filter, and test it with a salt of phosphorus bead. In case the precipitate is small, burn the paper containing it in a crucible, and test the residue.

Vanadium, V. — Usually pentavalent. Atomic weight, 51.4.

Occurrence. — Vanadium is a rare element found in the vanadates, or salts of vanadic acid, H,V04, which is closely related chemically to phos- phoric and arsenic acids. Vanadinite, Pb4(PbCl)(VOJ,, and descloizite, Pb(PbOH)V04, are the commonest vanadates.

Detection. — 1. Vanadium is usually detected by the color it imparts to the fluxes. With borax, in the oxidizing flame, the bead is yellow when hot* changing through yellowish-green to almost colorless when cold. In the re- ducing flame, it becomes dirty green when hot, changing to fine green when cold. In the salt of phosphorus bead, the color in the oxidizing flame is yellow to deep amber, fading slightly on cooling; while in the reducing flame, it becomes an indistinct dirty green when hot, changing to fine green on cooling. The amber color with salt of phosphorus, in the oxidizing flame, serves to distinguish vanadium from chromium.

2. To detect small quantities of vanadium, and in cases where other sub- stances are present which impart color to the fluxes, proceed as follows: Fuse the powdered mineral in a platinum spoon with about 4 parts of so* dium carbonate and 2 of potassium nitrate, and digest the fusion with warm water, in order to dissolve the soluble alkali vanadate. Filter, acidify the filtrate with a slight excess of acetic acid, and add a little lead acetate, which will precipitate a pale yellow lead vanadate (lead chromate, p. 70, § 3, is much yellower). Some of the precipitate collected on a filter-paper may then be tested with a salt of phosphorus bead.

Yttrium, Y. — Trivalent. Atomic weight, 89.

For the reactions of this rare element, see Cerium and the rare earth metals (p. 65).

Zinc, Zn. — Bivalent. Atomic weight, 65.4.

Occurrence.— Zinc occurs most abundantly as sphalerite, ZnS, and in addition to this, smithsonite, ZnCO, ; willemite, ZnaSiO ;

Zinc REACTIONS OP THE ELEMENTS. 131

calamine (ZnOH),SiO,; and zincite, ZnO with MnO, occur in suffi- cient quantities to be mined as ores of the metal. Zinc is also found in a number of other minerals,— franklinite, gahnite, auri- chalcite, and in small quantity in many sulphides.

Detection. — Zinc volatilizes when heated before the blowpipe, and is usually detected by the coating of oxide on charcoal, and also by the test with cobalt nitrate and the flame coloration.

1. Reduction of Zinc to the Metallic Stale and Formation of a Coating of Oxide. — The best method for the detection of zinc is as follows: Mix the finely powdered mineral with about J volume of sodium carbonate, and make into a paste with water. A little of this mixture is then taken up in a small loop on fine plat- inum wire and heated intensely, holding the loop about 10 mm. from a piece of charcoal, somewhat as represented by Fig. 49. An intense heat and strong reducing action are necessary to bring about reduction to the metallic state and volatilization of the zinc. The metal thus volatilized takes oxy- gen from the air and collects as a coating of ZnO, which is pale canary-yellow when hot and white when cold. The coating is near

where the heat strikes the chai-

Fift. 4ft. coal, and is not volatile in the

oxidizing flame. If the coating is made to deposit on a piece of charcoal previously moistened with cobalt nitrate, the zinc oxide will have a green color which is especially characteristic.

For a proper understanding of this test it must be borne in mind that the method demands the reduction of zinc to the metal- lic state, but no globules form, for, as fast as reduced, the metal volatilizes.

From many compounds, zinc may be reduced, and the coating of oxide obtained without the use of a flux, when a fragment of

132 REACTIONS OF THE ELEMENTS. Zlno

the mineral (about 2 mm. in diameter) is heated very hot on char- coal in a reducing flame, but some skill in manipulating the flame is needed in order that the fragment shall not be blown away. A good way to make the test is to take the fragment in the plat- inum forceps, and holding the latter against a piece of charcoal so that the assay is about 5 mm. from the surface, heat at the tip of the blue cone, as shown in Fig. 49.

a. In order to make a zinc oxide C9atingon charcoal, mix finely pow- dered calamine, (Zn.OH),SiO,, with volume of sodium carbonate, take up in a small loop on platinum wire and heat intensely, as directed. In this experiment the sodium carbonate answers a double purpose: it serves to hold the material on the platinum wire, and also to decompose the silicate, forming sodium silicate, thus setting free zinc oxide, which may be readily reduced. (Zn.OH),SiOs + Na.CO, 2ZnO + NaaSiO$ + CO, + H,0.

b. In order to produce the coating of zinc oxide without the use of a flux, experiment with fragments of smithsonite or sphalerite. With the lat- ter mineral, the oxygen of the air converts ZuS to ZnO, and by the reducing action of the flame, zinc oxide is changed to metallic zinc.

Note. — In the presence of lead, bismuth, cadmium, or antimony, which also give coatings of oxide on charcoal, the test for zinc with cobalt nitrate should not be made until the coating has been heated for some time in the oxidizing flame, in order to volatilize the oxides of the metals mentioned.

In the presence of much tin, it is difficult to recognize zinc with cer- tainty by the reaction on charcoal, as tin also gives a white coating of oxide, which when ignited with cobalt nitrate gives a bluish-green color. If, how- ever, the mineral is decomposed by nitric acid (stannite), the test may be made as follows : Treat with nitric acid, and separate the tin according to p. 126, § 2, then to the filtrate add solid sodium carbonate until the acid is neutralized, and a permanent precipitate forms, heat to boiling, filter, and wash once with water. The precipitate will contain all the zinc, and prob- ably basic carbonates of other metals, and a portion of it, mixed with sodium carbonate, may be tested on charcoal for zinc.

2. Flame Test. — From some minerals, metallic zinc is produced by heating in the platinum forceps in a strong reducing flame, and the metal, as it volatilizes and passes into the air, burns with a vivid, pale, bluish-green light, appearing usually as streaks in the outer part of the flame. The experiment does not succeed well when too small a fragment is used, and it is best to take one about 3 mm. in diameter.

Zirconium REACTIONS OF THE ELEMENTS. 133

Experiments may be made with smithsonite and sphalerite. When the former is used, the zinc carbonate changes readily to oxide, and, by reduc- tion, metallic zinc is slowly formed. With sphalerite, the assay must be first converted by oxidation to zinc oxide, and then by reduction to metallic zinc, but usually a point can be found a little beyond the blue cone of the blow- pipe flame, where oxidation and reduction go on simultaneously, and a con- tinuous zinc flame can be maintained.

3. Heating with Cobalt Nitrate, Co(NOs)s. — Some zinc minerals, 'when moistened with cobalt nitrate and heated, assume a green color, but this simple test can be applied only to infusible, white or light-colored compounds or those which become so on ignition. In making the test, a fragment held in the platinum f orceps may be used, but it is usually better to make the finely powdered min- eral into a paste with cobalt nitrate, and then to heat on charcoal in an oxidizing flame.

Silicates of zinc, when similarly treated, usually show a blue color, owing to the formation of a fusible cobalt silicate. If an experiment is made with a large fragment of calamine, it will some- times show blue where the heat was* most intense, and green at other parts.

4. Change of Color upon Heating. — The presence of zinc is often indicated by the change of color of the assay when heated ; i.e., to straw or pale canary-yellow when hot, becoming white when cold. This test can, of course, be applied only to compounds which are white or light-colored.

Zirconium, Zr. — Tetravalent. Atomic weight, 90.7.

Occurrence. — Although a rare element, zirconium is found abundantly in some regions, especially as zircon, ZrSi04, which, in small quantities, is almost an unfailing constituent in granites and rocks rich in alkalies. It is found in a number of rare minerals, examples of which are baddelyite, ZrOt, eudialyte, catapleiite, wohlerite, polymignite, etc.

Detection. — Zirconium gives no very characteristic tests which serve for its quick and sure identification. A solution must first be obtained, which usually is accomplished by fusing with sodium carbonate, and treatment as directed under silicates (p. 110, § 4). The decomposition, however, is not complete, and usually only a portion of the zirconium will be obtained in solution. The simplest test is with turmeric-paper, which, when placed in a

134 REACTIONS OF THE ELEMENTS. Zirconium

hydrochloric acid solution containing zirconium, assumes an orange color. As the color is not yery marked, it is best to make a comparison by taking two test-tubes, one containing turmeric-paper wet by the solution containing zirconium, and the other a paper wet by acid of about equal strength.

Ammonium, sodium, and potassium hydroxide throw down zirconium hydroxide as a bulky, gelatinous precipitate, insoluble in an excess of so- dium and potassium hydroxides, thus differing from aluminium and beryl- lium. The precipitate is filtered, washed with water, dissolved in a little hydrochloric acid, the solution evaporated until only a drop or two of the acid remains, the residue dissolved in water, and oxalic acid added, when, if zirconium alone is present, either no precipitate forms, or, if it does form, it goes almost immediately into solution (difference from the rare earth metals, cerium, lanthanum, etc., p. 65). A portion of zirconium hydroxide found by the previous test to contain no rare earth metals, or separated from them by means of oxalic acid, may be scraped from the filter-paper, and dissolved in the least possible amount of dilute sulphuric acid ; to the solution, pot- assium hydroxide is then added until a precipitate forms, afterwards dilute sulphuric acid is added a drop at a time, until the solution clears (if care- fully done the liquid at this point will be nearly neutral, and the volume should be small); finally, a little more than an equal volume of a boiling, saturated solution of potassium sulphate is added, which on standing pre- cipitates a double zirconium potassium sulphate as a white powder, and servesas a characteristic test for zirconium, although the precipitation is not complete. If the precipitate is filtered, and washed with a cold and satu- rated solution of potassium sulphate, then dissolved in warm hydrochloric acid, pure zirconium hydroxide may be precipitated by means of ammonia. On ignition, zirconium hydroxide yields the oxide ZrOt, and this, if pulver- ized, mixed with cobalt nitrate, and ignited before the blowpipe on charcoal, assumes a lavender or bluish slate-color.

Chapter Iv.

Tabulated Arrangement Of The More Important Blowpipe And

Chemical Reactions.

This chapter is intended to be used especially for the interpre- tation of unknown reactions which are encountered in blowpipe analysis. The tests, if made in the order given below, will serve as a systematic course of qualitative blowpipe analysis in examining unknown substances.

A. Heating in the platinum forceps : Flame coloration, p. 135.

B. Heating in the closed tube, p. 137.

C. Heating in the open tube, p. 140.

D. Heating on charcoal, both with and without fluxes, p. 142.

E. Treatment with cobalt nitrate, p. 146.

F. Fusion with the fluxes on platinum wire : Borax, p. 148 ; phosphorus salt, p. 149 ; and sodium carbonate beads, p. 151.

G. Treatment with acids, and reactions with the common reagents, p. 151.

A. Heating in the Platinum Forceps: Flame Coloration.

Suggestions concerning the use of the platinum forceps and the methods of heating substances in them have been given in Chapter II, p. 15. In testing minerals, any change which the material undergoes should be carefully noted, but for the identification of the elements, flame colorations are the most important. The colors may often be obtained best by heating on platinum wire, as sug- gested on p. 35.

If a black, magnetic globule or mass is obtained after heating in the reducing flame, it usually indicates iron, less often cobalt

Important Blowpipe And Chemical Reactions.

or nickel. If the mass left in the forceps after heating before the blowpipe gives an alkaline reaction when placed on mois- tened turmeric-paper, it indicates the presence of an alkali or alkaline earth; as sodium, potassium, calcium, strontium, barium, and possibly magnesium.

Table Of Flame Colorations.

/

Color.

Shade or Tone.

Element.

Remarks.

Bed.

Crimson.

Lithium.

The lithia minerals, which are either silicates or phosphates, do not become alkaline after ignition (difference from strontium).

Bed.

Crimson.

Strontium.

Carbonates and sulphates show the reaction, and become alkaline after ignition. Sili- cates and phosphates do not give the stron- tium flame.

Bed.

Yellowish to orange.

Calcium.

Only a few minerals give this color decisively when heated alone. Often, however, the color shows distinctly after moistening the assay with hydrochloric acid.

Yellow.

Intense.

Sodium.

This test is so delicate that great care must be exercised in using it (compare p. 115).

Green.

Yellowish.

Barium.

Carbonates and sulphates show the reaction, and become alkaline after ignition. Sili- cates and phosphates do not give the barium flame.

Green. /

v.

Yellowish.

Molybdenum.

If in the form of oxide or sulphide.

Green.

Bright, somewhat yellowish.

Boron.

The test with turmeric-paper in hydrochloric acid solution is decisive. The compounds rarely show an alkaline reaction after igni- tion.

Green.

Pure.

Thallium.

Green.

Emerald.

Copper oxide and iodide.

After moistening the assay with hydrochloric acid, the flame appears azure-blue, tinged with green.

Green.

Pale bluish. Phosphorus.

The color is not very decisive, but often aids in the identification of a phosphate.

Green.

Bluish.

Zinc.

Appears usually as bright streaks in the flame.

Green.

Pale. j Tellurium. Antimony.

'Lead.

Important Blowpipe And Chemical Reactions,

TABLE OF FLAME COLORATIONS. — Continued.

Color.

Shade or Tone.

Element.

Remarks.

Blue.

Azure.

Copper chlo- ride.

The outer darts of the flame are tinged with emerald-green.

Blue.

Azure.

Selenium.

Accompanied by a characteristic odor.

Blue.

Pale azure.

Lead.

Perceptibly tinged with green in the outer parts.

Blue.

Indium.

Blue.

Pale.

Arsenic.

Blue.

Greenish.

Phosphorus. Antimony.

Violet.

Pale.

Potassium. Rubidium. Caesium.

B. Heating in the Closed Tube.

Closed tubes and the nature of the reactions which may be ob- tained in them have been explained on p. 18. The phenomena which are to be especially observed are as follows :

a. Change in the condition or appearance of the assay.

b. The formation of gases which collect in the tube.

c. The formation of sublimates, liquid or solid, which condense on the cold walls of the tube.

a. Change in the Condition or Appearance of the Assay.

1. Fusion.— Only substances which melt very easily, below 1£ in the scale of fusibility, fuse in the closed glass tube.

2. Decrepitation.— Fragments of decrepitating minerals (com- pare* p. 34) snap and explode, and often break up into very fine powder or dust.

3. Phosphorescence and Glowing.— Some minerals when heated to a temperature below redness emit a bright, often beau- tif ully colored light, which may continue for a considerable time,

Important Blowpipe And Chemical Beaction8.

and is seen best in a dark room. A very few minerals glow, as if they had taken fire.

4. Change of Color. — Materials often change color after heating, owing to decomposition. Again, without any change in chemical composition, some substances when hot assume colors which are different from those they have when cold. The changes are very numerous, and only a few of the more important are given.

Table Giving Change Of Color In Substances When Heated

In The Closed Tube.

Original Color.

Color after Heating.

Substance.

Remarks.

Hot.

Cold.

Green or blue.

Black.

Black.

Copper minerals.

Green or brown.

Black.

Black.

Iron minerals.

Pink.

Black.

Black.

Manganese and cobalt minerals.

These changes usually occur when oxides of the metals result from the decomposition due to heating.

Dark red.

Black.

Dark red.

Ferric oxide.

White or color- less.

Dark yel- low to brown.

Pale yellow to white.

Lead and bis- muth minerals.

White or color- less.

Pale cana- ry.yel- low.

White.

Zinc minerals.

6. The Formation of Oases which Collect in the Closed Tube.

1. Carbon Dioxide, CO,. — Colorless and odorless. May be identified by introducing a drop of barium hydroxide into the tube (p. 64, § 2). Obtained from most carbonates.

2. Sulphur Dioxide, SO,. — Colorless, with strong, pungent odor. It is further characterized by the acid reaction it imparts to moistened blue litmus-paper. Formed from the decomposition of some sulphates, and in small quantities, also, when sulphides are heated, owing to the air in the tube.

3. Oxygen, O. — Colorless and odorless, but may be detected as

Im Poktant Blowpipe And Chemical Reactions.

described on p. 100, § 1. Formed when some higher oxides, especially those of manganese, are heated.

4. Ammonia, NH,. — Colorless, with characteristic odor.

5. Hydrofluoric Acid, HF. —Colorless, with pungent odor, etching of the glass, and strong acid reaction. From compounds containing fluorine with hydroxyl (p. 77, § 5).

6. Nitrogen Dioxide, NO,.— Red vapors, with pungent odor. From nitrates.

7. Bromine, Br. — Red vapors, with pungent odor.

8. Iodine, I. — Violet vapors, often accompanied by crystals of iodine.

9. Brown Smoke, accompanied by dark distillation products and empyreumatic odor. Organic material

c. The Formation of Sublimates which Condense on the Walls

of the Tube.

Table Op 8Ublimates Produced In The Closed Tube.

Color and Cod di lion.

Substance.

Remarks.

Hot.

Cold.

Colorless liquid; easily volatile.

Colorless liquid.

Water, H.O.

From all minerals containing water of crystallization and hydroxyl. Neutral if pure, but may be acid from hydro- fluoric, sulphuric, and hy- drochloric, or other volatile acid. Rarely alkaline from ammonia.

Pale yellow to colorless liquid; difficultly vola- tile.

Colorless to white globules.

Tellurous oxide, TeO,.

From tellurium and a few of its compounds.

Red to dark yel- low liquid; readilyvolatile.

Yellow and crys- talline solid; nearly white when in small quantity.

Sulphur, S.

From native sulphur and some sulphides (p. 119, § 4).

Continued.

Important Blowpipe And Chemical Reactions.

TABLE OF SUBLIMATES PRODUCED IN THE CLOSED TUBE. — Continued.

Color ami Condition.

Substance.

Remarks.

Hot.

Cold.

Deep red, almost black liquid; readily volatile.

Reddish-yellow, transparent solid.

Sulphides of ar- senic.

From realgar, AsS, orpiment, AssSs , and some compound* containing sulphur aud ar- senic, the sulpharsenites.

Black; difficultly volatile, solid.

Reddish-brown.

Oxysulphide of antimony, Sb*OS,.

From sulphide of antimony and some of its compounds with metallic sulphide*, the sulph- antimonites.

Brilliant black, solid ; often gray and crystalline near the heated end.

Arsenic, As.

From native arsenic and some arsenides. If the tube is broken off below the deposit and the arsenic volatilized, the characteristic garlic odor may be obtained.

Brilliant black, solid.

r

Sulphide of mer- cury, HgS.

If a little of the sublimate is removed and rubbed very tine, it yields a red jiowder.

Black fusible globules. The smallest ones transmit a reddish light.

Selenium, Se.

From selenium and some sele- nides. Usually accompanied by crystals of seletiious oxide, SeOa.

Black fusible globules.

Tellurium, Te.

From tellurium and some tel- lurides. Usually accompanied by fused globuiesof tellurous oxide, TeOa.

Gray metallic globules, which may be united by rubbing with a strip of paper.

Mercury, Hg.

From native mercury and amalgams.

White, solid.

Chlorides of lead and antimony.

Oxides of arsenic and antimony.

Ammonia salts.

C. Heating in the Open Tube.

Open tubes, the methods of manipulation, and the nature of the reactions which may be obtained in them, have been explained on p. 18. The phenomena which are to be especially observed are as follows :

Important Blowpipe And Chemical Reactions.

a. Odors.

b. The formation of sublimates which condense on the walls of the tube.

c. The character of the residues. .

a. Odors.

1. Odor of Burning Sulphur.— Very strong and pungent, due to oxidation and formation of sulphurous anhydride, SO,. A piece of moistened, blue litmus- paper placed in the upper end of the tube is reddened, owing to the acid character of SO,. If prop- erly oxidized, no sublimate of sulphur is formed. The test is exceedingly delicate, and is useful for the identification of sul- phides.

2. Garlic Odor. — Observed when arsenic is driven oflf rapidly from its compounds, and is not completely oxidized.

3. Odor of Selenium. — A peculiar odor, learned only by ex- perience. Obtained when selenium is volatilized from its com- pounds and not wholly oxidized.

4. Odor of Osmic Oxide. — Very pungent

b. Sublimates. table of sublimates produced in the open tube.

Color and Character.

Black; volatile.

Brown.

Yellow or orange; easily volatile.

Red; volatile.

Pale yellow when hot; white when cold.

Substance.

Arsenic and sulphide of mercury.

Oxysulphide of an- timony.

Sulphur and sul- phides of arsenic.

Selenium, Se.

Molybdenum triox- ide, MoOt.

Remarks.

These sublimates frequently result from too rapid heating of minerals contain- ing arsenic, mercury, antimony, and sulphur, but they will not form if the open-tube test is made properly, with sufficient draft, so that the oxidation is complete.

Often accompanies selenious oxide below).

Forms slowly when molybdenum oxide or sulphide is heated, and collects near the assay as a network of delicate crys- tals.

Continued.

Important Blowpipe And Chemical Beaction8.

Table Of Sublimates Produced

IN THE OPEN TUBE. — Continued.

Color and Character.

Substance.

Remarks.

White; readily vol- atile and crystal- line.

Arsenious oxide,

A8a0i.

The sublimate forms as a ring, and where it deposits on the warm glass it is distinctly crystalline (octahedrons).

White; readily vol- atile and crystal* line.

Selenious oxide, SeOa.

The sublimate usually appears as radi- ating, prismatic crystals, often ac- companied by a little finely divided selenium, which is red.

White to pale yellow globules ; slowly volatile.

Tellurous oxide, TeO,.

White; slowly vol- atile and crystal- line.

Antimonious oxide,

SbaO..

Obtained from antimony and its com* pounds, which do not contain sulphur The sublimate consists of two kinds of crystals, octahedrons, resembling AsaOs , and prisms.

Pale straw - yellow when hot; white when cold; in- fusible, non-vol- atile, and amor- phous.

Antimonate of anti- mony, SbiO.

Obtained from sulphide of antimony and sulphantimonites, as a dense white smoke, which passes up the tube and settles mostly on the under side. This sublimate is usually accompanied by the volatile one of Sb0.

White ; non- volatile and infusible.

Sulphite and sul- phate of lead.

Obtained from sulphide of lead as a slight deposit, collecting mostly on the lower side of the tube near the assay.

Gray metallic glob- ules; volatile.

Mercury, Hg.

By rubbing the minute globules with a strip of paper, they may be made to unite.

c. The Character of the Residue.

The residue left after heating in an open tube is usually an oxide, and if saved, it may often be found very useful, especially for treatment with the fluxes on platinum wire or reduction on charcoal.

D. Heating on Charcoal.

Suggestions concerning the use of charcoal, and the manner in which tests should be made, have been given on p. 39. The phenomena which are to be especially observed are :

a. Odors.

Important Blowpipe And Chemical Reactions.

b. Sublimates.

c. The formation of metallic globules or of a magnetic mass,

etc.

a. Odors.

1. Odor of Burning Sulphur.— Obtained by roasting sul- phides in the oxidizing iiame.

2. Odor of Garlic— Obtained by heating native arsenic and arsenides in the reducing flame.

3 Odor of Selenium. — A peculiar odor, which must be learned by experience. Obtained when selenium is volatilized from its compounds in the reducing flame.

- b. Sublimates.

Table Of Sublimates Produced On Charcoal.

Color and Character.

Near the Assay.

White ; very vol- atile, and mostly distant from the assay.

Steel-gray ; faint metallic luster, and very vola- tile.

Distant from the Assay.

Substance.

Remarks.

White to gray- ish.

White; very vola- tile and mostly distant from the assay.

White, frequent- ly tinged with red.

White and not very pro- nounced.

Dense white; vol- atile.

Gray, some- times slightly brownish.

Arsenious ox- ide, AssOs.

Selenious oxide, SeO,. The red is Se.

Obtained when arsenic, its sul- phides, and the arsenides are roasted in the oxidizing flame. Often the garlic odor is pro- nounced.

Oxide of thal- lium, T1,0.

The white is tellurous ox- ide, TeO,. The gray is Te.

Obtained by roasting selenides in the oxidizing flame. The sub- limate when touched with the reducing flame imparts an azure- blue color to the flame. The selenium odor is pronounced.

The sublimate heated in the re- ducing flame volatilizes, and imparts a green color to the flame.

The sublimate heated in the re- ducing flame volatilizes, and imparts a green color to the flame.

Continued.

Important Blowpipe And Chemical Reactions.

TABLE OF SUBLIMATES PRODUCED ON CHARCOAL. — Continued.

Color and Character.

Substance.

Remarks.

Near the Assay.

Distuut from the Assay.

Dense white; vol- atile, and de- posits quite near the assay.

Bluish.

Oxides of anti- mony, SbsOs and SbtO.

Obtained when antimony and its oxides and sulphides are roasted in the oxidizing flame.

White coatings may also result from the volatilization of a variety of compounds, especially chlorides' of copper, lead, mercury, ammonium, and the alkalies.

Canary - yellow when hot; white volatile in the oxidizing flame.

Faint white.

Faint yellow to Faint white, white when hot ;l white when cold. Not vol- atile in the oxi- dizing flame. #

Pale yellow wheiijBluish. hot; white when; cold; sometimes distinctly crys- talline. Vola- tile in the oxi- dizing flame.

Oxide of zinc, ZnO.

Oxide of tin, SnOi.

Yellow when hot; straw - yellow when cold. Vol- atile in both the oxidizing and reducing flames.

Dark yellow when hot; sulphur- yellow when cold. Volatile in both the oxi- dizing and re- ducing flames.

Dense white, with bluish- white border.

Bluish- white.

Oxide of mo- lybdenum, MoO,.

By heating some zinc minerals in the reducing flame, metallic zinc is produced, which volatilizes, becomes oxide, and condenses on the coal. If the coating is moistened with cobalt nitrate and ignited, it becomes green.

The coating moistened with cobalt nitrate and ignited assumes a bluish-green color.

The coating if touched for an in- stant with the reducing flame assumes a beautiful azmv-blue color. A copper- red sublimate of MoO* deposits nearer the assay than the MoOs coating.

A mixture of oxide, sul- phite, and sulphate of lead.

Oxide of lead, PbO.

This sublimate, strongly resem- bling that of antimony, forms when galena and other sulphides of lead are heated very hot on charcoal.

The coating when moistened with hydriodic acid and heated is changed to volatile, yellowish- green lead iodide.

Important Blowpipe And Chemical Reactions.

TABLE OF SUBLIMATES PRODUCED ON CHARCOAL. — Continued.

Color and Character.

Near the Assay.

Distuut from the Assay.

Substance.

Dark orange-yel- Greenish- white, low when hot ; orange - yellow when cold. Vol- atile in both the oxidizing and reducing flames.

Dark, almost

black; chauging in short dis- tance to red- dish - brown. Volatile in both the oxidizing and reducing flames.

Yellow.

Reddish to deep lilac.

Oxide of bis- muth, BisOs.

Remarks.

The coating when moistened with hydriodic acid and heated is changed to volatile, chocolate- brown bismuth iodide.

Cadmium ox- ide, CdO.

Silver when ac- companied by lead and anti- mony.

When it forms a very thin deposit, the coating often shows an iri- descence resembling peacock colors.

Pure silver when heated alone on charcoal for a long time gives a slight brownish coating.

c. The .Formation of Metallic Globules or of a Magnetic

Mass, etc.

In order to obtain metallic globules, the powder is usually mixed with sodium carbonate, and heated in the reducing flame.

1. Gold. — Rather easily fusible ; bright when hot and cold ; no coating on the charcoal ; color, yellow ; malleable.

2. Silver. — Rather easily fusible ; bright when hot and cold ; no conspicuous coating on the charcoal ; color, white ; malleable.

3. Copper. — Fusible at a rather high heat ; bright when in the reducing flame, but oxidizing and becoming black on exposure to the air ; no coating on the charcoal ; color, red ; malleable.

4. Lead. — Easily fusible ; bright when in the reducing flame, but oxidizing on exposure to the air ; a yellow coating of oxide of

146 Important Blowpipe And Chemical Reactions.

lead deposits on the charcoal ; the metal has a lead-gray color, and is soft and malleable.

5. Bismuth.— Easily fusible ; bright when in the reducing flame, but oxidizing on exposure to the air ; a yellow coating of oxide of bismuth deposits on the charcoal ; the metal has a lead- gray color, and is brittle, although it may at first flatten to some extent when hammered.

6. Tin. — Easily fusible; bright when in the reducing flame, but oxidizing on exposure to the air ; a white coating of oxide of tin deposits on the charcoal if the globule is heated intensely ; the metal has a white color, and is soft and malleable.

7. Easily Fusible Globules with metallic luster, bright when in the reducing flame, but tarnishing on exposure to the air, are frequently obtained when combinations of the metals with sulphur, arsenic, or antimony are heated on charcoal. These globules of sulphide, arsenide, or antimonide of the metals may usually be distinguished from pure metals by their brittleness.

8. Magnetic Globules or a magnetic mass will be obtained when substances containing iron, less often cobalt and nickel, are fused with sodium carbonate on charcoal.

9. Alkaline Reaction. — Provided sodium carbonate has not been used as a flux, a mass or residue, which, after strong igni- tion, gives an alkaline reaction when placed upon moistened turmeric-paper indicates one of the alkalies or alkaline earths; as sodium, potassium, calcium, strortiium, barium, and possibly magnesium.

10. Blackens Silver.— After fusion with sodium carbonate in the reducing flame and placing upon a clean, moistened silver surface, if a black stain is produced, it indicates some compound of sulphur (p. 119, § 5, and p. 122, § 2).

E. Treatment with Cobalt Nitrate.

The method of testing with cobalt nitrate has been given on p. 29. It is applicable only to infusible and light-colored com pounds, and is especially useful in detecting zinc and aluminium.

Important Blowpipe And Chemical Reactions.

Table Of Reactions With Cobalt Nitrate.

Color.

Pale pink or flesh- color.

Green ; seen best when cold.

Bluish-green.

Ultramarine-blue.

Ultramarine-blue.

Dirty green.

Yellowish-green.

Violet.

Lavender.

Substance.

Magnesia, MgO, and salts containing it.

Oxide of zinc, ZnO, and compounds containing it.

Remarks.

Oxide of tin, SnOs.

Aluminium oxide, AlaOs , and compounds contain- ing it.

Silicates of zinc.

Oxide of antimony. Oxide of titanium.

Oxide of silicon, quartz.

Oxide of beryllium.

The color is obtained only when very pure compounds are tested, and is not very decisive.

The test may be applied to fragments of minerals or to the coating of zinc oxide on charcoal.

Observed when a coating on charcoal is tested.

About the best test for aluminium, but must not be mistaken for silicate of zinc.

Due to a fusible silicate of cobalt.

These colors are rather indistinct, and not very satisfactory.

F. Fusion with the Fluxes on Platinum Wire.

These tests may be divided into three heads as follows :

a. Fusion with borax.

b. Fusion with salt of phosphorus.

c. Fusion with sodium carbonate.

It should be borne in mind that the colors given in the follow- ing tables are those which the pure oxides of the metals yie!d when dissolved in the fluxes, but it would be almost impossible to tabulate all the varieties of color given by mixtures of the oxides. If a substance which is to be tested is not an oxide, it may be frequently brought into that condition by roasting on charcoal or in an open tube.

Too much pains cannot be taken in making the beads of suit- able size, about 3 mm. in diameter, introducing the proper amount of material into them, and heating successfully both in the oxidiz- ing and reducing flames. Suggestions about making beads and fusing substances in them have been given on pp. 16, 24, and 25.

Important Blowpipe And Chemical Reactions.

a. Fusion with Borax on Platinum Wire.

Table Of Reactions Obtained With Borax.

Oxidizing Flame.

Amount

of Material.

Produced by

Reducing Flame.

Hot.

Cold.

Hot.

Cold.

Colorless.

Colorless.

Little or much.

Oxides of silicon, al- uminium; and tin.

! Colorless.

Colorless.

Colorless.

Colorless or opaque white, depending up- on the degree of saturation.

Little or much.

Oxides of calcium, strontium, barium, magnesium, beryl- lium, zinc, yttrium, lanthanum, thori- um, zirconium, tantalum, and co- lumbium.

Colorless, i

Colorless or opaque white, depending upon the de- gree of satu- ration.

Pale yellow.

Colorless or

white.

Much.

Oxides of lead, an- timony, and cad- mium.

Pale

yellow.

Colorless.

Pale yellow.

Colorless or

white.

Much.

Oxide of bismuth.

Gray.

Gray.

Pale yellow.

Colorless or

white.

Much.

Oxide of molybde- num.

Brown.

Brown.

Pale yellow.

Colorless or

white.

Medium.

Oxide of tungsten.

Yellow.

Yellow to yel- lowish brown.

Pale yellow.

Colorless or

white.

Medium.

Oxide of titanium.

Grayish.

Brownish- violet,

Yellow.

Nearly color- less.

Little.

Oxides of iron and uranium.

Pale green.

Nearly color- less.

Yellow.

Pale yellow.

Little.

Oxide of cerium.

Colorless.

Colorless.

Yellow.

Yellowish- green.

Little.

Oxide of chromium.

Green.

Green.

Yellow.

Yellowish- green, almost colorless.

Little.

Oxide of vanadium.

Dirty

green.

Fine green.

Deep yellow to orange- red.

Yellow.

Medium to much.

Oxide of cerium.

Colorless.

Colorless.

Deep yellow to orange- red.

Yellow.

Medium to much.

Oxide of uranium.

Pale green.

Pale green to nearly col- orless.

Important Blowpipe And Chemical Reactions.

TABLE OF REACTIONS OBTAINED WITH BORAX. — Continued.

Oxidizing Flame.

Amount

of Material.

Produced by

Reducing Flame.

Hot.

Cold.

Hot.

Cold.

Deep yellow to orange- red.

Yellow.

Medium to much.

Oxide of iron.

Bottle- green.

Pale bottle- green.

Deep yellow to orange- red.

Yellowish- green.

Medium to much.

Oxide of chromium.

Green.

Green.

Green.

Blue.

Little to medium.

Oxide of copper.

Colorless to green.

Opaque red with much oxide.

Green.

Yellow, green, or blue, of va- rious shades.

Medium.

Various mixtures of the oxides of iron, copper, nickel, and cobalt.

(?)

(?)

Blue.

Blue.

Little to medium.

Oxide of cobalt.

Blue.

Blue.

Violet.

Reddish-brown.

Little to medium.

Oxide of nickel.

Opaque

gray.

Opaque gray.

Violet. ; Reddish-violet.

Little.

Oxide of manganese.

Colorless.

Colorless.

Pale rose. iPale rose.

Much.

Oxide of didymium.

Pale rose.

Pale rose.

b. Fusion with Phosphorus Salt on Platinum Wire.

Table Of Reactions Obtained With Phosphorus Salt.

Oxidizing Flame*

Amount

of Material.

Produced by

Reducing Flame.

Hot.

Cold.

Hot.

Cold.

Colorless.

Colorless, but when strong- ly saturated the beads may in some cases appear opaque white.

Little or much.

Oxides of calcium strontium, barium, magnesium, berylli- um, zinc, alumin- ium, yttrium, lan- thanum, thorium, zirconium, tin, and silicon, the latter almost insoluble.

Colorless.

Colorless, but when strong- ly saturated the beads may in some cases appear opaque white.

Continued.

Important Blowpipe And Chemical Reactions.

TABLE OF REACTIONS OBTAINED WITH PHOSPHORUS SAXT. — Cont'd.

Oxidizing Flame.

Amount of . Material.

Produced by

Reducing Flame.

Hot.

Cold.

Hot.

Cold.

Very pale yellow.

Colorless.

Much.

Much.

Oxides of tantalum and cadmium.

Very pale yellow.

Colorless.

Very pale yellow.

Colorless.

Oxides of lead, anti- mony, and bismuth.

Gray.

Gray.

Very pale yellow.

Colorless.

Much.

Oxide of niobium.

Brown.

Brown.

Pale yellow.

Colorless.

Medium.

Oxide of tungsten.

Dirty blue.

Fine blue.

Pale yellow.

Colorless.

Little to medium.

Oxide of titanium.

Yellow.

Violet.

Yellow.

Colorless.

Medium.

Oxide of cerium.

Colorless.

Colorless.

Yellow.

Colorless.

Little.

Oxide of iron.

Very pale yellow- ish-green.

Colorless.

Yellow.

Pale greenish- yellow.

Medium.

Oxide of uranium.

Pale dirty green.

Fine green.

Yellowish- green.

Colorless.

Medium.

Oxide of molybde- num.

Dirty green.

Fine green.

Deep yellow to brown- ish-red.

Yellow to al- most color- less.

Medium to much.

Oxide of iron.

Red, yel- low, to yellow- ish-green.

Almost color- less to very pale violet.

Yellow to deep yellow.

Yellow.

Little to medium.

Oxide of vanadium.

Dirty ,Fine green.

green.!

Reddish to brownish- red.

Yellow to red- dish-yellow.

Little to medium.

Oxide of nickeL

Reddish to brown- ish-red.

Yellow to red- dish-yellow.

Green.

Rather pale blue.

Little.

Oxide of copper.

Pale yel- lowish- green.

Pale blue, nearly color- less; at times ruby- red.

Dark green.

Blue.

Medium.

Oxide of copper.

Brownish- green. !

Opaque red.

Green.

Yellow, green, or blue, of various shades.

Medium.

Various mixtures of the oxides of iron, copper, cobalt, and nickel.

?

?

Important Blowpipe And Chemical Reactions.

TABLE OF REACTIONS OBTAINED WITH PHOSPHORUS SALT.— Cont'd.

Oxidising Flame.

Amount

of Material.

Produced by

Reducing Flame.

Hot.

Cold

Hot

OoUL

Dirty green.

Fine green.

Little to medium.

Oxide of chromium.

Dirty green.

Fine green.

Blue.

Blue.

Little to medium.

Oxide of cobalt

Blue.

Blue.

Grayish- violet.

Violet.

Medium.

Oxide of manganese.

Colorless.

Colorless.

Pale rose.

Pale rose.

Much.

Oxide of didymium.

Pale rose.

Pale rose.

c. Fusion with Sodium Carbonate on Platinum Wire.

If heated in the oxidizing flame, an opaque bead, green when hot, blue when cold, indicates manganese. The color disappears in the reducing flame.

A yellow bead in the oxidizing flame indicates chromium.

A clear glass can be made by fusing with a sufficient quantity of silica.

G. Treatment with Acids, and Reactions with the Common

Reagents.

As a general rule, it may be recommended to treat 1 or 2 ivory spoonfuls of the finely powdered mineral in a test-tube with about 5 cc. of acid ; heat to boiling, and observe any changes which take place. For minerals without metallic luster, hydrochloric acid is usually the most convenient solvent, while for the sulphides and arsenides, which usually have metallic luster, nitric acid is best The following should be especially observed :

a. Evolution of Oases.

1. Carbon Dioxide, CO,. — Colorless and odorless. Obtained from all carbonates (p. 62, § 1).

152 Important Blowpipe And Chemical Reactions.

2. Hydrogen Sulphide, H,S. — Colorless, with disagreeable odor. Obtained from sulphides (p. 121, § 7).

3/ Chlorine, CI. —Nearly colorless, with disagreeable odor. Obtained from a few higher oxides when dissolved in hydrochloric acid (p. 101, § 2).

4. Nitrogen Dioxide, NO,. — Dark red vapors derived from nitric acid when oxidation is taking place (p. 120, § 6).

6. Color of the Solution.

A great variety of colors may be obtained, but only the oommon ones will be mentioned.

1. Amber to Brownish-Red. — Hydrochloric acid solutions containing ferric iron.

2. Green. — From mixtures of copper and iron, and also from nickel. Addition of ammonia in excess gives a blue color with cop- per and nickel, the former being more intense.

3. Blue. — From copper, and greatly intensified by adding an excess of ammonia.

4. Pink or Pale Rose. — From cobalt.

c. Insoliible Residue after Decomposing a Mineral.

1. A Jelly. — When this is obtained by evaporation of a solu- tion, and is insoluble upon subsequent addition of water or acid, it indicates a silicate (p. 108, § 1).

2. A Pulverulent Residue. — White, but more transparent in the acid than the original powdered mineral ; it may indicate a silicate (p. 109, § 2).

8. White Residues.— These may be obtained when minerals containing tin, antimony, and sulphide of lead are oxidized by nitric acid.

4. A Yellow Residue. — This may indicate tungsten. A spongy mass or fused globule of sulphur is also often obtained when sulphides are treated with nitric acid (p. 120, § 6).

Important Blowpipe And Chemical Reactions. 153

d. Precipitation by Adding Appropriate Reagents to the Clear

Solution.

Only those reagents which are most useful in making simple test-tube experiments will be mentioned.

1. Ammonia precipitates aluminium, beryllium, bismuth, chro- mium (trivalent), iron (ferric), lead, and the rare earth metals9 (p. 65), as hydroxides.

Under a variety of conditions, especially when phosphoric, arsenic, si- licic, and hydrofluoric acids are present, many other elements may be precipi- tated ; e.g., calcium phosphate is precipitated when ammonia is added to an acid solution of apatite (p. 60, § 4, b).

2. Ammonium Carbonate is especially convenient for precipi- tating calcium, strontium, and barium carbonates from solutions made alkaline by ammonia.

3. Ammonium Oxalate is useful for the precipitation of cal- cium oxalate from solutions made alkaline by ammonia. Barium and strontium are also precipitated.

4. Ammonium Sulphide precipitates, from solutions which are nearly neutral or alkaline, iron, zinc, manganese, cobalt, and nickel, as sulphides, and aluminium, chromium, and the rare earth metals, as hydroxides. It is also useful for dissolving freshly pre- cipitated sulphides of arsenic, antimony, and tin.

5. Barium Chloride precipitates barium sulphate from acid solutions, and serves, therefore, as a very delicate test for a sul- phate.

6. Hydrochloric Acid precipitates silver, lead, and mercu-

rou8 chlorides from nitric acid solutions.

7. Hydrogen Sulphide gas, when led into hydrochloric or sulphuric acid solutions, precipitates silver, lead, mercury, copper, bismuth, cadmium, arsenic, antimony, and tin, as sulphides. If the solution is in nitric acid, it is best to evaporate in a casserole with sulphuric acid, until the nitric acid is expelled, and then, after dissolving in water, to run in the hydrogen sulphide gas.

154 Important Blowpipe And Chemical Reactions,

8. Silver Nitrate precipitates silver chloride, bromide, or iodide from solutions of chlorides, bromides, or iodides, in water or dilute nitric acid.

9. Sodium Carbonate precipitates iron, zinc, manganese, co- bait, nickel, copper, magnesium, and many other metals, as basic or normal carbonates.

10. Sodium Hydroxide precipitates iron, manganese, cobalt, nickel, copper, bismuth, cadmium, magnesium, and the rare earth metals, as hydroxides, some of these only in the absence of ammo- nium salts.

11. Sodium Phosphate is useful for detecting magnesium in solutions which are not precipitated by ammonia and ammonium carbonate, or have been filtered from the precipitates produced by these reagents.

12. Sulphuric Aoid precipitates lead, barium, strontium, and calcium sulphates, the last, however, only when the solutions are concentrated

Chapter V.

