Microscopic examination of the ore minerals

Davy, W. Myron (William Myron) · 1920 · Historical

14 52

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

Microscopic Examination

Of

The Ore Minerals

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Pubiishers Of Books F O

Coal Age ' Electric Railway Journal Electrical World Engineering News-flecord American Machinist ingenieria Intemacional Engineerings Mining Journal Power Chemical 6 Metallurgical Engineering Electrical Merchandising

Miceoscopic Examination

Op

The Oee Minerals

By W. Myron Davy

And

C. Mason Farnham

FiBST Edition I (p 1 7

McGRAW-HILL BOOK COMPANY, Inc.

New York: 239 West 39Th Street

London: 6 & 8 Bouverie St., E. C. 4

coptkight, 1920, bt the McGraw-Hill Book Company, Inc.

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Introduction

The use of the reflecting microscope as a means of determining the identity, relationship, and significance of opaque minerals in ore deposits has been steadily increasi-ag since William Campbell, ' in 1906, first apphed the methods then used by metallographers in the studj of metals, to the examination of opaque minerals. Nearly a century ago Berzelius published the results of polishing a specimen of pyrrhotite and suggested the possibilities of exam- ining opaque minerals in this way, but no practical methods resulted from his observations at that time. Even after Camp- bell's paper, mining and geological literature did not reflect any great interest in the subject until six or seven years had passed, when some admirable papers described the studies on particular types of ores. About this time the laboratories of mining geology at the Massachusetts Institute of Technology, Harvard Univer- sity, and Leland Stanford University, as well as a few other in- vestigators, were carrying on extensive researches in this field of study. In 1916, Dr. Joseph Murdoch pubhshed the results of numerous microchemical tests, arranging them in a determinative table which was by far the most complete work on identification of minerals under the metallographical microscope, and his book deserves the credit for much valuable pioneer work. Several years have now passed and new ideas have originated as the result of further study along this line.

Work carried on steadily in the laboratories at the Massachu- setts Institute of Technology on a wide range of ores, and at Harvard University on the original collection of minerals that formed the basis of Dr. Murdoch's book, justifies the following conclusions:

1. Fine distinctions in color value between the many so-called white minerals cannot be depended upon as a safe property on which to base the major classifications in making identity deter- minations. It has been found that hardly any two persons can

'Campbell, W. "The Microscopic Examination of Opaque Minerals." Economic Geology, Vol. 1, 1906, p. 751.

Murdoch, J. "Microscopical Determination of the Opaque Minerals." Preface by L. C. Graton, John Wiley & Sons. 1916.

Vi Introduction

agree in the application of such terms as bluish white, pinkish white, creamy white, purplish white, etc. However, if two microscopes and a comparison eyepiece are used, or if a standard mineral can be mounted adjacent to the unknown, most observers will agree in pronouncing the unknown to be lighter, darker, or the same as the standard; but at best this method is awkward, especially when the unknown mineral does not occur on the edge of the section. Some minerals change color after polish- ing, the kind of light used effects the colors seen, and a few cases have been observed where two freshly polished specimens of the same mineral differed so greatly in color as to fall into widely separated groups. The observed color of a mineral may be greatly influenced by the colors of other minerals in the field, for example, chalcopyrite is yellow when seen alone, but if seen adjacent to native copper it will appear to be a decided olive green. For these reasons the scheme of identification used in this book is independent of color distinctions which are only used in conjunction with many other properties as an ultimate means of separating the different minerals that fall into a final group.

2. Detailed descriptions of the way in which microchemical reactions proceed are in many cases valueless because of the fact that two specimens of the same mineral seldom yield exactly identical results. In nearly every case, however, they will check as far as reacting positively or negatively with a reagent is con- cerned, which is all that is needed -for identification. Moreover, it has been found that slight differences in the character of the mineral surface, slight differences in the concentrations of the reagents, and sometimes even the crystallographic orientation of the polished section have an important influence upon the reactions.

3. The number of reagents which can be used advantageously throughout a determinative scheme is limited to four or five. Many others have been tried, but their application is very limited and as time goes on the tendency is more and more toward simplification. In this work no attempt is made to list all tests known to date, but only those supplementary ones are included which may be valuable in differentiating between two or more minerals falling in one final group. As emphasized in the fol- lowing paragraph, in most cases an easily applied blowpipe test is convenient and adds far more confidence to the determination.

4. As in the early application of new developments in all Hues,

INTRODUCTION vii

mineragraphy has been pushed beyond its natural limitations in displacing other determinative methods and now a slight reaction is setting in. This art gives us our most useful means for ex- amining into the genesis of ore deposits, and is in itself a very valuable method of mineral determination; in certain cases, the best known method. But in the determination of the minerals in an average polished section of ore it is a handicap to restrict the examination to mineragraphic tests alone. One of a group of possible minerals can usually be run down quickly and confi- dently by gouging out from the edge of the section a small piece seen to contain the unknown, and treating it on charcoal before the blowpipe, or heating it in the open or closed tube, etc. The objection has been raised that the unknown cannot be cleanly separated, but very often all the other minerals are known and the reactions yielded by them can usually be discounted. There is never any need to run through a blowpipe analysis as the micro- chemical reactions narrow the possibilities down to a few min- erals, and one or two tests suffice. Consequently it has been found exceedingly helpful to include the characteristic blowpipe reactions for each mineral along with its other properties in the tables.

The foregoing considerations have largely influenced the ar- rangement of the tables and the choice of the material to be included in them.

The microchemical reactions listed are from various sources. The authors have independently studied one hundred and forty- three mineral species, thus covering all except a few of the rarest varieties; and as most of these species are also listed in Dr. Mur- doch's book, it is believed that this triple check results in the accurate determination of the reactions.

Fourteen minerals not previously described in mineragraphy have been tested and included in this work. A few very rare and doubtful species and some mixtures described by Murdoch have been omitted as it is felt that their presence in the tables complicates and adds little of practical value for the average user. The impression must not be gathered, however, that the so-called rare minerals are unimportant for, although only the more common minerals are encountered in nine out of ten ores examined, it is of great importance to recognize the rarer ones when they do occur. Furthermore, these uncommon minerals are sometimes found in small quantities or as fine intergrowths

viu INTRODUCTION

and their presence is never suspected until examined micro- scopically with vertical illumination; consequently they become less rare and take on a greater importance in mineragraphic study than has been the case with former mineralogical methods.

Mineragraphy is used throughout the book to designate the art of polishing, identifying, and examining the ore minerals under the metallographic microscope. Minera is late Latin meaning ore and graphy has been borrowed from the well esta- blished metallography. Whitehead' first used this name in print, and although mineragraphy as a word is not altogether pleasing, a name is much needed and it is here used with the hope that something better will be suggested.

It is believed that an infallible determinative table has never been devised on any subject, and the task is even more difficult in this case where the available material is at best new and little- tried. The beginner, of course, must acquire familiarity with both the tables and the general appearance imder the micro- scope of the more common minerals, and even the experienced mineralogist must serve a short apprenticeship in order to obtain good results. In preparing this book it was felt that a text was needed which could be used by both the profession and the student of mining and geology. Communications addressed to the laboratories of economic geology of the Massachusetts Institute of Technology indicate that the study of ore minerals in reflected light is to be introduced into the curriculum of several more of the country's larger institutions, and that a statement of the latest practice was desired. It is hoped that this rather brief review of the subject will serve such a practical purpose until such time as the combined experience and dis- coveries of many workers greatly increase our present knowledge along this line.

The authors wish to express their appreciation to Professor Waldemar Lindgren whose able and patient guidance has made the book possible, and to Professor L. C. Graton whose keen interest in this work has ever been a helpful inspiration.

' Whitehead, W. L. "Notes on the Technique of Mineragraphy." Economic Geology, Vol. xii. No. 8, 1917, p. 697.

Table Of Contents

Paob

Introduction v

Previous work — Color an unreliable determinative factor — Lack of consistency in reactions — Advantages of employing few reagents in the tables — Necessity for utilizing all determinative means — Range of material examined — Definition of mineragraphy — Acknowledgments.

Chapter I

Technique of Polishing and Examining the Specimen 1

Necessity for specialized polishing methods — Grinding — Polishing — Field preparation of a specimen by hand — Examination of the specimen — Microscope used — Optical principle involved — Con- struction and use of finder — Method of applying tests — Electrical conductivity of minerals — Electropotential of minerals — Concen- tration of reagents.

Chapter Ii

Photomicrography of Polished Sections 12

Equipment — Need for color filters — Methods of determining proper exposure — Exposure curves — Developing and printing.

Chapter Iii

Use of the Determinative Tables 20

Procedure in making determinations— Abbreviations used in tables — Outline of the tables — Determinative tables.

Chapter Iv

Supplementary Tests 120

Tabular arrangement of the minerals according to : Color of surface ; Color of internal reflection; Color of powder; Electrical conduc- tivity; Electro-potential — Tests for the elements with minerals arranged according to elements — Mirochemical qualitative re- actions— Standard fusibilities — Heating on charcoal — Sublimates in the closed tube — Sublimates in the open tube — Bead colors with borax and salt of phosphorous.

Index 151

Microscopic Examination

Of

The Ore Minerals

Chapter I

Technique Of Polishing And Examining The Specimen

Preparation of the Specimen

The successful determination of the identity of minerals with the reflecting microscope depends primarily upon having all minerals in the section properly polished with little relief, free from scratches, pits, and vugs; and without having changed the chemical character of delicate sulphides during the grinding process. It has been observed, for example, that chalcopyrite if ground under pressure on a rapidly revolving dry lap will develop bomite and chalcocite; and that pyrite when treated likewise will develop limonite.

In 1917 W. L. Whitehead' pointed out the fact that minera- graphic sections require grinding and polishing treatment funda- mentally different from that of metals for metallographic study. A metal specimen is usually one of uniform hardness and possesses far more ductility and toughness than an ore section which often consists of several minerals of widely differing hardness and of more or less brittleness. Pyrite, a mineral harder than almost any metal, is so universally present in ores that it often must be polished in the same section with a mineral so soft as to be scratched by the finger nail. When purely metallographic methods are used in poUshing ores this difference in hardness presents formidable difficulties to good work. The soft broad- cloth surface of the wheel swells outward and rapidly wears down the soft minerals, developing a relief so pronounced that it is

' Whitehead, W. L. " Notes on the Technique of Mineragraphy." Economic Geology, Vol. xii, No. 8, 1917, p. 697.