Physical Properties Of Minerals.

In the foregoing chapters, minerals have been regarded from the standpoint of their chemical composition only, but they pos- sess in addition certain physical properties which may be very useful for their identification and recognition. The im- portant of these are crystallization, luster, color, hardness, fusi- bility, and specific gravity.

Crystallography.*

Crystallization. — When a mineral or chemical compound assumes a solid form, it does so by separation from a solution, or from a molten mass, or by condensation from a vapor ; and the molecules, or smallest particles of the substance, generally assume a definite arrangement. This process is called crystallization, and when it takes place under favorable circumstances it gives rise to crystals, or solids which have not only definite internal struc- ture or arrangement of tlie molecules, but also definite shapes bounded by flat surfaces.

Very little is known concerning the molecules which form crys- tals: they may correspond to the chemical molecules, but are probably larger, and aggregates of them ; and certainly in all in- stances they are excessively minute. It is a very important prop- erty of crystals that, during their growth, the molecules of the substance tend to arrange or group about themselves only those of

Owing to limited space, this important subject will have to be treated in a somewhat elementary manner, but it is hoped that the essential features can be presented with suf- ficient clearness to enable the student to become familiar with the more important, sim- ple, crystalline forms and combinations. To obtain a really satisfactory knowledge of the subject it is quite essential to supplement the text by a collection of crystals or models.

156 Cbystalliza.Tion.

the same kind. The crystallized condition of a compound is, there- fore, one of the very best proofs of its homogeneous character and purity.

That solids with plane surfaces may result from the arrange- ment of particles of the same kind is shown by Pig. 50, which rep-

Cube, octahedron, and dodecahedron made by tbe regular arrangement of shot. The arrangement of theebot la Identical la Che three models, but different layer* of *bot constitute the outer or limiting

resents geometrical shapes made by a regular arrangement of shot. If the shot were so exceedingly small that the individual ones could not be seen, the outer surfaces of the solids would appear perfectly smooth and flat. Such an arrangement is, however, some- what misleading, since the shot are in contact with one another, while in crystals the distances between the molecules are probably considerably greater than the diameters of the molecules them- selves. A more correct idea, therefore, of an arrangement of mole- cules in a crystal may be gained from Fig. 51. In a crystal the molecules are all of the same kind, and in any given direction they mast be equally distant from one another.

As in an orchard where the trees are evenly spaced one may look in different directions, ab, ac, af, etc., (Fig. 62), and see the trees in rows, so through a regular arrangement of particles, as in Fig. 51, there are certain definite directions in which the particles lie in planes. The crystal faces correspond to molecular planes, and have definite inclinations or angles, depending upon the mo- lecular arrangement.

Provided a crystal has not been hindered in its development it will be bounded by flat surfaces, which give it a regular external

Crystallization.

form, and this is one of its most striking features. It is only occa- sionally, however, that a crystal develops without interruption, for it usually is interfered with by others, or grows against some ob- stacle so that only a portion or perhaps nothing of its characteris- tic external form is produced. Even when the external form is wholly wanting, the crystalline nature of a substance, due to the regular arrangement of the molecules, may be revealed by soms, of the physical properties peculiar to crystals. Thus by the aid

/

/

/

Fig. 51.

Fig. 58.

of polarized light it could instantly be told that a transparent frag- ment of quartz possessed a crystalline structure and was not a bit of glass.

Most minerals have been observed in a crystallized condition, and it is important to bear in mind that only definite chemical compounds possess this peculiar property of crystallization.

Constancy of the Interfacial Angles of Crystals. — One of the most important features of crystals is that those of the same substance invariably exhibit the same angles between similar faces. It is evident that in an orchard one must look in definite directions, ab, of, ag, etc. (Fig. 52), to see the trees in rows, these directions depending upon the way in which the trees are planted. In Pig. 62 the trees are represented as equally spaced along the rows ab and ag, with these rows at right angles to one another. It must also follow that constancy of interfacial angles is a feature of crystals, provided each substance has its own defi-

G0Ni0Hetbr8.

nite molecular structure (Fig. 51), and that the faces correspond to layers of molecules.

Goniometers. — Instruments for measuring the interfacial an- gles of crystals are called goniometers.

The reflection goniometer consists of a divided circle turning

upon an axis, and provided with devices for holding and adjusting crystals so that the edge between the faces to be measured can be made to coincide with, and be paralled to, the axis of the instrument. Rays of light I (Pig. 53), either coming from a distant object, or made parallel by pass- ing through a lens, fall upon the face ac Fig. 58. 0f a cryg Qui some of them are reflected

In the direction of the observer ce. It is evident that in order to obtain a reflection in a similar direction from the face cby it will be necessary to turn the crystal through the angle /?, which is the supplement of the angle acb, the angles being read from a divided circle. Measurements can thus be made with great accuracy even on very small crystals. In studying and calculating the mathe- matical relations of crystal faces, the supplement angles are much more convenient to use than the actual ones, and are almost in- variably employed by crystallographers.

An inexpensive contact goniometer, designed by the author, consists of a graduated semicircle (Fig. 54) printed on cardboard, and provided with a measuring arm of transparent celluloid which is swiveled by means of an eyelet exactly in the center of the arc. A fine line, scratched on the under surface of the celluloid arm and blackened, and in exact alinement with the center of the eyelet, serves Fro- 64. (About natural size).

to indicate the angle. In using the instrument the edges of the

Chy8Tall0Gbaphic Axes.

card and measuring arm are brought as nearly as possible in con- tact with the crystal faces, care being taken that the plane of the card is held at right angles to the edge formed by the intersection of the crystal faces.

Crystallographic Axes. — In order to show the relations of crystal faces it is convenient to take certain directions within the crystals as axes. Usually three are chosen (Fig. 55), one a -a, going from front to back, another b -6, from right to left, and a third c -c, vertical. Positive and negative directions are assumed from the center, as indicated in the figure. Crystal faces intersect these axes, and, by measuring appropriate interf acial angles, the re- lative lengths of the axes, or their ratio to one another, can be de- termined. For exainple, sulphur crystals have the form of a pyra-

+a

i-o Fig. 55.

Fig. 56.

Fig. 57.

mid (Fig. 56), and the angles which are measured over the edges joining the a and 6, and the b and c axes, respectively, equal 36° 40£' and 94° 52'. From these angles it can be calculated, by simple mathematical processes, that, if the length op is assumed as unity, the lengths oa and oc are 0.813 and 1.903, respectively. Designat- ing the lengths of the axes oa, ob9 and oc as a, J, and c, the fore- going mathematical relation can be expressed as follows : a : b : o 0.813 : 1 : 1.903. This is known as the axial ratio of sulphur.

When the axes are not at right angles to one another the an- gles ay py and y (Fig. 67) must be determined.

Parameters.

Parameters. — Parameters are the distances from the center o (Pig. 56), at which crystal faces intersect the axes. For example, oa, ob, and oc are the parameters of the face abc. If oa, ob, and oc correspond to the characteristic lengths of the respective axes of any mineral, the face in question is then said to have the param- eters a:b:c.

It must be distinctly borne in mind that the parameter dis- tances oa, 06, and 00, or the axial lengths, are not expressed in terms of any unit of measure, but have only relative values. For example, no matter what length is chosen for the b axis, if a and c have relatively the lengths that have been determined for sul- phur, a : b : c 0.813 : 1 : 1.903, then the eight plane surfaces which intersect the extremities of the a, b, and c axes will form a pyra- mid (Fig. 56) whose interfacial angles will be like those of a sul- phur crystal.

Law of Definite Mathematical Ratio. — It is a very impor- tant feature of crystals that their faces, prolonged if necessary, will intersect the axes only at the ratio distances a, b, and 0, characteristic of each substance, or at simple multiples, or frac- tions, of these ratio distances. A plane may, however, be parallel to one or two of the axes, which is indicated by the sign of infinity. Given the axes a -a, b -b, and 0 -0 (Fig. 58) of the ratio lengths

characteristic for any substance, then possible crystal faces might have the parameter relations a : b : 0, 2a : b : 0, a : b : \c, etc., or 00 a : b : 0, 00 a : oo b : 0, etc. Experience has shown, more- over, that the multiples at which the characteris- tic axial lengths are cut, are most often unity (not expressed before the letters) and infinity, or such simple quantities as 2, 3, J, or £. When no sign is expressed, a positive one is always under- stood.

As a further illustration of this very impor- tant principle, suppose three wires are fastened together at right angles to one another, and cut off so that their relative lengths

Indices.

Fig. 59.

Fig. 60.

shall correspond to the crystallographic axes of sulphur, a:b:c 0.813 : 1 : 1.903 (Pig. 59),, then the eight planes joining the ex- tremities of the a, b, and c axes, and another set of eight planes going from the extremities of the a and b axes to i on the c axis, would have the direction, or make with one another, the character- istic angles of the faces p and s (Fig. 60) which occur on crystals of sulphur. It will be observed from a consideration of Figs. 69 and 60 that the faces p, having their origin at a and b, do not in- tersect the vertical axis, but, if extended, would do so at c. Also, the faces s, having their origin at a certain distance on the vertical axis, when extended would intersect the horizontal axes at points beyond a and b. The relative distances, however, at which the three axes are cut by the s faces are the same as those of the planes indicated by dotted lines in Fig. 59, going from a : b : \c, for the s faces are paral- lel to these.

It must be distinctly borne in mind that parameter relations furnish a means of expressing the directions of crystal faces when they are referred to axes of known lengths and position, but they in no way affect the size of the faces. A crystal face may be regarded as shifted to any extent, provided it is kept parallel to its original position, without in the least affecting the relative distances at which the axes are intersected.

Indices.— The position and direction of crystal faces with reference to axes can also be expressed by numbers, known as indices, which are the reciprocals of the parameters. The recip- rocal of a number is one divided by the number, i 0. In- dices are written as whole numbers, the reciprocal values being cleared of fractions when necessary, and the minus sign, when needed, is written over the number.

Symmetry,

The following examples will serve to illustrate the relations of parameters and indices :

Parameters,

Indices.

Parameters.

Indices.

a : b : c

2a : b : c

a : b : oo c

a : — |ft : 3c

coa : oob : — c

—a : b : $c

If one will keep in mind the reciprocal relation existing be- tween indices and parameters , it soon becomes an easy matter to use indices, and to conceive of the position and direction of crystal faces expressed by them. For example, 001 designates a plane parallel to the a and b axes, and intersecting the negative end of c. The indices 122 (read one, two, two) designate a face intersecting a, i&, and ; such a plane is parallel to, and, there- fore, crystallographically identical with, a plane expressed by the

parameter relation 2a : b : c (Pig. 61). The indices 321 designate a face intersect- ing ia, — iJ, and c, which is parallel to the face hav- ing the parameter relation a:-ib:3c (Pig. 62): Pig. 61. Fig. 62. It is important to note

the order in which the indices are written, the first, second, and third numbers referring invariably to the characteristic a, 6, and c axes.

Since indices furnish a very convenient method of expressing crystallographic relations, they have been almost universally adopted by crystallographers.

Symmetry. — Upon examining crystals it will be observed that there is a certain regularity in the recurrence of faces and angles of the same kind, which is designated as symmetry. The sym- metry of crystals is expressed in terms of imaginary planes and axes passing through them.

The Crystal Foiim. 163

Symmetry Plane. — A plane is called a symmetry plane when it divides a crystal in such a manner that the faces and angles on one side of the plane are repeated on the side directly opposite. Thus in Fig. 63 of orthoclase, the shaded plane divides the figure symmetrically. A symmetry plane is of such a nature that, if a crystal is held before a mirror with the symmetry plane parallel to the reflecting surface, the crystal and its reflection present the same appearance.

Symmetry Axis. — When a crystal, on being revolved, shows a recurrence of similar faces and angles, the direction about which the revolution has taken place is called an axis of symmetry. In Fig. 63 the direction at right angles to the face b is an axis of symmetry ; by a turning of 180° about this axis, the crystal would occupy the same position in space, and therefore present the same appearance. The symmetry of crystals as referred to axes is of four kinds : binary, trigonal, tetragonal, and hexa- gonal, according as the recurrence of similar parts or features takes place two, three, four, or six times during a revolution of 360", and the four kinds are indicated by the following signs :

Crystallographic axes, (page 159) correspond to axes of sym- metry whenever it is possible to make them.

Center of Symmetry. — A crystal is said to have a center of symmetry when it is so developed that for every face there is a possible one of exactly similar character, diametrically disposed with reference to a central point.

The Crystal Form.— All of the faces of the same kind which are possible on a crystal of given symmetry constitute a crystal form. For example, take the axes of binary symmetry, a -a, b -b, and c -c (Fig. 64), which are of unequal lengths and at right angles to one another, and assnme that there are three planes of symmetry, each passing through two of the axes ; the eight faces intercepting the extremities of the axes would then

The Crystal Form.

be alike and would produce a form known as a pyramid. In

giving the symbol of such a form it is custom- ary to give the parameters a : b : c, or indices (111) of only one of the faces, since the number of possible faces of the same kind can readily be told, provided the symmetry is known.

In Pig. 63, which represents an orthoclase crystal with one axis of binary symmetry and one plane of symmetry, there are three forms, by c, and y, each consisting of two faces, and a fourth form m, having four faces.

Normal or HolohedraZ Forms. — Pig. 64 rep- resents the most symmetrical arrangement of the crystal faces about the axes a -a, b -5, and c -c. Eight faces of the same kind are possible, all of which are developed, and the term normal form will be used for designating crystals of this charac- ter. It is also customary to designate such a form as holohedral (o\os, whole, and edpa, face).

Hemihedrism. — About a system of three, unequal axes, at right angles to one another, it is possible to have forms with a lower degree of symmetry than that of the pyramid (Pig. 64). For example, provided the axes are symmetry axes, and that there are no planes of symmetry, the form :b] a:b:c (111) would then consist of four faces (Fig. 65). Such a form is often designated as hemihedral {fini, half, and eSpa, face), since it has only half as many faces as are possible when the highest degree of symmetry prevails.

Hemimorphism. — This term is applied to the property, exhib- ited by some minerals, of having different crystalline forms at opposite extremities of an axis of symmetry. Thus, a crystal of calamine (Pig. 66) shows the forms lettered c, tf, and i above, which are different from v below. Crystals of tourmaline (Figs. 67 and 68) have very different forms at the upper and lower extremities

Fig. 65.

Crystal Habit.

of the vertical axis. Hemimorphic crystals show marked pyro- electricity, see p. 231.

FIG. 66. Fio. 67. Fro. 68.

Crystal Habit. — It is characteristic of every substance that its crystals possess a certain kind of symmetry, or belong to a cer- tain system of crystallization, although their forms or habit may be very different. Thus Pigs. 69, 70, and 71 illustrate the forms

of the cube, octahedron, and dodecahedron, which may be observed in fluorite. The Bhot models (Pig. 60, p. 156) also show these three forms, and will perhaps serve to explain why it is that there can be a difference in habit. The forms of the models depend upon the directions of the layers of shot which represent the outer or limiting surfaces, while the arrangement of the shot with reference to one another is the same in all three models. As explained on p. 156, each chemical substance possesses a definite arrangement of its crystal molecules, but layers of molecules having different directions may constitute the crystal faces.

Distorted Crystals. — It generally happens that daring the growth of crystals material is supplied more abundantly to some parts than to others, and consequently they do not attain an ideally

Crystal Combinations.

symmetrical development. For example, although pyrite crystal- lizes in cubes (Fig. 72), it is frequently found in forms having some faces larger than others (Figs. 73 and 74). These forms, although departing from the type of a geometrical cube, are considered, crys-

tallographically, as distorted cubes, since each interfacial angle equals 90°, and all the faces have similar physical properties. Fig. 75 represents a symmetrical octahedron and Fig. 70, a dis- torted one ; Fig. 77, a symmetrically developed quartz crystal, and Fig. 78, a distorted one with the corresponding faces m, r, and z differently developed.

Distorted crystals are the rule rather than the exception, al- though the distortion is not usually so great as represented by the foregoing illustrations. Moreover, it should be clearly understood that the characteristic interfacial angles of crystals are in no way affected by inequalities in the size of similar faces.

Crystal Combinations.— The occurrence of two or more dif- ferent forms, or dissimilar kinds of faces, on a single crystal is called a combination. Fig. 00 (p. 161) illustrates the way the forms p and combine on a crystal of sulphur, and Fig. 63 (p. 163), a com-

Twin Crystal8.

bination of the four forms &, c, y, and mona crystal of orthoclase. Farther on, when the systems of crystallization are described, this important subject of crystal combinations will be more fully illus- trated and explained.

Truncations. — When an edge which would be formed by the meeting of two crystal faces is replaced by a plane, that edge is said to be truncated. Fig. 79 represents a cube a whose edges are truncated by the planes d. The term truncation is generally used in a restricted sense, to denote that truncating planes make equal angles with the adjacent faces. When the angles on adjacent faces are unequal the term oblique truncation is used.

A solid angle is said to be truncated when it is replaced by a plane. Fig. 80 represents a cube a whose solid angles are truncated by the planes o.

Twin Crystals. — When crystals grow together in other than a parallel position, so that they have a certain crystallographic plane, or direction, in common, they are known as twin crystals. These generally present the appearance of two halves of a crystal (Fig. 81) united by a plane called the twinning-plane, and are known as contact twins. Twin crystals of this type are of such a

Fig. 79.

Pv*Ws

Fig. 80.

i/

?ig. 81.

Fig. 82.

Fig. 83.

nature that the form of a simple crystal would result if the twins were cut in two along the twinning-plane, and either one of the halves should be revolved 180° about an axis which is at right angles to the twinning-plane. Sucli an axis is known as the twin- ning-axis. For example, if the lower half of the twin crystal rep-

168 Twin Crystals.

resented in Pig. 81 was thus revolved, an octahedron (Fig. 82) would result ; hence such a crystal is called a twinned octahedron.

Two individuals may also appear as penetrating through one another (Pig. 83) and such are known as penetration twins. In this type of twins one of the individuals is brought into the same position as the other by a revolution of 180° about the twinning- axis. Por example, the cube a if thus revolved about the twin- ning-axis 1 1 would assume the position of the cube a.

A twinning-plane can never be a symmetry-plane, and is almost invariably parallel to a face having a simple relation to the crys- tallographic axes.

Pig. 84 represents a simple crystal of aragonite ; Fig. 86, a twin in which one of the m faces is the twinning-plane ; and Pig. 86, a repeated twinning, in which the parts I and III are in a parallel position, and have between them a lamella II in twin position. When there are a series of lamella; in twin position the twinning is said to be polysynthetic. Fig. 87 represents a piece of

oligoclase feldspar where the polysynthetic twinning has given rise to a surface which appears distinctly striated, and consists of a series of alternating re-entrant and salient angles. Pig. 88 represents a twin grouping of nitile prisms which cross one an- other at angles of about 60° and 120°; and Fig. 89, a repeated twinning of rutile where eight individuals unite to form a rosette. Twinning often gives rise to very complex forms.

The 8Y8Tem8 Of Crystallization.

Although re-entrant angles are a prominent feature of twin crys- tals, they are not to be taken as a necessary indication of twinning. Crystals grow together in parallel and all possible accidental posi-

Fig. 88.

Pig. 80.

Pig. 90.

tions, giving rise occasionally to groupings with re-entrant angles which may closely resemble twin crystals, but are entirely distinct from them. Pig. 90 represents a parallel growth of octahedrons of magnetite.

The Systems of Crystallization. — Although there is an almost unlimited variety in the forms of crystals, they can all be classified under the following six divisions,- or systems of crystallization : I. Isometric. III. Hexagonal. V. Monoclinic.

II. Tetragonal. IV. Orthorhombic. VI. Triclinia

The character of the different systems, and the prominent forms which they present, will be described on subsequent pages.

Isometric System.

The forms in this system can be referred to three axes, which are at right angles to one another and of equal lengths (Fig. 91). Since the axes are alike, they are all desig- nated by the symbol a, but in referring crystal faces to them a definite order is adopted, as ax , at , and at.

-aa

a,

nay

-a, Fig. 91.

Forms of the Normal Group. — Galena Type.

All the forms and combinations of this group are characterized by having three axes of tetragonal, four of trigonal, and six of

Isometric System.

binary symmetry (Fig. 92) ; also by having three axial and six diagonal planes of symmetry (Figs. 93 and 94).

Fib. 93.

Fig. 98.

Fig. 94.

Cube — The cube a (Fig. 95) has six square faces, each of which intersects one axis and is parallel to the other two. The symbol is (100). The interfacial angles are 90". The faces are all alike. This is also true of the eight solid angles and twelve edges. (Compare distorted cubes, p. 166.) Galena, fluorite, and halite commonly crystallize in cubes.

Octahedron. — The octahedron o (Fig. 96) has eight faces, each of which intersects the three axes at equal distances from the cen- ter. The symbol is (111). The faces are equilateral triangles and the interfacial angles are 70° 32'. The faces are alike, as are also the six solid angles and the twelve edges. (Compare distorted octahedrons, p. 166.) Galena, magnetite, and fluorite often crystal- lize in octahedrons.

. d V/

X/t

Fra. 95. Fig. 96. Fig. 97.

Dodecahedron. — The dodecahedron d (Fig. 97) called often the rhombic dodecahedron, has twelve rhombic faces, each of which intersects two of the axes at the same distance and is parallel to the third. The symbol is (110). The interfacial angles are 60". The faces are alike, and so also are the twenty-four edges, but the

Normal Group.

solid angles are of two kinds, namely : those at the extremities of the axes, made by the meeting of four faces, and those at the cen- ters of the octants, made by the meeting of three faces. Garnet and magnetite occorin dodecahedrons.

Crystals which show the combination of the cube a, the octa- hedron o, and the dodecahedron d, as illustrated by Pigs. 98 to 104, will often be found. None of these combined forms receive a spe- cial name, but can be designated as follows : Pig. 98, a combina-

Pia. 100.

Fig. 96. Fig. 99.

Hon of cube and octahedron ; Pig. 102, a combination of octa- hedron and dodecahedron ; Fig. 104, a combination of cube, do-

decahedron, and octahedron, etc. Galena, fluorite, and magnetite illustrate such combinations.

Trapezohedron.— The trapezohedron (Pig. 105) has twenty-four similar faces, each of which is a trapezium. Each face intersects one axis at a certain distance (unity) and the other two at equal multiples of unity. This form has two kinds of edges and three kinds of solid angles. A trapezohedron having the symbol (211) is the common form of garnet, analcite, and lencite. One with the symbol (311) would differ from the one figured in its Fio. Mh.

tnterfacial angles, although the arrangement of the faces would be similar.

Isometric System.

Pig. 106 (garnet) represents the trapezohedron n (211) in com- bination with the dodecahedron d ; Fig. 107 (analcite), a combina-

Fio. 106. Fig. 107. Fiu 108

tion of the same trapezohedron n with the cnbe a ; and Pig. 108 (magnetite), the trapezohedron m (311) with the dodecahedron d.

Trisoctahedron. — This form has twenty-four triangular faces, each cutting two of the axes at unity and the third at a multiple of unity. The one Bhown in Pig. 109 has the symbol (221). Fig. 110 represents a combination of this form p (221) with the octa- hedron o, which occurs in galena

Tetrahexabedron. — This form has twenty-four triangular

Fna. 109. Fig- 110. Fig. 111. Fig. 112

faces, each cutting one axis at unity, a second at a multiple of unity, and a third at infinity. The one shown in Fig. Ill has the symbol (210). Fig. 112 is a combination of/ (310) with the cube a, which occurs in fiuorite.

Hexoctahedron.— This form has forty-eight triangular facet.

Ptritohedral Group. 173

each catting one axis at unity and the other two at different multiples of unity. The one shown in Fig. 113 has the symbol (321). Fig. 114 (garnet) represents a combination of this form s (321) with the dodecahedron d, and Fig. 115 (fluorite), the hexoctahedron t (421) with the cube a. Such combinations are only occasionally observed. There are in all seven kinds of simple forms in the normal group : the cube, octahedron, dodecahedron, trapezohedron, tris- octataedron, terra hexahedron, and hexoctahedron. It is possible that an isometric mineral may crystallize in any of these forms, although usually there are certain forms and combinations which are especially common in and characteristic of individual species. Thus galena and fluorite crystallize usually in cubes and octa- hedrons, or their combinations ; magnetite, in octahedrons and dodecahedrons, or their combinations ; garnet, in dodecahedrons and trapezohedrons (211), or their combinations ; and leucite and analcite, in trapezohedrons (211). It is very seldom that galena is found in dodecahedrons, magnetite in cubes, or garnet in either cubes or octahedrons.

ISOMETRIC FORMS OF LOWER SYMMETRY THAN THAT PRESENTED BY THE NORMAL GROUP.

Pyritohedral Group. — Pyrite Type.

Crystals of this group are characterized by having three axes of binary and four of trigonal symmetry (Fig. 116) ; also three axial planes of sym- metry (Fig. 93, p. 170).

Pyritohedron. — This form (Fig. 117), some- times called the pentagonal dodecahedron, has twelve pentagonal faces, corresponding in position to the alternating faces of the terra- pia- n6*

hexahedron. The symbol of the pyritohedron figured is (210), the same as that of the tetrahexahedron (Fig. 111).

Diploid. — This form (Fig. 118) has twenty-four faces which cor- respond in position to half of the faces of the hexoctahedron. The symbol of the diploid figured is (321), the same as that of the hexoctahedron (Fig. 113).

Isometbic System.

The cube, octahedron, dodecahedron, trisoctahedron, and trap' ezohedron occur in this group, but they differ from the forma of the normal group in having a lower kind of symmetry. Thus it may generally be observed that the cubes of pyrite are striated,

the striae running in one direction on each cubic face, and at right angles to one another on adjacent faces (Pig. 119). The striations result from the tendency of the cube to crystallize in combination with the pyritohedron (Fig. 117). The crystallographic axes of such striated cubes are axes of binary symmetry, and not of tet- ragonal symmetry ; therefore the cubes are not normal ones. Turn a cube of galena about its vertical axis and it will present the same appearance four times during a complete revolution, but a striated cube of pyrite similarly turned will present the same appearance only twice.

Fig. 134. Fig. 126. Fig. 12.

The combinations of the cube a (100) and the octahedron o (111) with the pyritohedron e (210) and the diploid t (421), represented

Tetrahbdral Group. 176

by Figs. 120 to 125, illustrate forms which may be observed in pyrite and cobaltite, all of which serve to show the characteristic symmetry of this group. Fig. 126 represents a penetration twin of two pyritohedrons.

Tetrahedral Group. — Tetrahedrite Type.

Crystals of this type are characterized by having three axes of binary and four of trigo- nal symmetry (Fig. 127), and also six diagonal planes of symmetry (Fig. 94, p. 170). The com- monest form is the tetrahedron, from which the group derives its name.

Tetrahedron.— This form o ( 111) (Fig. : corresponding in position to the alternating faces of the octahe- dron (Fig. 96). The faces are equilateral triangles, and the inter- facial angles are alike, 109° 28'. Two tetrahedrons are possible which differ in position ; o (111) (Fig. 128) being designated as the positive tetrahedron and o, (111) (Fig. 139), as the negative. The crystallographic axes join the centers of opposite edges. The positive and negative tetrahedrons may occur in combination, as represented by Fig. 133.

Pig. 137.

has four faces,

Tristetrahedron. — This form has twelve triangular faces, corresponding in position to half of the faces of the trapezohedron (Fig. 106). The form represented by Fig. 130 has the symbol (211).

Possible forms in this group, which are occasionally seen in combination with other forms, are the deltoid dodecahedron (Fig. 131) Fia- 1W-

and the hexaJcistetrdhedron (Fig. 132), whose faces correspond

Isometbic System.

to half of those of the trisoctahedron (Fig. 109) and the hexocta- hedron (Fig. 113), respectively.

The cube a (100), the dodecahedron d (110), and the tetrahexa- hedron occur in combination with the foregoing tetrahedral forms. From Fig. 127 it may be seen that in the cube of this group the diagonally opposite solid angles are not alike. This is further shown by the combination of the cube and tetrahedron (Fig. 134). By comparing Figs. 134 and 137 with Figs. 98 and 103, respectively, it will be seen that both the cube and dodecahedron of this group differ from the normal cube and normal dodecahedron of the galena type.

Tetrahedrite, sphalerite, and boracite occur in tetrahedrons and tetrahedral combinations, and Figs. 133 to 138 represent some of the combinations which may be observed, where o is the positive

and y, the negative tetrahedron, a the cube, d the dodecahedron, and n the tristetrahedron (211).

Teth Agonal System.

Tetragonal System.- The forms in this system are referred to three axes, all at right angles to one another. The two lateral axes a (Pig. 139) are equal and interchange, while the vertical axis c differs from these in length and in charac- ter. The length of the vertical axis has to be determined by the measurement of ap- propriate angles for each substance crystal- lizing in this system. In zircon, for ex- Fia. 186. ample, c 0.640, a being taken as unity.

Forms of the Normal Group. — Zircon Type. The crystals of this group are characterized by having a vertical axis of tetragonal symmetry and four axes of binary symmetry (Fig. 140) ; also one horizontal and four vertical planes of sym- metry (Fig. 141).

The forms are of three kinds : pyramidal, when the faces intereept the vertical and one or both of the horizontal axes ; pris- matic, when the faces are parallel to the vertical axis ; and pina- coidal, when the faces are parallel to the horizontal axes.

Pyramids. — A form known, as the pyramid of the first order (Fig. 142) has the symbol (111), where the third index refers to the characteristic length of the vertical axis. This form is character- ized by having eight similar faces which are isosceles triangles, two kinds of edges, and two kinds of solid angles. (Compare the isometric octahedron (111), Fig. 06). Pyramids of this order are alike in the general arrangement of their faces, but those of differ- ent minerals will not have the same interfacial angles, since

Tetragonal System.

the lengths of their vertical axes are not alike. Fig. 14? represents the pyramid in zircon where c 0.640 ; Pig. 143, one of braunite where c 0.985 (the interfacial angles in this case are near those of the isometric octahedron, Fig. 96) ; and Fig. 144, one of octahedrite where c 1.777.

Another form, known as the pyramid of the second order (Fig. 145), has the symbol (101). This form, like that of the pyramid of the first order, has eight similar/aces which are isosceles triangles, two kinds of edges, and two kinds of solid angles. Fig. 145 repre- sents the pyramid of the second order of zircon where c 0.640.

On any mineral there may be steeper or flatter pyramids than the unit-forms (111) and (101), according as the faces intercept the .vertical axis at a multiple or fraction of its characteristic length.

Fig. 146 represents a form known as the ditetragonal pyramid, having eight similar faces above and eight below. Its symbol is (311), and the vertical axis corresponds to that of zircon, c 0.640.

Normal Group.

Prisms.— Square prisms are very common and characteristic forms in this group. The form m (110) (Fig. 147) is called a "prism, of the first order and the form a (100) (Fig. 148) a prism of the sec- ond order. Each consists of four similar faces with interfacial angles of exactly 90°.

Fig. 149 represents a form (210) which has eight similar faces and is known as a ditetragonal prism.

Fig. 150 is a plan, or horizontal projection of the lateral axes, together with the trace of the prism of the first order m and the second order a. The necessity for having prisms and pyra- mids of two orders will become evident when the tetragonal combinations are considered.

m

i ; no

m

ioo L

a

j

ooi! c;

alOO

a

Ho/

\ho

/no

a

Fig. 147.

Pig. 148.

Fig. 149.

a 100 Fig. 150.

There is nothing in the molecular character of a substance to determine the length of its prismatic forms, as the prisms which occur on a mineral may be either long or short, wholly inde- pendent of the characteristic length of the vertical axis c. The pyramidal faces which terminate the prisms have, however, definite inclinations, and from the angles of these the length of the vertical axis c is calculated.

Base or Pinacoid.— The form c (001) is a very common one, and consists of two similar parallel faces, the top and bottom ones in

Figs. 147 to 149.

Combinations.— The following examples will serve to show the variations in habit resulting from the combinations of tetragonal forms in different minerals. The frequent occurrence of the forms with simple indices is noticeable: a (100), c (001), m (110), p (111), and e (101).

Tetragonal System.

The interf acial angles a A a, m A m9 a A c, and m A c 00° and a A m 45°.

irara (Figs. 142 and 151 to 155).— Axis c 0.640. Angles p A jp 56° 40' and c A p 42° 10'. These crystals commonly pre- sent the combination of the prism of the first order m (110) with

n a

m

Fig. 151.

Pig. 152.

Fig. 158.

Fig. 154.

Fig. 155.

the pyramid of the first order p (111). The steep pyramid of the first order u (331) and the ditetragonal pyramid x (311) are occa- sionally observed. The base c (001) is exceeding rare on zircon crystals.

Vesuvianite (Pigs. 156 to 159). — Axis c 0.537. Angles? A p 50° 39' and c A p 37° IS'. These crystals usually show the prism of the first order m (110) and of the second order a (100), ter-

m

a

m

Fig. 157.

Fig. 15S.

Fig. 159.

Fig. 156.

minated either by the basal plane c (001), the pyramid of the first order j? (Ill), or by a combination of both c and p.

Cassiterite (Figs. 160 to 162).— Axis c 0.672. Angles p Ap 58° 19' and c AP 43° 33'. On crystals of this mineral the pyra- mid and prism of the first order, p (111) and m (110), and the prism of the second order a (100) are the prominent forms. The pyra- mid of the second order e (101) and the base c (001) occur in com-

Normal Group.

bination with these. Twin crystals are common with the pyramid

Pig. 160. Fig. 161. Fig. 162.

of the second order e (Oil) as twinning-plane.

Rutile (Figs. 163 to 166).— Axis c 0.644. Angles p Ap 56° 52' and c A p 42° 20'. The crystals are usually prismatic and often capillary. Prisms of the first and second orders, m (110) and

Fig. 168. Fig. 164. Fig. 165. Fig. 166.

a (100), occur and are terminated by the pyramids of the first and second orders, p (111) and e (101). Fig. 164 is a basal projection of Fig. 163, and shows the symmetrical development of the faces of a tetragonal crystal about the vertical axis. Twin crystals of rutile are very common, a pyramid of the second order (101) being the twinning-plane. Often a network of prisms, crossing at angles of nearly 60° and 120° (Fig. 165), and zigzag groups (Fig. 166) result.

Octahedrite (Figs. 167 and(168).— Axis c 1.777. Angles? /\p 82° 9' and c A p 68° 18'. The common form is the pyramid of the first order p (111) (Fig. 144). The forms shown in Figs. 167 and 168 are the flat pyramids of the first and second orders, z (113) and x (103), the prism of the first order a (100), and the base c (001).

Apophyllite (Figs. 169 to 172). — Axis c 1.261. Angles p Ap 76° 0/ and c A p 60° 32'. This mineral is characterized by the almost

Fig. 17.

Fig. 168.

Tetragonal System.

constant occurrence of the pyramid of the first order p (111) in

a

Fig. 169 Fig. 170. Fig. 171. Fig. 173.

combination with the prism of the second order a (100). The basal plane c (001) is usually present, and is often prominent (Pig. 172). The ditetragonal prism y (310) may also occasionally be observed.

Tetragonal Forms Of Lower Symmetry Than That Presented

. By The Normal Group.

Tri-Pyramidal Group. — Scheelite Type.

This group is characterized by having a vertical axis of tetrag- onal symmetry and one horizontal plane of symmetry. (Compare Figs. 140 and 141, p. 177).

The characteristics of the group may be illustrated by scheelite and scapolite.

Scheelite (Figs. 173 and 175).— Axis c 1.536. Angles? A p 79° 55' and c Ap 65° 16'. Fig. 173 represents a combination of

Fig. 178. Fig. 174. Fig. 175.

the pyramid of the first order p (111), of the second order e (101), and a form s having the symbol (131) and known as a pyramid of the third order. If the form s occurred alone it would be a tetragonal pyramid, with its horizontal edges having the directions 8 a : a on the lateral axes. A pyramid of the third order (133), not

Sphenoidal Oboup. 183

bo acute as the form s, is represented by Fig. 174. A common habit with scheelite is a combination of the pyramids of the first and second orders, p and e (Pig. 175).

Scapolite (Pigs. 176 to 178).— Axis e 0.438. Angles p Ap 43° 45' and cap — 31° 48'. The figures illustrate combinations of

Fig. 176. Fig. 177. Fig. 178.

the prisms of the first and second orders, m (110) and a (100), with the pyramid of the first order p (111); while Pig. 178 shows the additional pyramid z (311) of the third order.

It should be observed that the forms s (131) of scheelite and z (311) of scapolite are tetragonal pyramids, while the form with corresponding indices in the normal group is a ditetragonal pyra- mid (Pig. 146).

Sphenoidal Group.— Ohalcopyrite Type.

This group is characterized by having a vertical axis of binary symmetry and two horizontal axes of binary symmetry ; also two vertical planesof symmetry (numbers 4 and 5) (Fig. 141, p. 177). The forms are illustrated by chalcopyrite.

Chalcopyriie (Figs. 179 to 185).— Axis c 0.985. Angles? a ps= 70° 7f and c a p 54° 20'. The form p (111) (Fig. 179) is called a

Fia. 179. Fig. ISO. Fia. 181. 183.

sphenoid. It has four similar faces, which correspond in their re- lation to the axes to the alternating faces of the tetragonal pyra-

184 Hexagonal System.

mid of the first order (Fig. 143). The form is analogous to the isometric tetrahedron (Fig. 128), being almost identical with it in its interfacial angles, since the length of the vertical axis of chal- copyrite is so nearly equal to that of the lateral axes. The posi- tive sphenoid p (111) and the negative sphenoid p (111) occur in combination (Fig. 180), also twinned (Fig. 181). The acute sphe- noid r (Fig. 182) having the symbol (332) and the pyramid of the second order z (Figs. 183 and 184) having the symbol (201) are occasionally observed. The twinning-plane of Figs. 181 and 184 is (111). Fig. 185 represents a combination of an acute sphenoid

Fig. 188. Fig. 184. Fig. 185.

(772) with a form x (122)? known as a scalenohedron, but the symbols of these two forms are questionable, because the faces are striated and the inclinations therefore not accurately de terminecL

Hexagonal System.

The forms in this system are referred to four axes. The three lateral axes a„ an and a% (Fig. 186) are equal and inter- changeable, and cross at angles of 60° and 120°, while the vertical axis c is of different length and at right angles to them. The length of the vertical axis must be determined by the measurement of appropriate angles for each substance crystallizing in this sys- tem. In beryl, for example, c 0.499, the lateral axes being taken as unity.

Fig. 187 represents a plan of the lateral axes. In giving the parameters and indices of the forms, the order in which the axes are taken, a„ and a„ and also the positive and negative direc- tions, as indicated in the figure, should be carqfvMy observed.

Normal Group.

On account of the axial angles of 60° and 120° there are certain relations of the crystal faces to the horizontal axes, represented by Fig. 188, which should be carefully considered. A face intersect- ing the unit lengths of adjacent axes will be parallel to the third axis ; hence the parameter relation a, : oo a% : — a, and indices (101).

A face going from unity (a) on one axis to a multiple of unity

n

(na) on an adjacent axis will intersect the third axis at

n-1

a.

Thus when n 2, the face may have the parameter relation 2a, : 2at : — a% and indices (112). When n is a quantity greater than 1 and less than 2, for example the parameter relation may be \ax : 3a, : — a„ indices (213). In every case the third index will be

as -a,

-a

Of tat a,

Tat

+o,

Fig. 186.

Fig. 187.

Fig. 188.

equal to the sum of the first and second indices, with the opposite sign. In the complete symbols of hexagonal forms there will be a fourth index, expressing the relation on the vertical axis.

Forms of the Normal Group. — Beryl Type.

The crystals of this group are characterized by having a vertical axis of hexagonal symmetry and six horizontal axes of binary sym- metry (Pig. 189) ; also one horizontal and six vertical planes of symmetry (Fig. 190).

The forms are of three kinds : pyramidal, when the faces in- tersect the vertical and the horizontal axes ; prismatic, when the faces are parallel to the vertical axis ; and pinacoidal, when the laces arek parallel to the three horizontal axes.

Hbiagohal System.

Pyramids. — A form known as the pyramid of the first order (Pig. 191) has the symbol (1011). The twelve faces, six above and six below, are alike, and are isosceles triangles. The six upper ones have, respectively, the following indices : (1011), (Olll), (1101), (1011), (0111), (1101). A form known as the pyramid of the second order (Fig. 192) has the symbol (1152) ; in this the twelve faces are isosceles triangles, the six upper ones having the following indices: (1152), (1212), (3112), (1122), (1212), (2112). There may be steeper or flatter pyramids of either order, according as the

Pig. 181. Fio. 192. Fig. 198.

vertical axes are cat at a multiple or a fraction of the unit length.

Fig. 193 represents a form with twelve similar faces above and twelve below, known as the dihexagonal pyramid. It is only occasionally that a complicated form of this kind is observed in combinations. One is shown in Fig. 203 (beryl) lettered n. The form represented by Fig. 193 has the symbol (2131), where c 0.499, the length of the vertical axis of beryl.

Normal Group.

Prisms. — Corresponding to the pyramids are two hexagonal prisms : the prism of the first order, m (Fig. 194), with the symbol (1010), and the prism of the second order, a (Fig. 195), with the symbol (1120). Each kind of prism has six similar faces, with interfacial angles of 60°.

Fig. 104. Fig. 195.

Fig. 196 gives a plan of the horizontal axes, together with the trace of the prism of the first order m and of the second order a. The necessity of having pyramids and prisms of the two orders will become evident when some of the crystal combinations are considered.

Fig. 196. Fig. 197.

The rare dihexagonal prism having twelve similar faces is shown by Fig. 197, which represents the form (2130).

The prisms of a hexagonal mineral may be either long or short, wholly independent of the characteristic length of the vertical axis.

Base or Pinacoid.— The form c, having the symbol (0001), con- sists of two similar faces, the top and bottom ones of Figs. 194, 195, and 197. The basal plane is exactly at right angles to the pris- matic faces.

Hbxahokal Bt8Tkk.

Combinations. — The following representations of crystals of different minerals illustrate some combinations of hexagonal forms. In these the prevalence of the forms with simple indices, c (0001), m <10l0),andp(10Il) is noticeable. The interfacial angles m Ac and a a c 90°, m Am and a A a 60°, and iah 30°.

Beryl (Figs. 198-203).— Axis c 0.499. Angles p A p 28° 54' and e a p 29° 66'. The common habit of beryl is a combination of the prism of the first order, m (1010), with the base c (0001). Crystals showing pyramidal forms of the first order, p (1011), and of the second order, s (1151), and the prism of the second order, a (1130), are- rather exceptional. Fig. 202 is a basal

projection of Fig. 201, illustrating the development of similar faces in sets of six about the vertical axis. Fig. 203 represents a highly modified crystal, with the prism m, terminated by a dihex- agonal pyramid n (31ll), two pyramids of the second order, s and d (33B4), the pyramid of the first orders, and the base c.

Pyrrholite (Figs. 204 and 206). —Axis c 0.870. Angles P a p 41° 30* and c a p 46° 8'. The crystals of this mineral are usually tabular, owing to the prominence of the base c (0001), and

Pyramidal Group.

show the forms of the prism of the first order m (1010), and two pyramids of the first order, p (1011) and u (4011).