2 Microscopic Examination Of The Ore Minerals

impossible to focus upon two adjacent soft and hard minerals, especially at high magnifications.

In the laboratory, specimens are usually desired for two dis- tinct purposes; first, for visual examination and second, for photomicrographs. Comparatively little effort is required in polishing sections for the former purpose, and while a badly scratched and pitted surface should never be tolerated, very fine and shallow scratches do not interfere with visual study at any magnification. However, these comparatively minute scratches and pits make photography difficult, and they require exhaustive and careful polishing for their elimination.

The following procedure is in use at the Massachusetts In- stitute of Technology and with minor variations can easily be adapted to any grinding and polishing equipment. First, a portion of the specimen is chosen which appears to represent all the important features present, an area of a square inch or less usually being sufficient. This may be carefully chipped or cut off with a diamond saw. The latter method is by far the best when such equipment is available, as it rapidly yields an approxi- mately plane surface at any desired orientation and the opposite face of the cut can be made into a thin section if required. The saw used is 10 inches in diameter and is driven at 1600 R.P.M.

Any large inequalities in the surface chosen should be re- moved by grinding wet upon a steel lap wheel with 150 emery or alundum. A 10-inch horizontal wheel revolving at about 200 or 225 R.P.M. is used. After thorough washing of the hands and specimen the grinding is continued on an 8-inch horizontal glass wheel driven at 1800 R.P.M. and using the finest optical alundum (manufactured by Norton & Co., Worcester, Mass.) mixed to a very thin slime with water. This is perhaps the most important stage in the preparation. Considerable pressure may be exerted at first to quickly remove the scratches caused by the coarse abrasive; then grinding should be continued with light pressure until the surface is free of all except very fine scratches and pits. More than a minute or two is seldom re- quired at this stage, but when needed more time should be taken, as a minute spent here saves ten minutes later.

The true grinding part of the operation is completed and from now on the purpose of the work is to obtain a final polish. The same preparation of finest optical alundum is next used on a high speed 8-incb wheel covered with tightly stretched coarse linen

Polishing And Examining The Specimen 3

(about 15 threads per cm.). This wheel is horizontal and is driven at 1800 R.P.M. The specimen should be lightly held and constantly turned for 30 to 60 seconds, finishing up with about 30 seconds polishing without applying fresh alundum. The abrasive breaks down and developes a fine polish as seen by the naked eye.

This polish is improved by holding lightly for 30 or 60 seconds on a similar wheel covered with fine linen (30 threads to the cm. "I using a slime of rouge and water. This wheel is an 8-inch hori- zontal lap wheel driven at 1000 R.P.M. After thorough wash- ing and drying the final surface is obtained on a wheel similar to the preceding, but covered with tightly stretched calf skin. A split calf skin with the grease removed and finished with a very short nap on the flesh side is used. Care should be taken here to prevent overheating with consequent altering of the sulphides and burning of the leather. With a little practice 10 minutes will suffice for the entire process of cutting and polish- ing a surface comparatively free from scratches and trouble- some reUef, which can be satisfactorily studied even under the highest magnifications.

Out of a number of specimens studied from one deposit, two or three will usually be chosen for photographing, and these should receive additional preparation to eliminate the very fine scratches which cannot be avoided with the foregoing procedure alone. Chromic oxide has been found to yield the best results of all materials tried to date. Its use is introduced between the second optical alundum and the rouge wheels. The finest com- mercial chrome oxide is levigated to remove any coarse material and is used on a coarse linen wheel revolving at 1800 R.P.M. or faster. Careful treatment here eliminates the fine scratches pro- duced by the optical alundum. The specimen, as before, is finished on the rouge wheel.

In discussing a method of pohshing ore specimens no fixed rule can be formulated and the more work that is done the more evi- dent it becomes that each type of ore requires speciahzed treat- ment to obtain the best surface for photography. On the other hand, as previously stated, only a small portion of the specimens studied need be so prepared and the standardized and rapid method first described produces excellent results when only visual studies are to be made.

The quality of the illustrations in many of the recent papers

4 Microscopic Examination Of The Ore Minerals

on mineragraphic study proves that some of the laboratories have highly developed polishing methods and criticisms and sug- gestions from them should advance our knowledge of the subject.

Field Preparation Of A Specimen By Hand

The engineer studying or developing a prospect, or the geol- ogist in the field usually lacks the necessary equipment as above described, yet it is often important and helpful to clear up certain points without waiting until the apparatus is available. In this case fairly satisfactory results can be obtained by hand with a supply of coarse and fine emery or alundum, rouge and leather. They should all be used on surfaces similar to those described under mechanical polishing methods. So valuable does this Une of investigation promise to become for the examining engineer and geologist and so inexpensive is the microscopic equipment necessary that a supply of the requisite materials should be a part of every field outfit.

Examination Of The Specimen

A good microscope in common use is the Sauveur and Boyleston metallographic microscope manufactured by the Bausch and Lomb Optical Company, and illustrated in Fig. 1. It is very convenient for examination in daylight and with moderate mag- nifications. The objectives usually used are of the short mounted type and are of 16 millimeters and 4 millimeters focal length. Many types of microscopes, however, can be fitted with a vertical illuminating prism and be used for ordinary mineragraphic pur- poses. The simple optical principle involved is illustrated in Fig. 1. Light enters at and is reflected vertically downward by the prism, strikes the polished surface, and is reflected vertically upward. A thin plane glass illuminator is used in place of the prism at higher magnifications and with artificial illumination, as it gives a sharper image. The plane glass reflector, however, is unsuited for use with daylight as it does not give sufficient intensity. Recently a silvered reflector to replace the prism has been placed on the market and has proved satisfactory with all kinds of light.

A devise that gives the location of any particular feature in a polished section, and enables this feature to be brought again immediately into the field of the microscope, may be

Polishing And Examining The Specimen 5

easily constructed in a few minutes. (See Fig. 2.) A piece of metric cross-section paper ruled to millimeters is sealed between

Bell -Top Bottle

Pro. 1.

two thin pieces of glass which are about four and one-half centi- meters long and two and one-half centimeters wide. (Glass slides used in mounting thin sections may be used.) To the under

0 10 to 50 M

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:i

loE

:

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Finder

Polished Section

FiQ. 2.

side, two narrow strips of wood are glued to two adjacent edges so that their intersection will form a perfect right-angled comer. The cross-section lines should be considered coordinate lines and

6 Microscopic Examination Of The Ore Minerals

the point directly above the intersection of the wooden strips be considered the 0-0 coordinate. It is necessary that two sides of the pohshed section be ground so as to form a rightr-angled comer. This rough grinding requires only a few mhiutes additional work on the section, and the edges thus produced allow all minerals at the edges to be compared directly with standard minerals. In subsequent polishing, these sharp edges will not injure the polishing cloth, provided the comer is pointed in the direc- tion of revolution of the lap. When any feature in a polished section is to be located, the procedure is as follows: (1) raise the objective about a centimeter and gently place the finder upon the polished section, carefully fitting the comer of the sec- tion into the comer formed by the wooden strips on the finder; (2) focus upon the glass surface of the finder, using the 16-mm. objective, and place a minute drop of ink with a fountain pen in the center of the field ; and (3) remove the finder and read directly the location as x millimeters to the right of, and y miUimeters down from the coordinate 0-0. Relocation is made in reverse order. This method has been used on a large number of sections, and though rather crude, has been found to be simple and effect- ive, and almost indispensable with the highest magnifications.

The specimen is mounted by being pressed into a lump of modelling clay on a glass slide or similar surface. The polished surface must be perpendicular to the axis of the microscope and probably the most convenient method of leveling it accurately is by means of a screw bottom cup also illustrated in Fig. 1. A piece of 2-inch pipe about 2 inches long is threaded on the inner side and fitted with a threaded plug bottom. The slide with the specimen pushed approximately level into the clay is placed in- verted across the top of the cup. By adjusting the bottom the sUde is made to just clear the rim and it is then pushed firmly down. The surface of the specimen is now parallel to the slide which will rest upon the stage and consequently will be perpen- dicular to the axis of the microscope.

For preliminary study and when applying reagents the 16 millimeter (low power) objective is always used. Focus upon the surface to be examined and adjust the vertical illuminator until the surface appears brightest. The opaque minerals will appear white or colored, while the transparent gangue minerals will be black or very dark gray. Tests for hardness, sectility, color of powder, chemical behavior, etc., may now be applied.

Polish I No And Examining The Specimen 7

A fine sharp needle mounted in a small handle five or six inches long will serve to test for hardness or similar properties. The user should accustom himself to always holding it in about the same manner when testing for hardness in order to correctly com- pare results. Those minerals that scratch easily without pres- sure or with very light pressure are classified as of low hardness; those which scratch very slightly with light pressure or easily with heavy pressure are classified as of medium hardness; and those minerals which scratch very sHghtly or not at all with heavy pres- sure are classified as of high hardness. The opaque minerals range through a uniform gradation from the softest to the hardest, but after a short time it is not difficult to classify most of them readily. When a mineral is on the border line between two degrees of hardness it is usually found in both positions in the tables.

Sectility or brittleness determination is another convenient test which is sometimes of value. When testing for this property the needle is pushed across the mineral surface with a rotary motion; when the mineral is brittle the powder formed, if any, usually flies away from the edge of the scratch; if the mineral is sectile, little or no powder is formed and the needle penetrates more or less as in cheese.

When a heavy scratch is made by pushing the needle point across the mineral surface the color of the raised edge of the fur- row or of the powder formed is very characteristic in the case of certain minerals and this property is an important aid in identifi- cation in these cases. See Table 9, page 122.

The microchemical tests are by far the most important in identifying the minerals and should consequently be ap- plied with care and uniformity. The reagents are conven- iently applied to the polished surface by the use of a pipette with a fine capillary opening fitted with a small rubber bulb. With such a fine pipette a very small drop of the reagent can be applied exactly where desired and great nicety of manipulation is easily possible. It has been found desirable to use a bell top bottle in which the pipette fits as a ground glass stopper, as the microscope is. thus guarded from the acid fumes. A method of applying the reagents described by E. S. Bastin' has been found convenient in some oases, especially with the weaker reagents. In this method a small strip of blotting paper tapered at one end is used

' Economic Geology, Vol. xi, No. 7, 1916, p. 691.

8 Microscopic Ex Ami N A Tion Of The Ore Minerals

for touching the surface with the reagent and another clean strip is used for removing it to stop the reaction when desired.