Fig. 204.

Fig. 205.

Hanksite (Pig. 206).— Axis c 1.014. Angles p hp 44° 41'

and c a jp 49° 30'. The common combination is that of the prism and pyramid of the first order, m (1010) and p (1011), with the basal plane c (0001).

Fig. 206.

Hexagonal Forms Of Lower Symmetry Than That Presented

By The Normal Type.

Tri-Pyramidal Group. — Apatite Type.

This group is characterized by having a vertical axis of hex- agonal symmetry and one horizontal plane of symmetry. (Com- pare Pigs. 189 and 190.)

The characteristics of the group may be illustrated by apatite and vanadinite.

Apatite (Pigs. 207, 209 and 210).— Axis c 0.735. Angles p A p 37° 44' and c Ap 40° 18'. Pig. 207 represents a somewhat com- plex crystal, with the prisms of the first and second orders, m (1010) and a (1120), terminated by the base c (0001), three pyramids of the first order, y (2021), p (1011), and r (1012), a pyramid of the

Fig. 207.

Fig. 208.

second order s (llSl), and a hexagonal pyramid (2l3l), known as a pyramid of the third order.

Hexagonal System.

A pyramid of the third order having the symbol (1953), but not so acute as the form m, is represented by Pig. 208. It will be observed that the horizontal axes do not join the opposite solid angles, as in the pyramid of the first order (Pig. 191), nor the centers of opposite edges, as in the pyramid of the second order (Fig. 192). The simple crystals of apatite which are ordinarily observed (Figs. 209 and 210) do not appear to differ from forms of the normal group, but their peculiar symmetry can be revealed by etching with acid, as explained beyond under quartz (page 198).

Fig. 810.

h±£d#

Vanadinite (Fig. 211). — Axis c 0.712. The figure illustrates a rather simple combination of a prism of the first order m (1010) and base c (0001), with a pyramid of the third order ft (2131).

It should be observed that the form n (2131) in this group is a hexagonal pyramid, while in the normal group a form with corresponding indices is a dihexagonal pyramid (Fig. 193).

Hemimorphic Group. — Iodyrite Type.

This group is characterized by having a vertical axis of hex* agonal symmetry and six vertical planes of symmetry. The peculiarity of the crystals is the development of different forms at opposite extremities of the vertical axis, as illustrated by Fig. 212 of the rare mineral iodyrite, and Fig. 213 of zincite. The pyramids of iodyrite are u (4011) and n (4015).

Bhombohedral Group.

Rhombohedral Forms of the Hexagonal System. In crystals of this class the forms are referred to the hexagonal system of axes (Fig. 186), but the vertical axis c is one of trigonal and not of hexagonal symmetry. Many common minerals crystal- lize in this class, which is often designated as the rhombohedrai system. Forms of the Normal RhomboJtedral Group. — Calcite Type. The forms of this group are characterized by having a vertical axis of trigonal symmetry and three horizontal axes of binary sym-

Pig. 814. Fig. 216. Pig. 310.

metry (Fig. 214) ; also by having three vertical planes of sym- metry, 4, 5, and 6 (Fig. 190, p. 186).

Rhombohedrons. — A rhombohedron (Fig. 215) is characterized by having six similar faces which are rhombs and correspond in their axial relations to the alternating faces of the hexagonal pyra- mid of the first order (Fig. 191). Rhombohedrons are designated as positive (Fig. 215) when a face above is toward the observer, and negative (Fig. 216) when an edge above is toward the observer.

192 Hexagonal System.

When the faces intercept the vertical axis at unity, the symbols of these forms are, respectively, (1011) and (Olll). Furthermore, rhombohedrons are called obtuse or flat when the solid angles at the extremities of the vertical axis are obtuse, and aeute or steep when these solid angles are ante. Fig. 218 represents an obtuse, and Fig. 221, an ante rhombohedron of calcite. They also have two kinds of solid angles ; those at the extremities of the vertical axis, where the plane angles of the faces are alike, and six others in which the plane angles of the faces are of two kinds, either two acute and one obtuse (Fig. 218), or two obtuse and one acute (Fig. 221). The edges are of two kinds, six (three above and three be- low) running to the extremities of the vertical axis, and six going zigzag around the crystal

Scalenohedron. — This is a form (Fig. 217) having twelve similar faces, six above and six below, corresponding in position to the alternating pairs of faces of the dihexagonal pyramid (Fig. #193). The faces are scalene triangles, hence the name scalenohedron. The edges which meet at the extremities of the ver- tical axis are of two kinds, long and short, alter- nately disposed ; while the six middle edges are alike, and run zigzag around the crystal, as in the Fio. an. rhombohedron (Fig. 215). Fig. 217 represents the scalenohedron (2131) which commonly occurs on calcite.

Combinations. — Pyramids of the second ordere (Fig. 192), prisms m and a of the first and second orders (Figs. 194 and 195), the dihexagonal prism (Fig. 197), and the basal plane c (0001) oc- cur in combination with rhombohedrons and scalenohedrons. The basal plane c when it truncates the top of a rhombohedron is an equilateral triangle (Fig. 223).

Calcite (Figs. 218 to 233).— Axis c 0.864. Angles r A r 74° 55' and c a r 44° 36J'. This mineral presents a greater variety of habits than almost any other. Of the rhombohedral type the negative rhombohedrons e (0112) and / (0251) and the positive rhombohedron r (1011) are the commonest The angles of the neg-

Rhombohedral Group. 193

ative rhombohedron h (0332) are 91° 42'; hence this form, when it occurs without modifications, closely resembles a cube.

Fia. 280. Fig. 281. Pia. 283. Fio. 388

Fig. 222 is a combination of the two rhombohedrons r and f. Figs. 223 and 324 are combinations of the acute rhombohedrons M (40il) and p (16.0.15.1) with the base c. The last figure bears a close resemblance to the combination of the prism m of the first order and base c (Fig 225). A prismatic type is common, the prism

Hexagonal System.

being either long or Bhort and asually of the first order, m (1010). The prisma are terminated by the base c, by rhombohedrons, most often e (Pig. 226), and by scalenohedrons (Pigs. 232 and 233). The scalenohedron most often observed is v (2131) (Pigs. 229 to 233). The twinning-plane of Pig. 227 is r (Olll), and the vertical axes are inclined nearly 90" to one another. Fig. 230 is a twinned scalenohedron with the base as the twinning-plane.

Corundum (Figs. 234 to 236).— Axis c 1.363. Angles r a r 93° 56' and c A r 5T 34'. Crystals of this mineral asually show

Fig. 384. Fig. 385. Fie. 236.

the prism and pyramid of the second order, a (1120) and n (2233), in combination with the base c (0001) and rhombohedron r (1011).

Hematite (Figs. 237 to 241).— Axis c 1.366. Angles r A r 94° 0' and c A r 57° 37'. The rhombohedron r (10ll)(Fig. 237) oc- casionally occurs without modification and resembles a cube, since its angles are near 90°. Crystals usually show combinations of the

Fio. 340. Fig. 241.

rhombohedron r with the base c and a pyramid of the second order, n (2223). Very flat crystals (scales) are common with the basal plane c or fiat rhombohedrons u (1014) or x (0.1.1.12) prominent.

Rhombohedral Group.

Chabazite (Pigs. 242 and 243).— Axis c 1.086. Angles r A r 85° 14'. The common form is the rhorabohedron r (1011), which closely resembles a cnbe. Fig. 242 represents this form in com- bination with the negative rhombohedrons e (0112) and/ (0221).

Fig. 242. Fio. 343.

Fig. 243 is a basal projection of Fig. 242 and shows the symmetri- cal development of the rhombohedral faces r, e, and/ about the vertical axis.

RHOMBOHKDKAL FORMS OF LOWER SYMMETRY THAN THAT PRESENTED BY THE NORMAL TYPE.

HemimorpMc Group. — Tourmaline Type.

The crystals of this group are characterized by having a vertical axis of trigonal symmetry and three vertical planes of symmetry.

It is characteristic of crystals of this group that the faces at opposite extremities of the vertical axis are not alike. The forms occur on tourmaline (Figs. 244 to 247). — Axis c 0.448. Angles r a r 46° 62' and c A r 27° 20'. The crystals of this mineral

Fio. 244, Fig. S45. Fig. 340. Fro. 247.

usually present the combination of the triangular prism m (1010) and the hexagonal prism of the second order a (1120), which are terminated above by the forms r (loll), o (0251), and occasionally u (3251), and below by r (0111), o (2021), aod c (0001).

Hexagonal System.

Trirhombdhed/ral Group. — PJienacite Type.

The crystals of this group are characterized by having a verti- cal axis of trigonal symmetry and a center of symmetry, but no planes of symmetry.

The forms which are especially characteristic are hexagonal prisms, usually a (1150), and rhombohedrons of the first, second, and third orders. The three kinds of rhombohedrons correspond in their axial relations to one half of the faces of the hexagonal pyramids of the first and second orders (Figs. 191 and 192), and to one quarter of the faces of the dihexagonal pyramid (Fig. 193).

PJienacite (Fig. 248). — Axis c 0.661. The figure represents a prism of the second order a (1130), in combination with a rhombo- hedron of the third order x (2132;.

Fig. 84a Fig. 249.

Willemite (Fig. 249). — Axis c 0.677. Here the prism of the second order a is in combination with two rhombohedrons of the first order, r (1011) and e (0112), and a rhombohedron of the second order u (2113).

Dioptase (Figs. 250 and 261).— Axis c 0.534. The figures rep- resent combinations of the prism of the second order a, with a

Fig. 250.

Fig. 951.

Fig. 252.

rhombohedron of the first order s (0221), and of the third order x (13J1).

Tkapezohedral Group

Ilmenite (Pig. 252). — Axis c 1.385. The figure presents a combination of a rhombohedron of the first order r (1011), and one of the second order n (2213), with the base c (0001).

Trapezohedral Group. — Quartz Type.

The crystals of this group are characterized by having a vertical axis of trigonal symmetry and three horizontal axes of binary symmetry (Fig. 214), but no planes of symmetry.

Quartz (Figs. 253 to 264).— Axis c 1.100. Angles r a T — 85° 46', t f\z 46° 16' and r A m, 38° 13'. The forms which generally occur are the prism of the first order m (1010), and the positive and negative rhombohedrons, r (1011) and z (0111), often with the two last forms about equally developed (Figs. 253 and 254). An unequal development of these rhombohedrons (Fig. 255) is also common. Although not indicated by their simple

Fro. S58, Fig. 234. Fin. 365. Fro. 266. Fro. 867.

combinations, quartz crystals have a peculiar HgTU or left symmetry. This is shown by the development of the form x (5151), on the right-handed crystal (Fig. 256), and x (6131) on the left-handed crystal (Fig. 257). The form which the six x faces of one of these crystals would produce is known as a trapezohedron. Its faces correspond in their axial relation to one quarter of the faces of the dihexagonal pyramid (Fig. 193). The right- and left- handed trapezohedrons having the symbols (2131) and (3121) are shown by Figs. 258 and 259. These forms, like the right and left hand, are symmetrical with reference to a plane passed between them, bat cannot by any turning be made to occupy the same position. In this group the form (1121) (Fig. 256) develops as a triangular pyramid (Fig. 260), and has the same symbol as a

Hexagonal System.

pyramid of the second order of the normal group (Fig. 192). Pos itive and negative acute rhombohedrons, M (3031) and Mt (0331) (Figs. 261 and 262), often occur.

Twin crystals are very common, and are of a peculiar character.

Fig. 2S8. Fig. 250. Fig. 260.

The t winning- phi ne is usually the prism of the first order m, so that the positive rhombohedron r of the crystal in the normal position coincides with the negative rhombohedron z of the crystaf in the twinned position. The parts of the individual in the normal and twin position interpenetrate in a very irregular manner (Fig. 262), and the twin character of the crystal ia not usually revealed by its external form. Often, however, the faces of either the posi- tive or negative rhombohedrons are somewhat corroded (etched) (Fig. 262), and then the irregular lines of penetration between the r and z and the M and M, faces can be distinctly traced.

Fio. 261. Fig. 263. Pig. 368. Fib. 364.

Judging from the outward form alone, quartz crystals like Figs. 53 and 254 would appear to have the same symmetry as crystals

Okthokhohbic System. 199'

of the normal hexagonal type. This, however, is not the case, for if quartz crystals are subjected to the action of hydrofluoric acid artificial faces (corrosion or etching faces) are developed, which have a right- or left-handed distribution (Figs. 363 and 264), corre- sponding to that of the x faces on Figs. 256 and 257.

Okthobhombic System. In this system the forms are referred to three axes a, b, and c at right angles to one another and of unequal lengths (Fig. 266). Any one of these may be chosen for the vertical axes c ; the longer of the horizontal ones is then taken as b and is called the macro-axis; the shorter, as a and is called the brachy-axis. For each substance crystallizing in the system the ratio lengths of the axes must be determined from the measurement of appropriate angles. In sulphur, for example, the axial ratio is a: b: c 0.813 : 1 : 1.903 (see p. 159).

Ta

Forms of the Normal Group. — Barite Type.

The crystals of this group are characterized by having three axes of binary symmetry (Fig. 266) and three axial planes of sym- metry (Fig. 267).

The forms are of three kinds, as follows : pyramidal, when the faces intersect the three axes ; prismatic, when the faces

Zoo Obthorhombio System.

intersect two axes and are parallel to the third ; and pinacoidal, when the faces intersect one axis and are parallel to the other two.

Pyramids. — These consist of eight similar faces, and the form with the simplest symbol, p (111) (Fig. 268), is called the unit pyramid. In (Fig. 281) the form p (111) is shown in combination with a flatter pyramid s (113). it will be noticed that on the same crystal there may be different pyramids, bat under no condition can there be more than eight faces of the same kind.

Prisms. — These consist of four similar faces, Fig. jw8. parallel to an axis ; three kinds being possible, according as the faces are parallel to the c, the b, or the a axes.

Fro. 269. Fia. 270. Fie. 371.

Vertical Prisms. — A prominent prism on a crystal is commonly assumed to be the form m (110), which is known as the unit prism (Fig. 269). This form is a right rhombic prism, its four faces being at right angles to the terminal face c, bnt never at right angles to one another, since the a and b axes are not of equal length.

Besides the unit prism, others may occur whose faces have sach inclinations that they go from a to a multiple of b, or from b to a multiple of a, and are parallel to c. One of these is illustrated by topaz (Figs. 289 to 293), in which I is the prism (120).

Horizontal Prisms, or Domes. — When the prismatic forms axe parallel to the horizontal axes they are conveniently desig- nated as domes. Fig. 270 represents the form (101), known as

Combinations,

the macro-dome, because it is parallel to the macro-axis b and Fig. 271, the form (Oil), called the brachy-dome, because it is parallel to the brachy-axis a. Each of the macro- and brachy- domes has four similar faces. Domes are common forms which, on crystals illustrating combinations in this system, will often appear at one of the extremities as a pair of similar faces. For example, the two triangular faces r at the extremity of Fig. 298 are planes of the macro-dome (101). In many instances the domes intercept the vertical axis at a multiple, or fraction, of its unit length, as illustrated by topaz (Figs. 290 to 293), in which the brachy-domes/and y have the symbols (021) and (041) respectively.

Pinacoids. — Three pinacoids are possible, each consisting of two, similar, parallel faces. These forms, represented in Fig. 272, are the macro- pinacoid a (100), the brachy-pinacoid b (010), and the base or basal pinacoid c (001). The faces of these three forms are at right angles to one another.

Combinations. — The following examples will illustrate the great variety of habits which may result from the combinations of pinacoids, prisms, domes, and pyramids. It should be noticed that the forms with simple indices, a (100), b (010), c (001), m (110), and p (111), are prominent. The position in which the crystals are placed (the crystallographic orientation) is to a certain extent arbitrary, since any one of the axes of symmetry may be taken for the vertical axis c.

Barite (Figs. 273 to 277).— Axes a:b:c 0.815 : 1 : 1 .314. An-

Fig. 272.

Fig. 278.

j4'iq. 274.

Fig. 275.

€13

Fig. 276. Fig. 277.

gles m a m 78° 22' and c A o 52° 43'. The crystals commonly have the basal plane c prominent and are, therefore, tabular. The

OBTHOBhOMBIC SYSTEM.

prism m (110), the macro-dome d (102), and the brachy-dome o (011) are generally present

Celestite (Figs. 278 and 279).— Axes a : b : c 0.779 : 1 : 1.280. Angles m A m 75° 60' and c Ao 52° 0'. The crystals are often tabular like Figs, 273 to 275 of barite, and often they are lengthened out in the direction of the brachy-axis, having the brachy-dome o (011) prominent (Fig. 279). The prism m (110) and

Fig. 278.

Pio. 279.

the macro-dome d (102) are generally present, while I (104) occurs occasionally (Fig. 278).

Pig. 280.

Pig. 281.

Fig. 282.

Sulphur (Figs. 280 to 282).— Axes a : b : c 0.813 : 1 : 1.903 Angles m A m 78° 14' and c A n 62° 17'. A pyramidal habit, p (111), is common, often with the apex truncated by the pyramid s (113) or the base c. The brachy-dome n (011) is also often

present.

Stibnite (Figs. 283 and 284).— Axes a : b : c 0.992 : 1 : 1.018. Angles m A m 89° 34' and c A p 55° 19. The crystals are prismatic, with the prism m (110) and the brachy-pinacoid b (010)

Combinations.

prominent. They are often long and Blender, and are generally

terminated by the pyramidal forms p (111), s (113), and r (343).

Fig. 283. Fio. 8*4.

Arsenopyrite (Figs. 285 and 286). —Axes a :b:c 0.677: 1 : 1.188. Angles m A m 68° 13' and c A ? 49° 55'. A short prism m (110), terminated by the brachy-dome u (014), is the common habit. The brachy-dome q (Oil) terminating the prism is occa- sionally met with.

Ckalcocite (Figs. 287 and 288).— Axes a:bic 0.582 : 1 : 0.970. Angles m A m 60° 25' and c A d 62° 44'. The crystals are com- monly flat, with a striated basal plane c (001) and the brachy-dome

d (091) prominent. The prism m (110), two pyramids p (111) and v (113), and the brachy-pinacoid 5 (010) are common forms. Twin

204 Ortho Rhombic System.

crystals are very common, and frequently imitate forma of the hexagonal system, as will be explained under aragonite (p. 206)f

Topaz (Figs. 289 to 293). —Axes a : b: c 0.528 : 1 : 0.477. Angles m a m 55" 43' and c Ap 45° 36'. The crystals are gen- erally prismatic, with two prisms developed, m (110) and Z(120).

The forms which usually occur at the terminations are the base c, the brachy-domes /(021) and y (041), the macro-dome d (S01), and the pyramids o (221), p (111), and i (223). Doubly terminated crystals are rather exceptional.

Chrysolite (Figs." 294 to 296).— Axes a : b : c 0.466 : 1 : 0.586. Angles m A m 49° 57' and c a p 54° 16'. In the vertical zone

tW

the pinacoids a (100) and b (010) and the prism m (110) are usually present, and occasionally, also, a second prism s (120). The crystals

Combinations. 205

are terminated by the brachy -dome £ (021), the macro-dome d (101), the pyramid p (111), and occasionally, the basal plane c (001). Fig. 296 is a basal projection of Fig. 295, which shows the sym- metrical development of the orthorhombic forms when viewed in the direction of the vertical axis.

Staurolite (Figs. 297 to 300).— Axes a : b : c 0.473 : 1 : 0.683. Angle mAm B0° 40'. The crystals are generally prismatic, with the prism m (110) and the brachy-pinacoid b (010) developed.

1 m m

They are terminated either by the base c (001), or a combination of c and the macro-dome r (101). Penetration twins are very com- mon; the prisms crossing either at nearly 90° when a brachy-dome (032) is the twinning-plane, or at nearly 60° when a pyramid (332) is the twinning-plane.

Aragonite (Figs. 301 to 307).— Axes a : b : c 0.662 : 1 : 0.721. Angles m A m 83° 48' and c a k 36° 47'. Slender, needle-like

crystals, either tapering to a point or with well-defined faces (nsually the brachy-dome k (011) ) at the extremity, are common

Obthorhombic Bystem.

(Fig. 3i H). The indices of the steep pyramid i (661) and the brachy- donie j (0.12.1) are uncertain. Simple crystals (Fig. 302) show- ing the combination of the prism m, the brachy-pinacoid b, and the brachy-dome Jc are exceptional ; while twins (Fig. 303), often polysynthetic (Fig. 304), are more often observed, the prism m (TlO) being the twinning-plane. A complex method of twinning and intergrowth is common, from which a form resembling a hex- agonal prism results. The character of these apparently hexagonal crystals may be explained as follows : The cross-section of a sim- ple crystal like Fig. 302 is represented by Fig. 305. Three indi-

viduals I, II, and III (Fig. 306), each striated parallel to the brachy- axis, and crystallizing with their prismatic faces m, as the twin- ning-planes, would diverge at angles of about 120°. Provided that each crystal penetrated beyond the center, a six-Bided form would result, with the individuals meeting along the somewhat irregular lines of interpenetration (Fig. 307j. The complex charac- ter of such twins is generally revealed by striations on the basal planes, diverging as represented in Fig. 307, and also by small re- entrant angles.

There is a tendency in a number of minerals having a prismatic angle of nearly 60°, to occur in complex twin crys- tals like those of aragonite, which imitate forms of the hexagonal system.

Cerussite (Fig. 308).— Axes a : b : c=0.610 : 1 : 0.723. Angle m A m 62° 46'. The figure represents a form with deep re-entrant angles, resulting from Fro. .MS. the penetration of three individuals in twin posi- tion. (Compare Figs. 306 and 307 of aragonite.) Each crys-

Sphenoidal Group.

taJ has the brachy-pinacoid b (010) prominent, in combination with the prism m (110) and the pyramid p (111). Occasion- ally twin crystals of cerussite occur without the re- entrant angles, when they may appear like a com- bination of the pyramid and prism of the hexagonal system.

Childrenite (Pig. 309).— Axes a : b : c 0.778 : 1 : 0.526. Angle m a m 75° 46'. This example has been in- troduced to illustrate the combination of a pyramid Fig. 309. s (121) in combination with the pinacoids a (100) and b (010).

Orthorhombic Forms Of Lower Symmetry Than That

Presented By The Normal Group.

Hemimorphic Group, — Calamine Type.

♦ The crystals of this group are characterized by having one

axis of binary symmetry and two planes of symmetry. The

peculiarity of the crystals is that the forms at oppo- site extremities of the axis of symmetry are not alike.

Calamine (Fig. 310).— Axes a : b : o 0.783 : 1 : 0.478. Angle m A 76° 9'. The combination of the macro-pinacoid a (100), the brachy-pinacoid b (010), and the prism m (110), is terminated above by the

base c (001) and the brachy- and macro-domes i (031) and t (301),

while below the pyramid v (121) occurs.

Fig. 310.

Sphenoidal Group. — Ep somite Type.

Crystals of this group are characterized by hav- ing three axes of binary symmetry and no planes of LI

Epsomite (Fig. 311).— Axes a : b : c=0.990 : 1 : 0.571. Fig. 811. Angle m A m 89° 26'. The figure represents the prism m (110),

208 M0N0Clin1G System.

terminated above and below by two faces of the form z, having the symbol (111). The fonr z faces alone produce a form known as a sphenoid, similar to Pig. 65, p. 164. The faces correspond in their axial relations to the alternating planes of the ortho- rhombic pyramid (111) of the normal group.

Monoolinic System. In this system the forms arjs referred to three awes, a, b and c of unequal lengths, with a and c intersecting at an acute angle fi behind, while b is at right angles to a and c (Fig. 312). The axis b is called the ortho-axis, because it is at right angles to the other two ; and a is called the clino-axis, because it is in* clined to the vertical axis c. For each substance crystallizing in this system the ratio lengths of the axes and the axial inclina- tion fi must be determined from the measurement of appropriate angles. For gypsum the axial relation is a : b : c 0.690 : 1 : 0.412 ; /9 80° 42'.

Forms of the Normal Group. — Gypsum Type, The crystals of this group are characterized by having one axis of binary symmetry (Fig. 313), which is always taken as the crys- tallographic axis 6, and one plane of symmetry. The plane of

Via. 813. Fig. 818. Fig. 814.

symmetry (Fig. 314) iB always supposed to occupy a vertical posi- tion, and the a and c axes are located in it.

Monoclinic forms are of two kinds ; either prismatic with four similar faces, or pinacoidal with two parallel faces. It is con-

Normal Gbocp. 209

venient, however, to designate the forms according to their rela- tion on the axes : as pyramids, when the faces intersect ail three axes ; prisms or domes, when they intersect two axes and are parallel to one ; and pinacoids, when they intersect one axis and are parallel to the other two.

Pyramids. — The form (111) (Pig. 316) consists of four similar faces. These four faces really constitute a prism with its edges parallel to the direction a : c. The name pyramid is simply one of convenience for designating the particular kind of form which in- tersects the three axes. A somewhat similar, but different, and en- tirely independent form is (111) (Fig. 816), also consisting of four

Pia SIS. Fio. 818. Fig. 317.

similar faces. The solid represented by Fig. 317 is a combination of the two independent forms p (111) and o (111). It should be distinctly understood that no form in this system is more, compli- cated than the ones just explained. The symbol may be less simple, for example (321), but the symmetry demands the existence of only four faces of the same kind.

Prisms. — A prismatic form, consisting of four similar faces is commonly taken as the unit-prism m (110) (Fig. 318), Such a

K

%

no

y

Pis. 818. Pie. 819. Fig. 820.

.form is an inclined prism, the two faces in front making equal angles with the terminal face c, but not angles of 90°. Besides

Monoclinic Sy8Tbm.

the prism (110) others occur, whose faces are so inclined that they go from a to a multiple of &, or from ft to a multiple of a, and are parallel to c. Two prisms, m (110) and z (130), often occur on orthoclase (Fig. 328).

Domes. — The form (Oil) (Fig. 319) has four similar faces which make an inclined prism. It is convenient to designate this form, however, as a dino-dome, so named because the faces are parallel to the clino-axis a.

Owing to the symmetry of monoclinic crystals the form (101) occurs as a pair of similar faces. Fig. 320 represents two inde- pendent forms (101) and (101), called ortliodomes in combination with a terminal face b.

Pinacoids. — There are three forms, each consisting of two

parallel faces (Fig. 321), which are especially important : the ortho-pinacoid a (100), the clino- pinacoid b (010), and the base or basal pinacoid c (001). The clino-pinacoid 6, which is parallel to the symmetry plane (Fig. 313), is at right angles to both the base c and the ortho-pinacoid a, Fig. 821. while the two latter forms make an angle with

one another which is equal to the axial inclination /?.

Combinations. — The following examples will illustrate some of the various habits which may result from the combination of mon- oclinic forms, and it should be noticed that it is possible in almost all cases, to orientate the crystals so that the symbols of their forms can be expressed by very simple indices. The prevailing forms are the pinacoids a (100), b (010), and c (001), the prism m (110), and the pyramid (111).

Gypsum (Figs. 322 to 325).— Axes a : 6 : c 0.090 : 1 : 0.412 ; 0 80° 42'. Angles m A m 68° 30' andp A p 36° 12'. Crystals usually have the clino-pinacoid b (010) prominent, in combination with the prism m (110) and the pyramid p (111). The ortho-dome e (103) is often present. Twins are common, with the ortho-pina- coid (100) as the twinning-plane (Fig. 325).

The arbitrary method of orientating a monoclinic crystal and

Normal Gboup. 211

naming the forms is here brought to notice. The four faces of the so-called pyramid p, if placed vertically, could have been taken as the prism (110), when the m faces would most naturally be taken as the clinc-dome (Oil). A crystal of gypsum thus orientated

try

W

Fig 323. Fig. 828. Fig. 324. Fig. 825.

would, of course, have a different axial ratio than the one given above. The only form on monoclinic crystals which is actually determined by the symmetry is the clino-pinacoid 6 (010).

Orthoclase (Figs. 826 to 329).— Axes a : b : c 0.658:1:0.565; 0 63° 57'. Angles m A m 61° 18', c A x 50° 16', and c A y 80° 18'. The prominent forms are the prism m (110) and the pina-

/

Y/

A-

A

A

'"

w

/I

/

F

1o. 326

Fig. 327.

coids 6 (010) and c (001). . A second prism z (130), the ortho-domea x (t01) and y (301), and the pyramid o (111), are often present. A common kind of twinning consists of two individuals united with their b faces in common (Fig. 329). The twinning-axis is the ver- tical axis c. On the crystal in the normal i>osition the base c slopes toward the front, while in the twinned individual it slopes toward the back.

Pyroxene (Figs. 330 to 336).— Axes a ; b : c 1.092 : 1 : 0.589 ; 0 74° 10'. Angles m A m 92° 60', p A p 48° 29', and g A

312 Monoclinic System.

59° 11'. Prismatic crystals are common, the prisms m (110) being stout, nearly rectangular (m A m 92° 60'), and generally truncated by the ortho-pinacoid a (100) and the clino-pinacoid b (010). The crystals are variously terminated ; the prevailing forms being the base c (001), the ortho-domes d (101) and n (102), and the pyramids

Km. 880. Via. 881. Fig. 383. Fia. 888.

p (111), v (221), s (111), and o (321). Fig. 334 is a basal projection of Fig. 333, and shows the symmetrical development of the mono- clinic forms on either side of the symmetry plane, intersecting the

Via. 884. Fig. 88S. Fig. SSfl.

crystal parallel to the face 6. Figs. 336 and 336 represent the or- dinary development of crystals of augite, a variety of pyroxene common in volcanic rocks.

Amphibole (Figs. 337 to 339).— Axes 0.561 : 1 : 0.294 ; 73°68'. Angles A m 55° 49' and r A r 31° 32'. The crys- tals are commonly long and bladed, with the prism m (110) promi- nent, or apparently hexagonal a m nearly 60°), when m and the clino-pinacoid b are about equally developed. A second prism e (130) and the ortho-pinacoid a (100) are often present. The crystals are generally terminated by the faces of the clino-dome r (011).

Normal Oboup.

fggK,

$h

Kzy

Fib. 887. Fig. 888. FlO. 838.

Titanite or Sphene (Figs. 340 to 342).— Axes a : b : c 0.756 : 1 : 0.864; /? 60° 17'. Anglesm A m=66°2d',p Ap 43° 49', and c A p 38° 16'. The prism m (110) and the pyramid p (111)

Fjg. 840. Fia. 841. Fig. 842.

are generally prominent, and in combination with the base c (001) and the ortho-pinacoid a (100). The very obtnse interfacial angles of Fig. 341 are conspicuous, from which the name sphene, mean- ing a wedge, is derived.

Epidote (Figs 343 and 344).— Axes a : b : o 1.578 : 1 : 1.804 ; fi 64° 37'. Angles m Act 109" 56', n a 70° 29', andc Ar

Fig. 348. Fio. 844.

63° 42'. The crystals of epidote generally have a somewhat un- usual development, being long in the direction of the symmetry- axis, owing to the prominence of the base c (001), the ortho-pina-

214 Tbiclinic System.

coid a (100), and the ortho-domes r (101) and i (102). At the ends, the pyramids (111) is generally the most prominent form, while the other forms shown in Fig. 344 are the clino-pinacoid 6, the clino- domes o (Oil) and 1c (012), the prism m (110), and the pyramid? (111).

MONOOLINIO FORMS OF LOWER SYMMETRY THAN THAT PRE- SENTED BY THE NORMAL GROUP.

Two groups are recognized, but are, however, very rarely observed. One is hemimorphic, having an axis of binary symme- try but no plane of symmetry ; the other has a plane of symmetry, but no axis of symmetry.

Triclinic System,

In this system the forms are referred to three axes, a, b, and c, of unequal lengths, and, intersecting at oblique angles, /ff, and y (Pig. 345). The directions which are taken to represent the

axes correspond to prominent crystallographic features, but otherwise are arbitrarily chosen. Any one of the axes may be taken as the vertical axis c, and of the lateral ones, b is the longer or macro-axis and a the shorter or Fig. 845. brachy-axis. For each mineral crystallizing

in this system, the ratio lengths of the axes and the inclinations a, /?, and y must be determined from the measurement of appro- priate angles. In axinite, for example, a : b : c 0. 492 : 1 : 0.480 ; and a 82° 54', fi 91° 52', and y 131° 32\

Forms of the Normal Group.— Axinite Type.

Crystals of this group have a center of symmetry, but neither planes nor axes of symmetry. Each form consists of two sim- ilar parallel faces, diametrically disposed with reference to a central point.

Each form, since it consists of only two parallel faces, has the character of a pinacoid. It is convenient, however, to designate the forms according to their relations on the axes, as pyramids when they intersect the three axes, as prisms or domes when

Normal Group.

they intersect two axes and are parallel either to the vertical or to one of the horizontal axes, and as pinacoids when they inter- sect one axis and are parallel to the other two.

Pyramids.— The form (111) (Pig. 346) consists of two similar /aces, and is designated as a pyramid for the sake of convenience. Pour entirely different forms are possible, each of which intersects the axes at their unit lengths, (111), (111), (111), and (HI) (Pig. 347).

Fig. 846. Fig. 847. Fig. 348.

No single form can be more complex than the one represented by Pig. 346. The symbol may be more" complicated, for example (321), but the form can consist of but two faces.

Prisms.— The forms m (110) and M (HO) (Pig. 348) each consists of two simitar faces, and the four planes constitute a triclinic prism, whose faces do not make equal angles with the terminal plane c. ♦

Domes. — If the forms are parallel to the b axis, for example, (101) or (101) (Pig. 349), they are called macro-domes ; and if par- allel to the a axis, for example, (Oil) or (Oil) (Pig. 350), they are called br achy -domes.

Pinacoids. — When it is reasonable to do so, it is customary to select three prominent faces of a crystal to represent the macro-

Fig. 849. Fig. 850. Fig. 851.

pinacoid a (100), the br achy -pinacoid b (010), and the base or basal pinacoid c (001) (Fig. 351). These three forms are important, because their intersections determine the axial directions.

?,16 Triclinic System.

Combinations. — The following illustrations will serve to show some of the variations in habit which, may result from the combi- nation of triclinic forms. Since the crystals have neither a plane nor an axis of symmetry, any face may be taken as a pyramid, prism, dome, or pinacoid. In orientating a triclinic crystal the most important thing to be considered is the adoption of such a position that the prominent faces will have as simple indices as possible. It should be noticed, in studying the examples given below, that the crystals have been so orientated that, in most cases, the promi- nent forms are the pinacoids a (100), b (010), and c (001), and the prisms m (110) and M (110), all having very simple indices.

Ascinite (Fig. 362). — Axes a : b : c 0.492 : 1 : 0.480 ; a 64', £ 31° 62', and y 131° 32'. Angles I a A m 16" 34', a A M — 28" 66', m A p 30' 33', and M A r 45° 15'. Prominent forms are the two prisms m (110) and M(ll0), terminated by the pyra- mids p (111) and r (111), and the macro-dome s (201). The exceptionally acute and obtuse angles of the crystal are conspicuous, whence the name axinite (aSivrj, an axe).

Alhite (Figs. 353 to 356).— Axes a : b : c 0.633 : 1 : 0.558 ; a 04° 3', jS 116° 29', and y 88° 9'. Angles b A c 86° 24', m Ac 65° 18', 3f A c 69° 10', and m A 59" 14'. The crystals are

commonly flat (tables) with the brachy-pinacoid b (010) prominent. Combined with this are the two prisms m (110) and J/"(1I0), the base e (001), and the macro-dome x (101). The pyramids o (111) and q (III) are often present Twins are common, often polysyn-

Normal Group.

*Ig. 5557.

thetic (Fig. 356), the pinacoid b being the twinning-plane. The basal planes of polysynthetic crystals show a repetition of re- entrant and salient angles; and when the lamellae are numerous, as is often the case, the basal plane, or cleavage-surface, shows a series of fine striations (Fig. 87, p. 168). The similarity between albite and the closely related mineral orthoclase of the monoclinic system (p. 211), may be seen by comparing their axial ratios and interfacial angles. X"

Cyanite (Fig. 357).— Axes a : b : c 0.899 : 1 : 0.709 ; a 90° 5', /3 101° 2', and y 1C5° 44'. Angles a A ft 73° 56', a A c 78° 30', b A c 86° 45', and a A M 48° 18'. The crystals are generally long and bladed, owing to the prominence of the macro-pinacoid a (100), and are seldom terminated by distinct faces.

Rhodonite variety Fowlerite (Fig. 358). — Axes a : b : c

1.078 : 1 : 0.626 ; a 103° 39', /? 108° 48', and y 81° 55'. Angles c A a 72° 30', a A w 48° 33r, m A M 92° 49', cAm 68° 25', and c A Jf 86° 41'. The crystals are commonly somewhat tabular, with the base c (001) prominent. The two prisms m (110) and M (110) are common, while the pyramids n (221) and Jc (221) are usually subordinate. Rhodonite (m AM 92° 490 closely related to pyroxene (p. 210), in which m a m 92° 50'.

Chalcanthite (Blue Vitriol) (Fig. 359). — Axes a:b:c 0.566 :1 : 1.055 ; a 82° 21', ft 73° 11', and 77° 37'. Angles a A 6 100° 41', a Am 30° 51', A Jf 25° 59', and niAp 52° 20'. The crystals commonly have the two pinacoids a (100) and b (010) and the two prisms m (110) andJf (HO) prominent, and are terminated by the faces of the pyramid (111).

Fig. 858.

Fig. 869.

218 The Thirty-Two Classes Of Cby8Tals.

Teiclinic Forms Of Lower Symmetry Than That Presented

By The Normal Type.

Triclinic crystals have been observed which do not have a centei of symmetry, but no minerals belonging to this class are known. On the crystals, each form consists of a single plane, but the occurrence of any crystal face does not necessitate the existence of one parallel to it.

Note Concerning the Systems of Crystallization.

Although crystals are classified into six systems, according to their axial relations, each system is subdivided into groups with varying degrees or kinds of symmetry. Each of these subdivi- sions really constitutes a distinct class, characterized by a particu- lar kind of symmetry, which a substance crystallizing in that class will invariably show. From purely mathematical considerations it can be shown that there are thirty -two possible classes to which crystals can be referred, and all but three of them have been ob- served either among minerals or artificially crystallized salts.

The possible kinds of symmetry are shown in the table oppo- site. The references will serve to indicate the important classes which have been described in the foregoing pages.

Pseudomorphous Crystals.

Although the occurrence of a mineral in distinct crystals may generally be regarded as a proof of the homogeneous character and purity of the material (p. 156), this is not always the case. A sub- stance may either undergo chemical alteration or be replaced by material of entirely different character without perceptible change in the crystalline form, and thus crystals result which have the form of one mineral and the chemical composition of another. Such crystals are known as pseudomorphs (etwhfo false, and /*o/>07, form).

The Thirty -Two Classes Of Cry8Tals.

Table Showing The Symmetry Of The Thirty-Two Classes Of

Crystals.

An asterisk denotes the absence of a Center of Symmetry.

Group.

og

Axes of Symmetry. Hexagonal. Tetragonal. A Trigonal. Binary.

Qraatost Number of Similar

Face. Ponlble on a Crystal,

with Bflferenoe.

©

a s

8!

Normal Pyritohedral

Tetrahedral*

4i

8 0 4 A

8 + 4 A

44

48. Hexoctahedron, Fig. 118 24. Diploid, Fig. 118

24. Hoxaktstetrahedraa, F. 24. Bare, cuprite 12. Rare, laagbeinite

a

H

Normal Hemimorphic*

Tri-pyramidal

1

1

24. Dihexagonal pyr., F. 188 12. Rare (p. 190) 12. The it faces. Fig. 907 12. Rare, artificial salts

n

6. Rare, nephelinite

i A 1A

l A l A

12. Unknown

Hexagonal- rhombohedral.

Normal

Hemimorphic*

Tri-rhombohedral

Trapezohedral*

12. ScaJenohedron, Fig. 217

6. The u faces, Fig. 247

6. Rhombohedron. The a faces, Fig. 248

6. Trapezohedron, Figs. 258 and 259

6. Unknown

8. Rare, artificial salt

Normal

!♦

16. Dltetragonalpyr.,F. 146 8. Rare, artificial salts

Tri-pyramidal

Sphenoidal*

8. The t faces, Fig. 178 8. The x faces. Fig. 185 8. Rare, artificial salts .

4. Rare, wulfenite

4. Unknown

Ortho- rhombic.

Normal

Hemimorphic*

Sphenoidal*

8

8. Pyramid, Fig. 268 4. The e faces, Fig. 810 4. The 0 faces, Fig. 311 i

6 d

So

Normal

None

4. The;? faces, Fig. 822 ' 2. Rare, artificial salts

58

2. Rare, clinohedrite

Tri- clinic.

Normal

None None

2. Thep faces, Fig. 852 1. Rare, artificial salt

220 Pseudomobphous Crystals.

Pseudomorphs by Chemical Alteration of the Original Material. — Crystals of pyrite, FeS„ by long exposure may become oxidized and hydrated, and partly or wholly converted into limonite (iron rust), Fe4Ot(OH)e. Thus pseudomorphs of limonite after pyrite are formed. A similar change takes place when iron rusts from exposure. If a discarded rusty tool is found, the character of the implement may generally be determined from the shape of the mass of iron rust, even though the steel has wholly disappeared, and so, from the shape of a pseudomorphous crystal, the nature and name of the original mineral may generally be inferred. Other illustrations are the change by hydration and loss or gain of magnesium oxide, of the silicates chrysolite, MgtSi04, and en- statite, MgSiO„ to serpentine, H4MgtSi,0,.

2Mg,Si04 + 2H,0 less MgO H4Mg$Si,0,. 2MgSiO, +m&plus MgO H4Mg,Si,0,.

Pseudomorphs by Incrustation and Replacement. — Often crys- tals of fluorite become coated with quartz, and subsequently the former is removed by solution or other agency, and the space thus left vacant is wholly or partly filled by a deposit of quartz, thus producing pseudomorphs of quartz after fluorite. Another illustration is furnished by petrified wood. As the wood decays the silica which is dissolved in the percolating water is de- posited upon its fibers, often preserving the delicate structure of the wood in a remarkable manner.

Pseudomorphs Resulting from Molecular Change. — When molten sulphur is cooled, rather quickly, crystals belonging to the monoclinic system are formed, which cannot be preserved at ordinary temperatures, because they undergo a molecular change to the orthorhombic modification (p. 202). Similar changes in molecular condition, without the addition or removal of chemical constituents, take place in nature, giving rise to pseudomorphs ofcalcite after aragonite% rutile after brookite, amphibole after pyroxene, etc. These are also called paramorphs.

Structure.

Structure of Minerals.

In describing the structure of minerals a number of terms are conveniently employed which will need a little explanation.

Granular. — When a mineral consists of an aggregate of crys- talline particles of about the same size, as marble and some varieties of galena.

Compact. — Earthy.— A more or less firm consistency, resulting from a uniform aggregation of exceedingly minute particles, as kaolin (clay).

Massive. — "When a substance exhibits no crystal faces, although 't may possess a crystalline structure. Massive materials (pieces of quartz, chalcopyrite, etc.) are more often encountered than well- crystallized specimens.

Amorphous. — When no trace of crystalline structure exists. There are not many minerals which are truly amorphous, and they are not always easily distinguished from massive materials. Opal, amber, and obsidian (volcanic glass) are good examples.

Columnar. — When there is a parallel, or nearly parallel, group- ing of prisms or columns, as illustrated by some varieties of wollastonite and beryl.

Fibrous. — A structure similar to the foregoing, but in which the individuals are exceedingly minute, as illustrated by some va- rieties of serpentine (Fig. 360), amphibole (variety asbestus), and gypsum. The fibers may often be separated or pulled apart into fine shreds. Minerals possessing a fine Fibrous structure.— Serpentine, fibrous structure usually have a silky luster ; hence fibrous gypsum is called satin-spar.

Foliated. — When a mineral separates easily into plates, as in some varieties of serpentine and brucite.

Micaceous. — A structure similar to the foregoing, but in which

922 Btructubb.

the material can be split readily into exceedingly thin sheets, as muscovite (common mica).

Radiated. — When columns, fibers, or folise diverge from cen- tral points, as in pectolite (Pig. 361), wavellite, and pyrophyllite.

Renform and Mammillary. — These are terms applied to rounded masses, usually with a smooth exterior, which have a re-

no. 861. Fig. 862.

Radiated Structure.— Pectolite. Renirorm Structure.— Kidney- iron 01

Hematite.

semblance either to a kidney or to mamma;. They are illustrated by some varieties of hematite (Fig. 362) and malachite.

Botryoidal and Globular. — These terms are applied to rather small rounded or spherical prominences, found in some varieties of smithsonite (Fig. 363), opal (hyalite) and other minerals.

Fio. 863. Botrjoldul Structure.— Smithsonite.

Stalactitic. — When the material occurs in pendants (icicle-like .

forms), as limonite (Fig. 364) and some calcite (cave-stone). Stalac-

Cleavage. 223

tites form in cavities. The material is deposited generally from dripping water.

Cohesion Relations of Minerals.

Cleavage. — Crystallized substances ilsually exhibit a tendency to break more readily in some directions than in others, often yielding smooth surfaces which resemble crystal faces. This prop- erty is known as cleavage. The directions of cleavage are always parallel to possible crystal faces, and usually to faces with simple indices. Cleavage is a separation parallel to the molecular planes composing the crystal (Fig. 51, p. 157), and is due to the fact that the forces which unite the molecules are weaker in certain direc- tions than in others. Some substances, such as calcite, gypsum, and mica, can be cleaved with great ease. Such cleavage is designated as perfect, and if the cleavage-fragment is held in an appropriate position, close to the eye, a perfect reflection of distant objects will be obtained from its surface. In some minerals cleavage is poor, or can only be detected with difficulty. In studying minerals the ease with which cleavage can be produced and its direction, or its relation to the crystal form, should be carefully noted. Often the cracks in a crystal reveal both the presence and the direction of cleavage. To produce a cleavage, place the edge of a knife-blade or chisel on a crystal face, parallel to the direction in which the cleavage is supposed to exist, and strike a sharp, quick blow with a hammer.

In the isometric system cleavage may be cubic (Fig. 95, p. 170, and Fig. 365), as in galena and halite ; octahedral (Fig. 96, p. 170), as in fluorite ; or do decahedral (Fig. 97, p. 170), as in sphalerite.

In the hexagonal system cleavage is designated as basal or prismatic when parallel, respectively, to the faces lettered c or m (Fig. 194, p. 187). In the rhombohedral group it is often rhombo- hedral (Fig. 219, p. 193, and Fig. 366), as in calcite. This is char- acterized by being equal in three directions, but not at right angles to one another.

In the remaining systems cleavage is called basal when it is in one direction, parallel to the terminal face c (001) in the figures

Fia 865. Fia. 366.

Cubic Cletiviige. — Galena. Rhorabohedral Cleavage. — Cakite.

pp. 179 to 217, illustrated by apophyllite in the tetragonal, topaz in the orthorhombic, and orthoclase in the monoclinic systems. Cleavage is called pinacoidal when it is in one direction, parallel to the vertical pinacoids of the orthorhombic, monoclinic, or tri- clinic systems, as in stibnite (Fig. 383, p. 303) and gypsum (Fig. 333, p. 311), where it is parallel to the faces b (010). In orthoclase (Fig. 326, p. 211) there is a perfect basal cleavage parallel toe (001), and a less perfect cleavage at right angles to it, parallel to the clino- , pinacoid b (010). A cleavage is designated as prismatic when produced with equal ease in two directions, parallel to the faces 7(110) or a(l00) of the tetragonal system (pp. 179 to 183), or paral- lel to the faces m(110) in the orthorhombic and monoclinic systems (pp. 200 to 213). Amphibole furnishes a good example of prismatic cleavage.

Parting. — It is the case in some crystals that when they are subjected to strain or pressure there is apparently a slipping or gliding of the particles along certain molecular planes. This is accompanied at times by an overturning of layers of molecules into the position which they would occupy in a twin crystal. By this process a weakness along these planes is developed, and the crys- tal maty part or break with smooth surfaces. This phenomenon is called parting and is distinct, though not always readily distin- guished, from cleavage, from which it differs in that it takes

place only where the molecular structure has been disturbed by pressure or other agency, while cleavage in a given direction can be produced as readily in one part of a crystal as another.

Magnetite shows no perceptible cleavage, but specimens from certain localities show a perfect octahedral parting (Fig. 367).

Pie. 868. Twin Lamella; and — Basal Parti ug.—

Pig. 887. Pyroxene,

Octahedral Parting.— Magnetite.

Pyroxene has a rather poor prismatic cleavage, but some crystals show twin lamellae very distinctly and parting parallel to the basal plane (Fig. 368).

Fracture. — If a mineral has a poor cleavage, and separates or breaks almost as readily in one direction as in another, smooth, curved surfaces often result (Fig. 369). This kind of fracture is called conchoi- daly from its resemblance to the curved surface of a shell. It is especially characteristic of amorphous substances, such as glass, and of minerals having a poor cleavage, such as quartz, while it may occasionally be observed on min- erals which cleave readily, as calcite.

Fracture is said to be uneven when Fre- 8*8.

, . , , . . . , Conchoid nl Frafilnre.— Obsidian

rough, irregular surfaces are obtained ; or Volcanic GImss.

hackly when a jagged, irregular surface like that of broken

metal results ; and splintery when the substance breaks in

splinters or needles.

226 Hardness.

Tenacity. — A mineral is said to be malleable when it can be beaten out into plates by hammering ; sectile when it can be cnt with a knife, so that a shaving results ; flexible when it bends readily, but does not resume its shape when the pressure is re- lieved ; elastic when it bends and springs back to its original position.

Hardness. — The hardness of a mineral, or the resistance which it offers to being scratched, is expressed in terms of a scale of hardness , consisting of crystallized varieties of the following ten minerals :

Scale of Hardness.

1. Talc. 3. Calcite. 5. Apatite. 7. Quartz. 9. Corundum.

2. Gypsum. 4. Fluorite. 6. Orthoclase. 8. Topaz. 10. Diamond.

The hardness of a mineral is determined by drawing a point, or a sharp corner of it across smooth surfaces of the different min- erals in the scale of hardness until one is found which it will just scratchy while it will not scratch the next higher member in the scale. Thus if a mineral will scratch calcite but not fluorite its hardness will be between 3 and 4.

It is generally a simple matter to determine the hardness of a mineral, but there are some cases where considerable care and judgment must be exercised. For example, a soft mineral may crumble when drawn across a harder one, especially when the sur- face of the latter is rough, and leave a mark, similar to that of chalk on a blackboard, which readily rubs oflf and must not be mistaken for a scratch. Again, it is difficult to obtain the correct hardness of minerals which crumble readily or crystallize in fine needles or scales, for when drawn across the surfaces of the minerals in the scale of hardness they break down and do not offer sufficient resistance to make a distinct scratch on materials which may be considerably softer.

In determining the hardness of minerals a knife-blade will be found very useful. It will scratch apatite with some difficulty, but not orthoclase, and its hardness, therefore, is a little over &

Luster. 227

With a little experience an approximation to the hardness of the softer varieties of minerals may be obtained by noting the ease

with which they are scratched with a knife. The hardness of window-glass is about 5£, and some pieces of it will be found very useful. An ordinary brass pin will scratch calcite but not fluorite, and its hardness is, therefore, a little over 3. The finger-nail will scratch talc easily and gypsum with some difficulty.

Crystals exhibit varying degrees of hardness in different direc- tions, being softer parallel to a cleavage direction than at right angles to it. This difference, however, is usually not sufficiently great to be detected by the ordinary methods of testing hardness. Cyanite furnishes a striking example, for in the direction of cleavage (parallel to the longer axis of the splinters) it can be readily scratched with a knife, while at right angles to the cleavage the hardness is considerably greater than that of steel.

Propekties Depending upon Light.*

Luster. — The luster of minerals, or their appearance due to the reflection, absorption, or refraction of light, furnishes an im- portant means of identification, and is described by the following terms:

Metallic. — Having the luster and appearance of a metal, like lead or copper. Under this head those minerals are included which are opaque, that is, those which are not at all transparent when their thin edges are examined in a strong light. The powder of an opaque substance is black or very dark, because the small particles constituting it do not transmit any light ; therefore this property may be usefully employed in detecting metallic luster. Pyrite and galena are examples of minerals with metallic luster.

Sub-metallic. — Dark-colored minerals which lack the true luster

Though fully appreciating the importance of the application of polarized light in the study of crystals and the identification of minerals, it has seemed best not to include these methods in the present work. For a description of them the student Is referred to Idding's translation of Rosenbusch's Mikrothopuche Fhytiographit der petrogrophbch Minoralion or to Dana's Text-book of Mineralogy.

228 Streak.

of a metal are called sub-metallic. Such substances are generally slightly transparent in very thin splinters and give dark powders, although the colors are considerably lighter than those of the com- pact minerals. Chromite, limonite, and some of the dark varie- ties of sphalerite are examples of minerals with sub-metallic luster.

NoTwrietallic. — Transparent minerals are here included. If col- orless, white, or light-colored they will give white powders, and if of decided colors their powders will be of lighter shades than those of the compact minerals. For example, a dark-green epidote yields a very pale green powder.

Transparent minerals exhibit the following kinds of luster: Vitreous ', like the luster of glass. Adamantine, like the luster of a diamond. Minerals possessing this luster have a certain brilliancy, due to the strong refraction of light, i. e., they have a high index of refraction. Adamantine luster may be observed on some of the hard minerals used as gems and on cerussite and other transparent salts of lead. Resinous, or having the appearance of resin, as shown by transparent varieties of sphalerite. Or easy or oily, as if the mineral had a thin coating of oil over it, as shown by some specimens of serpentine and massive quartz. Pearly, like the luster of mother-of-pearl. This is due to the interference of light in minute cracks (Newton's rings). It may usually be observed on crystal faces parallel to which there is a perfect cleavage, as on the basal planes of an apophyllite crystal. Silky, like a skein of silk. This may be observed on minerals which have a fine fibrous structure.

Streak. — The streak of a mineral is the color of its powder. Provided the material is not too hard, this may be quickly de- termined by rubbing it on a piece of white, unglazed porcelain, and noting the color of the powder, or mark, which is left. Pieces of unglazed porcelain, called streak-plates, are made especially for this purpose.

Color.— The color of minerals is a property which should be carefully considered. A mineral with metallic luster will always

color, 229

show the same tone of color provided fresh, unaltered ma- terial or a freshly broken surface is examined. Thus, the color of chalcocite is steel-gray and of bornite brownish-bronze. On ex- posure to the air and light, however, the surfaces of minerals with metallic luster may become dull or tarnished and present quite a different appearance from that of the fresh material. For example, chalcocite becomes black, and a fresh surface of bornite tarnishes to a purplish tint in less than a day. A mineral without metallic luster has always a definite color provided it contains a constituent, like copper, iron, or chromium, which has the property of coloring its compounds. Thus, copper minerals are generally green or blue, those containing iron and chromium generally green, though of different shades, while chromates are red or yellow. Often, how- ever, the color of a mineral with non-metallic luster is variable, as illustrated by fluorite, which is colorless, yellow, pink, green, and violet, or by tourmaline, which ranges from colorless, or white, through varying shades of pink, green, blue, and brown, to black. The causes for the variation in color of some minerals cannot be detected, since it takes such minute quantities of certain materials to impart color to minerals. In a few cases the color disappears upon the application of heat, and is supposed to be of the nature of an organic pigment. In the majority of cases, however, varia- tion in color is due to the admixture of some isomorphous con- stituent which has the property of absorbing light. For example, the diopside variety of pyroxene, CaMg(SiO§)t, is colorless, but pyroxenes containing the isomorphous iron molecule CaFe(SiOt) vary from light to dark green, depending upon the amount of iron which they contain. As explained on p. 7, the variations in the color of sphalerite, from colorless, or nearly so, when pure ZnS, through brown to black, depend upon the amount of the iso- morphous iron sulphide molecule FeS which the mineral contains. Frequently a mineral is colored by some foreign constituent with which it is mechanically mixed. Thus jasper is quartz col- ored red or brown by an admixture of either hematite or limonite.

Fusibility.

Properties Depending upon Heat. " Fusibility. — The ease with which substances fuse, or their de- gree of fusibility, admits of approximate determination, and is of great assistance in the identification of minerals. In testing fusibility, splinters of nearly uniform dimen- should be employed, and pieces about m. in diameter (Fig. 370) may be as- i as the standard size. The splinter d be held in the platinum forceps so ts end projects beyond the metal, then . ?" .8I0' . heated as shown in the figure. Provided its

)f holding a frag- °

of standard s£e edges do not become rounded, a much finer

should be tested before deciding that the material is infusible. The fusibility of a mineral is determined by comparing its fusi- bility with that of a fragment of the standard size from the fol- lowing scale :

Scale of Fusibility.* 1 Wibnite f ratner kirge fragment fuses easily in

ay. a a luminous lamp or gas flame. Fusible in

la closed glass tube below a red heat.

f A fragment of the standard size fuses

2. Chalcopyrtte, J rathe,. s]owiy in a luminous lamp or gas

Our en,, j flame. small fragment fuses in a closed I glass tube at a full red heat. ( A fragment of the standard size fuses

3. Almandine readily to a globule before the blowpipe.

Garnet, J in a luminous lamp or gas flame only the Fe,Al,(SiOJ,. very finest splinters or thinnest edges are I rounded.

With the exception of chalcopyrile the scale here adopted la that of Von Kobell, who made use of natrollte No. 2. Natrollle, however, eeems poorly chosen, for the range between, atibnlte and natrollte is considerable, while between natrollte and garnet

the difference la slight.

4. Actinolite, Ca(Mg,Fe),(SiOi)4.

5, Orthoclase, KAlSi.O..

k.

Pyroelectricity. 231 '

The edges of a fragment of the standard size are readily rounded before the blow- pipe. A much finer splinter is easily fuse<l to a globule.

The edges of a fragment of the standard size are rounded with- difficulty before the blowpipe. It is only when very fine splinters are employed that the material can be fused to a globule.

6. Bronzite, j Only the finest points and thinnest edges (Mg,Fe)SiOt. become rounded before the blowpipe.

Glowing. — Some minerals glow, or emit a bright light, when heated intensely before the blowpipe. This is a property of in- fusible substances, and the oxides of calcium, magnesium, zirco- nium, and thorium possess it in a marked degree. Fragments of calcite CaCOt, brucite Mg(OH)„ and zircon ZrSi04, glow when in- tensely ignited. The Auer von Welsbach light is obtained by heat- ing a mantle of thorium oxide with a Bunsen-burner flame.

Phosphorescence. — Some minerals when gently heated become luminous and emit light for a longer or shorter period. This property, known as phosphorescence, may be tested by heating fragments of a mineral in a closed tube, and best in a dark room.. Many varieties of fluorite phosphoresce beautifully, with purple or green light. Some minerals phosphoresce when they are. struck or rubbed ; others after they have been exposed to sunlight or to an electric discharge.

Pyroelectricity. — Some minerals when they undergo a change of temperature become electric and have the property of attract- ing light bodies. This property, known as pyroelectricity, is espe-. cially characteristic of hemimorphic substances, i. e., those which show an unlike development of crystal forms at opposite extremi- ties of an axis of symmetry (p. 164). Two kinds of electricity ate always developed, positive at one end and negative at the other/.

To detect pyroelectricity a crystal, held in the platinum forceps* is heated gently (not much above 100° C), and as it cools it is brought

232 Pyroelectricity.

near some small bits of tissue-paper, which will be attracted. A cat's hair which has been rubbed between the fingers and become positively electrified is excellent for detecting pyroelectricity, fo? it will be attracted to that end of the crystal where negative elec tricity prevails, and repelled by the other. A hair for this purpose may be fastened to a cork by means of sealing-wax and kept in a vial. Another very beautiful method is tried with a mixture oi about equal volumes of red oxide of lead and flowers of sulphur. The mixture is kept in a vial, over the mouth of which two or three thicknesses of fine bolting-cloth are tied, so that the powder may be sifted out slowly. When agitated, the red oxide of lead becomes positively, and the sulphur negatively electrified, so that when the mixture is dusted upon an electrified body the red oxide of lead will be attracted to that part where there is negative, and the sulphur to where there is positive electricity. Experi- ments in pyroelectricity may be made with the light-colored varieties of tourmaline or with crystals or fragments of calamine. Generally the experiment succeeds best when a rather small fragment is employed.

Properties Depending upon Weight.

Specific Gravity. — The specific gravity of a substance is the ratio of its weight to the weight of an equal volume of water. For example, quartz has a specific gravity of 2.65, and is, there- fore, two and sixty-five hundredths times heavier than water.

Specific gravity is a definite property of all minerals which show no variation in chemical composition, and, when carefully

determined, can be used to great advantage as a means of identifi-

cation. There are, however, several conditions which must be carefully considered.

1. It is of the utmost importance that the material should be pure. If it is not, there is little or no advantage to be gained by taking its specific gravity.

2. A pure, transparent fragment of a mineral will apparently have a somewhat higher specific gravity than a piece which is full

Specific Gbavity. 233

of cracks, as the cracks contain air which tends to make the min- eral lighter. Air can generally be expelled from cracks by boiling the fragment in water for some minutes, when an accurate deter- mination may be made.

3. It is difficult and often impracticable to obtain the correct specific gravity of porous, earthy, and fine fibrous, or ecaly, min- erals because of the air which they confine. Moreover, the chances of their containing impurities are also great and must be taken into consideration.

4. Minerals which show a variation in chemical composition may exhibit considerable range in specific gravity. This is espe- cially true when there is an isomorphous mixture of two molecules with widely different molecular weights, as in the case of the niobate and tantalate of iron, explained on p. 7. In such cases, however, the specific gravity determinations may have great value, as furnishing a means of approximately determining the propor- tions of the isomorphous constituents.

In the tables for the determination of minerals, pains have been taken to give, as accurately as possible, the specific gravity of the pure crystallized varieties of each mineral. Variations from these figures should be small, provided the material that is tested is pure and its specific gravity is taken correctly.

The usual method for taking specific gravity is to weigh a sub- stance in air and then when immersed in water. The difference in these values is the weight of a quantity of water equal to the volume of the substance, for a body when immersed in water is buoyed up by a weight equal to that of the water displaced. If Wa is the weight of a substance in air and Ww its weight when immersed in water, its specific gravity is found by dividing Wa by Wa — Ww.

For very accurate determinations the weights should be taken on a chemical balance. The material is first boiled in water for some minutes to expel the air, then allowed to cool in the water to the temperature of the room. It is then conveniently placed in a wire basket, suspended from the arm of a chemical balance

234 Specific Gravity.

by a very fine platinum wire (Fig. 371), and the weight in water determined, from which the weight of the- empty basket in water — should be deducted. The material is then

weighed, after being thoroughly dried. For practical purposes corrections for temperature may be neglected, for they will be trifling if the weighings are made at the temperature of an ordinary living- room.

For quick results in the identification of minerals, the following simple methods will be found convenient and sufficiently reliable for all ordinary purposes.

The Spring or Jolly Balance. — With this apparatus (Fig. 372) the relative

Fm. 371. weights of a substance are determined

Method of Imaging wire baa- . .. . . . ,

ket on balance lieara for by the Stretch Of 0. Spiral

SffBr-ifiw*1* Two v*ns are

Me- ) carried at the lower end of

the spring ; the upper one c being in the air and the lower one d in water which is in a glass resting upon the sliding platform B. The stretch of the spring is read from a scale which is engraved upon a mirror fastened to the upright A. A white porcelain bead at m serves as a mark for noting the position of the spring with refer- ence to the scale. It is evident that in order to make these readings correctly, the eye must be on the same level as the bead. This is accom- plished by bringing the eye into a position where the top of tlie bead and its reflection in the mirror

coincide. The pans being empty and the lower „ , Fl°' 8ra-

° J Spring or Jolly Bd-

one a being suspended in the water near the ance for Specific

bottom of the glass, the position of the bead m

is noted on the scale, x. A fragment of mineral, sufficient

Specific Gravity.

to stretch the spring somewhat more than one half the length of the scale, is then placed in the upper pan and the platform lowered until the spring comes to rest, the pan d occupying the same relative position in the water as before, when the position of the bead is again noted, y. Hence y — x is the weight in air. The fragment is now transferred to the lower pan, and the platform raised until d occupies the same position in the water as before, when the position of the bead is again noted, z. Hence y — z is the loss of weight in water, and the weight in air divided by the loss of weight in water gives the specific gravity.

The Beam Balance. — This is a simple piece of apparatus (Fig. 878) which can be easily constructed. The beam of wood is sup-

i i i i i i i i i i i

nil* i-L-i-

&

Fig. 878. Beam Balance for Specific Gravity, Jtk Natural Size.

ported on a fine wire, or needle, at b and must swing freely. The long arm be is divided into inches and tenths, or into any decimal scale, commencing at the fulcrum b ; the short arm carries a double arrangement of pans, so suspended that one of them is in the air and the other in water. A piece of lead on the short arm serves to almost balance the long arm, and, the pans being empty, the beam is brought to a horizontal position, marked on the upright, near c, by means of a rider d. A number of counterpoises are needed, Which do not have to be of any specific denomination as it is their position on the beam and not their actual weight which is recorded. Most handy are bits of bent wire which may be used as shown at A. The beam being adjusted by means of the rider d, a frag- ment of mineral is placed in the upper pan and a counterpoise is chosen, which, when placed near the end of the long arm, will

236 Specific Gravity.

bring it into a horizontal position. The weight of the mineral in air, Wa> is given by the position of the counterpoise on the scale. The mineral is next transferred to the lower pan, and the same counterpoise is brought nearer the fulcrum b until the beam becomes again horizontal, when its position gives the weight of tho mineral in water, Ww. Wa divided by Wa — Ww gives the spe- cific gravity. The balance has been repeatedly tested with pure materials, and the variation from determinations made on a chemical balance has never exceeded two in the second place of decimals. It is reliable, quick, and sufficiently accurate for all ordinary uses.

The Heavy Solution. — By treating 50 grams of mercuric iodide and 40 grams of potassium iodide in a porcelain dish, or casserole, with a little water, and evaporating until a crystalline crust begins to form, about 30 cubic centimeters of a yellowish-green solution are obtained, which has a specific gravity of about 3.15. This may be cleared by filtering, diluted with water to any extent, and the dilute solution may be brought to its maximum concentration by evaporation. It will keep indefinitely without decomposition, pro- vided a few drops of mercury are added to it. It is very poison- ous. In determining the specific gravity of a mineral by means of the heavy solution, a fragment is placed in it, and then, by adding water cautiously, the specific gravity of the solution is lowered until it becomes exactly equal to that of the mineral, when the fragment will remain suspended in any position, neither sinking nor floating. The specific gravity of the solution may then be taken by some of the methods described beyond.

The Westphal Balance. — This consists of a metal beam (Pig. 374) with its long arm from I to h divided into tenths. A glass sinker r loaded with mercury, is suspended from h by means of a fine plati- num wire, and the apparatus is so constructed that, with the sinker in air, the beam-pointer can be brought to zero on the scale s by means of the set-screw o. Four wire riders w are needed, of such a weight that one of them, when hung at A, will bring the beam- pointer to zero when the sinker is immersed in water. There are

Specific Gravity. 237

also needed two lighter riders, one -fo and the other Tiu of the unit weight. When tlie sinker r is immersed in the heavy solution the riders are applied, as illustrated in the figure, until the beam- pointer stands opposite zero. The two unit-riders at the end and

Fro. 374. Westptml Baliiuce for Taklog the Specific Gravity of Liquids.

one at 6 on the beam indicate a specific gravity of over 2.6. The -iV and TJff riders, both at 5, furnish the second and third figures from the decimal point and indicate that the specific gravity of the solution is 2.655.

The beam-balance (Fig. 373) may also be employed. A sinker similar to r (Pig. 374) is suspended from a position marked by a notch near the end of the long arm. By putting shot in the pans and using the rider d the beam is brought to a horizontal position with the sinker r in air. The sinker is then immersed in the heavy solution and a weight is selected, which, when placed near the end of the beam, will bring the latter to a horizontal position. The position of this weight gives relatively the weight of the heavy solution displaced by the sinker. After washing, the sinker is immersed in water, and the same weight is placed nearer the

238 Specific Gravity.

fulcrum until the beam becomes horizontal. The position of this weight gives relatively the weight of the water displaced by the sinker. The larger weight divided by the smaller gives the desired specific gravity.

It may often be found convenient, in the identification of a gem, to use the heavy solution for comparing an unknown with a known

mineral, as follows : A stone supposed to be beryl and a known crystal of beryl are placed together in the heavy solution, and water is added to deter- mine whether they sink and float together, i. e., whether they are identical in specific gravity.

The heavy solution may also be used for obtain- ing a mineral in a state of purity when mixed with others of different specific gravity. The material is pulverized and sifted to a uniform grain, then intro- duced into the heavy solution. The specific gravity may then be adjusted, first so that everything heavier than the desired mineral will sink, and then so that everything lighter will float. The separa- tion can be most readily accomplished in the appa- ratus shown in Fig. 375.

Besides the potassium mercuric iodide solution, which is the cheapest, and also the easiest to pre-

Separatory Funnel, pare and to manipulate, tne following have proved

very useful : methylen iodide,* CH,I„ with a maxi- mum specific gravity of 3.3?, and asetylen tetrabromide,t CHBr, — CHBr„ with a specific gravity of 3.01, both of which may be diluted with benzol ; and barium mercuric iodide, with a maximum specific gravity of 3.55. The double salt, silver thallium nitrate, § melts at 75° C, giving a clear liquid with a maximum specific gravity of over 4.5, which, may be diminished to any desired extent by adding hot water.

R. Branus, Jahrbuch fur Mineralogie. 1886, Vol. II, p. 72. W. Muthman, Zeitechrif? far KrystaUographie. 1898, Vol. XXX, p. 78. C. Rohrbach, Jahrbuch far Mineralogie, 1888, Vol. II, p. 186. J. W. Retgers, Jahrbuch far Mineralogie, 1898, Vol. I, p. 90 ; Author, Am. Jour. of Sci., 1895, Vol. L, p. 446.

Chapter Vi.

TABLES FOR THE DETERMINATION OF MINERAL SPECIES BY MEANS OF SIMPLE CHEMICAL EXPERIMENTS IN THE WET AND DRY WAY AND BY THEIR PHYSICAL PROPERTIES.

Introduction to the Tables.

In the General Classification of the tables (p. 245) minerals are divided into two groups : I, with metallic or sub-metallic luster ; II, without metallic luster. According to the ex- planations on pp. 227 and 228 this division depends upon the fact whether the minerals are opaque and give black or dark streaks, or transparent and give white or light-colored streaks. Since, whether the luster shall be considered metallic or non-metallic is, at times, wholly a matter of judgment, pains have been taken to place many minerals whose luster might be considered doubtful in both sections. A further subdivision of each group depends upon whether a mineral is fusible or infusible. The directions given on pp. 33 and 230 concerning fusion must here be carefully considered. In making the test, the degree of fusibility and per- haps some behavior, such as flame coloration, may be recorded, which will be of service in the identification of the mineral. ' Each section is then further subdivided, the divisions being based upon some chemical constituent which may be readily detected, or upon the behavior with acids.

In the tables p. 246 et seq., the two vertical columns at the left give, respectively, the General Characters of groups of minerals and the Specific Characters of individual species, based, in most cases, upon simple blowpipe or chemical reactions. In the vertical columns headed Species the names of the minerals are given ; and, since the tables are intended to include all of the minerals which are recognized as distinct species, this number is necessarily large, amounting to nearly 800 names. To facilitate the identification of

240 Introduction To The Tables.

a single species from this large number the names are printed in three ways. Those in capitals indicate common minerals, that is, the ones which are found abundantly and are useful in the arts, or as ores of the metals, or are important geologically as con- stituents of rocks. Those in Fuii-fawd Typ indicate minerals which are valuable or important, but which do not occur often enough pr in sufficient quantity to be considered as common. Names in small type indicate rare minerals. It will probably be found that usually out of one hundred specimens to be identified fully seventy-five wiJl be the common minerals, printed in capitals,

With perhaps twenty Intermediate and five rare.

In the remaining columns the following important properties are recorded : Chemical Composition, pp. 3 to 9 ; Color, p. 228 ; Streak, p. 228 ; Luster, p. 227 ; Cleavage and Fracture, pp. 223 to 225 ; Hardness, p. 226 ; Specific Gravity, p. 232 ; Fusibility, p. 230 ; Crystallization, pp. 155 to 219.

Method Of Using The Tables.

The way in which the tables are used may be illustrated by the following examples :

Celestite. — Referring to the General Classification on p. 245 and examining the mineral, it will be seen that it is without metallic . luster, and therefore belongs in Group II. A small fragment heated in the forceps before the blowpipe fuses rather readily, about 3.5 according to the scale of fusibility (p. 230), thus determining the mineral to be in Section B. It should be noted that a red coloration was imparted to the flame, indicating, according to the table of flame coloration on p. 136, probably either strontium or lithium. The mineral is not to be found in Parts I and II under B, because when its powder is fused with sodium carbonate on charcoal it does not yield a metallic globule, and when fused alone it does not yield a black, magnetic mass. It must, therefore, be in the remaining Part III. It may readily be proved to be in Division 1 under Part III, for when a fused fragment is placed on moistened

Introduction To Thr Table8. 241

turmeric-paper, it shows an alkaline reaction. Further, a test-tube trial will show that the mineral is insoluble in water, and hence is in section b on page 273. Referring to that page the first section under General Characters comprises carbonates, which dissolve in hydrochloric acid with effervescence. A test-tube trial of some of the powdered mineral under examination indicates that it is very insoluble in acids, and therefore not a carbonate. That the mineral belongs to the next section which comprises sulphates may readily be proved by fusing a little of it with sodium carbonate and charcoal-powder, and thus obtaining a mass which gives a dark stain when placed on moistened silver. The mineral, moreover, gives no water in the closed tube, and is difficultly soluble in boiling, dilute hydrochloric acid, as shown by a previous experi- ment made when testing for a carbonate. Under Specific Charac- ters, the crimson flame coloration, tried best on platinum wire as directed on p. 35; determines the mineral to be celestite, strontium sulphate, SrS04. The physical properties given in the horizontal section should correspond : Color, colorless or white; Luster vit- reous ; Cleavage of two kinds, perfect in one direction, basal, and less perfect in two directions, prismatic, so that a form like Fig. 273, p. 201, may be produced ; Hardness 3 to 3.5, the material scratches calcite and is readily scratched by fluorite; Specific gravity 3.97 ; Fusibility 3.5, which was determined at the outset ; Crystallization, orthorhombic, crystals being perhaps like Figs. 278 or 279, p. 202. If the specific gravity had been taken at the begin- ning it would have served to distinguish celestite from all the other minerals in Division 1, b, pp. 273 and 274, for there are none which come at all close to 3.97.

Chromite. — The color of this mineral is black, and the powder, or streak, is dark brown ; hence the luster may be considered as sub-metallic, and the mineral classified in Group I, p. 245. At the beginning, the hardness may be determined as between 6 and 6, and the specific gravity as 4.6. When heated before the blowpipe there is no indication of fusion ; the mineral is therefore in Section B. Division 1, under B, includes minerals containing

242 Precautions In The Use Of The Tables.

iron, which become magnetic after heating, but if a trial is made it will be found that the mineral does not become magnetic. In Division 2 the minerals containing manganese are included. A test made with borax in the oxidizing flame, as directed, gives a bead which is yellow when hot and yellowish green when cold. This does not indicate manganese, but is a decided reaction for chromium, as may be seen by referring to the table of reactions obtained with borax on p. 148. Since the mineral fails to give re- actions for iron and manganese, it must belong in Division 3 — Not belonging to the foregoing divisions, p. 256. Referring to this page in the column General Characters, the mineral cannot be in the first section because of its hardness. It is, however, in the second section, since the borax-bead test, previously made, has indicated the presence of chromium. This reaction, as well as the determi- nations of hardness and specific gravity, agree with chromite, PeCr,04 FeO.Cr.O,. A test for iron may be made with the magnet after fusion with sodium carbonate on charcoal, as directed under Specific Characters. Had the chromite been considered as being without metallic luster, Group II, p. 245, it would have been found under C, Division 6, b, p. 298.

Precautions in the Use of the Tables.— The system adopted in the construction of the tables is that of eliminating one group of minerals after another until a species is found, whose properties, as given in the table, correspond to the mineral that is being tested. The process of elimination and identification is based largely upon a series of chemical tests which, in almost all cases, give an insight into the character of the material. There is dan- ger, however, that one may become so absorbed in following the tables mechanically, with the sole idea of determining the name of the species, as to wholly lose sight of the importance of making a careful study of the chemical reactions and physical properties of the minerals. It should be distinctly understood that little or nothing is to be gained by simply determining the name of a mineral. The chief aim should be to obtain a thorough knowl- edge of the chemical composition, physical properties, and gen-

Precautions In The Use Of The Tables. 243

eral appearances and associations of a mineral, not only that its uses and relations may be understood, but also that it may be easily recognized and identified when again encountered.

The general plan and arrangement of the tables must be ad- hered to rather closely, for if they are applied in the reverse direc- tion, that is, backwards, they may not lead to the desired result For example, if a mineral has metallic luster, is fusible, and gives a reaction for sulphur, it does not necessarily belong to Division 5 under I, A (p. 245), for most of the minerals containing arsenic (Division 1 ) and antimony (Division 4) also contain sulphur. It is, therefore, not correctly determined as belonging to Division 5 until proof has been obtained, not alone of the presence of sul- phur, but also of the absence of arsenic and antimony, as well as of the rare elements selenicum and tellurium (Divisions 2 and 3).

The tables are adapted to the determination of pure minerals. If it is thought that a mineral is not pure the nature of the im- purity must be taken into careful consideration. Thus, for ex- ample, many minerals are associated with calcite, CaCOs. If some of this is included in material that is being tested it will cause a slight effervescence with acids and an alkaline reaction when the ignited material is applied to moistened turmeric-paper, although both reactions are probably entirely foreign to the mineral which it is desired to determine. The best and almost the only rule to guide one in such cases is one's judgment. It would be impossible to devise blowpipe methods to meet the contingencies arising from the various mixtures of minerals. The one thing of the very utmost importance is the assurance of the purity and homo- geneous character of a mineral. Since, in most cases, only a very little material is required for the necessary tests, by careful selec- tion enough can generally be secured in a pure condition.

Record Op Mineral Te8Ts.

A careful record should be kept of all tests as they are made. It may be found convenient to record them, together with the

244 Record Of Mineral Tests.

physical properties, upon blanks similar to the accompanying sample. It is not intended that every test for which a space has been allotted should be made, but a convenient place has been fur- nished where the prominent blowpipe reactions may be recorded, provided tests in the closed or open tubes or with the fluxes, etc.,. have been made.

Record Of Mineral Tests.

Structure

SyBtem of crystallization.

Cleavage or fracture

Luster Color

Streak. Hardness.'. Sp. Gr.

Fusibility Flame color.

Effect of acids and reactions with the solution. .

Closed tube

Open tube ..?.

Alone on charcoal

With fluxes on charcoal

With fluxes on platinum wire

Miscellaneous

Name Composition.

Per cent of chief constituents

Mode and place of occurrence.

Associations

Uses

Number Date..

Fifty of these blanks, bound in book form, may be obtained from the publishers. 50 cents, net.

(Page 245.)

Analytical Table

Showing The

General Classification

Of

Minerals.

Abbreviations Used In The Text Of The Tables.

Amorpli...

Amorphous.

Isom. Tet.

Isometric Tetrahedral.

Appmx ...

Approximately.

iso. w . . . .

Lsomorphous with.

B. B

Before the blowpipe.

Mam in

Mnmmillary.

Botryoiil..

Bot.yoidal.

Ma mm ill..

Mam miliary.

Cleavage.

Massive.

Capill

Capillary.

Monucl . . .

Mouoclinic.

Class.

NmCOi . .

Sodium carbonate.

Columnar.

Oct

Octahedral.

Crystalline; in crystal*.

O.F

Oxidizing flame.

Direc

Direction.

Orthorh . .

Orthorhombic.

F

Fracture*

Perfect; referring to cleavage.

Fig

. Figure.

Pinac

Pinacoidal; in one direction.

Foliated.

Prism

Prismatic.

Fusibility.

Pseudom. .

Pse udomorphous.

Granular.

Pyram . . .

. Pyramidal.

H

Hardness.

Radiat. . .

. Radiated.

Hydrochloric acid.

R.F

Reducing flame.

Hno,

Nitric acid.

Sp. Or. . . .

Specific Gravity.

H,So. ...

Sulphuric acid.

Sph

, Sphenoidal.

Hemimor .

Hemiuiorphic.

Tabul

Tabular.

Hexag. . . .

Hexagonal.

Tar

Tarnish.

Hex. Rh..

Hexagonal Rhoinbohedral.

Tetrag

Tetragonal.

lncrust. ...

Incrustiug; incrustation.

Tet. Sph..

Tetnfgoual Sphenoidal.

Isom . . . .

Isometric.

U

Usually.

Isom. Pyr.

Isometric Pyritohedral.

Vol . ..

Volatile.

N.B. — The chemical symbols of the elements, together with the valences which they ordinarily exhibit in mineral combinations and their atomic weights, will be found in Chapter III, " Reactions of the Elements," pp. 41 to 184.

245 General Cl

OF" Success in using the following tables depends wholly upon locating a mir

initial reactions, as given in this GENERAL CLA

g3T In testing the solubility of minerals the importance of using ver I. MINERALS WITH METALLIC OR SUB-METALLIC LUSTER.

Note. — Minerals having metallic luster are opaque; hence the color of their powder, or their streak, is dark, though not necessarily black (p. 227). The minerals with sub-metallic luster which are included in this section all give dark-colored streaks. Many dark-colored minerals whose luster is doubtful have been placed here, and also in Section II.

A.— Fusible From 1—3, Or Easily Volatile.

Page

1. Roasted in the open tube, or B. B. on charcoal, give a volatile sublimate of Arsenious

Oxide (p. 48). Compare Antimony, Section 4 246

3. Roasted in the open tube, or B. B. on charcoal, give the characteristic radish-like odor of

Selenium, Impart an azure- blue color to the reducing flame (p. 107) 347

8. Treated in a dry test-tube with 8 cc. of concentrated H,S04 and gently heated, the acid

assumes a reddish- violet color characteristic for Tellurium (p. 124) 248

4. Roasted in the open tube, or B. B. on charcoal, give a dense white sublimate of Oxide of

Antimony (p. 44). The sublimate is less volatile than that of arsenic 249

5. Roasted in the open tube, or B. B. on charcoal, give the odor of Sulphurous Anhydride

(p. 118), but do not give the reactions of the preceding divisions 251

6. Not belonging to the foregoing divisions 258

B.— Infusible, Or Fusible Above 5, And Non-Volatile.

1. Become magnetic after heating B. B. in the reducing flame, Iron (p. 84) 255

2. A minute quantity of material imparts to the borax bead in O. F. a reddish-violet color,

Manganese (p. 98) 256

8. Not belonging to the foregoing divisions 256

Ii. Minerals Without Metallic Luster.

Note. — Minerals without metallic luster are transparent, although they may have such a dark color that they transmit light only through very thin edges. The color of their powder, or their streak, is generally white or light-colored, never black (p. 228).

A.— Easily Volatile, Or Combustible.

1. Rapidly disappear when heated B. B. on charcoal. Only a few minerals behave thus. 258

B.— Fusible From 1—5, And Non-Volatile, Or Only Slowly Or

Partially Volatile.

Parti.— Give a METALLIC GLOBULE on charcoal.

1. Fused B. B. on charcoal with sodium carbonate give a globule of Silver (p. 118) 259

2. Fused B. B. on charcoal with sodium carbonate and charcoal dust give a globule of Lead

and a coating of Lead Oxide (p. 87) 259

3. Fused B. B. on charcoal with sodium carbonate and charcoal dust give a globule of Bismuth '

and a coating of Bismuth Oxide (p. 54) 262

OSSIFICATION. m

erttl with certainty in the group to which it belongs; hence it is evident that the ISIFICATION, should be tried with the utmost care*

I fine powder, ground in an agate mortar, can not be overestimated*

Page

4. Fused B. 8. on charcoal with sodium carbonate and charcoal dust give a globule of Anti- mony and a coating of Antimony Oxide (p. 44) 208

5. Fused B. B. on charcoal with a mixture of equal parts of sodium carbonate and borax give a globule of Copper (p. 73). The powdered mineral on charcoal, after moistening with hydrochloric acid, imparts an azure-blue color to the blowpipe flame 263

Bart JT.— Become Magnetic after Heating before the blowpipe in the

reducing flame, Iron*

1. Soluble in hydrochloric or nitric acid without perceptible residue, and without yielding gela- tinous silica upon evaporation. Mostly Sulphates, Arsenates and Phosphates. 266

2. Soluble in hydrochloric or nitric acid and yield gelatinous silica on evaporation, or are decom- posed with the separation of silica, Silicates 869

3. Insoluble in hydrochloric acid 270

$

Bart III*— Do NOT give a metallic globule, and do NOT become magnetic.

1. Give an alkaline reaction on moistened turmeric-paper after intents ignition before the blowpipe, held either in the forceps or, if very easily fusible, in a loop on platinum wire. Salts of the Alkali and Alkali-earth Metals*

a) Easily and completely soluble in water 271

b) Insoluble in water, or difficultly or only partly soluble 273

2. Soluble in hydrochloric acid, but do not yield a jelly or a residue of silica on evaporation.

ti I Mostly Arsenates, Phosphates and Borates 275

$ 3. Soluble in hydrochloric acid and yield gelatinous silica on evaporation. Soluble Silicates.

a) In the closed tube give water '. , 278

b) In the closed tube give little or no water 279

4. Decomposed by hydrochloric acid with the separation of silica, but without going wholly into rk solution and without giving a jelly on evaporation. Decomposable Silicates.

ji a) In the closed tube give water 981

b) In the closed tube give little or no water 283

5. Insoluble in hydrochloric acid. Mostly Insoluble Silicates 283

C— Infusible, Or Fusible Above 5.