The tests should be watched under the microscope at all stages and the following points observed: (1) Is any effervescence pro- duced? (2) Does the surface change color? (3) Is there any structure developed (cracks or cleavage, etc., made more promi- nent) ? (4) Do the fumes of the reagent affect the mineral sur- face beyond the edges of the liquid ? After the reaction has proceeded for ten seconds or up to a minute, depending upon rate of attack, the specimen may be removed from the stage and washed by directing a fine stream of water on the surface from a small wash bottle or dropping tube. The section is again ex- amined under the microscope without rubbing and the following points noted: (1) Is the area covered by the liquid tarnished? (2) Is there any structure or etching developed in this area? (3) Is the area subjected to the fumes tarnished? The specimen is again removed from the stage, carefully dried, and rubbed lightly on a block covered with chamois skin, and again examined to determine whether or not the effects are persistent. Before rubbing, the surface is sometimes slightly dirty due to the evap- oration of some of the liquid even though the reaction is entirely negative. This should not be mistaken for a slight positive reac- tion and may usually be avoided by carefully blotting the washed surface with a soft handkerchief or cloth.

Electrical conductivity, in many instances, may serve to distinguish minerals of similar physical and microchemical properties. The test for electrical conductivity is made under the microscope, using a 16-mm. objective, and the equipment must be adapted to mineral surfaces as small as two millimeters in diameter. Therefore steel needles had to be used for contacts. At first it was thought that these contacts would have to be placed a fixed distance apart in order to give constant readings, but experiment has shown that the difference between having the terminals a centimeter apart and very close together, is too small to be recorded. The apparatus consists of two Columbia dry cells No. 6, and a Weston D.C. voltmeter connected in series. The voltmeter had a resistance of 251 ohms, and read 150 with the circuit closed. As would naturally be expected the needle points introduce additional resistance; and differences in read- ings arise from varying pressure with which the points are pressed upon the mineral surface, the fact that soft minerals

Polishing And Examining The Specimen 9

allow the points to penetrate further tnan do hard minerals; and that a rough surface will give a different reading from the same surface when perfectly polished. This method is, there- fore, qualitative rather than quantitative, but does serve to arrange the minerals in a series in proper order, beginning with those that do not conduct electricity, and ending with those that conduct electricity as easily as copper. Only minerals that arc found widely apart in this series may be definitely distinguished by this means. The mineral to be tested is brought into the center of the field of the microscope, the two steel needle points are placed upon the surface, and the voltmeter reading noted. The mineral will immediately give either a reading of zero, of 150, or an intermediate reading; thus, giving at once three groups: minerals apparently non-conductors, minerals with conductivity equal to or greater than copper, and minerals having electrical conductivity but with greater resistance than copper. Minerals belonging to these three groups will be found tabulated in Table 10, page 123. By this method plagionite may be distinguished from galena, stromeyerite from argentite, tennantite from tetrahedrite, pentlandite from chalmersite, etc.

Electrolysis may be used to etch and bring out the structure of minerals in polished sections. After a drop of the reagent is placed on the polished surface under the microscope, it was found that the chemical action could be "speeded up" by the use of a weak electric current. The current used was furnished by one dry cell of the same type as used in determining the comparative electrical conductivity; and the terminals were a sewing needle and a piece of fine platinum wire; the former being connected to the carbon pole, and the latter to the zinc pole of the dry battery. The needle is placed on the polished surface just outside of the drop of reagent, and the platinum wire brought into contact with the top of the drop of reagent. Using a 20 per cent, solution of FeCU a clot of metallic copper will be produced on the end of the platinum wire by algodonite, bornite, chalcocite, native copper, and covelite. With the same reagent a beautiful "wood grain" structure is developed on enargite, famatinite, and luzonite, which distinguishes them from tetra- hedrite and tennantite. The effects of a weak current on the microchemical reactions may be generalized as follows: (1) a reagent that is negative when used alone may be strongly

10 Microscopic Examination Of The Ore Minerals

reactive with the current; (2) any reagent that reacts alone will give a much more intense reaction with the current; and (3) if the reagent with the current gives no reaction, it is a good check that the reagent is truly negative.

The electro-potentials of minerals have been investigated not only as a possible means of identifying minerals, but also because of their important bearing upon the processes of en- richment of ore deposits. Although the results obtained cannot be considered as of general value for the purpose of identi- fication, still a summary of the work thus far accomplished is suggestive and may well lead to further investigation. The method used in making the test is very simple. A small drop of dilute nitric acid is applied to the mineral while under the microscope. The polished section is then removed and a minute primary cell is established by bringing a standard electrode into contact with the top of the drop and completing the circuit, into which has been introduced a millivoltmeter, with a wire placed on the mineral surface near the drop. Eight standard electrodes, which are wires composed of a solid solution of copper and gold and containing, respectively, 100 per cent., 95 per cent., 90 per cent., 80 per cent., 70 per cent., 60 per cent., 50 per cent, and 40 per cent, of copper, are used to determine the direction and intensity of the electric potential difference. The results of testing many of the minerals having high electrical conductivity are tabulated in Table 11, page 124, and indicate the position of the more common ore minerals in the electro- motive series. These tests have emphasized the fact that when an active reagent is placed upon the contact of two electrically conductive minerals, the reagent becomes the electrolyte of a primary cell in which the minerals in contact are electrodes, and a weak current will be produced. The result is that the mineral of lower potential will dissolve more rapidly than normally, and this demonstrates the fact that microchemical tests should only be made upon pure material, and that the influence of impurities may give conflicting microchemical observations.

The following reagents have been used in this work and their effects are briefly described in the determinative tables. They are of the same strength as those used by Murdoch and thus it has been possible to compare directly the results obtained.

Polishing And Examining The Specimen 1 1

HNO3 One part concentrated acid (sp. gr. 1.42)

and one part water. HCl One part concentrated acid (sp. gr. 1.19)

and one part water.

KCN 20 per cent, solution in water.

FeCla 20 per cent, solution in water.

HgClj Saturated solution in water.

KOH Saturated solution in water.

Care should be taken to use reagents of approximately the above strength as discordant results are otherwise often ob- tained." Care should be taken to confine the reagent to the sur- face of the mineral under examination also because reactions with soluble gangue substances sometimes confuse the results.

Finally, qualitative chemical tests for the elements can be applied under the microscope.* They are of great value in certain special problems and the mineragrapher must more and more resort to them. As a rule two or sometimes three reagents only are required for such a test and, with very little practice, results of such nicety can be obtained that, once used, microchemistry will always hold its place. A condensed list of the microchemical tests for elements commonly found in the ore minerals is given in Table 12, page 145.

' See Chamot, E. M. " Elementary Chemical Microscopy." New York, 1915.

Chapter Ii Photomicrography Of Polished Sections

For the mining geologist, photographs of the ore minerals and the relations between them, as seen by vertical illumination are almost indispensable in preparing reports. A well-chosen illustration will estabhsh a point more conclusively in the minds of the readers than pages of written description. For the student of ore deposits, such microphotographs are invaluable records to be preserved as reference material.

The arrangement is simple, there being a camera in which a microscope takes the place of the lens. Practically, however, good results require a high-grade specially designed microscope and strong artificial Ught. The procedure has been borrowed largely from metallography, except that metallographers seldom have to bring out color values by optical means, while in miner- agraphy the variety of different minerals in one section calls for rather refined methods of color screening or filtering. The large Leitz metallographic microscope has been used by the writers, but any good instrument made on the same optical principles such as the Leitz type manufactured by Bausch and Lomb would serve equally well. A 5-ampere D.C. arc lamp is used as the source of light with this microscope. A description of the construction and specialized directions for the use of such apparatus are out of place here and are always supplied by the makers with the instruments. We are, however, concerned with many factors dealing with the choice of subject and the technique of photomicrography in general.

First, it is well worth the time to search carefully over all the polished sections available in order to locate an area which will best illustrate as many as possible of the important features in one picture. In too many microphotographs which have appeared in the literature the reader has to accept on faith the writer's statement that some relationship is established by the illustration. It is true that two people may not always interpret a particular structure in the same way, but it is a rare specimen which justifies positive conclusions and which does not show an area illustrating them.

Pho Tomjcrograph Y Of Polished Sections 13

When the subject for the photograph has been chosen care should be taken to adjust the reflector in such a way as to obtain uniform illumination over the entire field, otherwise a negative of uneven density will result.

The proper color screen to bring out the contrasts between the various minerals must now be selected. The sensitiveness of the photographic plate to of different colors or wave lengths is very different from that of the human eye. Ordinary white light and light from most artificial sources is a mixture of of all wave lengths. The eye sees all of these colors through a rather wide range, while the photographic plate "sees" colors outside of the limits of this range and is "blind" to much that is within it. For example the eye registers red as a bright color, but the ordinary plate is unaffected by red light and in a picture all red objects would appear black. For a complete and inter- esting treatment of this subject the reader is referred to "The Photography of Colored Objects" by Dr. C. E. Kenneth Mees.' Certain dyes have the property of absorbing of certain wave lengths and by passing the light to be used through filters made with these dyes, color effects can be controlled upon the negative to a large, extent. Table 1 lists the Wratten M filters supplied by the Eastman Kodak Company and indicates the approximate range of light transmitted by each.

Experience has shown that a filter should be used at all times as several optical difficulties arise when photography is attempted without them especially at magnifications greater than 100 diameters. For the average section with a variety of minerals dearly distinguishable by the eye the K3 yellow filter most nearly reproduces the true values as seen (that is when used with the Wratten M plate described below). In many cases, however, when strong contrast is required between two minerals it is necessary to select one of the special filters described in Table 1, or. sometimes, one of the combinations of two filters. This is done usually by trial, the contrast obtained with each mineral being observed upon the ground glass screen. This visual trial method is only trustworthy when using a pan- chromatic plate which approximates the relative sensitiveness of the eye. The best panchromatic plate obtainable for this type of work is the Wratten M plate distributed by the East-

' Mees, C. E. Kenneth. "The Photography of Coloured Objects." Wratten and Wainwright, Ltd., London, 1913.

14 Microscopic Examination Of The Ore Minerals

Table 1'

Wratten filter

Visual color

Range of spectral transmission in mm of wave length

A

B

D

E

F

G

H

Ki

Kj

Ka

D and H. Cand H. B and C. Band H. Gand H. Band G. Band E. A and D.