1. Give an alkaline reaction on moistened turmeric-paper after intense ignition before the blow-

pipe. Salts of the Alkali-earth Metals 289

2. Soluble in hydrochloric acid, bat do not yield a jelly or a residue of silica on evaporation.

Mostly Carbonates, Sulphates, Oxides, Hydroxides and Phosphates 290

3. Soluble in hydrochloric acid and yield gelatinous silica on evaporation. Soluble Silicates. 294

4. Decomposed by hydrochloric acid with the separation of silica, but without going wholly into

solution and without giving a jelly on evaporation. Decomposable Silicates 295

5. Insoluble in hydrochloric acid.

a) Hardness less than that of glass or steel Can be scratched by a knife 296

b) Hardness equal to or greater than that of glass. Can not be scratched by a knife. 298

If

(Page 246.)

I. Mineeals With Metallic Or Sub-Metallio Luster.

A.— Fusible from 1-6, or Easily Volatile. Division 1.— Arsenic Compounds, in part.

L Minerals With Metallk

A.— Fusible from 1—

Division 1.— Arsenic Compounds. — When heated before the blowpipe on charcoal, a whit of arsenic is often obtained, p. 48. Of other reactions for arsenic, roasting in the open tube is especi

N. B.— The minerals in this division are chiefly

General Characters.

Specific Characters.

Name of Species.

B. B. volatile without fusion.

In the closed tube gives a sublimate of arsenic.

Arienic

B. B. on charcoal fuses, and gives a white coating of oxide of antimony.

In the closed tube gives a sublimate of arsenic, leaving a fused globule of antimony.

Allemontite.

Contain lead.— With NaCOi on charcoal give globules of lead and a coating of lead oxide.

Distinguished by crystallization and specific

gravity. Sartorite decrepitates strongly.

Sartorlte.

Dufrenoyslte.

Oxidized by concentrated HKOa with the separation of

Guitermanite.

lead sulphate.

Jord&nite.

Contains .— With Na,CO, on charcoal in 0. F., gives a globule of silver.

The dilute HNOt solution assumes a blue color when- treated with ammonia in excess (copper).

r*earoeife. $ee polybasite, p. 260.

Contain copper and tulphur. — Roasted on charcoal, then moistened with HC1 and again ignited, give a blue or green flame. The HNO, solution is rendered blue by addition of ammonia in excess. When

In the HNOt solution, ammonia produces a rather abundant precipitate ot ferric hydroxide.

Epigenite.

Contain little or no iron. Distinguished by

physical properties. Enargite is easily cleavable, the others are not

Enargite.

Tenaantife. See tetrahedrite, p.

roasted in an open tube the odor of sulphur dioxide is

Binnite.

evolved.

Lautite.

Distinguished by physical properties. All ex- hibit a brownish tarnish on exposed surfaces.

DomeyUte.

Contain copper, reactions as above, but no sulphur.

Algodonite.

Whltneyite.

With potassium iodide and sulphur, on char- coal, give the reaction for biemuth, p. 55, § 2. Distinguished by differences in crystallization.

Alloclaslte.

Contain cobalt. — Give to the borax bead a sapphire - blue color. The concentrated HNOt

Bismutoamajtlte.

Give a sublimate of arsenic in the closed tube,

and contain little or no sulphur. fgf* Compare Chloanthite, p. 247, which often

contains sufficient cobalt to give a blue color to

the borax bend.

Smaltite.

solution generally shows a del- icate rose color, thus distin-

8afflorite.

guishing the cobalt from the nickel minerals on the next

Skutterudite.

Give reactions for both sulphur and arsenic in the open tube. In the closed tube a sublimate of arsenic is not formed except upon intense ignition.

CobaHite.

Glaaeodot.

Division 1. — Arsenic Co in pounds. — Concluded on next page.

' Or Sub-Metallic Luster

or Easily Volatile.

coating of arsenious oxide deposits at a considerable distance from the assay, and a garlic-like odor illy recommended, and, in some cases, heating in the closed tube gives decisive results.

tie arsenide* and sulpharsenUes of Vie metals, p. 47.

Composition.

Color.

Streak.

Cleavage and Fracture.

Hard- ness.

Specific Gravity.

Fusi- bility.

Crystalli- zation .

As.

Tin-white. Tar. dark gray.

Gray.

G. Basal, per.

Vol.

Hex. Kb. U. gran.

As with 8b.

Tin-white. Tar. gray.

Gray.

C. Basal, per.

Hex. Rh. U. gran.

PbS.AssSs.

Lead-gray.

Dark brown to black.

C. Basal,

F. Conchoidal.

Orthorli.

2PbS.As.St.

Blackish-gray.

Dark-brown to black.

C. Basal, per.

Monocl.

3PbS.As,8.?

Bluish-gray.

Black.

F. Uneven.

Massive.

4PbS.As,S.

Blackish-gray.

Black.

C. Pinacoidal. F. Uneven.

Monocl.

9(Ag,cu).S.As,8,.

So iso. w. As.

Black.

Black.

F. Conchoidal.

Monocl.

4Cu,8.8FeS.As.S?

Steel-gray.

Black.

F. Uneven.

2?

Ortborh.

3CutaAs.Si.

Grayish-black

Gray-black.

C. Prism., per. F. Uneven.

Ortborh. U. cryst.

4Cu,S.As,S. Agt,Zn, and Fe too. w. Cut; 8b iso. w. As.

Blackish-gray.

Black to deep cherry-red.

F. Uneven.

Isom. Tet. Cryst. A Mass.

3Cu,8.2As,S..

Iron-black.

Black.

F. Conchoidal.

1.5?

Isometric.

CuAsS.

Iron-black.

Black.

C. not distinct.

1.5?

Prismatic.

CuiAs.

Steel-gray.

Gray.

F. Uneven.

Massive.

Cu#As.

Steel-gray.

Gray.

F. Uneven.

Massive.

CugAs.

Silver-white.

Silver-white.

Malleable. F. Hackly.

Massive.

Co(As,Bi)S.

Fe. too. w. Co.

Steel-gray.

Black.

C. Prism., per. F. Uneven .

2?

Ortborh. U. Colum.

Do(As,Bi)..

Tin-white.

Black.

2?

Isometric.

Fe and Ni Iso. w. Co.

Tin -white.

Black.

C. Octahedral. F. Uneven.

Isom.Pyr.

Tiu-white. Tar. dark-gray

Tin-white to lead -gray.

Black.

C. Pinacoidal. F. Uneven.

6.fr-7.3

Ortborh.

Black.

F. Uneven.

Isom.Pyr.

?oAsS.

Tin-white,with reddish tone.

Black.

C. Cubic. F. Uneven.

Isom.Pyr

Co,Fe)As8.

Grayish-white.

Black.

C. Basal. F. Uneven.

Ortborh.

(Page 247.)

I. Minerals With Metallic Or Sub-Metallic Luster,

A.— Fusible from 1-5, or Easily Volatile.

Division 1.— Arsenic Compounds, concluded. Division 2.— Selenium Compouuds, in part.

I. Minerals With Metall1

A.— Fusible from Division 1.— Arseni

General Characters.

Specific Characters.

Name of Species.

Contain nickel.— Impart to the borax bead a reddish-brown color. Give apple - green- colored solutions when dis- solved in HNO3, which be- come blue when diluted and

Give a sublimate of arsenic in the closed tube, and contain little or no sulphur.

Chloanthite.

Rammelsbergite.

On intense ignition in the closed tube gives a I slight sublimate of arsenic. 't3T Compare Breithauptite, p. 250.

Niooolite.

(Copper Nickel.)

treated with ammonia in ex- cess. (This reaction for nickel must not be confounded with the more intense blue which is

Gives reactions for both sulphur and arsenic in the open tube, but contaius no antimony. In the closed tube a sublimate of arsenic is not formed except upon intense ignition.

Qersdorfite.

produced when solutions con- taining copper are similarly treated. )

Give reactions for sulphur, antimony, and arsenic in the open tube.

Corynite.

Wolfachite.

Contain iron. — B. B. fuse to strongly magnetic globulps. The dilute HNO, solution,

Gives reactions for both arsenic and sulphur in the open tube. Gives an abundant sublimate of arsenic in the closed tube.

Ar8Enopvrite.

(Mtopickel.)

when treated with ammonia in excess, yields a reddish-browu

Contains no, or only a trace of, sulphur. Massive varieties can be identified with certainty only by means of a quantitative chemical analysis.

Lfflllngite.

precipitate of baste ferric ar- senate.

Leucopyrite.

Contains platinum. — Roasted in the open tube, at first very gently, a platinum spouge is left, which is insoluble in any single acid. Fuses readily to a globule when heated rapidly on charcoal. Test for platinum as directed on p. 103.

8 perry lite.

Division 2. — Selenium Compounds. — When heated before the blowpipe on charcoal, tfr azure- blue, p. 107.

N.B. — The minerals in this division are mostly the selenid

Contains tellurium. — B. B. wholly volatile.

Contain mercury. — Heated in the closed tube with Na9CO,, give

In the open tube a sublimate of TeO is formed, which fuses to colorless drops.

Fused with NaaCO on charcoal, gives globules of lead and a coating of lead oxide. metallic mercury (p. 94). Heat- Gi ve8 8uip/iur dioxide when heated in the open ed alone in the closed tube,) tube, give a metallic-gray sublimate

of mercuric selenide. B. B. Contains no, or only a trace of, sulphur, wholly volatile.

When heated alone, B. B. colors the tiame green (thallium).

Contain copper.— Fuse B. B. to Th? HNO, solution gives with HC1 a white pre-

Selen-tellurium.

Lehrbachite.

Onofrlte.

Tiemannite.

Crookesite.

globules which, after moisten injr with HC1, color the flame azure blue. The HNO* solu- tion is rendered deep-blue by addition of ammonia in excess.

cipitate of silver chloride.

The HNO, solution gives with H9SO a precipi- tate of lead sulphate.

Contain only selenium and copper.

Eucairite.

Zorgite.

Berxelianite.

Umangite.

Division 2.— Selenium Compounds.— Concluded on next page.

J Or Sub-Metallic Luster.

L— 5, or Easily Volatile. 1 Compounds. — Concluded.

Composition.

Color.

Streak.

Cleavage and Fracture.

Hard, i) ess.

Specific Gravity.

Fusi- bility.

Crystalli- zation.

NiAsa.

Ke and Co iso. w. Ni.

Tin-white.

Black.

C. Octahedral. F. Uneven.

Isoin.Pyr.

NiAs*.

Tin-white, with reddish tinge.

Black.

C. Prismatic. F. Uneven.

Orthorb.

NiAs.

SI) and S iao. w. As.

Pale copper- red.

Brownish-

black.

F. Uneven.

Hex tig U. mass

NiAaS.

Fe and Co Iso. w. Ni.

Tin -white.

Black.

C. Cubic. F. Uneven.

Is< in.Pyr.

Ni(As.Sb)S.

Tin-white.

Black.

F. Uneven.

isometric

Ni(As,Sb)S.

Steel-gray.

Black.

C. Prismatic. F. Uneven.

Onhorh, U. col ii in

FeAsS.

Occasionally Go iso. w. Fe.

Silver-white.

Black.

C. Prismatic. . F. Uneven.

Orthorh. U. cryst. Page 208.

FeAflj.

Silver-white.

Black.

C. Basal. F. Uneven.

Orthorh.

Fe,As4.

Silver-white.

Black.

F. Uneven.

Massive.

PtAs,.

Tin-white.

Black.

F. Conchoidal

Isom Pyr.

characteristic radish-like odor of selenium is obtained, and the reducing flame is tinged a beautiful

t of the metals. None of them are of common occurrence.

Te with Se.

Blackish -gray. Black.

C. Prismatic, perfect.

Hexag. , Massive.

;Pb,IIg)Se.

Lead - gray to iron-black.

Blackish-gray.

Black.

1 Massive.

Hg(S.Se).

Black.

F. Conchoidal.

8.0 Vol. 'Massive.

HgSe.

Blackish-gray.

Black.

F. Conchoidal

Vol.

Isom.Tet. U. mas>.

Cu,Tl,Ag),Se.

Lead-gray.

Black.

F. Uneven. ' 2.5-3

Massive.

uAg Se.

Lead -gray.

Shining. 2.5

Isometric U. mass

Pb,Cu,)Se.

Lead-gray.

Black. , 2.5

1 i

Massive. U. gran

L\iaSe.

is wo. w. Cu.

Silver-white jshining. F. Uneven. 1 2 ?

Massive.

3u,8e9.

Dark cherry- red.

Black.

Massive.

(Page 248.) I. MINERALS WITH METALLIC OR SUB-METALLIC LUSTER

A.— Fusible from 1-5, or Easily Volatile.

Division 2.— Selenium Compounds, concluded. Division 3.— Tellurium Compounds.

I. Minerals With Metallk

A.-— Fusible from 1— Division 2. — Selenium

General Characters.

Contain silver. — Give a globule of silver when heated B. B. on charcoal with borax. Compare Rucavrite, p. 247.

Specific Characters.

The HNO, solution gives with H,SO a precipi- tate of lead sulphate.

Give the odor of sulphur dioxide when roasted in the open tube.

Contains lend, but does not give the reactions of the foregoing groups. — Fused with NugCOi on harcoal, gives globules of lead, and a coating of lead oxide.

Contains bismuVi. — Heated on charcoal with the potassium iodide and sulphur mixture, gives a red sublimate (p. 55, § 2).

Name of Species.

Naumannlte.

Aguilarlte.

Clausthalite.

Guanajuatite.

Division 8.— Tellurium Compounds.— If a little of the powdered mineral is treated in beautiful reddish -violet color, p. 124.

N.B.— The minerals in this division are mostly the

T2 T2 vwtKsOIvt vr<-v1n4"l

On charcoal fuses, tinges the reducing flame green, and gives a white coating near the assay.

Tellurium.

is. is. wnony volatile.

Globules of mercury are obtained by heating with Na,COs in the closed tube (p. 94).

Coloradoite.

BismuVi.

With potassium iodide and sulphur on charcoal a red sublimate is obtained (p. 55. § 2). Grun- lingite and some varieties of Tel nuly mite react for sulphur in the open tube. Tapalpite reacts for both silver and sulphur.

Tetradymite.

GrUnliDgite.

Tapalpite.

Lead.

The HN08 solution with H,S04 gives a precipi- tate of lead sulphate.

Altai te.

With NaCO* on

Nagyagite.

charcoal in R. F. yield metallic globules.

Silver. G3F" Com- pare Tapal- pite above.

Alone on charcoal in 0. F. gives a globule of silver which may contain some gold.

H twite.

Gold, usually with Silver.

Slightly sectile to brittle.

Petzite.

Distinctly cleavable. Very brittle.

8ylvanito.

Krennerite.

Uneven to conchoidal fracture. Very brittle.

Celaverite.

Contains nickel. — fJ borax bead.

'he roasted i

nineral imparts a reddish-brown color to the

Melonite.

Or Sctb-Metallic Luster.

or Easily Volatile. oni pounds. — Concluded.

Composition.

Color.

Streak.

Cleavage and Fracture.

Hard- ness.

Specific Gravity.

Fusi- bility.

Crystalliza- tion.

(Ag„Pb)8e.

Iron-black.

Black.

G. Cubic.

Isometric. U. mass.

Ag98e.AgS.

Iron-black.

Black.

F. Hackly.

Isometric.

PbSe.

Lead-gray.

Black.

C. Cubic

Isometric. U. gran.

BiaSe.

Bluish-gray.

Black.

C. Pinacoidal, perfect.

Orthorh U. col u in.

i test-tube with about 3 cc. of concentrated sulphuric acid, and gently heated, the acid assume* a

Muridee of the metals. They are of rare occurrence.

Te.

Tin-white.

Gray.

C. Prismatic, perfect.

£-2.5

Hex. Rh.

HgTe.

Iron-black.

Black.

F. Uneven.

Massive.

BijTei, more often 2Bi,Te..Bi,8,.

Tiu-white.

Gray.

C. Basal, per.

Hex. Rh.

Bi4S.Te.

Pale steel-gray

Gray.

C. Basal, per.

Hexag.

3Ag,(S,Te).

Bi9(S,Te),.

Pale steel-gray

Gray.

Sectlle.

Massive.

PbTe.

Tin-white.

Gray.

C. Cubic.

Isometric. U. mass.

Au,PbM8bTe7S,7?

Blackish-gray.

Black.

C. Pinacoidal, perfect.

Orthorh. U. fol.

Ag,Te.

Au 180. w. Ag.

Steel-gray.

Gray.

F. Uneven.

Isometric

(Ag.Au),Te.

Iron -gray.

Gray.

F. Uneven.

Massive.

AuAgTe4.

Silver-white.

Gray.

C. Pinacoidal, perfect.

Monocl.

AuTe,. with Ag ' iso. w. Au.

Silver-white.

Gray.

C. Basal, per.

Orthorh.

AuTe*, with Ag iso. w. An.

Silver-white.

Gray.

F. Uneven.

Monocl.

1) 1 Cj.

Reddish-white.

Dark-gray.

C. Basal, per.

Hexag.

) .

(Page 249.)

L Minerals With Metallic Ok Sub-Metallic Lusteb

A.— Fusible from 1-5, or Easily Volatile.

Division 4.— Antimony Compounds, in part.

/

I. Minerals With Metallic

A.— Fusible from 1—6,

Division 4. — Antimony Compounds. — When heated before the blowpipe on charcoal the< with the open tube muy also be recommended.

N. B. — Most of the minerals in this division are the sulphantimonites ofi

General Characters.

Easily and completely volatile when heated B. B. on charcoal. Do not give reactions for lead.

Contain lead.— After carefully roasting on charcoal (p. 39) the residue, when scraped up with Na*COi and fused in R. F., gives globules of metallic lead.

The iodine tests for lead (p. 89) are very decisive.

When roasted alone on charcoal are nearly or completely vol- atile.

Oxidized by concentrated nitric acid, with the separation of metantimonic acid (p. 46, § 6), lead sulphate, and usually of sulphur.

Compare Galena (p. 251), which, when roasted alone on charcoal, sometimes gives a coating resembling that of antimony (p. 88).

Specific Characters.

In the open tube yields a white, slowly volatile, crystalline sublimate of SbtOi (p. 45).

In the open tube yields SO* and for the most

gart a dense, white, non-volatile sublimate of b,0 (p. 45).

Name of Species.

Antimony.

Reacts for mercury when tube with NaCOi.

heated in the closed

Contains capper. — When decomposed by HNOg and treated with ammonia in excess, the solu- tion assumes a deep blue color.

Contains bismuth. — Fused on charcoal with potassium iodide aud sulphur gives a red sub- limate.

Contain silver. —The HNO, solution, filtered if necessary, gives with HC1 a precipitate of stiver chloride which is insoluble in hot water (differ- ence from lead chloride, p. 89, §4).

A globule of silver is obtained by continued heating on charcoal in O. F.

Cou tain tin. — When heated in O. F. on charcoal leave an infusible mass of oxide, which, when mixed with Na*CO and charcoal powder, and fused in R. F., gives a malleable metallic globule.

Contain neither copper, bismuth, tin, nor silver. — The minerals are distinguished by differences in crystallization and physical properties.

Stibnite.

(Antimony Glance.)

Lfringstonite.

Bournonito.

Kobellite.

Andorite.

Bronguiardite.

Diaphorite.

Freieslebenite.

Cvlindrite. (Kjlindrite.)

Franckeite.

Zinkenite.

Plagionite.

Warren ite.

Jametonite.

(Feather Ore.)

Semseyite.

Boulangerite.

Meneghinite.

Geocrinite.

Kilbrlckenite.

Epiboulangerite.

Division 4 —Antimony Compounds.— Continued on next page.

Or Sub-Met *Llic Luster.

U$

or Easily Volatile.

i dense white coating of oxide of antimony deposits near the assay (p. 44). The test for antlmooy

the metal*. The sulphur may be detected by roasting in the open tube.

Composition.

Color.

Streak.

Cleavage and Fracture.

Hard- ness.

Specific Gravity.

Fusi- bility.

Crystalli- zation,

8b.

Tin-white.

Gray.

C. Basal, per.

Hex. Rli. U. gran.

Sb,S,

Lead-gray.

Gray-black.

C. Pinacoidal, perfect.

P. Uneven.

Ortborb. Page 2U&

HgS.2Sb,S..

Lead-gray.

Reddish.

? Prismatic

2PbS.Cu,S.Sb,Si.

Steel-gray.

Black.

F. Uneven.

Orthorh. U. cryat.

2PbS.(Bi,Sb),S,.

Blackish-gray.

Black.

Massive. Prismatic.

3PbS.Ag,S.3Sb,S.

Dark steel- gray.

Black.

F. Conchoidal.

Orthorh.

PbS.Ag,S.SbtSs.

Grayish-black.

Black.

F. Uneven.

Massive.

5(Pb,Ag,)S.28b,8..

Steel-gray.

Black.

F. Uneven.

Ortborb.

5(Pb,Ag,)8.2Sb,S,.

Steel-gray.

Black.

F. Uneven.

Mouocl.

3PbS.68uS..Sb,St.

Blackish-gray.

Black.

F. Uneven.

Rolls.

jPbS.2SnSt.Sb,S,.

Blackish-gray.

Black.

C. Pinacoidal.

Tabular.

Pb8.Sb,S.

Steel-gray.

Black.

F. Uneven.

Orthorh.

)PbS.4Sb,S.

Blackish -gray.

Black.

F. Uneven.

Monocl.

5PbS.28b,St.

Blackish-gray.

Black.

Capillary.

*PbS.Sb,S,.

Blackish-gray.

Black.

C. Basal, per. F. Uneven.

Orthorh. U. CJipill.

rPbS.3Sb,88.

Gray.

Black.

C. Pyramidal.

Monocl. U. tabul.

IPbS.Sb,S,.

Bluish lead- gray.

Black.

F. Smooth.

Gran. & Compact.

PbS.Sb,S,.

Blackish-gray.

Black.

C. Pinac, per.

Ortborh. U. prism.

sPbS.SbiS,.

Lead-gray.

Black.

C. Prismatic. F. Unevon.

Ortborb. U. mass.

iPbS.Sb9S?

Lead -gray.

Black.

Massive.

:PbS.8baS..

Blackish -gray.

Black.

Ortborb.? Prismatic.

s.

(Page 250.)

I. Minerals With Metallic Ob Sub-Metallic Luster.

A.— Fusible from 1-5, or Easily Volatile. Division 4 —Antimony Compounds, concluded.

I. Minerals With Metallic

A.— Fusible from 1 Division 4.— Antimon

General Characters.

Contain silver, but do not give the foregoing reactions for lend. — After decomposing with HNOs and filtering, the solu- tion reacts for silver with HC1.

Wheu only the volatile elements, antimony and sulphur, are present with silver, a globule of the pure metal may be ob- tained by fusion and coutinued heating on charcoal in O. F. The coating of oxide of anti- mony in this case assumes a reddish to deep lilac tint (p. 114). Often, after the volatile constituents have to a large

; extent been driven away, the Addition of a little NaaCOi, or borax, assists in the formation of the silver globule.

Specific Characters.

Contain copper.— When decomposed by HNOs and treated with ammonia in excess, a deep blue solution is obtained. Compare PolybasUe, below.

Name of Species.

Stylotypite.

Contain copper, but neither lead nor silver.— The dilute HNO solution, filtered if necessary, gives a deep blue color with ammonia in excess.

Sulphantimonites of silver, containing no, or only traces of, copper. Give the odor of sul- phur dioxide when roasted in the open tube.

The crystals of Stepbanite are usually stout, six- sided prisms. Those of Polybasite six-sided plates, with triangular markings on the basal planes.

Freibergite.

(Sliver Tetrahedrite.)

Mlargyrite.

Pymroyrite. (Dark Ruby-silver.)

Reacts only for antimony and silver.

Gives globules of mercury when heated in a closed tube with dry NaCOs (p. 94, § 1).

Distinguished by differences in crystallization and physical properties.

Contains iron, but does not give the reactions of the foregoing Fuses to a strongly magnetic globule, divisions.

Contains nickel. — The roasted mineral gives with borax in O. F. a brownish bead.

React for sulphur in the open tube. With potassium iodide and sulphur give the test, for bismuth (p. 55. § 2).

Reacts for sulphur, but contains no bismuth.

Contains little or no sulphur. Some varieties react for arsenic.

Stephanite.

Polybasite. See pearceite, p. 246.

Polyargyrite.

Dyscrasite.

Schwatztte. (Mercurial Tetra- hedrite.)

Chalcostibite. (Wolfebergite.)

Falkenhaynite.

Tetrahedrite.

(Gray Copper.)

Famatinite.

Berthierite.

Kallilite.

Haucbecoroite.

UUmannite.

Breithauptlte.

J Or Sub-Metallic Luster.

—5, or Easily Volatile. y Compounds. — Concluded.

Composition.

Color.

Streak.

Cleavage and Fracture.

Hard- ness.

Specific Gravity.

Fusi- bility.

Crystalli- zation.

3(Cut,Ag„Fe)8.

SbtSt-

Iron-black.

Black.

P. Uneven.

Orthorh.

KCu,Ag),S.Sb.8..

Pe and Zn iso. w. Out.

Gray.

Black.

F. Uneven.

Isom. Tet. Page 175.

A.g,S.Sb,St.

Iron-black.

Dark - red to black.

F. Uneven.

Monocl.

3Ag.S.Sb,Ss.

Deep - red to

black.

Indian -red.

0. Rhomboh. F. Conchoidal.

Hex. Rh. Hemimor.

CMS, p. 319.

>Ag,S.Sb,8t.

Iron-black.

Black.

F. Uneven.

Orthorh.

Ag,Cu),8.8b83. is iso. w. Sb.

Iron-black.

Black.

F. Uneven.

Monocl.

l2Ag,S.Sb,St.

Iron-black.

Black.

C. Cubic.

Isometric.

A.gSb.

Silver-gray. Tar. black.

Gray.

C. Basal.

Orthorh.

4(Cu,,Hg)S.8b,S.. Fe and Zn iso. w. Cu.

Dark-gray.

Black.

F. Uneven.

Isom. Tet. Pnge 175.

Cu,S.8btSs.

Blackish-gray.

Black.

C. Basal, per.

a-4

Orthorh.

)Cu,S.SbaSt.

Grayish-black

Black.

Massive.

4CuaS.Sb,8..

FV,Zn,Pb and Ag, iso. w. Cn,; As iso. w. Sb.

Gray.

Black.

F. Uneven.

Isom. Tet. Page 175.

iCu2S.Sb9S6.

Gray, with reddish tone.

Black.

F. Uneven.

Orthorh.

FcS.Sb,S,.

Steel-gray.

Black.

C. Longitudi- nal.

Prismatic. Fibrous.

Ni(Sb,Bi)S.

Light bluish- gray.

Black.

Massive.

Ni(Bi,Sb,S).

Bronze-yellow

Black.

Tetrag. U. mass.

XiSbS.

Silver-gray.

Black.

C. Cubic, per.

6.&-6.7

Isometric. C1.5.p.l20

XiSb.

As iso. w. Sb.

Copper- red, violet tone.

F. Uneven.

Hexag.

(Page 251.)

1. Minerals With Metallic Or Sub Metallic Luster.

A.— Fusible from 1-5, or Easily Volatile. Division 5.— Sulphide*, in part.

I. Minerals With Metallic

A.— Fusible from 1—

Division 5.— Sulphides.— When roasted in the open tube sulphur dioxide (sulphurous an by a piece of moistened litmus-paper placed in the upper end of the tube. The reactions of the force<

N.B. — The minerals in this division are mostly sulphides of the metals. Sulphides containing will be met with later on among the minerals without metallic luster.

General Characters.

Contain only silver and sulphur. — When fused ulone on char- coal in O. F. a globule of pure silver is obtained.

Specific Characters.

Sectile, can be cut with a knife like lead.

Name of Species.

Argentite.

Acauthite.

Reacts only for sulphur and bismuth.

Contain ttsmutfi. — Mixed with potassium iodide and sulphur, and fused on charcoal in O. F. a red sublimate is obtained (p. 55, § 2).

When lead is present, the yellow coating of lead iodide may ob scure the foregoing reaction for bismuth. In order to make decisive tests for the two ele ments it is recommended to proceed as follows: Treat an ivory-spoonful of the powder- ed mineral in a test-tube with 8 cc. of HNOs and 1 cc. of concentrated HsS04 , and boil until the nitric acid is expelled. After cooling, add 5 cc. of water, boil for about a minute in order to dissolve the bismuth sulphate, and filter on* the in- soluble lead sulphate. This may be tested by fusing with Na*COs on charcoal. In the filtrate precipitate the bismuth as hydroxide with ammonia, filter, and test some of it by fusing on charcoal with the potassium iodide and sulphur mixture. If copper is present the ammoniacal filtrate from the bismuth will be blue.

Contains lead, but no bismuth. — With Na3C08 on charcoal gives globules of lead and a yellow coating of lead oxide.

Contain lead and silver.— Decompose with HNOs, dilute with water, and filter. In the filtrate HC1 will produce a precipitate of silver chlo- ride which is insoluble in boiling water.

Bismuth in ite.

(Bismuth Glance.)

Schirmerite.

Contain lead, and not more than traces of silver. — Aikenite is characterized by containing cop- per, otherwise it may not be possible to identify the rare minerals in this group without a quan titative chemical analysis.

Contain copper. — When decomposed by nitric acid, the dilute solution is rendered blue by the addition of ammonia in excess.

Schapbachite.

ChiTiatite.

Rezbanyite.

Galenobiamutite.

Cosalite.

AJkinite.

Lillianite.

Beegerite.

Cuprobismu tite.

Empiectite.

Contains silver, but neither lead nor copper. — Gives a globule of silver when fused with borax and Na9COs on charcoal.

Oxidized by concentrated nitric acid with the separation of lead sulphate and usually, also, of some sulphur.

Compare Cylindrite and JFranekeite (p. 250), which do not give very distinct antimony reactions.

Klaprotholite.

Wittichenite.

Matildlte.

Galena.

Division 5.— Sulphides.— Continued on next page.

Or Sub-Metallic Luster.

., or Easily Volatile.

ride) is formed, which may be recognized by its odor, and by the acid reaction which it imparts to og divisions should not be obtained.

-senic, antimony, selenium, and tellurium will be found in the foregoing divisions. A few sulphides

Composition.

Color.

Streak.

Cleavage and Fracture.

Hard- ness.

Bpeciflc Oravity.

Fusi- bility.

Crystalli- sation.

Ag.S.

Blackish-gray.

Blackish- gray.

F. Conchoidal.

Isometric.

AgsS.

Iron-black.

Black.

F. Uueveu.

Orthorh.

Bi,S,.

Lead-gray.

Gray.

C. Pinacoidal, perfect

Orthorh Prismatic.

3(Ag,,Pb)8.2Bi,S,.

Lead-gray.

Grayish-black.

F. Uneven.

1-1.5?

Massive.

PbS.Ag,S.Bi,S,.

Lead-gray.

Grayish-black.

0. Basal.

1-1.5?

Orthorh. ?

2Pb8.3Bi,8,.

Lend -gray.

Grayish-black.

C. Distinct.

1-1.5?

Foliated.

lPl>S.5Bi,S,.

Light lead- gray.

Grayish-black.

F. Uneven.

1-1.5?

Massive.

PbS.Bi,8,.

Lead-gray.

Grayish-black.

1-1.5?

Columnar

3PbS.Bi,S. *K.Ciii & Feiso.w.Pb.

Lead-gray.

Grayish-black.

F. Uneven.

Orthorh. U. mass.

*(Pb,Cu.)S.Bi,S,.

Blackish lead-

Grayish- black.

F. Uneven.

Orthorh. Acicular.

JPbS.Bi,8i. \e, too. w. Pb; Sb Iso. w. Bi.

Steel-gray.

Grayish-black.

1-1.5?

Massive.

5PbS.Bi,S.. \uri i-*o. w. Pb.

Gray.

Grayish-black.

C. Cubic?

1-1.5?

Isometric?

)CutS.4Bi,Ss. is.-*, w. Cn

Bluish-black.

Black.

blender prism 8.

0/ 11 a5. lilaiSs.

Grayish-white.

Black.

C. Pinacoidal, perfect.

Orthorh.

*CuaS.2Bi,S3.

Si eel-gray.

Black.

F. Uneven.

4.6?

Orthorh.

3C:i.S.Bi,8s.

Grayish -white.

Black.

F. Conchoidal.

Orthorh.

YgsS.BiaS*.

Gray.

Gray.

2-8?

1-1.5?

Slender prisms.

Lead-gray.

Grayish-black.

C. Cubic, per.

Isometric, U. cryst. or gran.

(Page 252.)

I. Minerals With Metallic Or Sub-Metallic Luster.

A.— Fusible from 1-6, or Easily Volatile. Division 5.— Sulphides, continued.*

?52

I. Minerals With Metalli

A.— Fusible from Division 5. — Si

General Characters.

- 0.2 3 O

S.-S

as

-§3*gg£J!

O

Couttiin tr<w, and fuse to magnetic globules. — From the HN03 solu- tion ammo- nia precipi- tates ferric hydroxide.

Contain cobalt.

Specific Characters.

Color brass-yellow. — When massive, Cubanite can scarcely be told from Cbalcopyrite except by a quantitative chemical analysis.

Color pur,.li>li, and somewhat variegated on ex- posed surfaces, but brownish-bronze on a fresh fracture.

Compare Chalircite below, which at times contains sufficient iron as an impurity to make it magnetic after, heating.

Fused alone on charcoal the coal near the assay becomes covered with a white coating of oxide of tiu. Only slightly magnetic after heatingB.B.

Contain neither iron nor cobalt. Do not fuse to magnetic glob- ules.

Comp. Sftan- nite above, which does not become mag- netic except af- ter long heating B. B.

a $

u

a

o 0 am

a o bo,s

b bog e

3'2"H

it

Contains rifoer

Contains co6ai<. — The roasted mineral colore the borax bead blue.

Contain nickel. —The roasted mineral color* the borax bead in O. F., violet when hot and reddish - brown when cold.

The roasted minerals impart a blue color to the fluxes.

From the HNOB solution tilver chloride is precip- itated by the addition of HC1.

The finely powdered mineral, after careful roasting on charcoal (p. 40), gives in R. F. a globule of copper. Gives no sulphur in the closed tube.

Reacts like the foregoing, except that much sul- phur is obtained by heating in the closed tube.

Name of Species.

Chalcopyrite.

(Copper Pyrites.)

Cubanite.

Bornite.

( VariegatedCopper Peacock Ore.)

Stennite. (Tin Pyrites.)

Carrollite.

Sychnodymite.

Stromeyerite.

Chalcocite.

(Copper Glance.)

Fused with borax on charcoal in O. F. gives a globule of silver.

Gives sulphur in the closed tube when heated in- tensely. Usually reacts for nickel when fused with borax on charcoal (p. 98).

Give sulphur when heated intensely in the closed tube. Millerite occurs usually in capillary crystals, sometimes in velvety incrustations.

Contains zinc— Test as directed on p. 181 (Fig.

m.

Contain only iron and sul phur.

In the HNO solution ammonia produces an abundant precipitate of ferric hydroxide.

After heating B. B., and volatilizing some of the zinc, the residue is slightly fusible and mag- netic. Luster sub-metallic.

Give little or no sulphur in the closed tube. Usually slightly magnetic before heating, but sometimes scarcely at all so. Troilite is found only in meteorites.

Covellite.

Sternbergite.

Linnstite.

Millerite.

Polydymite.

Pntfandite.

Sphalerite.

(Zinc Blende,Blacl Jack.)

Pyrrhotite.

(Magnetic Pyrites. Sometimes nicke Ferous.

Troilite.

Give much k ilphur in the closed tube. Are not magnetic l>efore heating. Pjrrite dissolves completely when 3 ivory-spoonfuls of its very fine powder arc treated in a test-tube with 3 cc. of concentrated HNOSf allowed to stand until vigorous action ceases, and then boiled. Mar casite when similarly treated yields some sep- arated sulphur.*

Pyrite.

(Iron Pyrites.)

MAR CASITE. (White Iron tes.)

Pyri

The nitric acid for this experiment should be strong enough to act upon powdered p

Division 6.— Sulphides.— Coucluded on next page.

Or Sub-Metallic Luster.

-6, or Easily Volatile. riiides. — Coutinued.

Composition.

Color.

Streak.

Cleavage and Fracture.

Hard- nesH.

Specific Gravity.

FlIRi-

bility.

CrvRtalH-

uFeS9.

Brass-yellow.

Greeuish-

.

F. Uneven.

Tet 8ph. Pnpre 188.

uFe84.

Brouze to brass-yellow.

Black.

C. Cubic, in traces.

Isometric.

Brownish- bronze.

Purplish

tarnish.

Grayish-black.

F. Uneven.

Isometric. U. mass.

a,S.Fe8.8nS- i i8o. w. Fe.

Steel-gray.

Black.

F. Uneven.

Massive.

uCoaS4.

Light steel- gray.

Grayish-black

F. Uneven.

Isometric. U. mass.

:u,Co)Si.

Steel-gray.

Isometric.

uAgS.

Dark steel- gray.

Dark-gray.

F. Uneven.

Orthorh. U. mass.

t

Steel-gray. Blackish tarnish.

Dark-gray.

F. Uneven.

Orthorh. Page 208. U. mass.

u8.

Indigo-blue.

Grayish-black.

C. Basal, per.

Hexag. U. mass.

gFe.S,.

Brownish- bronze.

Black.

C. Basal, per.

Orthorh.

'0,Ni)tS4.

and Cu iso. w. Co.

Pale steel- gray.

Grayish-black.

F. Uneven.

Isometric.

Figs. 96

and 100.

Is.

Brass-yellow.

Black, some- what greenish

C. Rhoinboh. F. Uneven.

Hex. Rh.

Light- to

steel-gray.

Grayish-black.

F. Uneven.

Isometric.

"'Fe)S* bronze.

Black.

Parting, oct. F. Uneven.

Isometric.

i),Fe)S.

e pages 7 and 8.

Dark-brown to coal-black.

Light to dark - brown.

C. Dodecahe- dral, per.

Isom. Tet. Page 175.

!iiSii,perhapsFeS iso. w. Fe. Test (p.

n, i 4).

Brownish- bronze.

Black.

Parting, basal. F. Uneven.

Hexag. Page 188. U. mass.

;8.

Brownish- bronze.

Black.

F. Uneven.

Massive.

Pale brass- yellow.

Black, some- what brownish.

F. Uneven.

Isom.Pyr. Page 178. U. cryst

s,.

Pale-yellow to almost white. Yellowish

tarnish.

Black, some- what grayish.

F. Uneven.

Onhorh Tabular, pyram., prismatic.

i energetically, and decompose it completely, even without the application of heat.

(Page 253.)

I. Minerals With Metallic Or Sub-Metallic Luster.

A.— Fusible from 1-5, or Easily Volatile.

Division 5.— Sulphides, concluded. Division &

I. MINERALS WITH METALLl

A.— Fusible from 1- Di vision 5. — Sul

General Characters.

Specific Characters.

Name of Species.

Contain manganese. — The roust- ed mineral imp'irts a reddish- violet color lo the borax bead In 0. P.

Gives little or no sulphur in the closed tube.

Atabandit*.

Gives abiiudunt sulphur in the closed tube.

Hauerite.

Cumulus mercury.— Gives glob- ules of the metal when heated i.i u closed lube with NaC0.

in the closed tube volatile, and gives a black

sublimate of HpS. Compare (Jin unfair 'r> 258).

Metacinuabarite.

Coninina germanium. — When ro of germanium oxide collect nc coating collects which has a

Contains tin. — When fused on ct covered with a coating of oxidi may also be obtained.

asted on charcoal, transparent and white globules jar the assay, while farther out a lemon-yellow iculiar glazed (fused) surlace.

Argyrodite.

tarcoal the globule and the coal near it become e of tin, while a slight reaction for germanium

Canfieldite.

D i vision 6. — Not belong!

.a — bo

is

in

cs

s£

e E J 0) jj

%- a

(A —

'.2

K °

Soluble In boiling, dilute HNO, (1 part HNO. : 2 parts of water).

Insoluble in nitric acid.

t- bo

B

§ 5 bo

CD Ij

53aSL.fi 3S 5 6 i2

Anhydrous. — Give little or no water in the closed tube.

tW Compare LudwigiU (p.

I Hydrous. — Give water in the closed tune.

After fusing on charcoal the metal is bright, and no conspicuous coating of oxide is formed on the coal. From the HNO, solution HC1 precipi- tates silver chloride. Compare Amalgam.

The HNO, solution is made deep-blue by addi- tion of ammonia in excess.

Easily fusible, and five yellow coatings of oxide on charcoal. When heated with potassium iodide and sujpbur on charcoal, lend gives a greenish-yellow and bismuth a brilliant red sublimate. Bismuth is brittle.

B. B. on charcoal gives a coating of zinc oxide.

Healed in tho closed tube globules of mercury are obtained. Mercury is wholly volatile, and amalgam leaves a residue of silver.

Characterized by its color and high specific gravity.

Paler color than gold, and of lower specific gravity.

Oxidized by HNOs yieldiug a white residue of meta stannic acid (p. 126).

Strongly magnetic before beating. "Compare Titanic Iron (p. 2A5).

Characterized by its reddish - brown streak. Slightly or not at all magnetic before heating.

Silver.

Copper.

Lead.

Bismuth.

Zinc.

Mercury.

Amalgam.

Gold.

Electrum.

Tin.

Magnetite.

(Magnetic Iron.)

Hematite.

(Specular Iron.)

Imparts a green color to the NasCO bead in O. F. {manganese).

Bixbyite.

Gives globules of lend when fused with Na9COs on charcoal.

Difficultly fusible. Turgite generally decrepi- tates, and breaks up to a fine powder in the closed tube. Gothite generally crystallizes in prismatic forms.

Melanotekite.

Turgite.

(Hydro-hematite.

Goethite.

Limonite.

(Brown Hematite

Hi vision 6.— Concluded on next page.

l OR SUB-METALLIC LUSTER. 5, or Easily Volatile, hides. — Concluded.

Composition.

Color.

Streak.

Cleavage and Fracture.

Hard- ness.

Specific Gravity.

Fusi- bility.

Crystalli- zation.

MnS.

Iron-black. Brown turnisU.

Olive-green.

C. Cubic, per.

Isoni. Tel. Cryst rare

MnS,.

Brown lo brownish- black.

Reddish- brown.

F. Uneven.

Isold. Pyr. U. octahe- drons.

HgS.

Grayish-black.

.

F. Uneven.

Vol.1. 5

Isom. Tet.

4Ag,S.Ge8f. Hg iw>- w. Ag & So w. Ge.

with bluish tone.

Grayish-black.

F. Uneven.

Isometric. U. mass.

4Ag,S.(Sn,Ge)S9.