Scarlet

Green

Blue-violet

Purple

Orange

Pure red

Strong yellow

Blue

Pale yellow (very pale)

Pale yellow

Yellow

Violet

Blue

Blue-green

Bluish-green

Pure green

Yellowish-green

Greenish-yellow

Deep red

From 580 to red end

From 460 to 600

From 400 to 510

From 380 to 460 and from 040 to

red end From 560 to red end From 610 to red end From 510 to red end From 420 to £40

Wide range of lower spectrum

About 450 About 480 About 500 About 520 About 535 About 550 About 575 About 660

man Kodak Company. It has all the color sensitiveness of the true panchromatic plate, being even more sensitive to red light, and has an extremely fine-grained emulsion especially designed for microscopic photography. The worker along this line cannot do better than to use it exclusively. All of the data concerning proper filters and some of the factors for calculating exposures contained in this chapter are applicable only for use with the Wratten M plate.

Having chosen the proper filter, accurate focusing is the next important step. It is impossible to obtain sharp, clear cut negatives by focusing upon the ground glass screen alone. After an approximate focus is obtained on this screen it should be replaced by a plain glass screen upon which the final focus is made with the use of a lens. This screen should be very carefully removed and the photographic plate put in its place. Everything should now be ready for the exposure.

The data for calculating the proper exposure for different magnifications, sources of light, filters, etc., has been assembled

' From the booklet " Photomicrography " published by the Eastman Kodak Co.

Photomicrograph Y Of Polished Sections 15

by the Eastman Kodak Company and Tables 2 and 5 have been taken from their booklets.' The formula for calculating expo- sures gives an approximate figure which should be tested ex- perimentally for different types of subjects. The formula does not take this latter factor into consideration, but the same exposure obviously will not give equally good results on a section composed largely of white minerals and one in which dark gray minerals are dominant. The method of making the test exposure is as follows : If the formula indicates that an exposure of 20 sec. is about right, expose successive portions of the plate for 5, 10, 20, 40, and 80 sec. by pulling out the slide and then pushing it in one-fifth the width of the plate at the end of each of the above periods. The exposure should increase by geo- metric progression as indicated rather than by arithmetical progression such as 10, 15, 20, 25, and 30 sec, as the difference in density of negatives exposed 10 and 20 sec. respectively is twice as great as in those exposed 20 and 30 sec. respectively. With this test plate as a guide, the proper exposure can be easily determined.

In making the original exposure calculation the following for- mula is used :

Standard exposure X N.A. factor X source factor X magnifica- tion factor X filter factor exposure in seconds.

The standard exposure used in the above empirical equation is taken as 10 sec.

The exposure varies inversely as the numerical aperture, N.A. of the objective. (The numerical aperture is an optical constant for a lens of given focal length.) The factors for the N.A. of the objectives are given in Table 2.

The source of naturally is of the greatest importance in determining the length of exposure. In past pubUcations the factors for the source of light have been adopted from data for transmitted light conditions. This has led to confusion because the polished surface does not reflect all of the by any means, and consequently requires a longer exposure. Experience has shown that, on the average, the factor for reflected light is two to four times that for direct transmitted illumination. These factors for various sources of light are given in Table 3.

' "Photomicrography, Color Plates and Filters for Commercial Photography, and Reproduction Work with Dry Plates." Eastman Kodak Company, Rochester, N . Y.

1 6 Microscopic Ex Ami N A Tion Of The Ore Minerals

Table 2

Focal length objective

Average N.A.

Approximate ex-

posure factor

Inches

Millimeters

H

K

Im

H

H

H

H

Va

H

H

H2

Table 3

Exposure factor for M plate

Source of light

Oil 3

Incandescent gas 1

Nernst lamp (1 amp.) Ji

Acetylene

Direct current arc (5 amps.)

Direct current arc (10 amps.) Js

Direct current arc (30 amps.) 330

(It should be understood that the above factors are by nature very approximate, dependent entirely on arrangement and power.)

no

n

r-

y

/

r

y

ff

/

y

(

n

k n

A

w

'

tf-

/

/

y'

?)W

/

/

y

/

/

/

y

r

cy

u

eg Fic

I0( nifi

Co"

ion

Photomicrography Of Polished Sections

The greater the magnification, the longer is the required expo- sure. The degree of magnification depends upon the focal length of the objective, the projection eyepiece, the distance of the photographic plate from the objective, etc. It will be found convenient to prepare a set of curves for the instrument used, similar to those in Fig. 3, which have been calculated for the Leitz metallographic microscope.

In Table 4 the exposure factors for different magnifications are listed.

Table 4

Magnification

Exposure factor for M plate

Magnification

Exposure factor for M plate

Koo

K6

The factor for any magnification may be calculated on the basis that it increases with the square of the diameter.

The last variable in the exposure equation is the factor for the filter used. These factors are dependent upon the source of illumination since the different artificial lights have widely differ- ing color values. Table 5 lists the multiplying factors for the filters, singly and in pairs, calculated for the open arc and the Wratten M plate.

Table 5

Filter

Factor (M plate and open arc)

Filter

Factor (M plate and open arc)

A

Only used in combination

Kj

B

Ks

43

DandG

Aand D

Band E

GandH

BandC

Band G

Dand H

D

E

F

G

H

K,

m

The foregoing tables are used as follows: the approximate exposure for a photograph using a 16- mm. objective (Leitz

18 Microscopic Examination Of The Ore Minerals

No. 3), a 5-amp. D.C. arc, magnification 50, and screen K3 would be:

10 sec. X 2 X M X X M S sec. (approximately)

Fig. 4.

Izoo

1 —

y

/

&'

Zoo

/

6

D 9

0 n

0 Is

Exposure In Seconds Fig. 5.

Figures 4 and 5 give the approximate exposures for an average specimen consisting, say, of galena, chalcopyrite, and sphalerite. These curves are calculated solely for the Wratten M plate. They are for the 5 amp. open arc, wide open stop, and without

Photomicrograph Y Of Polished Sections 19

filter. When a filter is used the value obtained from the curves should be multiplied directly by the filter factor taken from Table 5. These curves are plotted from theoretical values checked in practice and may be multiplied by a suitable factor when another light source is used.

The Wratten plate is very sensitive to red and con- sequently must be opened and developed either in total dark- ness or in the light of the Wratten Safelight, series 3, a faint green light. With each box of plates an instruction sheet is enclosed giving the developing formula, proper temperatures, and times of development. These instructions, when followed, yield excellent results and should only be varied by the most experienced worker. In the course of the dark room treatment it will be found advisable to wash the carbon backing off the plates with a soft sponge while rinsing before placing in the fixing solution.

In preparing positives a glossy paper usually yields the most satisfactory detail and reproduces best. After developing and fixing the print should be pressed face down upon a ferrotype plate with a rubber roller and allowed to dry thoroughly, when they will peel off without sticking providing a sufficient amount of hardening solution has been used in the fixing bath. Small amounts of a special polishing solution can be used on the ferro- type plate when necessary and will eliminate sticking entirely. Such a solution is sold by Burke and James of Chicago, 111.

Chapter Iii

The Use Of The Determinative Tables

The tables have been arranged with the idea of enabling the student to apply a uniform series of simple and positive tests at one time to all the different minerals present in appreciable amoimts in the section. The following procedure in making determinations has been found to yield rapid and exact results. It must be appreciated that, as in all other things, experience and practice make for greater skill and, although it has been demonstrated that beginners can mechanically follow the tables with fair success, familiarity with the appearance and micro- chemical behavior of the common ore minerals naturally gives confidence to the worker. No one should attempt a serious application of this method of study to any problem without first applying it to a few of the common minerals.

FiQ. 6.

The polished section of ore pictured in Fig. 6 has been chosen as an example. This particular ore is of value in this connection because it illustrates the variety of tests which go toward exact mineral determinations under the metallographic microscope.

The preliminary examination of the material should be done

The Use Of The Determinative Tables 21

systematically and the results recorded somewhat as in Table 6. The different minerals should be temporarily designated by num- ber and a brief description of their appearance. The reagents used in the scheme of identification are preferably applied in their order in the tables and the reactions, if any, observed and recorded.

Table 6

1. Creamy white mineral 2. Yellow

3. Violet white

with high relief

Hn03

Unaffected for some time, Neg.

Slowly effervesces and

but slowly tarnishes

turns bluish

. brown with very slow

effervescence

HCl

Neg. Neg.

Neg.

Kcn

Neg. Neg.

Neg.

Hardness Very high Medium

High to medium

FeCla

Neg. Neg.

Neg.

(Pyrite) (Chalcopyrite) (Polydymite)

In first running down the unknown it is often most convenient to use the outline of the determinative tables, especially if the worker is familiar with the more common minerals by sight, be- cause larger groups of minerals are seen at one time and slight uncertainties as to the results of one or more tests can be elim- inated. (1) Readily falls out as pyrite, (2) as chalcopyrite, and (3) is limited to a small group of minerals. Of these, arsenopy- rite, willyamite, kallilite, and niccolite all contain arsenic or antimony. Blowpipe tests appUed to a small piece of the mate- rial gouged from the edge reveal neither of these elements and polydymite is indicated by a process of elimination.

However, since the mineral was dissolved readily by nitric acid, a qualitative microchemical test for nickel should be easily applied. (See Table 12, page 145, for list of these tests.) After a drop of nitric acid has remained on the supposed polydymite for a minute or two a drop of tartaric acid is added to keep iron in solution when a drop of concentrated ammonium hydroxide is next added to make the solution alkaline. If a drop of a solution of dimethyl glyoxime ih alcohol is now added, a beautiful scarlet-red crystal- line precipitate appears under the microscope. This proves the presence of nickel in the imknown and leads to the conclusion that it is polydymite.

22 Microscopic Examination Of The Ore Minerals

The foregoing illustrates the general method to be followed in making identity determinations. All reactions and properties are utiUzed when necessary and the individual must be the judge as to how much evidence is needed in each case before reaching a decision. This in turn is dependent upon the individual's experience and familiarity with the properties of the different minerals as seen under the microscope in reflected light.

Abbreviations used in the Tables

B.B. Before the blowpipe.

C. Color seen megascopically. Fus. Fusibility. HNO3 -E Reacts with HNO3 with effervescenoe.

HNO3 Visible reaction such as tarnish, etc. (Without effervescence in the case of HNO3.) HNO3 -N No visible reaction with HNO3. H Hardness high. L Hardness low. M Hardness medium. Microchem. Microchemical tests. O.F. Oxidizing flame. R.F. Reducing flame. S.Ph. Salt of Phosphorus. Str. Streak.