Black wiih bluish tone.*

Grayish-black.

F. Uneven,

Isometric.

% to the foregoing divisions.

Ag.

Occasionally with Au, Cu, and Hg.

Silver-white. Tarnish gray to black.

Silver-white, shiny.

F. Hackly.

Isometric. U. mass., aciculuror in plates.

Cu.

Copper-red. Tarnish black.

Copper-red, shiuy.

F. Hackly.

Isometric. U. mass.

Pb.

Lead-gray.

Lead-gray, shiuy.

F. Hackly.

Isometric.

Bi.

Silver-white.

Silver- white, shiny.

C. Basal and rhombohe- dral, per.

Hex. Rh. U. gran.

Zn.

Grayish-white.

Grayish-white, shiuy.

C. Basal, per.

Hex. Rh.

Hg.

Tin-white.

Liquid.

Hg with Ag.

Silver- white.

Silver- white, shiny.

F. Uneven.

Isometric.

Au, always with some Ag.

Gold-yellow.

Gold-yellow, shiny.

F. Hackly.

when pure.

Isometric. U. mass.

A.u with much Ag.

Yellowish-

white.

Yellowish- white, shiny.

F. Hackly. 2.5h-3

Isometric.

8n.

Tin-white.

Tin-white, shinv.

F. Hackly. ! 2

FesO*

FeO + Fe,09.

Iron-black.

Black.

F. Uneven. ' A - 1Q Parting oct. ° ' 5*18

Isometric.

Fe,0,.

Dark steel- gray to iron- black.

Dark reddish- brown, Indian- red.

F. Uueven.

Parting rhom- 5.5-6.5 5.20 bohedral. '

Hex. Rh. Page 194.

FeMnOs

FeO.MnO,.

Black.

Black.

F. Uneven. 6-6.5

Isometric.

Fe"/40,)Pb,(Si04)3

Dark brown to: Yellowish - black. 1 brown.

F. Uneven. 5-5.5

Orthorh. Prismatic.

2Fe,0, + H,0.

Reddish-black

Dark reddish- brown.

F. Splintery.

Botryoid. Incrust.

FeO(OH)

2Fe,Os + 2H.O.

Dark-brown to black.

Yellowish -

brown.

C. Pinac, per.

Orthorh.

Fe40,(OH). 2FeaO, + 8H.O.

Dark- brown to black.

Yellowish -

brown.

F. Splintery. ' 5-5.5

Botryoid. Stalnotitic

(Page 254.) I. MINERALS WITH METALLIC OR SUB-METALLIC LUSTER.

A.— Fusible from 1-5, or Easily Volatile. Division 6, concluded.

I. Minerals With Metal.L

A.— Fusible from 1-

Division 6

General Characters.

Silicates. — Ilvaite and Allauite are decomposed by- HC1, and yield gelatinous silica upon evaporation. Neptunite is in- soluble iu HC1, but may be tested for n silicate ub directed ou p. 110. §4.

N.B. — These silicates have n pitchy or resinous luster, and they, as. well as others which are black owing to the presence of iron, are more properly classified in subsequent sec- tions under minerals uitfiout metallic luster.

Compare Melanotekite, Ken- trolite. aud Braunite, of (his division.

Contain' tungsten. — Fuse with NaCO, pulverize the fusion, digest with boiliug water, and filter. The filtrate made acid with HC1 and boiled with tin assumes a blue color (p. 129,

The high specific gravity is

noticeable.

Contain niobium.— Fused with borax, then dissolved in HC1 and boiled with tin, the solu- tion assumes a blue color (p.

99.81)- The high specific gravity is

noticeable.

Specific Characters.

Intumesce8 slightly when fused B. B. The globule is decidedly magnetic.

Intuniesees strongly when fused B. B. The globule is sometimes magnetic. Gives reactions for the rare- earth metals (p. 05).

Fuses B. B. to n black globule and colors the flame yellow. Reacts for titanium when tested as directed on p. 127, § 2.

Imparts to the Na*CO, bead in O. F. a green color {manganese). Fused on charcoal with a little NaaCO yields a magnetic mass.

Contains little or no manganese. Fusible B. B. to a magnetic mass.

Reacts for iron and usually also for manganese when tested as directed above for wolframite.

React for uranium and the rare-earth metals when tested as directed on p. 129, § 2, and p.

Characterized by its sub-metallic luster and red streak (see p. 263).

Contain copper. — B. B. alone, or with Na*COs, on charcoal, give a globule of copper. After

moistening with HC1 impart Tenorite crystallizes in scales; paramelaconite iu azure-blue aud green colors to prisms the blowpipe flame (p. 72, § 1).

When liea ted in the closed tube yields fusible

Contains lead. — With Na9C08 onj lead oxide and oxygen gas. Test as directed on

charcoal gives globules of the' p. 100. § 1.

metal and a coating of lead ,-,..., , , ,

oxi(je Imparts a reddish -violet color to the borax bead

in O. F. (manganese). Compare Melanotekite.

The tine powder is slowly soluble in HCl.

Contaiu manganese, but do not Yields a small amount of gelatinous silica on give the reactions of the fore-j evaporation.

4 going sections. — Impart to the<

borax bead in 0. F. a reddish- Gives a slight coating of oxide of antimony when violet color. i heated with NuaCOi ou charcoal.

Name of Species.

Ilvaite.

(Lievrite )

Allanite.

Neptunite.

Wolframite.

Compare hubner He, p. 888.

Wolframite, in part.

Reinite.

Columbite.

Samarskite.

AannerOdite. (OnnerOdite.)

Cuprite.

Tenorite. (Melaconite.)

Paramelaconite.

Piatt nente.

Kentrolite.

Braunite.

Laaoffbanite. (Loiifrbauite.)

C Or Sub-Metallic Luster.

5, or Easily Volatile.

—Concluded.

Composition.

CaFe"9(Fe'".OH) (SiO)9.

R"a(R".OH)R'".

(SiO),.

R"=Ca and Fe. R'"=A1. Fe, Ce, La, and Di.

Color.

(Na,K)(Fe,Mn) I TiSi40„.

(FefMn)W04.

,FeW04.

Iron-black.

Brown to pitch-black.

Black.

Black.

Black.

Fe\V04.

i(Fe,Mn)(Nb,Ta),0..

iR",R'",(Nb.Ta).Oai

R" Fe, Ca,UO,; R"=Wand Y earths.

'Uncertain. Nb, U, Y. Th, Ce, Pb, Fe, Ca, H, O.

Blackish- brown.

Iron-black.

Streak.

Black.

Gray.

Cleavage and Fracture.

F. Uneven.

Hard- nera.

F. Uneven to conchoid al.

Cinnamon-

brown.

Black.

Black.

Brown.

Velvet-black.

Cu,0.

CuO.

CuO?

PbOa.

(Mn"'403)Pb8

(SiO),.

MnMnOj with a little MnSiOi.

Black.

Deep-red.

Steel- to iron- gray.

Purplish- to pitch-black.

Iron-black.

Black.

Black.

Dark reddish- brown.

Brown to blackish

brown.

Brownish-red, Indian -red.

Grayish-black.

C. Prismatic. F. Conchoidal.

C. Pinac., per. F. Uneven.

C. Pinac, per.

F. Uneven.

F. Uneven.

F. Conchoidal.

F. Uneven.

F. Conchoidal or uneven.

C. Basal, per. F. Uneven.

F. Uneven.

Chestnut- brown.

Brown.

F. Uneven.

Sh-6

a-4

F. Uneven.

Black.

Brownish- ;C Pyramidal, black. F. Uneven.

Uncertain. Mi), Fe, Si, and Sb Iron-black, oxides.

Dark reddish- brown.

:F. Uneven.

Specific Gravity.

Fusi- bility.

Crvjtnlli. zation.

Orthorh. iU. prism.

Monocl. U. mass.

Monocl.

MonocL U. cryst.

Monocl.

Tetrag.

Ortliorh. U cry st.

Orthorh. U. mass.

Orthorh.

Isometric. CU.p.219

Monocl. Massive.

Tetrag

Tetrag. U. mass.

2-2.5 Orthorh.

! Telia u

4.5-5 Fig 14:3. pa ire 17*

Hex. Rh.

b

(Page 255.) I. MINEBALS WITH METALLIC OR SUB-METALLIC LUSTEB.

B.— Invisible or Fusible above 5, and Non-volatile. Division 1.— Iron Compounds.

S55

I. Minerals With Metalli

B.— Infusible, or Fusible

Division 1.— Iron Compounds.— Strongly attracted by a magnet after being heated before

N.B. — The minerals in this division are chiefly the oxides and hydroxides of iron. Several of tb slowly. The solutions, after dilution with water, may be tested tor ferrous and ferric iron with pot

General Characters.

Strongly magnetic without heat iug. Malleable.

Compare platinum (p. 267).

Strongly magnetic without heat- ing. Brittle.

Contain 8 titanium. — After fusion with Na2CO the mateiial can be dissolved by HC1, and the solution when boiled with tin becomes violet (p. 127, § 2).

Contain manganese. — Impart to the Na,CO, bead in O. F. a green or bluish-green color.

Give water in the closed tube. Difficultly fusible. Fus.

Give little or no water in the

closed tube. Dnubreelite reacts for sulphur

when roasted in an open tube. ISfConipare Tripuhyite (p. 268).

Specific Characters.

When treated as directed on p. 97, §4, meteoric iron has always, and terrestrial irons have often, reacted for nickel.

Characterized by containing much nickel.

Very slowly attacked by HC1. Reacts for titanium (p. 127, § 2).

The fine powder is slowly, but completely, solu ble in HCl. The solution reacts for both fer- rous and ferric iron. Fus. 5-5.5.

Name of Species.

Iron. (Meteoric Iron.)

Awarulte.

ILMENITE (Titanic Iron, in part.)

Reacts for magnesium when tested as directed on p. 91, g 1. b.

Gives a coating of oxide of antimony when fused with NaiCOs on charcoal.

Distinguished by differences in crystallization and physical properties.

Gives a coating of oxide of zinc when the tery fine powder, mixed with a little NaaCO, is heated intensely on charcoal.

Gives a coating of oxide of antimony when treated as above.

Does not give the foregoing reactions.

Water about 5£. Generally decrepitates violent- ly when heated in the closed tube.

Water about 10*. Generally crystallized in prisms.

Water about 15& Mammillary and stalactitic (p. 222). Often impure. Distinct crystals un- known.

Streak brownish-red (Indian-red, red-ocher). Sometimes slightly magnetic before heating. Fus. 5-5.5.

Magnetite.

Magnesioferrite.

Derbylite.

Ilmenite.

(Titanic Iron.)

Pseudobrookite.

Franklinite.

Melanostibian.

Jacobs! te.

Turgite

(Hydro-hematite.)

Goethite.

Limonite.

(Brown Hematite.)

Hematite. „

(Specular Iron.)

Imparts a green color to the salt-of-phosphorus Daubreelite. bead {chromium). Compare Ghromite (p. 256). (Meteoric only.)

3 Or Sub-Metallic Luster.

above 6, and Non-volatile.

the blowpipe in the reducing flame (ibe test must not be made while the fragment is hot, p. 84, % 1).

are important us ores of tie meii.l. Generally they dissolve in hydrochloric acid, though often issium ferri- and ferrocyanides, as directed on p. 85, § 4.

Composition.

Color.

Streak.

Cleavage and Fracture.

Hard- ness.

Specific Gravity.

Crystalli- zation.

Fe, also Fe with Ni.

Steel-gray. Steel-gray.

C. Cubic. F. Hackly.

Isometric. U. mass.

FeNi,.

Steel-gray.

Steel-gray.

F. Hackly.

Maroive.

FeTiOs with Fe,0, in varying proportions.

Iron -black.

Black.

F. Uneven.

Hex. Kb. U. mass.

Fe,04=FeO.Fe,Ot.

Iron-black.

Black.

Parting octa- hedral. F. Uneven.

Isometric.

Figs. 96,

97 & 102.

MgFe,0=MgO.Fe,0.

Iron-black.

Black.

F. Uneven.

Isometric.

5FeTiO,.FeSb,0..

Pitch-black.

Brown.

F. Conchoidal.

Orthorh.

FeTiO,=FeO.TiO,.

Msr isp. w. Fe.

Iron-black.

Black.

F. Uneven.

Hex. Rh.

Fe4(Ti04),.

Brownish- black.

Yellowish- or reddish-brown

F. Uneven.

On horn.

(Fe,Zn,Mn)0.(Fe,Mn),0,. Fe,04 with Zn and Mn iso.w.Fe

Iron-black.

Dark-brown.

F. Uneven.

Isometric.

Figs. 96

and 102.

6(Fe,Mn)O.Sb,0.

Black.

Cherry-red.

C Two direc- tions. 90°.

Orthorh.?

(Mn,Mg)0.(Fe,Mn),0,.

Black.

Brownish- black.

F. Uneven.

Isometric.

Fe40(OH),=2Fe,0.HaO

Black to red- dish-black.

Brownish-red, Indian-red.

F. Spliutery.

Massive. Mnmmill.

FeO(OH)=2Fe,0,.2H,0.

Dark-brown to black.

Yellowish- brown, yellow-ocher.

C. Pinacoidal, perfect.

Orthorh. Prismatic

Fe40,(OH).=

2Fe.0..3HtO.

Dark-brown to nearly black.

Yellowish- brown, yellow-ocher.

F. Splintery.

Orthorh. U. fibrous.

Steel-gray to iron-black.

Brownish-red. Indian-red.

F. Uneven, scaly, fibrous.

Hex. Rh. Page 194.

FeS.Cr,S.

Black.

Black.

C. One direc.

Massive. Scaly.

'Pi

(Page 256.)

L Minerals With Metallic Ob Sub-Metallic Luster.

B.— Infusible, or Fusible above 6, and Non-volatile. Division 2. — Manganese Compounds.

Division 8, in part.

L Minebals With Metallic

B.— InfUsible, or Fusible i

Division 2.— Manganese Compounds.— A trifling quantity of tbe material will impart which manganese compounds impart to the sodium-carbonate bead in tbe oxidizing flame is also a

N.B. — The minerals in this division are chiefly oxidee of manganeu. They dissolve in hydroc heated in a closed tube (p. 100, § 1).

General Characters.

Give little or no water when heated in tbe closed tube.

Specific Characters.

Cou tains copper, and imparts to the blowpipe flame a blue or green color after moistening with HC1.

Reacts for titanium when tested as directed on p. 129, §2.

Compare 277).

Pinakiolite (p.

Give much iter when heated in i ho closed tube.

Compare AtboUU and Wad (p. 292).

Give oxygen gas when heated iu the closed tube (p. 100, § 1). Pyrolusitc is perhaps always a pseudomorph after other minerals (often after inanganite). It is soft, and contains about 2 per cent of water.

Name of Species.

Crednerire.

Pyrophanlte.

Polianite.

Do not give oxygen gas when heated in the closed tube (p. 100, § 1). Finely pulverized braunite is slowly decomposed by HC1, and the solution yields gelatinous silica upon evaporation.

The prismatic crystallization and dark-brown streak are characteristic. Compare Pyrolueite.

B. B. on charcoal gives a coating of oxide of zinc.

Does not crystallize. The HC1 solution generally gives a white precipitate of barium sulphate upon addition of H9SOi.

Pyrolusite.

BraunHa.

Hausmanntta..

Manqanite.

Chalcophanite.

P8Ilomelane.

Division 3. — Not belongii

Very soft. Readily mark paper and soil tbe fingers.

Contains chromium. — Imparts a green color to tbe borax and salt of phosphorus beads.

Heated B. B. in the forceps colors the flame yellowish-green. Roasted in the open tube gives the reactions for a sulphide and for molybdenum (p. 95).

Does not give the foregoing reactions. Very re fractory.

Chromite.

(Chromic Iron.)

Finely powdered chromite mixed with NaCO,, in equal proportions, and intensely heated on charcoal, gives a mass which is attracted by a magnet (iron). Magnesian -chromite mnv con-( tain too little iron to give the foregoing reaction. nesfan-chromlte

Molybdenite.

Graphite.

(Black Lead.)

Division 3. — Concluded on next page.

Or Sub-Metallic Luster

above 6, and Non-volatile.

to the borax bead in the oxidizing flame a reddish-violet or amethystine color. The green color ry delicate and decisive test.

iloric acid with evolution of chlorine gas (p. 101 , § 2), and many of them yield oxygen gas when

Composition.

Color.

Streak.

Cleavage and Fracture.

Hard- ness.

Specific Gravity.

Crystalli- zation.

CusMn09.

Iron-black.

Brownish- black.

C. Basal, per.

Monocl. Foliated.

MnTiO. MnO.TiO,.

Deep-red.

Ocher-yellow.

C. Rhombohe- dral, per.

Hex. Rh.

Ul. 14. p. 210.

WnOa.

Steel-gray.

Black.

0. Prismatic, perfect.

Tetn.g.

MnO, with about 2% H.O.

Iron-black.

Black.

F. Splintery.

Massive. Pseudom.

WnMuO, with a little MnSiO,

Black.

Brownish- black.

C. Pyramidal. F. Uneven.

Tei rag. Fig. 143.

tfD,04. .

Black.

Chestnut- brown.

C. Basal. F. Uneven.

Tel rag.

WnO(OH) Mn,O..H,0.

Steel-gray to iron-black.

Dark-brown.

(J. Plnacoidal, perfect.

Orthorh. Prismatic.

(Mn(Zn)MiiaOft.HiO.

Bluish- black.

Durk chuco- late-brown.'

C. Basal, per.

Hex Uli.

Uncertain.

HnO* with MnO, H,0, and often BaOand K0.

Iron-black.

Brownish-

black.

F. Uneven.

About

Massive.

I to the foregoing divisions.

XoS,.

Lead-gray.

Grayish-black.

C. Basal, per.

Hexag.?

Folmied.

Iron black.

Black.

0. Basal, per.

Hex. Rh. Foliated.

Essentially FeCr.O,

FeO.Cr,0.

Iron-black to brownish- black.

Dark-brown.

F. Uneven.

Isometric. U. mass.

FeCr,0 with MgAl,0.

Brownish- black.

Brown.

F. Uneven.

Isometric. U. mass.

(Page 257.)

1. Minerals With Metallic Or Submetallio Luster.

B.— Infusible, or Fusible above 5, and Non-volatile.

. . Division 8, concluded.

L Minerals With Metallic

B. —Infusible, or Fusible

Division 3

General Characters.

Contain titanium. — Fused with borax, then dissolved in HCl aud boiled with tin, the solu- tion becomes violet (p. 127, g 2).

ESTCompare Rutile, Octahedrite, and BrookiU (p. 299), which sometimes are black and have a sub-metallic luster.

Specific Characters.

After the violet color of titanium has been ob- tained, by continued boiling with tin the solu- tion finally assumes a blue color {niobium, p. 99, § 1).

Compare Polymignite, below.

Fused with the acid sulphate of potash and fluorspar mixture, momentarily colors the flame green (boron). Kus. 5.5

Contain niobium. — Fused with borax, then dissolved in HCl and boiled with tin, the solu- tion assumes a blue color (p. 99, £1). The high specific gravity is noticeable.

Compare the difficultly fusible niobium minerals on p. 254, and those with resinous to sub-metallic luster on pp. 298 and 800.

Contain tantalum (p. 128), but jrivc no, or only slight, reac tions for niobium. Character- ized by exceptionally high specific gravity.

Contains uranium. — Imparts to the salt of phosphorus bead in O. F. a yellowish-green and in R. F. a green color.

Compare Baddeleyite, Zr02 (p. 802).

Contain platinum or the metals ot the platinum group (pp. 108 and 104). — These minerals are characterized by exceptionally high specific gravities, and by their insolubility in any single acid.

A little of the fine powder mixed with an equal volume of NaaCOj and fused intensely in char- coal gives a mass which is attracted by a mag net (see p. 255).

After fusing with NaaC08 and dissolving in HCl the titanium may be precipitated by am- monia. In the filtrate calcium may be detect- ed by ammonium oxalate, and magnesium by sodium phosphate.

Generally imparts to the NaCO bead in O. F. a green color (manganese). Fused on charcoal with a. little Nat CO s yields a magnetic mass. For variations in specific gravity see p. 7.

In making the reduction test with zinc the violet color of titanium appears before the blue of niobium (p. 99, §2).

React for iron and sometimes, also, for manga- nese when tested as directed above for colum- bite.

Give reactions for tin and uranium when tested as directed on pp. 126, § 8, and 129, §2.

Soluble in dilute H,S04 with the slight evolution of a gas (helium). The high specific gravity is noticeable.

Gives sulphur dioxide when roasted in the open tube. HT Compare Sperrylite, p. 247.

Malleable. B. B. unaltered. Sometimes mag- netic.

Malleable. Loses its tarnish wheu heated B. B. in R. F., but regains it by heating in the open tube.

Slightly malleable to brittle. Heated in the open tube gives the odor of osmium oxide.

Does not react for osmium.

Name of Species.

Dysanalyte.

Warwickite.

Ilmenite.

(Magnesian Variety.)

Pseudobrookite.

Perovskite. (Perofsldte.)

GeJkielite.

Columbite.

Mosaite.

Polymignite.

Tantalite.

Tapiolite.

Hielznfte.

Uraninito.

(Pilch Blende.)

Baddeleyite.

Latirite.

Platinum.

Palladium.

Iridoemine.

Iri.lium.

) OR SUB-METALLIC LUSTER, above 5, and Non-volatile. — Concluded.

Composition.

Color.

Streak.

Cleavage and Fracture.

Hard- ness.

Specific Gravity.

Crystalli- zation.

CaTiO,, with some (Fe,Ca)Nb90and rare- earth metals. Formula uncertain.

Black.

Gray.

C. Cubic. F. Uneven.

Isometric. Cubes & Oct a he- d roiis.

(Mg,Fe)4B,TiO.?

Dull-black.

Black.

C. One direc- tion, per. F. Uneven.

Orthorh. Prismatic.

(Mg,Fe)TiO.=

(Mg.Fe)O.TiO,.

Iron -black.

Black.

F. Uneven.

He*, lih. Page 197.

Fe(Ti04)..

Brownish- black.

Yellowish- cu- red dish-brown

F. Uneven.

Orthorh.

CaTiO,..

Brown to

black.

Grayish.

F. Uneven.

Isometric.

MgTiO,. Fe iao. w. Mg.

Blue-black.

C. Perfect.

Hex. Rh.?

Essenttally(Fe,Mn)Nb,0., with (Fe,Mn)Ta,Of.

Black.

Dark - red to black.

F. Uneven.

Orthorh. U. prism.

Fe(Nb,Ta),Of.

Black.

Black.

F. Uneven.

Tetrag.

Uncertain.

Nb, Zr, Tl, Ca, Th, Oe, Y, F©"', Fe", 0.

Black.

Dark-brown.

F. Conchoidal.

Orthorh.

(FcMnyTifcO,.

Nb Ibo. w. Ta.

Black.

Black.

F. Uneven.

Orthorh.

FeTa,0.

Nb Iso. w. Ta.

Black.

Black.

F. Uneven.

Tetrag.

Uncertain.

Ta, Nb. 8n, U, Y, Ce, Fe", Mn, Ca, H, 0.

Black.

Grayish-black.

F. Uneven.

Orthorh.

Uncertain.

UO, UO,, Th, Y, Pb, and He.

Black.

Brownish- black.

F. Uneven.

Isometric. U. mass.

£rOa.

RuS,.

Us iso. w. Ru.

Iron-black.

Dark-gray.

C. Octahedral. F. Conchoidal.

Isometric

Ft, with Fe and the rare platinum uutaU.

Whitish steel- gray.

Gray, shiny.

F. Hackly.

[sometrfr.

Pd, with ?t and Ir.

Whitish steel- gray.

Gray, shiny.

F. Hackly.

Isometr.c

Ir, with Os, Ru. and Pt.

Tin -while.

Gray.

C. Baan 1, per.

Hex. Rlk

Ir, with Pt.

Tin-white

Gray. |7. Hackly.

6-7 22.7

Isometric.

(Page 258.)

Ii. Minerals Without Metallic Luster.

A.— Easily Volatile or Combustible,

Ii. Minerals With

A.— Easily Vola

N.B. — The few minerals which are included in this section entirely disappear when heate charcoal, or still better in most cases in a closed tube,* when the material should volatilise com pi falls to a fine powder when heated, and therefore cannot be retained in the platinum forceps nor

General Characters.

t

Specific Characters.

Name of Specie*

Burns with a blue flame and gives the strong odor of sul- phur dioxide.

The sublimate in the closed tube is a red to dark yellow liquid when hot, a pale yellow solid when cold.

Sulphur.

Contain arsenic. — Yield the vol- atile, crystalline sublimate oi

Imparls a decided green color to the blowpipe flame (tJiaUium).

Lorandlte.

arseniQus oxide when heated in the open tube (sulphides must be roasted very slowly and carefully). An arsenical mirror may be obtained by mixing the mineral with six volumes of dry Na,CO, and a little

The sublimate in the closed tube is a deep-red, almost black liquid wheu hot, a reddish-yellow, transparent solid when cold.

Realgar.

Orpiment.

Yield the white crystalline sublimate of arsenious oxide wheu heated in a closed tube. Volatile with only a slight tendency to fuse.

Arsenoltte.

charcoal powder and heating in a closed tube (p. 51, § 1, b).

Claudetlte.

Contain antimony. — B. B. on charcoal fuse and coat the coal with a dense white subli- mate of the oxides of ariti-

In the open tube gives sulphur dioxide.

Kermesite.

Fuse easily when heated in the closed tube, and give a slight white sublimate consisting often of prisms and octahedrons of SbtOs.

8enarmontito.

mony.

Vslentinite.

Contain ammonium. — Give the odor of ammonia when heated in a closed tube with lime (ig-

Volatile without fusion. The aqueous solution gives a precipitate with silver nitrate.

Sal-ammoniac.

nited calcite), or boiled in a test - tube with potassium hydroxide.

Fusible. The aqueous solution gives a precipi- tate with Lariuui chloride.

Mascagnite.

Contain mereurp. — Give a subli- mate of mercury when heated in a closed tube with dry sodium carbonate (p. 94, § 1).

Streak red. Gives sulphur dioxide and mercury in the open i in. e (p. 94, § 2). Gives a black sublimate (HgS) in the closed tube.

Cinnabar.

After testing for the mercury with NaiCOs, the contents of the tube, when dissolved in water and HNOi, will give a precipitate with silver nitrate.

Calomel.

Contains lead. — Gives a globule of the metal and a coating of oxide when fused with NatCO* on charcoal.

Quite soluble in hot water. On cooling, the solution deposits lead chloride.

Ootunnite.

Contain sodium or potassium. — Color the blowpipe flame yel- low or violet, respectively. 1

After ignition B. B. the residue imparts an alka- line reaction to turmeric paper.

A number of tt will be found

;t metallic luster.

a, or Combustible.

B. B., provided tbey are pure. It may be recommended to heat a small fragment B. B. alone on ly uud condense as a sublimate. It is not an indication tbat a mineral is volatile if it decrepitates, or charcoal.

Composition.

Color.

Luster.

Cleavage or Fracture.

Hard- ness.

Specific Gravity.

Fusi- bility.

Crystalli- zation.

S.

Pale yellow.

Resinous.

F. Concboidal or uneven.

Orthorh. Page 202.

TIAsS,

Tl,S.As,S,.

Carmine-red.

Adamantine.

C. One direc- tion, perfect.

Monocl.

AsS.

Aurora-red.

Resinous.

C. Piuacoidal. P. Conchoidal

Muuocl. U. cry st.

As? ids.

Lemon-yellow.

Pearly, resi li- ons.

C. Pinacoidal, perfect

Monocl. U. foil.

kASaO,.

Colorless to

white.

Adamantine.

P. Uneven.

Vol.

Isometric.

ASaO,.

Colorless to

white.

Brownish-red, maroon.

Pearly.

C. Piuacoidal, perfect.

Vol.

Mouocl. Tuliular.

Sb,8,0.

Adamantine.

C. Pinacoidal, perfect.

Mouocl. Acicular.

Colorless or white.

Adamantine.

P. Uneven.

Isometric. Fig. 96.

8b,0,.

Colorless or white.

Pearly, ada- mantine.

C. Pinac, per. and prismatic.

Orthorh. Prismatic

Colorless or white.

Vitreous.

F. Conchoidal.

Vol.

Isometric. C1.4,p.219

(Nh4),804.

Colorless or white.

Vitreous.

F. Uneven.

Orthorh.

HgS.

Red. Vermilion.

Adamantine.

C. Prismatic,

perfect. F. Uneven.

Vol.

Hex. Rh.

Cluss 15, p. 219.

HgCl.

Colorless or white.

Adamantine.

F. Conchoidal.

Vol.

Tetrago- nul.

PbCla.

Colorless or white.

Adamantine.

F. Uneven.

Orthorh.

minerals containing the alkali metals are wholly volatile if heated for a considerable time. They however, among the fusible minerals on p. 271.

(Page 259.) II. MINERALS WITHOUT METALLIC LUSTER.

B.— Fusible from 1-5, and Non-volatile, or only Slowly or Partially

Volatile.

Part I. — Give a metallic globule when fused with sodium carbonate on

charcoal.

Division 1.— Silver Compounds.

Division 2.— Lead Compounds* in part.

Division 1.— Silver Compounds.

globule Trill be brittle.

II. MINERALS WITHOl

B.— Fusible from 1—5, and Non-volatU

Part I. — Give a metallic globule when 1

-A globule of silver is obtained by fusing on Charcot

General Characters.

Specific Characters.

Name of Specie

Conlaiu sulphur.— Heated in the open tube yield sulphur di- oxide and tiie oxides of either arsenic or antimony.

If the globule obtained by heat iug on charcoal with NasCOs is brittle, it may be converted to pure silver by heating in O. P. with borax.

gy Compare Miargyrite and Polybasite (p. 250).

When heated in the closed tube readily yield an abundant. sublimate of sulphide of arsenic, deep red. almost black when hoi. reddish -yellow when cold (p. 140), and beyond this a slight sublimate sulphur.

Prouttits.

(Ruby Silver.)

Xanthoconite. (Rittingerite.)

Upon intense and prolonged heating in the closed tube a slight sublimate of oxysulphide of anti- mony deposits where the glass is very hot. This is black when hot, reddish-brown when cold (p. 45, § 8), and beyoud it there is a slight deposit of sulphur.

Pyrs ray rite. (Dark-red Silver Oi

PyrostUpnite. (FJreblende.)

The sublimate (lead chloride) is white, both when hot and cold.

Cersrgy rite.

(Horn Silver.)

Contain chlorine, bromine, or

The sublimate (lead bromide) is sulphur-yellow when hot, but white when cold. The chlorine in emboli te may be detected as directed on p. 69, § 5.

Embolite.

iodine.— Sublimates of the chlo- ride, bromide, or iodide of lead are obtained by heating with galena in a closed tube as di- rected on p. 68, § 4. The chloride and bromide are sectile and can be cut with a

Bromyrite.

The sublimate (lead iodide) is dark orange- red when hot, lemon-yellow when cold. Cupro- iodargyrite may be identified by its reactions for copper.

Miersite.

lodyrite.

knife like horn.

Iodobrotnite.

Cuproiodargyrite.

Division 2.— Lead Compounds.- Globules of lead aud a yellow coating of lead oxide are e: gives a very similar reaction, but the globules of bismuth are brittle. The pale azure-blue flame lead minerals dilute nitric acid (1 part HNOs to 2 of water) should be used, and in the solutions hyd

N.B. — The various salts of lead will be found in this division, with the exception of those com

Carbonates. — Soluble in warm dilute acids with evolution of carbon dioxide (efferves- cence).

Generally it is best to employ dilute HNO, but for Lead- hill ite use dilute HCI.

Heated in the closed tube a sublimate of lead chloride is obtained, which fuses to colorless globules.

The dilute HCI solution gives with barium chlo- ride a precipitate of barium sulphate. Gives a little water in the closed tube.

Hydrocerussite.

Gives water in the closed tube, but dots not re- act for a sulphate.

Gives none of the above reactions. In the closed ' tube, usually decrepitates and is changed tojCERUSSITE. lead oxide, which is dark yellow when hot.

Phoagenite.

Leadhillite.

Division 2.— Lead Compounds.— Continued on next page.

Metallic Luster. 259

or only Slowly or Partially Volatile.

ed with sodium carbonate on charcoal.

ivith sodium carbonate. When antimony is present, some of it will alloy with the silver and the

Composition.

Color.

Luster.

Cleavage and Fracture.

Hard- ness.

Specific Gravity.

Fusi- bility.

Crystalli- sation.

3AgaS.As,Ss.

Ruby-red.

Adamantine.

F. Conchoidal.

Hex. Rh. Hemimor.

3AgiS.As,Ss.

Orange-yellow to clove-brown

Adamantine.

C. Basal.

Mouocl. Tabular.

3Ag,S.Sb,Ss.

Dark-red to black.

Adamantine.

F. Conchoidal.

Hex. Rh. Hemimor.

3AgS.SbtSs.

Hyacinth-red.

Adamantine. .

C. Pinacoidal.

4.3?

Monocl. Tabular.

AgCl.

Pearl-gray to colorless.

Adamantine.

F. U i) even or hackly.

Isometric.

Ag(Cl,Br).

Green or yel- low.

Adamantine.

F. Uneven.

2-y

5.8U

Isometric.

AgBr.

Green or yel- low.

Adamantine.

F. Uneven.

Isometric.

Agl.

Cu is->. w. Ag.

Yellow.

Adamantine.

Isom Tet,

Agl.

Lemon -yellow

Resinous.

C. Buxal. F. Uneven.

Hexag. Puge 190.

A.g(Cl,Br,I).

Sulphur-yel- low to green.

Resinous.

F. Uneven or hackly.

Isometric.

kgl.CuI.

Sulphur- yellow.

Massive.

y obtained by fusion on charcoal with sodium carbonate and a little charcoal powder. Bismuth ation, and the conspicuous iodine tests for lead (p. 89), can be recommended. For the solution of ;hloric and sulphuric acids will give precipitates of lead chloride and lead sulphate, respectively.

unds (mostly sulphides) which have a metallic luster.

PbCl),CO.

PbCO..PbCl,.

Colorless or white.

Adamantine.

C. Basal and prismatic.

Tetrag. U. cryst.

>ba(Pb.OH),(CO,), SG4 2PbCO.. (Pb.OH),S04.

Colorless or white.

Pearly, ada- mantine.

C. B;isal, per. Uneven.

Monocl. U. cryst.

(Pb.OHMCO*),.

Colorless or white.

Pearly

lr.5

Hexag. Tabular.

'bCO,.

Colorless or white.

Adamantine.

F. Conchoidal.

ft

Orthorh. Page 206.

(Page 260.)

Ii. Minerals Without Metallic Luster.

B.— Fusible from 1-5, and Non-volatile, or only Slowly or Partially

Volatile.

Part I. — Give a metallic globule when fused with sodium carbonate on

charcoal.

Division 2. — Lead Compounds, continued

Ii. Minerals Witiio

B.— Fusible from 1—5, and Non-volati Part I. — Give a metallic globule when

Division 2. — Lead O

General Characters.

Specific Characters.

Name of Species.

Sulphates. — When mixed with

Give water iu the closed tube. The HC1 solu- tion gives a blue olor when ammonia is added in excess.

Linarite.

NiigCOs and a little charcoal powder, and fused in R. F. on charcoal, a mass containing sodium sulphide is obtained which blackens a moistened

Caledonite.

B. B. gives a strong soda flame.

Caracolite.

silver surface (p. 122, § 2). The fine powder is rather soluble in boiling dilute HC1. The so-

Gives much water in the closed tube. Reacts

for ferric iron, and a phosphate or arsenate. [y Compare Lossenite, beyond.

Beudantite.

lution on cooling deposits lead chloride, and, after filtering, it gives with barium chloride a precipitate of barium sulphate.

Give none of the above reactions.

Anglesite.

Lanarkite.

Phosphates, — A few drops of the dilute HNO solution, when added to ammonium molyb- date, give a yellow precipitate

(p. 103, 8 1). (QgT Compare the Arsenates, be- low.

Fusible B. B. alone on charcoal to a globule which, on slow cooling, generally becomes distinctly crystalline. B. B. in a closed tube gives a slight sublimate of lead chloride.

Pyromorphite.

Imparts a green color to the salt of phosphorus bead in 0. F. (chromium).

Vauquellnite. (Lazmaonite.)

Gives much water in the closed tube.

Plumbofcummite.

The dilute HNOs solution rives with silver nitrate

a precipitate of silver chloride. £39~Compare Endlichite, below.

Mintotite.

Arsenates. — A fragment of the

Ecdemite.

mineral when placed in a closed tube with a few splin- ters of charcoal, and heated in- tensely B. B., gives a deposit of arsenic (p. 61, § 1, a).

Fuse B. B. to a magnetic mass. Lossenite reacts for a sulphate (p. 122, § 1).

Carminite.

Lossenite.

The HNOs solution is rendered blue by ammonia (copper).

Bayldonite.

Imparts a bluish-green color to the NaaCOs bead iu 0. F. {manganese).

Caryinite.

The dilute HNO solution gives with silver

nitrate a precipitate of silver chloride. Endlichite is a variety containing a little arsenic.

Vanadinite.

(Endlichite.)

The HNOi solution is rendered blue by addition of ammonia {copper). Cuprodescloizite is a variety of the following miueral.

Psittacinite.

Vanadates. — Impart to the salt of phosphorus bead in 0. F. a yellow to deep amber color which iu R. F. is changed to green.

Cuprodescloizite.

Gives water iu the closed tube. Reacts for zinc.

Detoloizite.

Gives water in the closed tube. Contains neither ziuc nor copper.

Brackebuschlte .

Division 2.— Lead Compounds.— Continued on uext page.

T Metallic Luster.

b, or only Slowly or Partially Volatile. fused with sodium carbonate on charcoal.

mpounds. — Coulinued.

Composition.

Color.

Luster.

Cleave and Fracture.

Hard- ness.

Specific Gravity.

Fusi- bility.

Cryslalll- zaliou.

[(Pb,Cu)OH]aS04.

Azure-blue.

Vitreous.

C. Piuac, per. F. Couchoidal.

Monocl.

[(Pb,Cu)OH],S04?

Bluish -green.

Resinous.

C. Basal, per.

Orthorh.

Pb(OH)Cl.Na,S04

Colorless or white.

Vitreous.

F. Uueven.

f

1.5-2 Jorthorh.

Uncertain. Fe"\ Pb, Cu, S04, (P,As)04.

Olive-green, brown, black.

Resinous.

C. Basal.

Hex. Rh.

PbS04.

Colorless or white.

Adamautine.

C. Basal.

F. Conchoidal.

Orthorh. U. cryst.

lPbaO)S04.

Pale-yellow or while.

Pendantine C" Bft8al> V-

Monocl.

Pb4(PbCl)(P04), 3Pb,(P04)a.PbCU.

Green, brown, yellow, gray, while.

Resinous.

F. Uneven.

Hexag. C1.8.p.219 U. pris- matic.

Pb,Cu)s(P04).. 2(Pb,Cu)Cr04.

Uncertain.

P04), Pb,Al,H,0.

Green and brown.

Resinous.

F. Uneven.

5.&-6.1

2?

Monocl.

Yellow, brown and green.

Gum-like.

F. Uneven.

2?

Hexag. Globular.

Pb4(PbCl)(As04),= *Pba(As04)a.PbCl,.

Colorless, yel- low,' orange, brown.

Resinous.

F. Uneven.

Hexag. Cl.y.p.219 U. prism.

Pb4As90,.2PbCl?

Yellow to green.

Greasy.

C. Basal.

1.5?

Orthorh.

Pb3Fe/,/10(AsO4)1,?

Carmine-red.

Vitreous.

C. Prismatic.

2-3?

Orthorh.

Fe'".OH),(As04).. PbS04.12HaO.

Yellow to brownish-red.

Resiuous.

F. Uneven.

Orthorh.

Pb,Cu)3(As04)a. Pb,Cu)(OH),.HaO.

Grass- to black- ish-green.

Resinous.

F. Uneven.

2-3?

f

Mam mill.

iiaAssOa.

Mn, Ca, & Pb.

Brown.

Resinous.

C. Pinacoidal. F. Uneven.

Massive.

3Pb,(V04),.PbCla.

Ruby- red, brown and yellow.

Resinous.

F. Uneven.

Hexag. Page 190. U. prism.

J n certain.

V04). Pb, Cu, HaO

Green.

2?

Mam mill, earthy.

*(R.Oh)V04.

1 - Pb, Zn & Cu.

Brown to green ish-

black.

Resinous,

greasy.

F. Uneven.

Orthor. Radiated.

(Pb.OHjVO,.

in iso. w. Pb.

Brownish - black, brown and red.

Resinous,

greasy.

F. Uneven.

Orthorh. U. cryst.

Tncertnin. VO). Pb, Fe, Mn,

Dark brown.

Monocl.

(Page 261.)

Ii. Minerals Without Metallic Luster.

B.— Fusible from 1-5, and Non-volatile, or only Slowly or Partially

Volatile.

Part I. — Give a metallic globule when fused with sodium carbonate on

charcoal.

Division 2. —Lead Co in pounds, continued.

Ii. Minerals Withou

B.— Fusible from 1—6, and Non-volatile Part I. — Give a metallic globule when I

Division 2. — Lead Cei

General Characters.

Chromates. — Impart to tbe salt of phosphorus bead in O. F. a green eulor.

Molybdate. — Gives the test for molybdenum when treated as directed on p. 96. § 4.

Twigstate.— Decomposed by boil- ing with HC1, leaving a yellow residue of tungstic oxide.

Specific Characters.

Streak orange-yellow.

Streak brick-red.

With salt of phosphorus the bead in R. F. is green, but in O. F. it is yellowish-green when hot, almost colorless when cold.

If the tungstic oxide (after decanting off the HOI) is treated first with ammonia, then with HC1 in excess, and boiled with tin, a fine blue color is obtained (p. 128, § 1).

Contain antimony. — Alone on charcoal in R. F. give a malle- able lead globule and coatings of both lead and antimony In the closed tube give a sublimate of lead oxides. Mixed with three chloride, which fuses to colorless globules, volumes of NaCOt aud fused in charcoal in R. F., give a

somewhat brittle globule (alloy

of lead and antimony) which

yields a sublimate of oxide of!in tfce dosed tube gives water.

antimony when roasted in a

bent open tube (Fig. 17, p. 19).

Contain chlorine, but do not give the reactions of the foregoing sections. — Soluble in warm, dilute HNOb. The solution gives with silver nitrate a pre- cipitate of tilv&r chloride.

Contains iodine. — The dilute HNOs solution gives with silver nitrate a precipitate of silver iodide.

B. B. give a blue or green flame. The HNOs solution is rendered blue by addition of ammonia (copper).

Give no water in the closed tube, but yield a sublimate of lead chloride which fuses to color less globules. Cot u unite is wholly volatile when heated in the closed tube, while the others leave a residue of easily fusible lead oxide.

Gives sublimates of both water and lead chloride in the closed tube.

Gives a sublimate of lead iodide (dark- red when hot, yellow when cold) and iodine vapors in the closed tube.

Name of Species.

Croooi

Phoenlcochroite.

Wulfenite.

Stolzite.

Raspite.

Nadorite.

Ochroiite.

Bindheimite.

Percylite. (BolGlte.)

Cumengite.

CotuDDite.

Penfleldite.

Mat lock ite.

Mendipite.

Laurionite.

'cliwartxenberpte.

Division 2.— Lead Compounds. — Concluded on next page.

It Metallic Luster.

5, or only Slowly or Partially Volatile. fused with sodium carbonate on charcoal. ni pounds. — Continued.

Composition.

Color.

Luster.

Cleavage and Fracture.

Hard, ues*.

Fpeciflc (iravitj.

Fusi- bility.

Cry mu Hi-

Zulu D.

PbCr04.

Bright-red.

Adamantine.

F. Uneven.

Mniiorl. U. rrvM.

2PbCrO.PbO.

Hed. Resinous.

C. Pitmcoidal. perfect.

3-3.5 5.75? t

OlIlM'I'll

U. ITiMSP.

PhMoO.

Yellow, orange, red, gray, while.

Vitreous to adamantine.

F. Uneven.

Tetrag

01.28.11.?!%,

U. tabular

PbW04.

Lighi green, yellow, bn-wii or red.

Resinous.

F. Uueven.

Tetrag.

C1.20, p.21.

Wax-brown. Resinous.

C. Pinacoidal, perfect.

Monocl.

PbClSbO,.

Smoky- to yellowish- brown.

Resinous.

C. Pinacoidal, perfect.

ft

1.5?

Orthorh.

PbSbaC.PbCl,?

Sulphur- to grayish-yellow

Adamantine.

Orthorh.

Uncertain. fcybttOs. PbO and 11,0.

Gray, yellow, brown.

Resinous to dull.

F. Uneven.

Amor])b.

PbCuCl9(OH).

Indigo-blue.

Brilliant.

C. Cubic, per.

Isometric. Cubic.

PbCuCla(OH),.

Indigo-blue.

Brilliant.

C. Pyramidal.

Tetrag.

PbCli.

Colorless or white.

Adamantine.

F. Uneven.

Orthorh.

2PbCl,.PbO.

Colorless to white.

Vitreous to greasy.

C. Basal, per. F. Uneven.

2.5 j

Hexag. Prismatic.

PbCla.PbO.

Pale yellow to white.

Adamantine, pearly.

C. Baud. F. Uneven.

Tetrag. Tabular.

PbCla.2PbO.

Pale yellow to white.

Pearly to adamantine

Prismatic, per. and basal.

Orthorh. Columnar

PbCl(OH).

Colorless or white.

Adamantine.

F. Uneven.

Orthorh.

PI (I,Cl)a.2PbO.

Honey- to straw-yellow.

Adamantine.

Hex. Rh.

'%

(Page 262.)

Ii. Minerals Without Metallic Luster.

B.— Fusible from 1-6, and Non-volatile, or only Slowly or Partially

Volatile.

Past I. — Give a metallic globule when fused with sodium carbonate on

charcoal.

Division 2. — Lead Compounds, concluded. Division 8.— Bismuth Compounds.

Ii. Minerals Witho

B.— Fusible from 1—6, and Non-volat

Part I. — Give a metallic globule when

Division 2.— Lead C

General Characters.

Silicates, — The three first min- erals are readily decomposed by HNO ami yield gelatinous silica upon evaporation. Mela- no tekite and Eentrolite are best decomposed by HC1, but contain loo little silica to give h good jelly. They leave a residue of silica, however, when the HC1 solution is evaporated to dryness aud then treated with acid. Hyalotekite is insoluble in acids, but may be tested as directed on p. 110, § 4.

Oxides. — Do not give the reac- tions of the foregoing minerals.

Specific Characters.

Gives the reaction for sulphur (p. 122, § 2). The only mineral coutaiuing the sulphite radical.

Name of Species.

Distinguished by differences in physical proper- ties aud by the presence of calcium (CaO 9%) in Ganomalite.

Roeblingite.

Barysilite.

B B. in R. F. fuses to a magnetic bead.

Imparts a reddish-violet color to the borax bead in O. F. (manganese). Soluble in HC1 with evolution of chlorine.

Reacts for barium (p. 58, £ 3, b) and boron (p. 56, § 2).

The colors of the different minerals are very characteristic. Plattnerite and Minium give oxygen gas when heated in the closed tube (p. 100. § 1) and leave readily- fusible lead oxide (PbO).

Ganomalite.

Melanotekite.

Kentrolite.

Hyalotekite.

Plattnerite.

Minium.

Massicot.

Division 3. — Bismuth Compounds. — Globules of bismuth which are brittle and a yellow r red sublimate obtained by heating on charcoal with a mixture of potassium iodide and sulphur (p. 5

Carbonates. — Dissolve in HC1 In the closed tube gives little or no water, with evolution of carbon di-

oxide (effervescence).

Contains Marine. — The dilute HNO$ solution gives with silver nitrate a precipitate of silver chlotiile.

Silicates.— Soluble in HG1, and yield gelatinous silica upon evaporation.

Vanadate.— Imparts to the salt of phosphorus bead in O. F. a yellow and in R. F. a green color.

Arsenates. — A fragment of the mineral when placed in a closed tube with a few splin- ters of charcoal, and heated Intensely B. B., gives a deposit of arseuic (p. 51, § 1, a). Compare Mixite (p. 264).

In the closed tube gives water.

In the closed tube gives water.

Bismutospbeerite.

Biamutito.

Distinguished by differences in crystallization.

Soluble in*HCl.

Imparts to the salt of phosphorus bead in R. F. a green color (uranium).

Daubreelte.

Eulytite.

AgriooHte.

Pucherite.

Walpurglte.

React only for arsenic, bismuth and water. Atelesite decrepitates.

Teilurate. — When mixed with NaaCOs and charcoal powder and heated in a closed tube, sodium telluride is formed, which, when treated with water, yields a reddish- violet solution (p. 124).

Atelestite.

Rhaglte.

Montanfte.

T Metallic Luster.

e, or only Slowly or Partially Volatile.

'used with sodium carbonate on charcoal. m pounds.— Concluded.

Composition.

Color.

Luster.

Cleavage and Fracture.

Hard- ness.

Specific Gravity.

Fusi- bility.

Crystalli- sation.

5H3CaSi04.

! 2(PbOCa)SOa.

White.

Dull-white.

Qrunular.

Pb3Si,0T.

White.

Pearly.

C. Basal.

tiexag. LumeTlar.

Pb3SiaO,.(Ca,Mn), 1 Si04.

Colorless to gray.

Resinous to vitreous.

F. Uneven.

3?

Tetrng.

l(Fe'"403)Pb3(Si04)3

Dark- brown to black.

Sub-metallic.

F. Uneven.

On horn.

(Mn40.)Pb,(Si04). Fe iso. w. Mn.

Black.

Sub-metallic.

F. Uneven.

5-5.5 6.19

Orthorh.

U4(F,OH)B(8i03)..

Li PU Ka & Cl.

White to gray.

Vitreous to greasy.

C. Two direc- tions.

3?

Massive.

PbOa.'

Brown-black.

Sub metallic.

F. Uneven.

1,5

Tetrag. mass.

P1>S04.

Red.

Dull or greasy.

4.6?

Pul viru- lent.

Pl)G.

Sulphur- to red- dish-yellow.

Dull.

Massive. ; Scaly.

ting of bismuth oxide are easily obtained by fusion B. B. on charcoal with sodium carbonate. The , § 2) may be recommended as a very characteristic test for bismuth.

(BiO),CO.

White or gray. JDull.

F. Uneven.

Botrvoid. Massive.

(BiO)(Bi.20H)COa.

White, green, yellow.

Dull.

Amorph. Earthy.

2Bi,0,.BiC1..3H,0.

Yellowish- to grayish- white.

Dull.

1.5?

j

Auiorph. Earthy.

Bi4(Si04),.

Hair-brown, yellow, colorless.

Resinous to adamantine.

F. Uneven.

Isom. Tet. U. cry st.

Bi4(Si04)a.

Yellow, hair- brown.

Adamantine.

3?

6?

Monocl. Globular.

BiV04.

Reddish- brown.

Vitreous to adamantine.

C. Basal, per. F. Uneven.

Orthorh. U. cryst

Bi,0(UO,),(OH),4

(As04)4.

Wax-yellow.

Adamantine to greasy.

C. Pinacoidal.

Triclinic,

(Bi.20H)(BiO)„

As04

Sulphur- yellow.

Adamantine

F. Uneven.

Monocl.

3Bi(OH),.2BiAs04?

Yellowish- green to wax- yellow.

Resiuous to adamantine.

F. Uneven.

1.5?

Mamraill.

[Bi.20H),Te04.

Yellow, greenL n and white, |Uul1-

1.5?

Massive. Early.

(Page 263,)

Ii. Minerals Without Metallic Luster.

B.-Fusible from 1-5, and Non-volatile, or only Slowly or Partially

Volatile.

Part I. — Give a metallic globule when fused with sodium carbonate on

charcoal.

Division 4.— Antimony Compounds.

Division 5. — Copper Compounds, in part.

Ii. Minerals Withou

B.— Fusible from 1—5, and Non-volatile

Pabt I. — Give a metallic globule when f

Division 4.— Antimony Compounds. — Globules of antimony which are brittle, and a wh

General Characters.

Specific Characters.

Name of Species.

Fused with Nu,CO$> then treated with HC1 and boiled with tin,

Mauzeliite gives a reaction for lead. JST Compare IhrbyUU (p 255 1.

Mauzeliite.

the solution assumes a violet color (titanium, p. 127, §2).

Lewisite.

Gives no reaction for titanium.

B. B. fuses to a magnetic mass.

Tripuhyite.

B. B. fuses to a dark non-magnetic slag.

Romeite.

Division 5.— Copper Compounds.— A globule of copper may be obtained by mixing a se tome cases (when iron is present) it is advisable to use a little borax with the sodium carbonate in oi & somewhat brittle globule containing arsenide of copper will result. Moisteued with hydrochloric i in acids the solutions are rendered deep- blue by addition of ammonia in excess.

N.B. — Nearly all of the minerals containing copper which have non-metallic luster will be foun<

Characterized by a deep-red

color. Note the reaction for cuprous

oxide.

Carbonates. — Soluble in HC1 with evolution of carbon di- oxide (effervescence).

Contain chlorine — Impart to the blowpipe flame an azure-blue color without previous moist- ening with HC1. Silver nitrate gives precipitate of silver chloride when added to the dilute HNOa solution.

Contains iodine. — Colors the blowpipe flame intense green.

An ivory-spoonf ul of the powdered mineral dis- solved in 1 c.c. of boiling HC1, then treated with cold water, will give a white precipitate of cuprous chloride <p. 74, § 5).

Give water in the closed tube. Readily distin- guished by their color.

The HC1 solution gives a slight precipitate with

barium chloride (sulphate). Spaugolite exhibits pyro-electricity (p. 281).

Gives no water in the closed tube.

Give acid water in the closed tube.

Heated with potassium bisulphate in a closed tube gives vapors of iodine.

Cuprite.

(Ruby Copper.)

Malachite.

Azurite.

Spangolite.

Connellite.

Naotokite.

Ata Canute.

Footeite.

Marshite.

Division 5.— Copper Compounds.— Continued on next page.

T Metallic Luster.

9, or only Slowly or Partially Volatile.

'used with sodium carbonate on charcoal.

iite coating of antimony oxide, are obtained by fusing B. B. on charcoal with sodium carbonate.

Composition.

Color.

Luster.

Cleavage and Fracture.

Hard- ness.

Specific gravity.

Fusi- bility.

Crystalli- sation.

(CatPb,Nai)4

TiSb4OM.

Brown.

Iso metric.

Honey -yellow to brown.

Resinous.

C Octahedral.

3-4?

Isometric.

Fe",8baO,.

Greenish -

Resinous.

4-5?

?

2aSbf04.

Hooey-yellow.

F Uni'veu.

Tut rag.

tall quantity of the mineral with sodium carbonate and fusing on charcoal in a reducing flame. In ler to make the copper unite to a globule (p. 73, §2). When arsenic is present it may happen that cid and heated B. B. the minerals color the flame azure-blue or green (p. 72, § 1). When dit*oived

in this division. Most of them have either a green or a blue color.

Du.O.

Intense ruby- red.

Adamantine.

F. Conchoidal or uneven.

Isometric. Ol.4,p.2l0 Figs. 05 lo 104.

Cu.OH),CO. CiiCO..Cu(OH),.

Bright greeu.

Vitreous.

C. Basal, per. P. Uneven.

Moloch

U.,

Cu.OH),CiuCOa), 2CuCO,.duOH),

Intense azure- blue.

Vitreous.

F. Conchoidal or uneven

a

Monocl. U. cryst.

A1C1)S<)4. 6Cu(OH),.0H8O

Dark-green, j Vitreous.

C. Busnl, per.

Hexag. r\. 18 p. aim.

Ju,.(Cl,OH)SO,.. 15H,0.

Buuuiiful-blue

Vitreous.

F. Uneven,

o.3G

Hexiig. Piitwitfa

SuCl.

Coli'riHhS or white.

Adamantine.

F. Conchoidal.

Isometric,

::u,ci(OH),

CtiCla.8Cu(OH)i.

Deep emerald- green.

Adamantine, vitreous.

C. Pinac, per. F. Conchoidal.

Orthorh. U. cryst.

*Cu(OH),.CuCl,.

4H,0?

Deep blue.

Monocl.

3ul.

Reddish -

brown.

Resinous.

F. Uneven.

1.5?

IsodlTbc

(Page 264.)

Ii. Minerals Without Metallic Luster.

B.— Fusible from 1-5, and Non-volatile, or only Slowly or Partially

Volatile.

Part I. — Give a metallic globule when fused with sodium carbonate on

charcoal.

Division 5.— Copper Compounds, continued.

Il Minerals With<

B.— Fusible from 1—6, and Non-vola Part I. — Give a metallio globule when

Division 5. — Coppe

General Characters.

Specifio Characters.

Sulphates.— The di- lute HC1 solution gives with barium chloride a precip- itate of barium sulphate. Give the sulphur reac- tion on moistened silver after previ- ous fusion with NaCOa and char- coal powder (p. 122, § 2).

Wholly sol- uble in wa- ter.

Insoluble or only partly soluble in water.

Gives much water in the closed tube. Character- ized by its color.

Gives little or no water in the closed tube.

Yields a magnetic mass after heatiug B. B. on charcoal.

Imparts a yellow color to the blowpipe flame (sodium).

Reacts for potassium (p. 106, § 3).

Gives little or no water in the closed tube.

The HC1 solution gives with ammonia a precipi- tate of aluminium hydroxide (seen with diffi- culty unless filtered).

Gyanotrichite. (Lettsomite.)

Gives the reaction for an arsenate (p. 51, § c).

Nitrate.— Heated in the closed tube gives red vapors of nitro- gen dioxide, NOa.

Arsenates. — When heated in tensely B. B. in a closed tube with a few splinters of char- coal, most of these minerals (all of the easily fusible ones) are reduced and an arsenical mirror is formed (p. 51, § a). When the foregoing treatment does not yield a satisfactory result, the method given on p. 51, § c, may be used.

Arsenates concluded on next page.

Distinguished by differences in crystallization

and color. Herrengrundite reacts for calcium.

Gives strongly acid water in the closed tube.

Fuses B. B. on charcoal to a magnetic mass. Reacts tor ferric iron (p. 85, § 4).

A drop of dilute H,SO produces in the concen- trated HC1 solution a precipitate of calcium sulphate (p. 59, § 8).

Gives a coating of oxide of zinc when fused on charcoal in & F. with a little Na,COi.

Heated on charcoal with potassium iodide and sulphur gives a red sublimate (p. 55, §2).

Imparts to the salt of phosphorus bead in R. F. a green color (uranium). .

Barium chloride produces in the dilute HOI solu tion a precipitate of barium sulphate.

B. B. cracks and then fuses. Reacts for alumin ium (p. 42. § 2).

Has a tendency to exfoliate and fall to pieces when heated B B.

Name of Species.

Chaloanthite. (Blue Vitriol.)

Hydrocyanite.

Pfsanite.

KrShnldte.

Qyanochroite.

Dolerophanlte.

Lindackerite.

Broohantite.

Langite.

Herrengrundite.

Gerhard tite.

Chenerixite.

Oonichaldte.

Tyrolite.

Vesaelyite.

Mizite.

Zeunerite.

Lindackerite.

Urooonite.

Clinoobttte.

QivisioN 5.— Cooper Compounds.— Concluded on next page.

It Metallic Luster.

le, or only Slowly or Partially Volatile. used with sodium carbonate on charcoal.

Compounds. — Continued.

Composition.

Color.

Luster.

Cleavage and Fracture.

Hard- ness.

Specific Gravity.

Fusi- bility.

Crystalli- sation.

CuS04.5H,0.

Azure-blue (rather deep).

Vitreous.

F. Concholdal.

Tricliuic, Page 217.

CuS04.

Pale green, brownish- yellow.

Orthorh.

(Fe,Cu)80.7H,0.

Bright-blue.

Vitreous.

C. Basal.

a-4

Monocl.

CuS04.Na,S04.

2H,0.

Azure-blue.

Vitreous.

C. Prismatic. F. Conchoidal.

Monocl.

CuS04.K,S04.

Ch.O.

Blue.

Vitreous.

l?

Monocl.

(Cu.O)S04.

Brown.

Monocl.

Cu4Al,SO,0.8H,O.

Clear-blue.

Pearly.

Orthorh. U. capilL

(Cu.OH)4Cu,Ni, (S04)(As04)4.5H,0.

Verdigris- to apple-green.

Vitreous.

2-8?

Orthorh.

CuS04.8Cu(OH).

Deep emerald- green.

Vitreous.

C. Pinac., per. F. Uneven.

Orthorh. U. cryst.

CuS04.8Cu(OH),. H.O.

Blue to green- ish-blue.

Vitreous.

C. Pinacoidal.

. . t

Orthorh.

2(Cu.OH),S04.

Cu(OH),.8H.O. Ca iso. w. Cu.

Emerald- green.

Vitreous.

C. Basal, per.

Monocl.

Cu(NO.),.

3Cu(OH),

Deep emerald- green.

Vitreous.

C. Basal, per.

Orthorh.

Cu,(FeO),

(AsO)t.8H,0.

Dark-green to olive-green.

Dull.

F. Uneven.

Massive. Compact.

(CufCa)(Cu.OH) (As,p)04.JH,0.

Emerald-green

Vitreous.

F. Splintery.

a

Massive. Mam mill.

(Cu,ca)(Cu.OH)4 (As04),.7H,0.

Pale apple- green.

Pearly and vitreous.

C. Basal, per.t foliated.

2-2,5

Orthorh.

7(Cu,Zn)0.

(As,P),0.9H,0?

Greenish-blue.

Vitreous ?

Triclinic?

Cu,(Cu.OH)8

. Bi(As04).7H,0?

Pale-green.

Vitreous.

,8.79

Capillary.

Cu(UO,),(A804),. 8H,0.

Emerald- green.

Pearly and vitreous.

C. Basal, per. F. Uneven.

Tetrag U. tnbul.

(Cu.OH)4Cu,Ni, (S04)(As04)4.5H,0

Verdigris- to apple-green.

Vitreous.

2-8?

Orthorh.

(Cu.OH)9

[AUOH).l_ (AsO4)6.20H,O ?

Sky-blue, at times greenish.

Vitreous.

F. Uneven.

Monocl.

(Cu.OH).As04.

Dark-green or bluish-green.

Pearly and vitreous.

C. Basal, per.

Monocl.

(Page 265.)

Ii. Minerals Without Metallic Luster

B. -Fusible from 1-5, and Non-volatile, or only Slowly or Partially

Volatile.

Pakt I. — Give a metallic globule when fused with sodium carbonate on

charcoal.

Division 5.— Copper Compounds, concluded.

Ii. Minerals Without

B.— Fusible from 1—6, and Non-volatile, Part I. — Give a metallic globule when fa

Division 5.— Copper C

General Characters.

Specific Characters.

Decrepitates violently when heated in the closed tube.

Arsenates, concluded. — When heated intensely B. B. in a closed tube with a few splin- ters of charcoal, most of these minerals (all of the easily fusi- ble ones) are reduced and tin arsenical mirror is formed (p. 51, § a). When the foregoing treatment does not yield a satis- factory result, the method given on p. 61, §e, may be used.

After fusing B. B. in the forceps the globule appears distinctly crystal Hue. Euchroite con- tains water of crystal lizai ion, and loses it readily in a closed tube like gypsum (p. 82, §1,6). Oliviuite gives a little water at a faint red heat.

As these minerals have not been observed in dis- tinct crystals, a quantitative determination of some of their constituents may be necessary for identification. Erinite contains 5 percent of water, Ooruwallite 8, Leucochalcite 10, and Trichalcite 16.

Name of Species.

Chalcophylllte.

Olivenito.

Euchroite.

Erinite.

Cornwallite.

Fuses B. B. on charcoal to a magnetic mass. Reacts for ferric iron (p 85, §4).

Imparts to the salt of phosphorus bead in R. F. a green color {uranium).

Phosphates.-A.ttti\e of theHNO, solution when added to ammo- nium molybdate gives a yellow precipitate (p. 102, § 1).

Distinguished by differences in crystallization and physical properties.

Leucochalcite.

Trichalcite.

Chalcoaiderite.

Torbernite.

(U ran -mica.)

Libethenite.

Dihydrlte.

Vanadates. — Give the reaction for vanadium when treated as directed on p. 130, £ 2. Culciovolborthite contains 5 and Volborthite 84 per cent of water.

Tung*iaui. — Decomposed by boiliug HC1, leaviug a yellow residue of tungstic oxide (p. 128, § 1).

SeUnite. — When heated in a closed tube, a little water and a. less volniile, liquid sublimate of selenions aittf are obtained. Breuk off the end of the tube and test the volatile sublimate for the Annie color.-ition ns directed on p. 107.

Pseudo-malachite.

Tagilite.

CalcJoTolbortbite.

Volborthite.

Ciiprotungstite.

Chalcomenite.

Metallic Luster.

or only Slowly or Partially Volatile. ed with sodium carbonate on charcoal.

impounds.— Concluded.

Composition.

Color.

Luster.

Cleavage and Fracture.

Hard- ness.

8peclflo Gravity.

Fusi- bility.

Crystalli. sation.

(Cu.OH),As04. Cu(OH),.&iH,0.

Grass-green.

Pearly and vitreous.

C. Basal, per.

Hex. Rh7 U. tabul.

Cu(Cu.OH)As04.

Blackish- and olive - green to brown.

Vitreous to adamantine.

F. Uneven.

&-2.5

Orthorh. U. prism.

Cu(Cu.OH)As04. 3H,0.

Emerald-green

Vitreous.

F. Uneven.

Orthorh.

Cu(Cu.OH)4(As04),

Emerald-green

Dull to resin- ous.

F. Uneven.

Mammill.

Cu(Cu.OH)4

(As04),.3H,0.

Emerald-greeu

F. Uneven.

—

Massive.

Cu(Cu.OH)As04.

H,0.

White to pale- green.

Silky.

Capillary.

Cu.(As04),.5H,0.

Verdigris- green.

Silky.

Column. Radiated.

Cu(Fe,Ai),FeO)4

(P04)4.8H,0.

Light- to dark- green.

Vitreous.

C. Pinac, per.

Triclinic.

Cu(UO,),(P04),.

8H,0.

Emerald- to apple-green.

Pearly and vitreous.

C. Basal, per.t foliated.

Tetrag. U. tabul.

Cu(Cu.OH)P04.

Dark-green to olive-green.

Resinous.

F. Uneven.

Orthorh.

Cu(Cu.OH)4(P04),.

Dark emerald- green.

Vitreous.

F. Uneven.

Monocl.? Triclinic ?

(Cu.OH)aP04.

Emerald- to dark-green.

Emerald-green

Vitreous.

F. Uneven.

Massive. U. botryo.

Cu(Cu.OH)P04.

HaO.

Vitreous.

F. Uneven.

Monocl. U.fibrous.

(Cu,Ca)(Cu.OH)

Green to gray.

C. Pinacoirial.

Tabular. Granular.

(R.OH),V04.6H,0. R Cu, Ca, Mff & Ba.

C. Pinac, per.

1.5,?

Tabular.

CuW04. Ca iso. w. Cu.

Pistachio- to i olive-gn'on

Vilrvous.

C. Pinacoidal.

3?

Granular.

CuSeO,.2H,0.

Beautiful-blue

Vitreous

F. Uneven.

Monocl

(Page 266.)

Ii. Minerals Without Metallic Luster.

B.— Fusible from 1-5, and Non-volatile, or only Slowly or Partially

Volatile.

Part II. — Become magnetic after heating before the blowpipe in the

reducing flame.

Division 1. — Soluble in hydrochloric or nitric acid without a perceptible residue and

without yielding gelatinous silica upon evaporation.

Ii. Minerals With0

B.— Fusible from 1—5, and Non-volati

Part II. — Become magnetic after heating before the blowpi

Division 1. — Soluble Id hydrochloric or nitric acid without a perceptible residue and without J see Part III, Division 2, p. 275.

General Characters.

Oxides and hydroxides of iron. — Difficultly fusible. Become stronglv magnetic after heat- ing B.'B. in R. F. Hematite is anhydrous, the others give water in the closed tube.

Carbonate.— Soluble in hot HC1 with effervescence.

o

O bo

5©

U

g bo go

a £

T3 O 0) ►J- 4-1

at £

So

w

a2 fief's

d3.2 AS g

d 9

Si 07 o X

React for /<w- twn trim, but not for ferric.

Specific Character**.

Streak brownish-red (Indian-red, red-ocher). Compare Turgite and Hematite (p. 258).

Name of Species.

HEMATITE.(Earthy lion-crystalline.)

Streak yellowish-brown (yellow-ocher). Gothite is generally found in distinct crystals, while the others are not.

In the closed tube becomes black and magnetic.

Wholly soluble in cold water.

Wholly soluble in cold water.

React for both ferrous and ferric iron.

React for ferric iron, but not for ferrous. Wholly sol- uble in cold water.

React for ferric iron, but not for ferrous. Insoluble, or only partially soluble, in cold water. — Cont'd

Gives with the salt of phosphorus bead a chro- mium reaction.

Partly soluble in water, leaving generally a yel- lowish, ocher-like residue.

Imparts a yellow color to the blowpipe flame (sodium).

Qoethite.

Limonite.

(Brown Hematite.)

Xanthosiderite.

8Iderite.

(Spathic Iron.)

Melanterite.

(Copperas.)

Halotrichite.

Homesite.

Knorvlllite.

Botryogen.

Voltaite.

Metavoltaite.

Contain no other base than iron.

Imparts an intense yellow color to the blowpipe name (sodium).

Does not give water in the closed tube at low temperature. Reacts for potassium (p. 105,

With ammonium molybdatc gives the tenctinn for a phosphate (p. 102, §1).

Ferronatrite.

Coquimbite.

Queustedtite.

Ibleite.

Sideronatrite.

Jarosite.

Diadochite.

Division 1. — Continued on next page.

T Metallic Luster.

, or only Slowly or Partially Volatile.

3 in the reducing flame. — Iron, Cobalt and Nickel Compounds.

siding gelatinous silica upon evaporation. For details concerning tbe method of making this test.

Composition.

Color.

Luster.

Cleavage and Fracture.

Hard- ness.

Specific Gravity.

Fusi- bility.

Crystals zation.

Indian-red.

Dull.

F. Splintery.

Earthy. Keniform.

FeO(OH)

Fe,O..H.O.

Dark* to yel- lowish-brown.

Adamantine to dull.

C. Pi nnc, per. F. Splintery.

Orthorh. U prism.

b,e40>(OH)e

2FeOs.8HiO.

Dark- to yel- lowish-brown.

Silky or dull.

F. Splintery.

Mnmmill. Stalactitio

FeaO(OH)4

Fe,0..2H,0.

Ocher-yellow.

Silky or dull.

Capillary. Earthy.

FeCO,.

ag. Mn, & Ca fso.w.F*.

Light- to dark- brown.

Vitreous to pearly.

C. Rhombo- hedral. per.

Hex. Rh. U. cryst.

FeS04.7H,0.

Apple-green.

Vitreous.

C. Basal, per.

Monocl.

FeAla(S04)4.24H,0

Yellowish- white.

Silky.

Mouocl.? Triclinic?

Fe"Fe'",(SO)4.

12HaO.

Light- to dark- brown.

Vitreous.

C. Pinac, per.

Triclinia

Fe.Mg)

[(Fe,Cr,Al)OH], (S04)..5HaO?

Green ish-

yellow.

G. Basal, per.

4.5-5?

Orthorh.

Mg,Fe)(Fe.OH) (S04),.7H.O.

Hyacinth-red.

Vitreous.

C. Prismatic.

Monocl. U. botry- oidal.

e'.(Fe.OH),

(Fe,Al)4(SO4)10. 14H.0 ?

K- Kf. Nft9 ixo. w. Fe.

Oil-green to greenish-black

Resinous.

F. Uneven.

1?

Isometric?

K.„Na1,Fe)'.Fe/", (Fe'".OH)4(S04)„. 16H,0?

Yellow.

Hexag.

Scales.

fla.Fe(S04)s.8H,0.

Pale greenish- white.

Vitreous.

C. Prismatic, perfect.

Hex. Rh. U. radiat.

re,(SO)a.9HiO.

White, green, amethystine.

Vitreous.

F. Uneven.

Hex. Rh. U. cryst.

e9(SO4)..10H,O.

Reddish-violet

Vitreous.

C. Pinacoidal, perfect.

Monocl.

>e2(S04),.12HaO.

Orange-yellow

Botryoi- dal.

fa,(Fe.OH)(804),. 2H90.

Orange to straw-yellow.

Silky. 'c. Pinacoidal.

Orthorh. Fibrous.

:(Fe.20H)s(S04). a iso. w. K.

Ocher-yellow to clove- brown.

Vitreous.

C. Basal.

Hex. Rh.

U. tryst.

,Fe.OH)S04.

2FeP04 HaO.

Yellow or yel- lowish-brown.

Resinous.

F. Conchoidal.

3? Monocl.

(Page 267.)

Ii. Minerals Without Metallic Luster

B.— Fusible from 1-5, and Non- volatile, or only Slowly or Partially

Volatile.

Past II. — Become magnetic after heating before the blowpipe in the

reducing flame.

Division 1, continued

Ii. Minerals With01

B.— Fusible from 1—5, and Non-volatil Pabt II. — Become magnetic after heating before the blowpi]

Division

General Characters.

Specific Characters.

Yield an arsenical mirror when placed in a closed tube with a fragment of charcoal, and heated intensely before the blowpipe (p. 51, §a).

Sulphates, concluded. — Barium chloride when added to the dilute HC1 solution gives a precipitate of barium sulphate (p. 122. §1).

When heated in the closed tube give acid water, and. gener- ally, the odor of sulphur di- oxide is perceptible at the end Except in the case of Cyprusite, which contains a of the tube. little aluminium, these minerals have only iron

React for ferric iron, but not for as the base. When heated in the closed tube ferrous, when tested as directed a residue of fernc oxide is left, which, when on p. 85, § 4. crushed, gives a red mark (red-ocher).

Insoluble, or only partially sol- uble, in cold water.

Name of Species.

Pltticite.

Losaenite.

Castanite.

Copiapite.

Utahite.

Amarantite.

Fibroferrite.

Raimondite.

Carphosiderite.

Arsenates. — "When heated in tensely B. B. in a closed tube with a fragment of charcoal the arsenate is reduced and an arsenical mirror is formed (p. 51. § a).

Provided the mineral contains much calcium it is best to heat in a closed tube with Na,CO aud charconl-dust, as directed on p. 51, §6.

Give a blue color to the borax bead {cobalt). The HOI solution has a rose color.

Annabergite below sometimes contains suffi- cient cobalt to give a blue color to borax.

Color the borax bead in O. F. violet when hot, brown when cold. The HOI solutions have a green color. Cabrerite is a variety of anna- bergite containing magnesium.

Coutain ferric and no ferrous iron. The HC1 solutions have u yellow color, and the addition of ammonia in excess produces a reddish- brown precipitate of basic ferric -arsenate.

Glockerite.

Cyprusite.

Erythrite.

(Cobalt Bloom.)

Forbesite.

Annabergite.

(Nickel Bloom.)

Cabrerite.

Pharmaoosid erite.

8corodite.

Mazapilite.

Areenfosiderite.

Division 1. — Concluded on next page.

fT METALLIC LUSTER.

or only Slowly or Partially Volatile.

e in the reducing flame. — Iron, Cobalt and Nickel Compounds.

. — Continued.

Composition.

Ficertain. *Y,uVsO).(S04),

H,0.

[Fe.OIU.AsOJ,. PbSQ4.13H,0.

[Fe.OII)S64.

Fea(Fc.OH),(S04)8. : 17HaO.

Color.

Luster.

Cleavage and Fracture.

Hard- uees.

Yellowish- to reddish-

brown.

Vitreous,

greasy.

Specific Gravity.

Fusi- bility.

Cry stall*. z&tioiL.

Yellow to brownish- red.

Chesinut-

brown.

H,FeS.O„.

;Fe.0H)S04.3Ha0.

Fe.OH)S04.

4jtf,Q.

E\-7(Oh).(S04),.

b'eOHMBOOl.-" 411,0.

Fe.20H)3S04. tFu(OII)..HiOr

tiulphur-

yellow.

Resinous.

Vitreous.

F. Uneven. 3-4

Pearly.

Orange-

yellow. |8ilky-

Orange- to brownish-red.

C. Pinacoidal. 2.5

Pale-yellow.

Resinous.

Honey- to

Silky.

xuuty- w peftrlv ocher-yellow.lrearly-

H(FeO)7(S04)..

7H,0.

?os(As04)a.8HaO.

fl(xNi,Co)As04.

31H,0.

Straw-yellow.

Resinous.

Brownish- black to ocher-yellow.

Yellow.

Crimson to peach-red.

Sia(As04)i.8H,0.

!*o iko. w. Ni.

Xi,Mg),(As04),.

8H,0.

Fe(Fe.Oil),

(As04),.6HaO.

reAs04.2H,0.

Fe4(OH).]Ca. (As04)4.8HaO.

Fc(OH).](Ca.OH)a

(As04),.

Grayish- white.

Apple-green.

Resinous. Earthy.

C. Two direc- tions, per.

C. Basal, per.

C. Basal.

Pearly,

vitreous.

Silky.

Pearly,

vitreous.

Apple-green.

Green, yellow, brown, red.

Pale-green or brown.

Black to brownish -red.

Yellowish to golden-brown.

Pearly.

Adamantine.

Vitreous.

Sub-metallic.

Silky.

C. Pinac, per.

C. Pinac, per.

F. Uneven. 2.5

F. Uneven. ' 3.5-4

F. Uneven. I 4.5

Fibrous.

2?

Massive. Rem' form.

Orthorh.

2-8?

Mouocl. Prismatic.

Mou cl. Tabular.

Hex Rh. Tabular.

Tri clinic. Prismatic.

Moiioci.? Fibrous.

Hexag. Tubular.

Hex. Rh.? Reiiiform.

Massive. Earthy.

Hexag. Tubular.

Mouocl. Prismatic

Fibrous.

Monocl. Capillary.

Monocl. Prismat.

Isom. Tet. U. crysi.

Orthorh. U. cryst

OrthorbT Prismat.

Fibrous.

(Page 268.)

Ii. Minerals Without Metallic Luster.

B.— Fusible from 1-5, and Non-volatile, or only Slowly or Partially

Volatile.

Pabt II. — Become magnetic after heating before the blowpipe in the

reducing flame.

Division 1, concluded.

Ii. Minerals Withot

B.— Fusible from 1—5, and Non-volatil Part II. — Become magnetic after heating before the blowpij

Division* 1.

General Characters.

JEn-i"

O

© ©

§5

a. 2

'l

a

©.a ©

"©

Specific Characters.

Name of Species.

Colore the blowpipe flame red {lithium). Gives Triphyiite. See Utile or no water in ihe closed tube. WAophihte, p. sre.

Triplito.

Contain manganese. — Impart to the borax

bead in O. F. a red-'React8 for fluorine (p. 76t §0). Gives little or (tub - violet color, j no water iu tbe closed lube (OH w F)

React for ferrous iron ] '

when the dilute HCliri. . 4, . . A . , I

solution is tested with Glves. water m the closed tube. B. B. fuses1

potassium ferrocyan- easlly-

ide (p. 85, § 4). j

Give8 Water in lhe Cl°8ed tube' B' B- exfoliates Children!*. See

plates 01 iron and and afterwards fuses on the edges. , eo*phonte,v.m>.

manganese on p. 276. . 6 !

Triploldite.

z z ©

s s

a o

RCt°rRTfriWhen gently heated in a closed tube, Vivianite (p.80, &4). contain, whiteus> whi]e Ludlamite darkens. Both

Vivianite.

little nese.

or no manga- darken on intense ignition.

Ludlamite.

After precipitation of the iron with ammonia audi filtering, the solution has a blue color (copper). Chalcosiderite.

If a drop of dilute Ha804 is added to the concen- trated HCU solutiou, a precipitate of calcium sulphate will be formed.

Borickite.

Calcioferrite.

3 7 Heart for ferric iron Heads for aluminium, after separating the iron

2 § g, wien 1 dllute HC With potassium hydroxide as directed on p. 111. £ "5. solution is tested with 3 © potassium ferrocyau-i 5 id- (p. 85, §4). -T=?2— All of the mine

Barratidite.

O -

5T ©

I 2

H.5 fir5

tC 05 r; 08

All of the minerals in

Dufrenite.

this

water

tube.

section give in the closed

Contain only iron as the base.

Beraunite. (EleoDorite.)

Phosphosiderite.

Strengite,

Koninckite.

Cacoxenite.

Borate. — When heated with the potassium bisulphate and fluorite mixture, momen-j

tarily colors the flame green (p. 56, $ 1). Reacts for both ferric and ferrous iron, j Ludw|K|le-

Telluri*em — Gives a fusible sublimate of TeOa in the open tube. Reacts for ferric!

iron.

Durdenite.

r METALLIC LUSTER.

, or only Slowly or Partially Volatile.

in the reducing flame. — Iron, Cobalt and Nickel Compounds.

Concluded.

Composition.

Color.

Luster.

Cleavage and Fracture.

Hard- ness.

Specific Gravity.

Fusi- bility.

Crystalli- zation.

ii(Fe,Mn)P04.

Light blue, green, or gray

Resinous.

C. Basal, per., & Pinacoidal.

Orthorh. U. mass.

i(RF)P04. : Fe & Mn. with a little Ca & Mg.

Chestnut* to blackish- brown.

Resinous.

C. Two direc- tions. F. Uneven.

4r-5.5

3.6—8.8.

Monocl. U. mass.

t(R.OII)P04.

Fe und Mn.

Yellowish- to reddish- brown

Vitreous,

greasy.

C. Pinac, per. F. Uneven.

Monocl. Prismat.

Fe,Mn)(A1.20H)

P04.HaO.

Yellowish- brown to brownish- black.

Vitreous,

resinous.

C. Pinacoidal. F. Uneven.

Orthorh. Fig. 809, Page 207.

e3(P04)a.8HaO.

Blue, bluish- . green to colorless.

Pearly to

vitreous.

C. Pinac., per.

Monocl. U. prism.

'e5lFe.OH)a

(P04)4.8HaO.

Pale-green.

Vitreous.

C. Basal, per.

2-r2.5

Monocl. U. tabular

A

!iHFe,Al)a(FeO)4 (P04)4.8HaO.

Light to dark green.

Vitreous.

C. Pinac, per.

Triclinic

!u(Fe.20H)4

(P04)a.3HaO?

Reddish- brown.

Wax-like.

Massive. Ren i form

fos(FcOH),

(P04)4.8H,0.

1 iso.w.Fe&Mjf.w.Ca

Sulphur- to greenish- yellow.

Pearly.

a-

C. One direc- tion, per.

Massive. Foliated.

ll,Fe)P04.2HaO.

Pale blue, greeu or yel- low.

Vitreous,

greasy.

F. Splintery.

Spheroid- al. Radiated.

e9(OH),P04.

Dull olive- to blackish -green

Silky.

F. Splintery.

Orthorh. y. Fibrous

Fe.OH),(P04),.

2JHaO.

Reddish- brown.

Vitreous.

C. Pinacoidal.

Monocl. U. foliat.

FeP04.8JHaO.

Pale-red or reddish -violet.

Vitreous.

C. Pinac, per.

2.5-3?

Orthorh.

eP04.2HaO.

Pale-red or reddish-violet.

Vitreous.

C. Pinacoidal. F. Uneven.

Orthorh. U. cryst.

eP04.3HaO.

Yellow.

Vitreous.

F. Splintery.

Radiated.

re9(OH),P04.

4Jh.O.

Golden-yellow

Silky.

Radiated.

MgBa04.

Fe"Fe"'a04.

Blackish-green nenrly black.

Dull, silky.

F. Splintery.

Orthorh. Fibrous.

:ea(TeO,),.4HaO.

Greenish- yellow.

Vitreous.

Massive Mam mill.

(Page 269.)

Ii. Minerals Without Metallic Luster.

B.— Fusible from 1-5, and Non-volatile, or only Slowly or Partially

Volatile.

Part II. — Become magnetic after heating before the blowpipe in the

reducing flame.

Division 2. — Soluble in hydrochloric or nitric acid, and give gelatinous silica upon evaporation, or decomposed with the separation of silica.

269 II. MINERALS WITHOl

B.— Fusible from 1—6, and Eon-volati

Part II. — Become magnetic after heating before the blowpij

Division 2.— Soluble in hydrochloric or nitric acid and give gelatinous silica upon evapor this test see Part III, Division 8, p. 27a, and Division 4, p. 281.

General Characters.

Specific Characters.

Name of Specie*.

©

.a

a

Gelatinize with hydro- chloric acid.

tSf Compare AUanite be- low, which often contains considerable water. '

Cronstedtite occurs usually in crystals with tri- angular cross-section Thuringite in aggrega- tions of minute scales.

Cronstedtite.

Thuringite.

Give much w closed tube.

Decomposed by hydro- chloric acid with the sep- aration of silica, but without forming a jelly.

Radiated or foliated.

Stilpnomelane. (Chalcodite.)

Gives a reaction for chlorine when tested as directed on p. 68, § 3.

Pyrosmalite.

Soluble in HC1 with slight evolution of hydrogen sulphide.

The fine powder when fused with a little NaCO, on charcoal gives a coating of zinc oxide.

Danalite. (HelTite).

Micaceous or foliated.

Gelatinizes with HC1.

Lepidomelane.

o

©

Slightly attacked by HC1 with separation of silica.

BIOTITE. See the micas, p. 284.

Readily decomposed by HC1 with separation of silica. The solution when boiled with tin be- comes violet {titanium, p. 127, § 2).

Attropkyllite.

©

Gelatinize with hydro - chloric acid Give decid-

Fuses quietly.

llvaite. (LfeTrite.)