The Use Of The Determinative Tables

Outline Of The Determinative Table

Effervesces with HNO3

Color

Mineral

Formula Page

HCl

Kcn

M

FeClj

Cream

WkitneyiU

CuiAs

Creamy white

Huntilite

AgjAs

Grayish white

Cuprite

CusO

FeCh

Creamy white

Chihnile

Ag.Bi

Creamy white

Domeykite

CuaAs

Purple

Rickardite

Pink

(Native copper)'

Cu

Bluish white

(Chalcocite)

CujS

Galena white

(Hessite)

AgiTe

Creamy white

{Aikinite)

3(Cu2Pb)S.Bi!S,

Kcn-N

H

FeCla-N

White (violet)

iPotydymite)

NLSj

M

FeClr-N

Grayish white

Alabandite

MnS

FeCli

White

Naumanmte

(Ag2Pb)Se

White

Altaite

PbTe

Creamy white

Native silver

Ag

Creamy white

Native bismuth

Bi

Creamy white

Tapalpaile

3Ag.(STe).Bij-

(STe),

Galena white

Playionite

5PbS.4Sb2Si

Galena white

(Galena)

PbS

FeCl3-N

Galena white

Semseyite

7PbS.3SbjS3

White

(Aikinite)

3(CujPb)S.BiiS3

Galena white

{Plagionite)

5PbS.4Sb2S3

Galena white

{Dognacskaite)

Cu, Bi, and S

Grayish white

(Jamesonite)

2PbS.Sb!S3

Grayish white

(Alabandite)

MnS

Galena white

{Horsfordite)

Cu.Sb

HCl-N KCN

H

FeCl>-N

White

{Polydymite)

Ni4S.

M

FeCU

Pink

(Native copper)

Cu

FeCh

Pink

Native copper

Cu

Bluish white

Chalcocite

CujS

Pinkish brown

(Bornite)

CuiFeS.

FeCls-N

Pinkish brown

Bornite

CusFeSi

Creamy white

(Aikinite)

3(PbCu2)S.BiiS,

Galena white

(Stibnite)

SbjS,

Kcn-N

H

FeCU

Creamy pink

Niccolite

NiAs

Pinkish white

Maucheritc.

NiaAsj

White

Smaltite

CoAsj

1 Parentheses about a mineral indicate that it is not in its normal position

24 MICROSCOPIC EXAMINATION OF THE ORE MINERALS Effervesces with HNO3

Color

Mineral

Formula

Page

FeCls-N

White

Arsenopyrite

FeAsS

Violet white

Polydymite

White

Willyamite

(CoNDSbS

White

Kallilite

Ni(SbBi)S

Creamy white

Pyrite

FeS,

Creamy white

Marcasite

FeSj

Creamy pink

(NiccoUte)

NiAs

M

FeCU

Creamy white

Cosalite

PbiBijS.

Galena white

Native arsenic

As

FeCh

Cream

Melonite

Ni,Te.

Creamy white

Calaverite

AuTei-Ag

White

Native tellurium

Te

Galena white

Rezbanyite

4PbS.5Bi.S,

Galena white

Tetradymite

Bii(Te, S),

Creamy white

(Krennerite)

AuTei-Ag

Creamy white

(Native silver)

Ag

Galana white

{Plagionite)

5PbS.4Sb2S3

Grayish white

(Pefaite)

(Ag, Au)2Te

FeCh-N

Creamy white

Krennerite

AuTej-Ag

Creamy white

EmplectUe

CuBiSj

Creamy white

Chiviatite

PbiBijSii

Creamy white

Aikinite

3(PbCu,)S.Bi,S

Galena white

Dognacskaite

Cu, Bi. and S

Galena white

Boulangerite

SPbS.SbiSi

Galena white

Horsfordite

CutSb

(jalena white

Bismuthinite

BijSs

Grayish white

Realgar

AsS

Grayish white

Jamesonite

2PbS.SbsS,

Grayish white

Zinkenite

PbS.SbjS,

Bluish Gray

Tungsteniie

Ws.

White

(Native tellurium)

Te

Galena white

(Stibnite)

SbjS,

THE USE OF THE DETERMINATIVE TABLES Reacts with HNO3 — does not Effervesce

Color

Mineral

Formula

Page

HCl

Kcn

M

FeClj-N

Creamy white

Sutvanite

CusVSi

Galena white

(.Guejarile)

CujSbjS?

FeCIj

Creamy white

Dyscrasile

AgjSb, Ag.Sb

etc. 67

Galena white

Hessite

AgjTe

Grayish white

Argentite

AgiS

Grayish white

StTomeyerite

(Ag,Cu)iS

Grayish white

Jalpaite

SAgiS.CujS

Brown

(Pyrolusite)

MnOj

FeCl.-N

Bluish white

Brongniardite

PbS.AgiS.SbiS, 69

Kcn-N

H

FeCl,-N

Gray

Psilomelane

H4MnOi

M

FeCl,

Grayish white

Tenorite

CuO

FeCIj-N

Gray

Cuprodescloizite

(PbZnCu)4VjO..-

HiO

Gr4y

(Sphalerite)

ZnS

Grayish white

(Tenorite)

CuO

FeCh

Purple

Umangite

CusSei

White

Clausthalite

PbSe

Galena white

Galena

PbS

Galena white

LilUaniie

SPbS.BiiSi

Grayish white

Teallite

PbSnSj

Grayish white

Cylindrite

Pb.SbiSnjSsi

Grayish white

Aguilarite

AgiS.AgiSe

White

(Native antimony)

Sb

Creamy white

(Native silver)

Ag

FeCl,-N

Galena white

Meneghinite

4PbS.Sb!S8

Galena white

Geocronite

5PbS.Sb,S,

Grayish white

Franckeite

PbsSnjSbiSij

White

(Eucairite)

CuiSe.AgjSe

Grayish white

(.Cylindrite)

PbjSbzSnsSii

Ha-N

Kcn

M

FeCh

Grayish white

(P0Ltba8Ite)

Ag.SbS,

FeCl.-N

Pinkish white

Luzonile

CuiAsSi

Brownish white

Enargite

CusAsS*

Pinkish white

Famatinite

CusSbSi

Galena white

Guejarite

Cu2SbSj

Grayish white

Freibergite

(Cu, Ag).SbjS

7 82

Yellow

(Chalcopyrite)

CuFeSj

Creamy white

(Sulvanite)

CujVS.

Grayish white

(Tennantite)

CuiAsjSj

Grayish white

(Tetrahedtite)

CujSbjSi

FeCl,

Grayish white

Pearcite

Ag.AsS.

Grayish white

(Argentite)

AgjS

Grayish white

(Poltbasite)

AgiSbS,

Grayish white

(Jalpaite)

SAgiS.CujS

Bluish white

(Polyargyrite)

AgijSbiSii

26 MICROSCOPIC EXAMINA TION OF THE ORE MINERALS Reacts with HNO3 — does not Effervesce

Color

Mineral

Formula

Page

FeClt-N

Galena white

Stibnite

Galena white

Kermesite

SbjSiO

Grayish white

P0Ltba8Ite

AgiSbSt

Galena white

(Jjivingsionile)

HgSbiSi

Kcn-N

H

FeCh

White

Chloanthite

NiAs2

White

Rammelsbergite

NiAsi

White

Gebsdobffitb

NiAsS

FeCl,-N

White

LDUiigite

FeAsi

White

Ultmannite

NiSbS

Creamy white

Linnceite

Co.S*

Pinkish white

Glaucodot

(Co,Fe)A8S

Cream

Hauchecornite

(NiCo)7(SSbBi)

Cream

(Pyrrhotite)

FeS(S);,

Creamy white

(Pyrite)

FeSi

White

(Chloanthite)

NiAs2

White

(Gersdobpfite)

NiAsS

M

White

(Willuamite)

(CoNi)SbS

FeCli

Pink

Breithauptite

NiSb

Pale yellow

Millerite

NiS

Cream

Pyrrhotite

FeS(S),

Cream

Chalmersite

CuFejSj

Creamy white

Pentlandite

(Fe.NDS

Creamy white

WiUicheniU

CuaBiSa

Galena white

Andorite

PbAgSbsS.

Grayish white

BotTBNONITE

(PbCuOiSbjSi

Grayish white

Stylotypite

3(Cu!AgjFe)- S.SbiSi

Grayish white

Stannite

SnCuiFeS<

Grayish white

Crookesite

(CuTIAg)iSe

Grayish white

Hauerite

MnS,

Gray

Sphalerite

ZnS

Yellow

(Chalcopyrite)

CuFeSi

Creamy white

iSulvanite)

CuiVS.

Pinkish white

(Famatinite)

CusSbS.

Gray

(VolUile)

ZniS(0

Grayish white

(Tennantite)

CusAsjSi

FeCl.

White

Berzelianite

CuiSe

White

Eucairite

CuiSe.AgjSe

White

Native a-ntimony

Sb

Creamy white

Kalgoorlite

HgAuiAg.Te.

Grayish white

PeUite

(Ag,Au)iTe

Grayish white

Coloradoite

HgTe

Grayish white

Molybdenite

MoS.

Creamy white

(Native silver)

Ag

Galena white

(Plagionite)

5PbS.4SbjS.

Grayish white

(Aguilarite)

Ag2S.Ag2Se

THE USE OF THE DETERMINATIVE TABLES Reacts with HNO3 — does not Effervesce

Color

Mineral

Formula Page

FeClj-N

Pale brown

Sternbergite

AgFesS,

Galena white

Lengenbachite

Pbj(AgCu)jA8.S

Galena white

Rathite

Pb(AsSb)S

Galena white

Jordanite

PbiAsiSi

Galena white

Guitermanile

SPbS.AsjSi

Galena white

Bpiboutangerite

PbjSbiSs

Galena white

Gatenobismutite

PbBijS.

Galena white

Beegerite

PbsBiiSt

Galena white

Freieskbenite

(PbAgijtSbiSii

Galena white

Nagyagite

AujPbioSbjTe.Su 98

Creamy white

Syhanite

AuAgTej

Creamy white

Guanajuatite

BijSej

White

(Eucairite)

CuiSe.AgjSe

White

(Berzelianite)

CujSe

Creamy white

(Emptectite)

CuBiSs

Galena white

(Stibnite)

SbiS3

Galena white

(Geocronite)

SPbS.SbiSj

Galena white

(Andorite)

PbAgSbjSj

Grayish white

(Crookesite)

(CuTlAgjjSe

Grayish white

(Regnolite)

CurAssSij

Grayish white

(Jamesonite)

2PbS.Sb!S3

28 MICROSCOPIC EXAMINATION OF THE ORE MINERALS Does not React with HNO3

Color

Mineral

Formula

Page

HCl

Kcn

FeCl.