J3

ft* ©

ed reactions for both fer- rous and ferric iron (p. 85, §4).

Swells and froths during fusion. The presence of the rare-earth metals may be detected as directed on p. 65.

Atlanta.

O

ft*

o

Gelatinizes imperfectly. Characterized by its iso- metric crystallization.

Reacts mostly for ferric, although it may also contain some ferrous, iron.

Andradite.

(Calcium-iron

Garnet.

Jg

Gelatinize. Give strong reactions for ferrous iron, and little or none for ferric.

Sometimes magnetic before heating, owing to the presence of included particles of magnetite.

Fayaltte.

(Iron Chrysolite.)

Closely related to FayalUe, but differing in con- taining some magnesium, manganese or sine, isomorphous with the iron. Test for manga- nese with the NaaCOs bead, for zinc by fusing with Na,CO$ on charcoal, and for magnesium as directed on p. 01, § 1, b.

Hortonolite,

Knebellte.

Rooppertte.

r METALLIC LUSTER.

or only Slowly or Partially Volatile.

i in the reducing flame. — Iron, Cobalt and Nickel Compounds.

ion, or decomposed with the separation of silica. — For details concerning the method of making

Composition.

Oolor.

Luster.

Cleavage and Fracture.

Hard- ness.

Specific Gravity.

Fusi- bility.

Crystalli- zation.

H.Fe"4Fe"'48i,0,.? ng iso. w. Fe.

Black to brownish- black.

Vitreous.

C. Basal, per.

Hex. Rh. Hemimor.

HiaFe".(Al,Fe).

Si.041?

Olive- to pis- tachio-green.

Dull.

F. Tough, uneven.

Compact. Scaly.

a.(Fe,Mg),(Fe,Al), SI.O,.?

Greenish- to yellowish- bronze.

Pearly,bronze- Hke.

C. One direc- tion.

Foliated. Velvety.

a,(FeClXFe,Mn)4 (8i04)4.

Pistachio- green to

brown.

Pearly to Vitreous.

G. Basal, per.

Hezag. Prismatic.

a(R,8X8i04),.

1 Be, Fe, Zn & Mil

Flesh-red

to gray.

Vitreous,

resinous.

F. Uneven.

Isom. Tet,

K.HkFe'VFe.Al), (8i04),?

Black, greenish-black

Adamantine to pearly.

C. Basal, per.

Monocl.

K,HMMg,Fe),

(Al,Fe),(Si04),.

Green to greenish-black

Splendent,

pearly.

C. Basal, per.

Monocl.

K,Na,H)4

(Fe,Mn,Mg,Ca)4

fjr iso. w. Si.

Bronze- to golden-yellow.

Pearly.

C. Pinac, per.

Orthorh.

;aFe",(Fe'".OH) (Si04).

Iron-black.

Black.

F. Uneven.

Orthorh. U. prism.

*",(R"\oh)R",

(8i04).. t" Ca & Fe. t'"= Al, Fe.Oe, LA,ADi

Brown- to pitch-black.

Gray.

F. uneven to conchoidal.

Monocl. U. mass.

?a,Fe,(8i04),.

*e, Mn & Mgiso. w. Ca; Al iso. w. Fe.

Wine, greenish yellow, green, brown.

Vitreous, adamantine.

F. Uneven.

Isometric* Figs. 97, 105, 106.

i'e,Si04.

Yellow to dark yellowish- green.

Resinous.

C. Pinacoidal. F. Uneven.

Orthorh. U. mass.

Fe,Mg,Mn),8i04.

Yellow to dark yellowish- green.

Resinous.

C. Pinacoidal. F. Uneven.

Orthorh. U. mass.

Pe,Mn,MK),8I04.

Gray, browu, green.

Greasy.

C. Pinacoidal. F. Uneven.

Orthorh. U. masf

fcMn.Mg.Zn),

SiQ4.

Yellow to dark yellowish- green.

Greasy.

C. Pinacoidal. F. Uneven.

Orthorh. U. mass.

(Page 270.)

Ii. Minerals Without Metallic Luster.

B.— Fusible from 1-5, and Non-volatile, or only Slowly or Partially

Volatile.

Part II. — Become magnetic after heating before the blowpipe in the

reducing flame.

Division 3. — Insoluble in, or only slightly acted upon by, acids.

ii. MINERALS WITHOUf

B.— Fusible from 1—5, and Non-volatile Pakt II. — Become magnetic after heating before the blowpipe

Division 8. — Insoluble in, or only si

General Characters.

Contains tungsten. — Character- ized by an exceptionally high specific gravity.

Micaceous.

Distinguished by its isometric crystallization.

Specific Characters.

Name of Species.

Test for tungsten as directed on p. 129, §2. Color* the Ka*COs bead in O. F. green (man- ganese).

Easily fusible. Tinges the blowpipe flame red (UUiium).

Difficultly fusible.

Fused garnet is soluble in HC1, and yields a jelly on evaporation.

Quietly and difficultly fusible.

Fusible B. B. with intumescence, and impart a decided yellow color to the flame {sodium).

The perfect prismatic cleavage of these minerals at angles of about 125° and 55° is charac- teristic.

Compare these members of the Am pinhole Group of min erals with those on p. 288.

Wolframite. t

(Manganese variety.) '

Zionwaldite.

BIOTITE. 8ee the I micas, p. 884.

Almanoite.

(Iron-aluminium Garnet.)

Often has a peculiar metal-like schiller.

Compare Anthophyllite (p. 287), which may become magnetic after heating B.B.

Contains titanium (p. 127, § 2). The iron is chiefly ferrous (test as directed on p. 86).

The iron is chiefly ferrous.

Hypertthene.

ISnigmatlte.

Usually has a fibrous structure. The iron is both ferrous and lerric.

ArrVedsoatito.

Contains both ferrous and ferric iron.

Fuses quietly B. B., coloring the flame yellow (sodium). The fused globule is not very mag netic.

Fuses quietly, and without marked flame coloration.

The prismatic faces make nearly a right angle (93°) with one another. The cleavage is not very perfect.

Contains both ferrous aud ferric iron and much calcium.

Crocidolito.

Biebeckite.

Aemite.

CSfeirite.)

Babingtonite.

Compare the dark-green and black varieties of Pyroxene, Amphibole, Tourmaline and other Bit magnetic when heated before the blowpipe.

r METALLIC LUSTEXL

t, or only Slowly or

Volatile.

tin the reducing flame. — Iron, Cobalt and Nickel Compounds. lightly acted upon by, acids.

Composition.

Color.

Luster.

Cleavage and Fracture.

Hard- ness.

Specific Gravity.

Fusi- bility.

Crystalli- zation.

Mn,Fe)WO.

Black.

Sub-metallic.

C. Pinac, per. F. Uneven.

Monocl. U. cryst.

K,Li),Fe"(A10) AlF,)Al(8iO,)..

)H iso. w. P.

Gray, brown, violet.

Pearly.

C. Basal, per.

Monocl.

K:.H),(Mg.Fe),

(Al.Fe),(8i04)t.

Green to greenish -black

Splendeut,

pearly.

C. Basal, per.

Monocl.

re",Al,(SiO),. In. Mr & Ca iso.w. Fe; Fe iso. w. Al.

Deep-red to brownish-red.

Vitreous.

F. Uneven.

isometric. Figs. 97, 105. 106.

Mg,Fe)SiO,.

Greenish- black, bronze- brown.

Bronze-like.

C. Pinac., per. F. Uneven.

Orthorh. U. mass.

J n certain. Fe",Mn,Ca),

(Fe"',Al),Na,

(Ti.Si),0.

Black.

Vitreous.

C. Prismatic. F. Uneven.

Triclinic.

Fe.Na,fCa)4(8iO,) re,(Al.Fe),8i,0„.

Blac*.

Vitreous.

C. Prism., per. F. Uneven.

Monocl. Prismatic

4NnFe'"(SiO.),. HFe",Mg,Ca)SiO,.

In tense lavender-blue.

Silky.

F. Fibrous.

Fibrous.

S 2NaFe'"(8iO.),. ) (Fe,Ca)SiO,.

Black.

Vitreous.

0. Prism., per.

6?

3?

Monocl.

raFe'"(SiO,),.

Greenish- to brownish- black.

Vitreous.

C. Prismatic. F. Uneven.

Monocl. Prismatic.

(Ca,Fe,Mn)SIO,. Fe,(8i03)i.

Greenish-black to black.

Vitreous.

C. One direc- tion, perfect. F. Uneven.

Triclinic, U. cryst.

%tes in Division 5, p. 283, which may contain sufficient Iron to cause them to become somewhat

(Page 271.)

Ii. Minerals Without Metallic Luster.

B.— Fusible from 1-5, and Non-volatile, or only Slowly or Partially

Volatile.

Part III. — With sodium carbonate on charcoal do not give a metallic glob- ule, and when fused alone in the reducing flame do not become magnetic.

Division 1. — After intense ignition before the blowpipe, either in the forceps or on

charcoal, the ignited material gives an alkaline reaction when placed on turmeric-paper.

Section a. — Easily and Completely Soluble in Water.— In part.

/

Ii. Minerals Witk

B.— Fusible from 1—5, and Non-volati

Part III. — With sodium carbonate on charcoal do not give a metallic gh

Division 1. — After intense ignition before the blowpipe, either in the forceps or on charco

Section a. — Easily and a

N.B. — The minerals iu this section are chiefly salts of the alkali metals, sodium and potassium, taste. Flame tests will generally serve to identify the metals, and it is recommended to make the te (p. 115, § 1), but only those containing sodium as an essential constituent give an intense and persistei color when viewed through rather dark blue glass (p. 105, § 1).

General Characters.

Pi

a

Combinations of a chloride with a sul- phate.— The aqueous solution made acid with a little HC1 gives a precipitate with barium chlo- ride (p. 122, § 1).

03

Do not give the fore- going reaction for a sulphate.

Specific Characters.

Gives a slight effervescence when a fragment is dropped into acid.

Name of Species.

Hanksite.

Does not effervesce. Gives a yellow flame a .. . m (sodium). Reacts tor fluorine (p. 75, § 1). uipnonaute.

Does not effervesce. Gives a violet flame' (potassium).

Gives an intense yellow flame (sodium).

Gives a violet flame (potassium). Sylvite is an- hydrous. Carnallite contains much water.

Kainlte.

Halite.

(Common Salt.)

8Ylvite.

Carnallite.

Give a yellowish-red flame (calcium). Deliquesce Hydrophffite. readily. Tachydrite melts in its water of crystallization.

Carbonates. — Effervesce when Mells in *ls of crystallization when gently treated with acids. All miu-i heated in a closed tube. Water 63 per cent.

era Is in this section give a Gives water and cuihon dioxide (p 64, §2) when yellow flame (sodium). Their gently beatty (not to fusion) in a closed tube, aqueous solutions give an alka-

line reaction with turmeric- Givrs water (14 per cent) but no carbon dioxide paper. I when gently 7ieated iu a closed tube.

Tachydrite.

Natron. (Sal-eoda,)

Trona.

Thennonatrite.

Division J, Section a.— Continued on next page.

Out Metallic Luster.

e, or only Slowly or Partially Volatile.

*7i

bide, and when fused alone in the reducing flame do not become magnetic.

il, the igoited material gives an alkaline reaction when placed on moistened turmeric- i>aper.

mpletely soluble in water.

ith volatile acids (hydrodiloric, carbonic, eulphuric, and nitric). Most of them have a decided saline its on platinum wire as directed on p. 85. Most minerals will impart some yellow color 10 the Urn. e t yellow. The violet flame of potassium, which may not be very evident, has a decided purpli>h red

Composition.

Color.

Luster.

CtaivRfTP and Fracture.

Hard- ness.

Specific Gravity.

Fusi- bility.

CryKialll-

zaiiou.

9Na,S04.2Na,COt.

Kc1.

Colorless or white.

Vitreous.

C. Basal. F. Uneven.

Page 180.

2Na,804.NaCl.

NaF.

Colorless or while.

Vitreous.

F. Uneven.

Isometric. Fig. 97.

MgS04.KC1.8H,0.

Colorless or white.

Vitreous.

C. Pinacoidal.

Monocl.

NfaCl.

Colorless, white, red, blue.

Vitreous.

C. Cubic, per.

Isomeirir. U. cubic.

feci.

Colorless or white.

Vitreous.

C. Cubip, per.

1.Im.0

Isometric Figs. 98.99

MgCl9.KC1.6HfO.

Colorless, white, red.

Vitreous.

F. Conchoidal.

Ortborh.

JaCl9.

Colorless or white.

Vitreous.

2:2

Isometric.

!M*CI..CaCl..

12H.O.

Wax- to honey- yellow.

Vitreous.

2.5 !

Hex. nil.

Sa3CO.10H,O.

Colorless, gray, white.

Vitreous.

C. Bnsul.

F. Conchoidal.

Monocl

Sa,CO..HNaCO,. 2H.O.

Colorless, gray, white.

Vitreous.

C. Pinac. pei-. F. Un*'von.

Monocl.

STaaCO,.HaO.

While, gray, yellow.

Vitreous.

Somewhat

sect ile.

Ortborh.

(Page 272.)

Ii. Minerals Without Metallic Luster.

B.— Fusible from 1-6, and Non-volatile, or only Slowly or Partially

Volatile.

Part III. — With sodium carbonate on charcoal do not give a metallic * ule, and when fused alone in the reducing flame do not become magnetic.

Division 1. — After intense ignition before the blowpipe, either in the forceps or on

charcoal, the ignited material gives an alkaline reaction when placed on turmeric-paper.

Section a.— Easily and Completely Soluble in Water.— Continued.

m

Ii. Minerals With01

B.— Fusible from 1—6, and Kon-volati]

Part III. — With sodium carbonate on charcoal do not give a metallic gU Division 1. — After intense ignition before the blowpipe, either in the forceps or on charcc

Section a. — Easily and compU

General Characters.

S2&

9 O.S?

-

9? O

-B

Give no water in the closed tube, and are thus distinguished from the sulphates in the following sections.

c °

©

£3 -

s

sir?

Ill's

erg w:s

Contain aluminium. — In a solution made acid with HC1, am- monia gives a precip- itate of aluminium hydroxide (p 42, § 2).

Contain magnesium. — In a solution made acid with HC1, am- monia produces ' no precipitate (provided the solution is not too concentrated), but sodium phosphate, added to the solution made alkaline with ammonia, gives a pre- cipitate of ammonium magnesium phos - phatefp. 91, § 1).

Contain sodium. — Im- part an iu tense yel- low color to the blow- pipe or Bunsen-burn- er flames, but do not give the reactions of the foregoing divi- sions.

Contain potassium. — Impart a violet color to the flame, but do not give the reactions of the foregoing divi

sions.

Specific Characters.

Gives a yellow flame (sodium), which appears purplish -red wheu viewed through blue glass {potassium).

Name of Species.

Aphthltalite.

Gives a yellow flame. Contains no potassium.

Thaaardits.

Gives a violet flame [potassium). Reacts for am- monium (p. 48).

B. B. swells and gives a yellow flame (sodium).

B. B. swells and gives a violet flame (potassium).

Gives the odor of ammonia when heated in a closed tube with lime (p. 48).

Give no pronounced flame coloration. The alka- line reaction may not be very strong. Have a bitter taste.

Compare Sulphates, Division 2, p. 275.

Give a yellow flame coloration (sodium).

Give a violet flame coloration (potassium). Langbeinite is anhydrous.

Heated in a bulb tube with potassium bisulphate yields red vapors of NO, (nitrate test), p. 100.

Gives the odor of ammonia when heated in a closed tube with lime (ignited calcite).

Gives much water (55 per cent) in the closed tube.

Has a sour taste.

Sparingly soluble in water. Reacts for calcium (p. 60, § 6).

Taylorite.

Mendoslte.

Kalinita. (Potash Alum.)

Bousslngauitite.

Epsomite.

(BpsomSait)

Kieaerite.

LGweite.

BUSdite.

Langbeinite.

Picromerlte.

Darapskite.

Lecontite.

Mirabilita.

(Glauber SalO

Miaenite.

Syngeutte,

Division 1. Section a. — Concluded on next page.

T Metallic Luster.

, or only Slowly or Partially Volatile.

vie, and when fused alone in the reducing flame do not become magnetic.

1, the ignited material gives an alkaline reaction when placed on moistened turmeric-paper.

ly soluble in water.— Continued.

Composition.

Color.

Luster.

Cleavage and Fracture.

Hard- ness.

Specific Gravity.

Fusi billty.

Crystalli- zation.

K,Na)a804.

Colorless or white.

Vitreous.

C. Prismatic.

2.6o

Hex. Rh.

fa,S04.

Colorless, white, brownish.

Vitreous.

C. Basal. P. Uneven.

Orthorh.

Yellowish- white.

Vitreous.

1.5?

Massive.

raAl(S04),.12H.O.

White.

Silky-vitreous.

F. Fibrous.

1?

Massive. Fibrous.

:Ai(S04),.i2H9o.

Colorless or white.

Vitreous.

F. Conchoidal.

Isora.Pyr. U. fibrous

[gS04.(NH),S04. 6H,0.

Colorless or white.

Vitreous.

1.5-2?

Monocl.

[gS047H,0.

Colorless or white.

Vitreous.

C. Pinac, per. F. Conchoidal.

Orthorh. Page 207.

[gS04.H,0.

White, gray, yellow.

Vitreous.

C. Prismatic.

Monocl.

gS04.Na,804.

2*H,0.

White,yellow, red.

Vitreous.

C. Basal.

F. Conchoidal

Tetrng

gSO4.Na.SO4.

4H,0.

Colorless or white.

Vitreous.

F. Uneven.

Monocl.

S04.K.S04.

Colorless or white.

Vitreous.

F. Conchoidal.

Isometric C1.6.p.219

gS04.K,S04.

6H.O.

White.

Vitreous.

Monocl.

a9S04.NaN0,.

H.O.

Colorless or white.

Vitreous.

C. Pinac., per.

1?

Monocl. Tabular.

ia,NH4,K),S04. 2H,0.

Colorless or white.

Vitreous.

Orthorh.

&9So.10H,O.

Colorless or white.

Vitreous.

C. Pinac, per.

Monocl.

Cso4.

Colorless or white.

Vitreous or silky.

Fibrous.

K,(S04)..H,0.

Colorless or white.

Vitreous.

C. prism., per. F. Conchoidal.

1.5-2 'Monocl.

(Page 273.)

Ii. Mineeals Without Metallic Luster.

B.— Fusible from 1-5, and Non-volatile, or only -Slowly or Partially

Volatile.

Part III. — With sodium carbonate on charcoal do not give a metallic glob- ule, and when fused alone in the reducing flame do not become magnetic.

Division 1. — After intense ignition before the blowpipe, either in the forceps or on

charcoal, the ignited material gives an alkaline reaction when placed on moistened turmeric-paper.

Section a. — Easily and completely soluble in water. — Concluded.

Section b. — Insoluble in water, or difficultly or only partially soluble. — In part.

Ii. Minerals Withou

B.— Fusible from 1—5, and Non-volatile

Part III. — With sodium carbonate on charcoal do not give a metallic g

Division 1. — After intense ignition before the blowpipe, either in the forceps or on cbarc

Section a. — Easily and

General Characters.

Specific Characters.

Name of Species.

Nitrates. — When heated in a

Gives an intense yellow flame {sodium).

Soda Niter.

bulb tube with potassium bi- sulphate, red vapors of N02

Gives a violet flame (potassium).

Niter.

are given off (p. 100).*

Gives a yellowish-green flame (barium). Test on platinum wire (p. 85).

Nitrobarite.

Borate. — Give the boracic acid reaction with turmeric-paper (p. 56, § 2).

When taken up in the loop on platinum wire swells when first heated, and fuses finally to a clear glass.

Borax.

Give iodine vapors when heated in a closed tube.

tW Compare the difficultly soluble iodates, Lau- tarite and Dietzeite, in the next section.

Nitrates of calcium and magnesium, containing water of crystallization, have been identified.

Section b. — Insoluble in rooter, a

N.B. — The minerals in this section are chiefly salts of the alkali-earth metals, calcium, strontiu advantageously in identifying the metals, and it is recommended to make the tests on platinum w hydrochloric acid, and then introducing it into the flame, serves in many cases to bring out the col

Silicates and other compounds which do not properly belong to this section at times give an all with i he common miueral Calcitefa. 280), and that the alkaline reaction is due to traces of the calcii will be decomposed and a misleading alkaline reaction will not be obtained.

A 3

S

9-3

lid

Give water in the closed tube. B. B. give an intense yellow flame (sodium).

Gives water in the closed tube, but does not con- tain sodium.

Give no water in the closed tube.

When treated with boiling water, calcium carbo- nate separates, and the soluble sodium carbo- nate renders the solution alkaline. Pirssonite exhibits pyroelectricity (p. 231).

Ammonia gives a precipitate of aluminium hy- droxide when added to the dilute HC1 solution (p. 42, § 2).

The dilute HC1 solution gives a precipitate with barium chloride (p. 122), and a residue of silica when evaporuted to dryness (p. 109).

Gives a yell>wisli-given color to the flame (barium). Test ou platinum wire (p. 35).

Gives an intense yellow flame (sodium). Reacts for chlorine (p. 67, § 1) and magnesium (P- 91. § 1).

Gay-Lutsife.

Pirssonite.

Dawsonite.

ThaumasSte.

Witherite.

Northupite.

Division 1. — Concluded on uext page.

Metallic Luster.

or only Slowly or Partially Volatile.

bide, and when fused alone in the reducing flame do not become magnetic,

il, tbe ignited material gives an alkaline reaction when placed on moistened turmeric-paper.

mpletdy soluble in water.

Composition.

Color.

Luster.

Cleavage and Fracture.

Hard- ness.

Specific Gravity.

Fusi- bility.

Crrstalll- cation.

NaNO,.

Colorless or while.

Vitreous.

C. Rhombo- bedral, per.

Hex Rh.

Kno,.

Colorless or white.

Vitreous.

C. Prism., per. F. Conchoidal.

,1

Orluorh. U. neicul.

Ba(NO,).

Colorless or white.

Vitreous.

F. Uneven.

Isometric. C1.5,p.219

Na,B4O,.10H,O.

Colorless or white.

Vitreous.

C. Pinac, per. F. Conchoidal.

Monocl.

Mfficultly or only partially soluble.

and barium, with volatile acids (carbonic, sulphuric, and hydrofluoric). Flame tests may be used e as directed on p. 35. After the mineral has been fused on the wire, touching it to a drop of

more decidedly.

line reaction after ignition. It will generally be found, however, that such minerals are associated which permeate minute cracks in the crystals. If such minerals are thoroughly fused the calcite

NaaCO,.CaCO.. 5H,Q.

NaaCO,.CaCO,.

2H,0.

Na(A1.20H)CO,.

CaCO,.CaSiOs.

C804.15H,0.

BaCO,.

MgCOa.Na.CO,

NaCl.

Colorless white, gray.

Colorless, white, gray.

White.

White,

colorless.

Colorless, white, gray.

Colorless, white, brown.

Vitreous.

Vitreous.

Vitreous,

silky.

Vitreous.

Vitreous.

Vitreous.

C. Prismatic. F. Conchoidal.

F. Conchoidal.

F. Longitu- dinal.

F. Splintery.

F. Uneven.

7. Conchoidal.

Monocl. U. cryst.

Orthorh. Hemimor.

Monocl.

Blarled.

Radiated.

Uexag. Column., fibrous.

Orthorh. Twinned.

oqo 1 1 it Isometric. 3 88 1-1.5 F.s

(Page 274.)

Ii. Minerals Without Metallic Luster.

B.— Fusible from 1-5, and Non-volatile, or only Slowly or Partially

Volatile.

Part III. — With sodium carbonate on charcoal do not give a metallic glob' uley and when fused alone in the reducing flame do not become magnetic.

Division 1. — After intense ignition before the blowpipe, either in the forceps or on

charcoal, the ignited material gives an alkaline reaction when placed on moistened turmeric-paper.

Section b. — Insoluble in water, or difficultly or only partially soluble. — Concluded.

Ii. Minerals Witho

B.— Fusible from 1—6, and Non-volatj

Part III. — With sodium carbonate on charcoal do not give a metallic gl

Division 1. — After intense ignition before the blowpipe, either in the forceps or on charc<

Section b. — Insoluble in water, or diffleul

General Characters.

5*8 %sf

"*r- a o 9

O 'rj a

- ZSjZ

- as ss fa

- c be 5? T

© g .2 Scot

wo— ?3

less:?*

Give much water in the closed tube. The fine powder is readily soluble in boiling, dilute HC1.

Give little or no water in the closed tube.

Glauberite is read- ily, and Anhy- drite slowly, sol- uble in boiling dilute HC1, while Celestite and Ba- rite are almost in- soluble.

Specific Characters.

Ammonia gives n precipitate of aluminium hy- droxide when added to the HC1 solution.

Name of Species.

Gives no decided flame coloration when heated alone B. B.

Ettringite.

Gives a yellow flame (sodium).

Gypsum.

(Alabaster.)

Wattevillite.

Give a violet flame (potassium), seen best through PolyhaJite.

blue glass. Polyhalite reacts for magnesium t

(p. 91, § 1). Syngenite.

Gives a yellow flame (sodium).

Gives no decided flame coloration when heated alone B. B.

Gives a crimson flame (strontium).

Gives a yellowish-green flame (barium).

Compare the magnesium sulphates on page 272, some of which mav be difficultly soluble iu water.

°3 Os —

-2 Is"

8 " s

J2 .

§ 3 c

X T3

2

ce a 22

oj>

so IS

as

2=5 coo

3 a a

cS O O

Give little or no water in the closed tube.

Give acid water iu the closed tube, often accom- panied by etch- ing of the glass, and a deposit of silica (p. 77, § 5). Compare Pro- sopite p. 2l>0).

Easily fusible. Color the flame yellow (sodium). Powdered cryolite is scarcely visible in water because of its low index of re f motion.

Gives a reddish flume (calcium). Often phos- phoresces (p. 231) aud decrepitates when heated in the closed tube.

Generalhr decrepitate to a fine powder when heatea in a closed tube. Thomsenolite occurs in rather stout, and Pachnolite in very slender, prisms.

Ibdal Fuse mid give iodine vipors when heated in a closed

Occurs as an earthy powder. Contains no sodium.

DkUeite is readily distinguished by its reaction for chromium with the salt of phosphorus bead.

G leu be rite.

Anhydrite.

Celestite.

Barite.

(Heavy Spar.)

Cryolite.

Chiolite.

Fluorite.

(Fluor Spar.)

Thomsenolite.

Pachnolite.

Gearksutite.

Lautartte.

DleUeite.

T Metallic Luster.

27A

or only Slowly or Partially Volatile.

mle, and when fused alone in the reducing flame do not become magnetic.

i, the ignited material gives an alkaline reaction when placed on moistened turmeric-paper.

i or only partially soluble. — Concluded.

Composition.

Ca.OH).(SO)a.

Color.

Luster.

Colorless or

2(011)8.2411,0?, wbite.

Vitreous.

:uS0.2H,0.

'aSO, .NaaS04.

4H90. U i*o. w. Ca. &K w. Na.

° whlJT W Vitreous, wnite, gray.

White.

Silky,

vitreous.

Cleavage and Fracture.

F. Splintery.

Hard- ness.

C. 8 directions. Piuac, per.

Brick-red to K,S04.2H,0. yellow.

!aK2(S04)9.H„0.

:aS04.NaaS04.

?nS()4.

rH04.

-aSU4.

Colorless or white.

Vitreous to resinous.

iC. Pinacoidal. 'F. Splintery.

2.&-S

Vitreous.

;C. Pinac, per.\ 0 - IF. Conchoidal.l

Colorless, white, gray.

'Vitreous.

jC. Basal, per. |F. Conchoidal

Colorless, ,TT.4

white, blue, VUreouB,

gray, red.

Colorless, white, blue, red.

pearly.

Vitreous,

pearly.

C. 3 directions (pinacoidal) at 90°, per.

C. Basal, per. & prismatic.

Colorless, white, blue, yellow, red.

Vitreous,

pearly.

C. Basal, per.& prismatic.

:a8AlF„

3NaF.AlF,.

Colorless, LTl4 . Iri t. :j

snow-white, |Vitreous to !C. Pinacoidal. Kw,™ ' ! jrreasy. F. Uneven.

brownish.

SaF.3AlF,.

nF,.

CnAlF..H,0.

Snow-white. Vitreous.

IF. Uneven.

Colorless, violet, green, yd low, pink.

aCaAlF..H,0.

*F3.A1(F,0H)S.

H.O.

i(IOa),.

?a(IO,),.8CaCK)4.

Colorless, white, brown.

Colorless or white.

White.

Sulphur- yellow to colorless.

Golden-yellow

Vitreous.

C. Octahedral,

perfect. F. Uneven.

Pearly, C. Basal, per.

vitreous. F. Uneven.

Vitreous.

F. Uneven.

Dull.

2?

Vitreous.

Vitreous.

C. Prismatic. F. Conchoidal.

F. Uneven.

8peciflc Gravity.

Fusi- bility.

Crystalli- zation.

Hexag. Needles.

Monocl. Page 210.

1.5-2 ,Acicular.

Monocl. ? 'Column.

1.5-2 Monocl.

Monocl. iU. tabul.

Orthorh. U. mass.

Orthorh. iPage 202.

Orthorh." Page 201.

- - 'Monocl. iU. mass.

i'iv

- K Tetrag. 1,0 U. mass.

Isometric. Figs. 95. 96, 96, 113, 115.

I Monocl. 1.5 jCryst. & I massive.

1 .Monocl. v° iPrismntic

iPlllVlTU-

1.5-2 leut.

Enrihy.

i

Monocl. Prismatic

Mt-nocl. (Tabular-

(Page 275.)

Ii. Minerals Without Metallic Luster.

B.- Fusible from 1-5, and Non- volatile, or only Slowly or Partially

Volatile.

Pakt III. — With sodium carbonate on charcoal do not give a metallic glob- uhy and when fused alone, in thekTedu*citigame do not become magnetic.

Division 2. — Soluble in hydrochloric acid, but do not yield a jelly or a residue of silica

upou evaporation. — In part.

275 Il Minerals W1Thc

B.— Fusible irom 1—6, and .Non-volat Part III. — With sodium carbonate on charcoal do not give a metallic

Division 2. — Soluble iu hydrochloric acid, but do

In order to determine whether ;i mineral belongs to this divisiou treat cue or two ivory-spoonfi until not over 1 cc. remains. The concentrated solution thus obtained should be a clear liquid (in or deposits on the sides of the tube, it should go wholly into solution upon addition of water and w

General Characters.

Specific Character*.

Name of Species

Sulphates. — The dilute UC1 solution gives with barium chloride a precipitate of barium sulpht they give a faint and not very decided alkaline reactiou. A number of the sulphates of al ignition they yield an infusible mass of oxide and will be found, therefore, on subsequent pagi

wt

°©°

Qb 00 Q)

B"° 93

S

8J~

s -. °9

5.=

22

§ S 2

Contain fluorine. — When heated iu a bulb tube with potassium bisul-

Imparts an intense yellow color to the blowpipe flame (sodium).

Durangite.

and'a oVrihW**1™ no decided ame coloration. The coucen-

ana a aepOSU OI S1I1CI tnLt0x Tin\ onlntmn with dilute JT.ftn. a

forms on the walls of the tube (p. 76, § 2).

When heated in R. F. on charcoal with a little NasCOt, give a coating of tine oxide.

Contain manganese.— Im part a reddish - violet color to the borax bead in O. F.

Contains cobalt. — Imparts a blue color to the borax bend.

trated HC1 solution gives with dilute HS04 a precipitate of calcium sulphate (p. 59, § 3).

Gives 3 per cent of water in the closed tube (Ay- dromyl, p. 81, § 1, b).

Gives 28 per cent of water in the closed tube (water of crystallization, p. 81. §1, b).

Soluble in HC1 with evolution of chlorine.

Soluble in HC1 without evolution of chlorine.

Berzeliite is anhydrous; the rest give water in the closed tube. The calcium in Berzeliite and Brandtfte may be detected by adding a drop of dilute H9SO to the concentrated HC1 solution (p. 59, g 3).

TUasite.

Srabite.

Adamite.

KOttiglte.

Synadelphite.

Flinkite.

Berzeliite.

Brandtite.

Larldnlte,

Hemaflbrite.

Allactite.

Reacts for calcium when a drop of dilute HtS04 to added to the concentrated HC1 solution (p. Roeelite. 59, § 3).

Contain uranium. — Give a green color to the salt of phosphorus bead in R. F. Uranospinite contains calcium, but the test with H,S04 (p. 59, § 3) must be made very carefully, as the amount is small.

Contain calcium, but do not give the reactions of the foregoing divisions. — The concentrated HC1 solution ives a precipitate of calcium sulphate upou addition of a drop of dilute H,S04 (p. 59, § 8).

Ammonia when added to the dilute HC1 solution gives a crystalline pre- cipitate of ammonium magnesium arsenate.

TrSgerlte.

Uranospinite.

Adelite.

Haidingerite.

Pharmacol! te.

HcBrnesite.

Division 2.— Continued on next page.

Jt Metallic Luster. 275

e, or only Slowly or Partially Volatile.

obule, and when fused alone in the reducing flame do not become magnetic.

ot yield a jelly or a residue of silica upon evaporation.

b of finely pulverised material in a test-tube with from 8 to 5 cc. of hydrocloric acid, and boil thick and gelatinous, indicating a silicate), or, in case any solid material separates from the solution tning.

Composition.

Color.

Luster.

Cleavage and Fracture.

Hard-

Specific Gravity.

Fusi- bility.

Crystalli. sat ion.

(p. 122, § 1). The magnesium sulphates (p. 272) might possibly be referred to this rinium, zinc, manganese and nxtkel may swell and show signs of fusion when first devoted 'o infusible minerals.

divisiou, because heated, but after

Na(AlF)AsO.

Ff M.i i.4u. w. Al.

Light to dark orange-red.

Vitreous.

C. Prismatic. F. Uueveu.

Monocl.

Ca(MgF)As04.

Gray to violet.

Vitreous,

greasy.

C. Pinac, per.

4-5?

Foliated.

Ca4(CaF)(A804)„

OH iso. w. F.

Colorless.

Vitreous,

jrreasy.

C. Prismatic.

Hexag.

Zn(Zn.OH)AsO.

Pale green, yellow, violet, colorless.

Vitreous.

C. Prismatic. F. Uneven.

Orthorh.

Zn,(As04),.8H,0.

Pale-red, pink.

Silky.

C. Pinac, per.

8?

Monocl. Fibrous.

2(Mn,Al)As04.

5Mu(OH)i. Mjr & Ca Iso.w. Mn.

Brownish- black to black.

Vitreous,

greasy.

F. Uneven.

2-8?

Monocl.

MnAs04.Mn(OH)t.

Greenish -

brown.

Vitreous.

greasy.

2-8?

Orthorh.

Ca,Mg,Mu),

(As04),.

Sulphur- to orange-yellow.

Resinous.

F. Uneven.

Isometric.

Z?a*Mn(As04)s.

2H.O.

Colorless or white.

Vitreous.

F. Uneven.

Triclinic,

M[n(Mn.OH)As04.

Flesh-, rose-, or yellowish -red.

Greasy.

C. Prismatic. F. Uneven.

Monocl.

Un,(As04),.

3Mn(OH),.

2?

Orthorh.

dn3(As04),.

4Mn(OH)9.

BrowDish-red.

Vitreous,

greasy.

C. One direc. F. Uneven.

,2?

Monocl.

Ca,Co,Mg)f(As04),. 2H.O.

Rose-red.

Vitreous.

C. Pinacoidal.

Triclinio,

CO,),(As04),.

12H.O.

Lemon-yellow.

C. Pinac, per.

Monocl. U. tabul.

;a(UO,),(As04),. 8H.O.

Bright-green.

C. Basal, per.

%

Orthorh." U. tnbul.

?a(Mg.OH)As04

Gray. White.

Monocl.

[CaAs04.H,0.

Pearly,

vitreous.

C. Pinac, per.

,2.5

Orthorh.

tCnAs04.2H,0.

White or grayish.

C. Pinac, per. F. Uneven.

Monocl. U. fibrous.

[g.(As04),.8H,0.

Snow-white.

Pearly.

C. Pinac, per.

2-8?

Monocl

(Page 276.)

Ii. Minerals Without Metallic Luster.

B.— Fusible from 1-5, and Non-volatile, or only Slowly or Partially

Volatile.

Part III. — With sodium carbonate on charcoal do not give a metallic glob- ulc, and when fused alone in the reducing flame do not become magnetic.

Division 2. — Soluble in hydrochloric acid, bat do not yield a jelly or a residue of silica

upon evaporation. — Continued.

Ii. Minerals Withc

B.— Fusible from 1—6, and Non-volat Part III. — With sodium carbonate on charcoal do not give a metallic g

Division 2. — Soluble ia hydrochloric acid, but do not yie

General Characters.

§S8

Contain uranium.— Im- part a green color to the salt of phos- phorus bead in R. F.

Contain manganese. — Impart a reddish violet color to the borax bead in O. F.

Ferrous iron (isomor- phous with the man- ganese) is present in almost all cases. Test with potassium ferri- cyanide as directed on p. 85, § 4

When calcium is pres- ent it may be detected by adding a drop of dilute H,SO to the concentrated HC1 so- lution (p. 60, § 8).

Contain much calcium. — In the concentrated HC1 solution a pre- cipitate of calcium bulphate forms upon addition of a drop of dilute sulphuric acid (p. 59, §8).

£3f" Compare Bobierrite (p. 277), which may contain a little cal- cium.

Specific Characters.

Autunite and Uranocircite react for calcium and barium, respectively, when their HC1 solutions are treated with dilute HtSO (p. 59, §8, and p. 52, § 8).

Nome of 8pecies.

AtrhinrU.

Urauoclrcite.

Gives a red flame (litltium), tried best on platinum wire (p. 85).

Give an intense yellow flame (sodium), and no water or only a little in the closed tube.

B. B. cracks open, swells, and whitens, then fuses to a dark brown or black mass.

Fuses to an orange or reddish-yellow globule.

Contains much calcium.

Contains only traces of calcium.

Anhydrous. Gives a slight reaction for fluorine p. 76, § 2), and often also for chlorine (p. 67,

1).

Gives a little water when intensely heated in the closed tube, and also vapors of hydrofluoric acid which etch the glass (p. 77, § 5).

Give a little water in the closed tube (not over 7 per cent). That the quantily of water is small may be determined by comparing the closed-tube test with oue made upon au equally large frngmeut of gypsum which' has 21 per cent of water.

Give mucli water in the closed tube (20 per cent or over). Compare the quantity of water with that obtained from gypsum which has 21 per cent.

Phosphuranylise.

Lithiophilite. See triphylite, p. 9$.

Katrophllifie.

Diddnsonite.

OTUowite.

Eosphorite. See childrenite, p. 288.

Hureaulite.

FairfleldJte.

Reddingite.

Apatite.

Herderito.

Hydro-herderH*.

Cirrollte.

Uonetite.

CoUophoaite.

Isoclaslte.

Brush* te.

Division 2. — Concluded on next page.

r METALLIC LUSTER.

or only Slowly or Partially Volatile.

ule, and when fused alone in the reducing flame do not become magnetic. jelly or a residue of silica upon evaporation. — Continued.

Composition.

Color.

Luster.

Cleavage and Fracture.

Hard, ueas.

Specific Gravity.

Fusi- Crystalu- bility. cation.

i(UO,),(P04),.

8H.O.

Lemon- to sul- phur-yellow.

Pearly to sub- adamantine.

C. Basal, per.

On hoi h. Tubular.

Ortborh. 'tabular.

'Pulveru- lent.

i(UO,),(P04)9.

8H,0.

Yellowish- green.

Pearly to sub- ndamantine.

C. Basal, per.

8?

I01),(P04),.6H,0

Deep lemon- i yellow. |Pearly-

3-f?

i(Mn,Fe)P04.

Salmon -color, . clove-brown. Resinous.

C. Basal.pw. & pinacoidal.

4.&-5

2-2 Y

Ortborh.

a(Mn,Fe)P04.

Deep wine- yellow.

Resinous.

C. Basal, per.

4.&-5

Ortborh.

[u,Fe.Ca,Nai)s (P04)a.iH,0.

Olive-, oil-, or grass-green.

Vitreous,

pearly.

C. Basal, per.

2,5-8

Alonocl. Foliated.

[u,Fe,Ca.Na,). (P04),.*H,0.

Wax-yellow to

brown. (Greasy-

C. Basal. F. Uneven.

Monocl.

[n,FeXA1.20H)

P04.H,0.

Delicate rose- pink.

Vitreous, jC. Pinacoidal. resinous. F. Uneven.

Orthorh.

,(Mn,Fe).(P04)4. 4H.O.

Pale-rose, or- ange, brown.

Vitreous,

greasy.

C. Pinacoidal.

Monocl.

,Mn(P04),.2H,0

ISO. w. Mn.

Colorless to greenish-white

Pearly to sub- adamantine.

C. Pinac, per.

Triclinic.

a,(P04),.3H,0.

Iso. w. Mn.

Pale-rose to

brown.

Vitreous to

resinous.

F. Uneven.

Orthorh.

4<CaF)(P04),.

too. w. F.

tarely Mn iso. w. Ca.

Green, blue, violet, brown, colorless.

Vitreous,

greasy.

C. Basal. F. Uneven.

Hexag., Page 189.

[Be(OH,F)]P04.

White to pale- green or yellow.

Vitreous to

resinous.

F. Uneven.

a oo

Monocl.

(Be.OH)P04.

White, pale- green, yellow.

Vitreous to resinous.

F. Uneven.

Monocl.

i.OH),Al,(P04),.

White to pale yellow.

Vitreous.

F. Uneven.

Massive.

?aP04.

Yellowish- white.

Vitreous.

C. Pinacoidal. F. Uneven.

Triclinic.

(P04),.H,0.

Colorless, white, yellow.

Dull.

F. Concboidal.

4.5-5?

Amorpb.

(Ca.OH)P04.

2H,0

Colorless or white.

Vitreous,

pearly.

C. Pinac, per.

4?

Monocl.

2aP04.2H0.

Colorless to pale-yellow.

Vitreous,

pearly.

C. Pinac., per.

Monocl.

(Page 277.)

Ii. Minebals Without Metallic Lustee.

B.— fusible from 1*5, and Non-volatile, or only Slowly or Partially

Volatile.

Part III. — With sodium carbonate on charcoal do not give a metallic gloh ule, and when fused alone in the reducing flame do not become magnetic.

Division 2.— Soluble in hydrochloric acid, bat do not yield a jelly or a vendue of silica

upon evaporation. — Concluded.

II. MINERALS WITIIOl

B. —Fusible from 1—5, and Non-volatil Part III. — With sodium carbonate on charcoal do not give a metallic gh

Division 2. — Soluble in hydrochloric acid, but do not

General Characters.

Specific Characters.

Phosphates —Concluded.

not give l lie foregoing renc-

lions for uranium, muugauese

and ca'ciunt.

A Tew phosphates which

me difficultly soluble in HC1