Grayish white

Stephanite

AgiSbS

Brown

Pyrolusite

MnO.

Grayish white

{Jalpaite)

SAgiS.CujS

Bluish white

(Proustite)

AgiAsSj

Kcn-N

M

FeClj-N

Grayish white

Delafossiie

CuO, PeiOi.

HCl-N

Kcn

M

FeCl,

Grayish white

(Polybasite)

Ag.SbS.

FeCls-N

Yellow

(Chalcopyrlte)

CuFeSj

Brownish white

(Enargite)

CujAsS

Grayish white

(PYRAROyRITE)

AgjSbSa

FeCl.

Bluish white

Proustite

AgsAsSa

Bluish white

PolyaTgyrite

AgnSbjSu

Grayish white

Cerargyrite

AgCl

Grayish white

{Jalpaite)

SAgsS.CuiS

Grayish white

(.PearcUe)

Ag>AsSs

FeClj-N

Blue

CoTellite

CuS

Yellow

Native gold

Au

Galena white

Livingstonite

HgSb.S7

Bluish white

Onofrite

Hg(SSe)

Grayish white

Ptrargtbite

AgjSbSj

Bluish white

Miargyrite

AgSbSj

Grayish white

Argyrodite

Ag.GeS.

Grayish white

Orpiment

AsiSz

Bluish white

(Proustite)

AgiAsSa

Grayish white

(Polybasite)

Ag,Sb8,

Kcn-N

H

FeCl,

Gray

Uraninite

UOi, etc.

FeCl,-N

White

Sperrylite

PtAs,

Pinkish white

Cobaltite

CoAsS

Creamy white

Hematite

Fe,0,

Grayish white

Magnetite

FejO.

Grayish white

Ilmenite

FeTiOi

Grayish white

Rutile

TiO.

Us

Grayish white

Franklinite

(FeZnMn)O. (FeMn)20j

Grayish white

Manganese Oxides

Grayish white

Wolframite

(FeMn)W04

Grayish white

Rare earths

Gray

Cassitebite

SnOj

Gray (variable)

Limonite

2Fe203.3H!0

Gray

Chromite

FeCr!04

White

(LSllingite)

FeAsj

THE USE OF THE DETERMINATIVE TABLES Does not React with HNO3

Color

Mineral

Formula

Page

M

FeCls-N

Yellow

Chalcopyrite

CuFeSj

Galena white

Chatcostibite

CuSbSi

Galena white

Berthierite

FeSbiSi

Grayish white

Baumhauerite

PbjAstSii

Grayish white

Tetrahedrite

CusSbjST

Grayish white

Tennantite

Gray

Voltzite

ZnjS40

Gray

Erythrozincite

(MnZn)S

Pale yellow

(MiLLEBITE)

NiS

Cream

(Pyrrhotite)

FeS(S)x

Cream

(Chalmersite)

Cure2S3

Creamy white

(Pentlandite)

(Fe,Ni)S

Grayish white

(Boubnonite)

(PbCu2)3SbiS.

FeCli-N

Galena white

Dufrenoysite

PbjAsjSs

Galena white

Matitdite

AgBiSj

Galena white

Lehrbachite

PbSe + HgSe

Bluish white

Tiemannite

HgSe

Bluish white

Vrbaite

TlAs.SbSi

Bluish white

StUUite

Ag.Te

Grayish white

Regnolite

CutAsiSu

Grayish white

Seligmannite

CuPbAsS.

Grayish white

Cinnabar

HgS

Grayish white

MetacinnabaHte

HgS

Grayish white

Patronite

Vs4

Gray

Lorandite

TlAsS,

Galena white

(Freieslebentie)

(Pb, Agj)jSb4Sn 98

Galena white

(Berthierite)

FeSbiS.

Galena white

iLengenbachite)

Pb.(AgCu)iA8iSi, 99

Galena white

(Ralhile)

Pb4(AsSb)S

Grayish white

{Baumhauerite)

Pb4A8Sii

Grayish white

(Molybdenite)

MoSj

Gray

{Erythrozincite)

(MnZn)S

Determinative Tables

See summary of reactions at upper right

hand comer of each page to locate

minerals between thumb tabs.

HNOa-E HCl DETERMINATIVE TABLES KCN

Med. Feci,

Cream Whitneyite CuAs (Very Rare)

Microchem. HNO3, Effervesces and turns brown; rubs gray. HCl, Tarnishes and rubs to faint gray showing structure. KCN, Tarnishes brown; rubs gray with structure. FeCls, Quickly blackens; rubs to gray. HgCU, Quickly blackens with structure; rubs light brown with structure. KOH, Tarnishes faintly.

Hardness, Medium. 3.5. Very Sectile, Gray powder when scratched.

Description. C. and Str. — Silver-white. Usually massive.

B.B. Yields arsenic coat on charcoal (Chap. IV, 2, o) and mirror in closed tube (IV, 2, c). Gives azure-blue copper chloride flame with HCl (IV, 6, b). Fus.— 2.

Creamy White Huntilite AgsAs? (Very Rare)

Microchem. HNO3, Effervesces and quickly blackens; rubs to roughened surface. HCl, Liquid scarcely affects surface, but fumes tarnish per- sistently. FeCla, Tarnishes iridescent; rubs to faint iridescence. KOH, Neg.

Hardness, Medium. KCN, Slowly turns dark; rubs to clean roughened

surface.

Description. C. — Dark gray to black. Described from Silver Islet, Lake Superior, as massive in occurrence.

B.B. Yields arsenic coat on charcoal (IV, 2, a) and mirror in closed tube (IV, 2, c). When reduced with the fluxes yields metallic silver (IV, 18, a).

Gratish White Cuprite CuiO

Microchem. HNO3, Effervesces and forms a deposit of metallic copper; washes to coat of metallic copper; rubs gray. Fumes tarnish. HCl, Quickly darkens, forming a white coating as seen by inclined light; rubs faint. Fumes tarnish. KCN, Develops structure; rubs grayish. FeCls, Tarnishes; rubs to iridescence. Fumes tarnish. HgClj, Neg. KOH, Neg.

Hardness, Medium. 3.5-4. Slightly brittle. Blood red powder when scratched. Internal reflection seen by inclined light is deep red.

Description. C. — -Red to nearly black. Str. — Shades of red or brown. With metallic copper it is found in the oxidized zone of all copper de- posits.

B.B. In R.F. on charcoal yields metalUc copper and colors the flame an emerald-green. Fus. — 3.

' The microchemical reactions for minerals marked with an asterisk are from Murdoch, Joseph. "The Microscopical Determination of the Opaque Minerals." John Wiley & Sons. 1916.

HNOr-E HCl

Determinative Tables Kcn

Low FeCl,

Ckeamt White Chilenite* AgBi (Very Rare)

Microchem. HNO3, Effervesces and blackens; rubs to roughened surface.

HCl, Turns brown ; rubs to iridescent roughened surface. KCN, Turns

brownish; rubs clean. FeCls, Tarnishes iridescent; rubs gray. KOH,

Neg. Hardness, Low. Description. C. — Silver-white, tarnishing to yellowish. Described as

amorphous and granula. B.B. When reduced with the fluxes yields metallic silver (IV, 18, a).

With KI & S flux yields brick-red bismuth coat (IV, 3, a).

Cbbamt White Domeykite CujAs (Very Rare)

Microchem. HNO3, Quickly effervesces and blackens. HCl, Most specimens develop structure. KCN> Some portions tarnish faintly, some practically negative. FeCU, Quickly tarnishes; rubs to rough- ened surface. HgCU, Tarnishes brown; rubs faint. KOH, Quickly tarnishes; rubs clean.

Hardness, Low to medium. 3-3.5.

Description. C— Steel gray. Str. — Gray. Occurs reniform, botroidal, massive, and disseminated.

B.B. Yields arsenic coat on charcoal (IV, 2, a). Gives aanire-blue copper chloride flame with HCl (IV, 6, 6).

Purple Rickardite CuiTea (Very Rare)

Microchem. HNOa, Blackens with violent effervescence. HCl, Turns pale bluish and dissolves to pitted surface. KCN, Bleaches to a pale tint. FeClj, Bleaches to brownish. HgClz, Bleaches to bluish-green. KOH, Tarnishes iridescent.

Hardness, Low. 3.5. Brittle.

Description. C. and Str.— Purple. Massive: fracture irregular.

B.B. On charcoal fuses easily to a brittle globule, yielding a pale azure- blue flame tinged with green, and a white tellurium coat. Fus. — 1.

PiWK Native Copper See page 51.

Bluish White Chalcocite See page 51.

Galena White Hessite See page 66.

HNOs-E HCl DETERMINATIVE TABLES KCN

Low FeClrN

Cbeamt White Aikinite See page 63.

HNO,-E HCl DETERMINATIVE TABLES KCN-N

High FeClr-N

Violet Whitb Polydymite See page 57.

HNOr-E HCl

Determinative Tables Kcn-N

Med. FeClrN

Grayish Whitk Alabandite MnS

Microchem. HNO3, Effervesces and tarnishes; rubs gray, showing solu- tion pits. Fumes tarnish brown. HCl, Nearly the same as with HNO3. KCN, Neg. FeCla, Neg. HgClz, Fumes tarnish faintly; washes to pale brown; rubs clean. KOH, Neg.

Hardness, Medium. 3.6-4. Sectile, but slightly brittle. Olive green powder when scratched.

Internal reflection seen by inclined Ught is green.

Description. C. — Iron black. Str. — Green. Has perfect cubic cleavage.

B.B. Shows manganese with the sodium carbonate bead (IV, 11, a). Fus.— 3.

HNOr-E HCl DETERMINATIVE TABLES KCN-N

Low FeCl,

White Naumannite* (Ag2Pb)Se (Very Rare)

Microchem. HNO3, Quickly effervesces and blackens; rubs to roughened surface. HCl, Tarnishes slowly to iridescence. KCN, Neg. FeClj, Tarnishes slowly brownish; rubs clean. KOH, Neg.

Hardness, Low. 2.5.

Description. C. — Iron-black. Str. — Black. Massive with cubic cleav- age.

B.B. Selenium odor and coat on charcoal (IV, 17, a and 6). With KI & S flux yields lemon-yellow lead coat on charcoal (IV, 10, a). Yields silver button on cupellation (IV, 18, a). Fus. — 2. White AUaite PbTe (Very Rare)

Microchem. HNO3, Effervesces and quickly darkens, developing crys- tals and tree-like forms resembling microhtes; rubs to grayish etched surface. Fumes tarnish iridescent. HCl, Quickly browns; rubs to pale brown with white patches. KCN, Neg. FeCls, Quickly tar- nishes brownish iridescent; rubs to gray, roughened surface. HgClj, Neg. KOH, Neg.

Hardness, Low. 3. Sectile. Gray powder when scratched.

Description. C. — Tin-white. Str. — Gray. Has cubic cleavage.

B.B. Yields tellurium flame and coat on charcoal (IV, 20, a). With KI & S flux gives a lemon-yellow lead coat on charcoal. Fus. — 1.5. Creamt White Native Silver Ag

Microchem. HNO3, Effervesces slightly for a moment; rubs to gray, roughened surface. Fumes tarnish. HCl, Fumes tarnish slightly; rubs clean. KCN, Neg. FeClj, Tarnishes iridescent; rubs to irides- cence. HgClj, Tarnishes gray; rubs to brownish gray. KOH, Neg.

Hardness, Low. 2.5-3. Very sectile.

Description. C. — Silver-white. Str. — Silver-white. Usually in arbor- escent, sheet, and wire forms.

B.B. Fuses easily on charcoal and yields a brown coat of silver oxide. (For other tests see IV, 18, a.) Fus.— 2. Creamy White Native Bismuth Bi (Very Rare)

Microchem. HNO3, Quickly effervesces and darkens; rubs to brownish gray. HCl, Slowly darkens; Fumes tarnish brown. KCN, Neg. FeCU, Darkens quickly. HgCh, Slowly deep brown; rubs to Isrown. KOH, Neg.

Hardness, Low. 2-2.5. Very Sectile.

Description. C. — Reddish silver-white. Str. — Silver-white. Arbores- cent.

B.B. On charcoal fuses easily and volatilizes completely, yielding yellow sublimate. With KI & S flux gives brick-red coat on charcoal. Creamy White Tapcdpaite* 3Agj(STe).Bi2(STe)j? (Very Rare)

Microchem. HNOs, Quickly effervesces and darkens; rubs to dark, rough surface. Fumes tarnish. HCl, Faintly tarnished ; rubs clean. Fumes same. KCN, Neg. FeCl, Quickly darkens; rubs to gray, roughened surface. KOH, Neg.

Hardness, Low.

Description. C. — Pale steel-gray. Str. — Gray. Massive.

B.B. Yields tellurium flame and coat on charcoal (IV, 20, o). With KI & S flux gives brick-red bismuth coat on charcoal (I V , 3, a) . Fus. — 1 . Galena White Plagionite 5PbS.4Sb2S3 (Very Rare)

Microchem. HNO3, Slowly darkens with slight effervescence; rubs to light gray. HCl, Acid negative, but fumes tarnish bright brown. KCN, Neg. FeCU, Turns brown; rubs pale brown. HgClj, Neg. KOH, Slowly iridescent; rubs clean.

Hardness, Low. 2.5. Brittle. Gray powder when scratched.

Description. C. — Blackish gray. Str. — Black.

B.B. Yields antimony coat and sublimates (IV, 1, a-d). With KI & S flux gives lemon-yellow lead coat (IV, 10, a). Fus. — 1. Galena White Galena See page 77.

Determinative Tables

HNO3-E HCl

Kcn-N

Low

FeCl,-N

Galena White SemseyUe TPhS.SShSa (Very Rare)

Microchem. HNO3, Slowly effervesces and blackens; rubs gray. Fumes tarnish brown. HCl, Slowly faint brown ; rubs clean. Fumes tarnish. KCN Neg. FeCla, Neg. HgCU, Neg. KOH, Some specimens unaf- fected; others faintly tarnish brown.

Hardness, Low. Brittle. Gray powder when scratched.

Description. C. — Gray. Str. — Black. Tabular.

B.B. Yields antimony coat and sublimates (IV, 1, a-d). With KI & S flux gives lemon-yellow coat (IV, 10, o). Fu8. — 1.

White

Galena White Galena White Grayish White Gbatish White Galena White

Aikinite See page 63.

Plagionite See page 43.

Dognacskaite See page 63.

Jamesonite See page 62.

Alabandite See page 41.

Horsfordite See page 63.

HNOs-E HCl-N DETERMINATIVE TABLES KCN

High FeCls-N

Violet White Polydymite See page 67.

HNOa-E HCl-N DETERMINATIVE TABLES KCN

Med. FeCla

Pink Native Copper See page 51.

HNOa-E HCl-N DETERMINATIVE TABLES KCN

Low FeCl,

Pink Native Copper Cu

Microchem. HNOj, Effervesces without tarnishing; rubs to roughened

surface. HCl, Neg. (Sometimes tarnishes faintly.) KCN, Slowly

browns; rubs to clean roughened surface. FeCls, Quickly darkens

and dissolves. HgCU, Quickly blackens; rubs to iridescence. KOH,

Slowly turns brown to bluish ; rubs bluish. Hardness, Medium. 2.5-3. Sectile. Pink when scratched. Description. C. — Copper-red. Str. — Shining. Malleable, ductile. Shows

arborescent and irregular structures. Occurs in oxidized zone of all

copper deposits. B.B. Easily fusible, yielding an emerald-green flame in the O.F. On

charcoal becomes black after fusion.

Bluish White Chalcocite CujS

Microchem. HNOj, Effervesces vigorously, turning blue, and developing cracks or cleavage; rubs same. HCl, Tarnishes very slightly. KCN, Quickly blackens; rubs to etched surface, with structure. FeCla, Tarnishes slightly. HgClj, Tarnishes slightly. KOH, Neg.

Hardness, Low. 2.5-3. Very Sectile. Gray powder when scratched.

Description. C. and Str. — Dark lead-gray, tarnishinj; to blue on ex- posure. Occurs in zone of secondary enrichment in all copper de- posits.

B.B. Fuses easily and boils with spirting. Powdered and roasted with- out fusing, then heated in R.F., yields metallic copper. Fus. — 2-2.5.

Pinkish Bbown Bomtte See page 63.

HNO,-E HCl-N DETERMINATIVE TABLES KCN

Low

Pinkish Brown Bomite CusFeS

Microchem. HNO3, Effervesces and turns yellowish brown; rubs to

brown etched surface. Fumea tarnish. HCl, Neg. KCN, Browns;

rubs to dark etched surface. Fumes tarnish. FeCls, Neg. HgCU,

Neg. KOH, Neg. Hardness, Low. 3. Sectile. Golden-brown powder when scratched. Description. C. — Copper-red to brown; purplish bronze from tarnish.

Str. — Grayish black. Massive. Common in most copper deposits. B.B. Fuses easily on coal in the R.F. to a magnetic globule. Roasted

and reduced with sodium carbonate, yields malleable copper buttons

(IV, 6, a), Fus.— 2.

Creamy White Aikinite See page 63. Galena White Stibnite See page 87.

HNOs-E HCl-N DETERMINATIVE TABLES KCN-N

High FeCla

Creamy Pink NiccoUte NiAs

Microchem. HNO3, Effervesces and tarnishes with etching; rubs to gray, etched surface. Fumes tarnish. HCl, Neg. KCN, Neg. FeCla, Slowly tarnishes brown; rubs to pale brown. (Some specimens show this reaction very weakly.) HgCl2, Tarnishes brown; washes to per- sistent brown. KOH, Neg.

Hardness, High. 5-5.5. Very brittle. Gray powder when scratched.

Description. C. — Pale copper-red. Str. — Brownish. Occurs massive and disseminated.

B.B. Fuses easily on coal to brittle globule, yielding arsenical odor and possibly a white coat of oxide. With dimethyl glyoxime gives a red precipitate (IV, 14, b).

Pinkish White MaucherUe NijAsj (Very Rare)

Microchem. HNO3, Effervesces and blackens quickly; rubs to gray,

rough surface. HCl, Neg. KCN, Neg. FeCU, Slowly tarnishes

brownish; rubs faint. HgCU, Faintly browns; rubs clean. KOH,

Neg. Hardness, High. 5. Very brittle. Gray powder when scratched. Description. C. — Reddish silver-white, tarnishing gray copper-red.

Str. — Blackish gray. B.B. Same as niccolite. (Note: Temiskamite is not a mixture, but a homogeneous mineral

identical with Maucherite.)

White Smaltite CoAsj

Microchem. HNO3, Quickly effervesces and darkens; rubs to gray, show- ing lath structure. Fumes tarnish. HCl, Neg. KCN, Neg. FeCU, Slowly tarnishes brownish, showing structure ; rubs pale. (This reaction is not always decisive.) HgClj, Slowly browns; rubs clean. KOH, Neg.

Hardness, High. 5.5-6. Brittle.

Description. C. — Tin-white. Str. — Gray-black. Occurs massive.

B.B. Easily fusible on charcoal, yielding a magnetic globule and an arsenical odor; may yield a white arsenic coat. With borax shows a persistent cobalt blue (IV, a). Ftis. — 2.6.

(SafflorUe is the same as smaltite.)

HNOrE HCl-N

Determinative Tables Kcn-N

High FeCl3-N

White Arsenopyrite FeAsS

Microchem. HNO3, Slowly effervesces and quickly tarnishes through iridescence to deep brown; rubs to roughened surface. HCl, Neg. KCN, Neg. FeCh, Neg. HgCla, Neg. KOH, Neg.

Hardness, High. 6.6-6. Brittle. Gray powder when scratched.

Description. C. — Silver-white to steel-gray. Str. — Grayish black. Oc- curs as orthorhorabic crystals, massive, granular, or compact.

B.B. On charcoal fuses easily to brittle magnetic globule and evolves arsenic odor. In the closed tube it yields first an arsenious sulphide subUmate and then an arsenic mirror. Fus. — 2.

Violet White Polydymite Ni4Ss (Very Rare)

Microchem. HNO3, Slowly effervesces and turns to brownish or bluish;

rubs to brown or blue, showing structure. HCL Neg. (Acid turns

green, but surface washes clean.) KCN, Neg. FeCU, Neg. HgClj,

Neg. KOH, Neg. Hardness, High. 4.6. Brittle. Description. C. — Steel-gray. Str. — Grayish black. B.B. With dimethyl glyoxime yields red precipitate (IV, 14, 6). Fus. —

White WiUyamite* (CoNi)SbS (Very Rare)

Microchem. HNO3, Slowly effervesces and turns dark brown; rubs gray, showing etching. HCl, Neg. KCN, Neg. FeCl,, Neg. KOH, Neg.

Hardness, High. 5.5.

Description. C. — Tin-white to steel-gray. Str. — Grayish black. Per- fect cubic cleavage. Massive.

B.B. Tests for cobalt, nickel, and antimony in Chapter IV.

White Kallilile* Ni(SbBi)S7 (Very Rare) Microchem. Like WiUyamite. Hardness, High to medmm.

Description. C. — Light bluish gray. Str. — Black. Massive. B.B. Tests for nickel, antimony, and bismuth in Chapter IV.

Creamy White Pyrite FeSj

Microchem. HNO3, Very slowly effervesces and faintly browns; rubs to faint brown. Fumes tarnish slowly. Other reagents negative. Hardness, High. &-6.6. Cahnot be scratched. Description. C. — Light brass-yellow. Str. — Greenish to brownish black.

Pyrite is the most common of all sulphides and usually the oldest. B.B. Becomes magnetic on charcoal m the R.F. Fus.— 3.

Creamy White Marcasite FeSj Microchem. Like Pyrite. Hardness, High. &-6.5. Description. Like Pyrite except in crystal form and in occurrence. It

occurs always as a secondary mineral. B.B. Like Pyrite.

Creamy Pink Niccolite See page 55.

HNOr-E HCl-N DETERMINATIVE TABLES KCN-N

Med. Feci,

Creamy White Cosalite PbjBijSs (Very Rare)

Microchem. HNOs, Instantly effervesces and blackens; rubs to dark gray. Fumes tarnish. HCl, Neg. (Sometimes slowly faint tarnish; rubs clean.) KCN, Neg. FeCU, Very slowly taint brown; sometimes appears negative. HgClj, Fumes tarnish; rubs clean. KOH, Tar- nishes brown to iridescent.

Hardness, Medium to low. 2.5-3. Brittle. Gray powder when scratched.

Description. C — Lead-gray. Str. — Grayish black.

B.B. With KI & S flux shows both lead and bismuth (IV, 3 and 10). Fus.— 1.5.

Galena White Native Arsenic As (Very Rare)

Microchem. HNOs, Instantly blackens with slow effervescence; rubs to

brownish gray. HCl, Neg. KCN, Neg. FeCls, Quickly darkens

to persistent brownish. HgCU, Slowly tarnishes pale brown; rubs

faint. KOH, Neg. Hardness, Medium to low. 3.5. Sectile, but slightly brittle. Gray

powder when scratched. Description. C. — Tin-white. Str. — Gray. Has a basal cleavage. B.B. Yields white arsenic oxide coat on coal and easily volatilizes without

fusion.

HNOi-E HCl-N DETERMINATIVE TABLES KCN-N

Low FeCla Cream Melonite* Ni2Te3 (Very Rare)

Microchem. HNO3, Quickly effervesces and blackens; rubs gray. HCl, Neg. KCN, Neg. FeClj, Slowly tarnishes; rubs faint. KOH, Neg. Hardness, Low.

Description. C. — Reddish white. Str. — Gray. Has basal cleavage. B.B. Easily fusible, but not entirely volatile, yielding white coat on charcoal and coloring flame bright green (IV, 20, a). With dimethyl glyoxime gives a red precipitate (IV, 14, 6).

Creamt White Calaverite AuTcz + Ag

Microchem. HNO3, Slowly effervesces and turns brown; rubs to lighter

brown with etching. HCl, Neg. KCN, Neg. FeCls, Slowly tarnishes

brown; rubs to faint brown. HgClj, Neg. KOH, Tarnishes pale

brown; rubs to faint brown. Hardness, Low. 2.5. Brittle. Gray powder when scratched. Description. C. — Silver-white. Str. — Gray. B.B. Gives white coat on charcoal and colors flame bright green.

Roasted and reduced with sodium carbonate, yields gold and silver;

sometimes reduces to gold bead easily without soda. Fus. — 1.

White Native Tellurium Te (Very Rare)

Microchem. HNO3, Quickly effervesces and blackens; rubs to gray,

rough surface. HCl, Neg. KCN, Neg. FeCU, Slowly tarnishes

iridescent. KOH, Neg. Hardness, Low. 2-2.5. Somewhat sectile. Gray powder when

scratched. Description. C. — Tin-white. Str. — Gray. Has prismatic cleavage. B.B. Easily fusible and volatile, yielding a white coat on charcoal and

coloring the flame bright green (IV, 20, a). Fus. — 1.

Galena White Rezbanyite 4PbS.5Bi2S3 (Very Rare)

Microchem. HNO3, Effervesces and tarnishes iridescent; rubs to gray

etched surface. Fumes tarnish. HCl, Neg. KCN, Neg. FeCh,

Slowly faint brown. HgCU, Neg. KOH, Neg. Hardness, Low. 2.5-3. Brittle. Gray powder when scratched. Description. C. — Lead-gray. Str. — -Grayish black. Massive. B.B. With KI & S flux .shows both lead and bismuth (IV, 3 and 10).

May be isomorphous with small amounts of copper and silver.

Galena White Tetradymite Bi2(Te,S)3

Microchem. HNO3, Quickly tarnishes with vigorous effervescence; rubs

iridescent. HCl, Neg. KCN, Neg. FeCU, Tarnishes slightly,

developing scratches. HgClj, Neg. KOH, Neg. Hardness, Low. 1.5-2. Slightly sectile. Description. C. — Steel-gray, splendent. Str. — Gray. Perfect basal

cleavage. Soils paper. B.B. On charcoal fuses, gives white fumes and entirely volatilizes; tinges

the R. F. bluish-green; coats the charcoal at first white and finally

orange yellow

Creamy White

Krennbrite

See page 63.

Creamy White

Native Silver

See page 43.

Galena White

Plagionite

See page 43.

Grayish White

Petzite

See page 97.

Galena White Bismuthinite 61283 (Very Rare)

Microchem. HNO3, Blackens with slow effervescence; rubs to gray,

roughened surface. HCl, Neg. KCN, Neg. FeCU, Neg. HgCU,

Tarnishes brown; rubs to faint brown. KOH, Neg. Hardness, Low. 2. Slightly brittle. Gray powder when scratched. Description. C. — Lead-gray. B.B. With KI & S flux gives a brick-red bismuth coat on charcoal

(IV, 3, a). Fus.— 1.

Gratish White Realgar AsS

Microchem. HNO3, Effervesces without visible change. HCl, Neg. KCN, Neg. FeCU, Neg. HgCU, Neg. KOH, Tarnishes brown to black with solution.

Hardne.ss, Low. 1.5-2.

Internal reflection seen by inclined light is orange.

Description. C. — Dark orange-red. Str. — Lighter. Occurs with anti- mony, arsenic, and silver ores.

B.B. On charcoal in the O.F., burns, yielding arsenic odor and no residue when pure. In closed tube yields cherry-red sublimate of arsenic sulphide. Fus. — 1.

Grayish White Jamesonite 2PbS.Sb2S3

Microchem. HNO3, Quickly brown to black with very slow effervescence (Eff. often not detected); rubs to iridescent gray. HCl, Neg. F\imes tarnish slowly; rubs faint. KCN, Neg. FeCU, Neg. HgClo, Neg. KOH, Slowly develops grain structure; some grains are iridescent, others gray.

Hardness, Low. 2-3. Brittle. Gray powder when scratched.

Description. C. — Steel-gray. Str. — Grayish black. Perfect basal cleav- age. Occurs fibrous or massive.

B.B. Yields antimony and lead coat on charcoal (IV, 1 and 10;. With KI & S flux gives lemon-yellow lead coat on charcoal (IV, 10, a). Fus.— 1.

Grayish White Zinkenite PbS.Sb2Sj (Very Rare) Microchem. Like Jamesonite. Hardness, Low. 3-3.5. Description. C. and Str. — Steel-gray. Occurs in columnar crystals,

striated lengthwise, also fibrous and massive. B.B. Like Jamesonite.

Bluish Gray Tungstenite WS2(?) (Very Rare)

Microchem. HNO3, Does not change color, but effervesces after a few moments. HCl, Neg. KCN, Neg. FeCls, Neg. HgCU, Quickly tar- nishes brown; rubs clean. KOH, Neg.

Hardness, Low. 2.5.

Description. C. — Dark lead-gray. Str. — Dark gray. Marks paper.

B.B. See tests for tungsten (IV, 25).

White Native Tellurium See page 61.

Galena White Stibnite See page 87.

fa

HNOa-E HCl-N DETERMINATIVE TABLES KCN-N

Low FeCls-N

Creamy White Krennebitb AuTej + Ag

Microchem. HNOa, Slowly effervesces and turns brown; rubs to lighter brown with etching. HCl, Neg. KCN, Neg. FeCU, Neg. HgCU, Neg. KOH, Tarnishes pale brown; rubs to faint brown.

Hardness, Low to medium. 2.5. Sectile, but slightly brittle. Gray powder when scratched.

Description. C. — Silver-white. Str. — Gray. Has perfect basal cleav- age. (Calaverite lacks this perfect cleavage.)

B.B. Gives white coat on coal and colors flame bright green. Roasted and reduced with sodium carbonate yields gold and silver; sometimes reduces to gold bead easily without soda. Fus. — 1. Creamy White Emplectite CuBiSi! (Very Rare)

Microchem. HNOs, Effervesces slightly and tarnishes pale brown; rubs clean. Fumes tarnish faintly. HCl, Neg. KCN, Neg. FeCla, Neg. HgClj, Neg. KOH, Tarnishes very slowly brown; rubs clean.

Hardness, Low. 2. Slightly brittle. Gray powder when scratched.

Description. C. — Grayish white. Str. — Black.

B.B. Yields azure-blue copper chloride flame with HCl (IV, 6, 6). With KI&S flux gives brick-red bismuth coat on charcoal (iV, 3, a). Fus. — 1. Creamy White Chiviatite* PbjBijSu (Very Rare)

Microchem. HNO3, Slowly effervesces and turns iridescent to gray; rubs to clean, somewhat roughened surface. HCl, Neg. KCN, Neg. FeCh, Neg. KOH, Neg.

Hardness, Low.

Description. C. — Lead-gray. Str. — Grayish black. Commonly foli- ated.

B.B. With KI & S flux shows both lead and bismuth (IV, 3 and 10). Creamy White Aikinite 3(PbCu2)S.Bi2S3 (Very Rare)

Microchem. HNO3, Effervesces and blackens; rubs to heavy gray. Fumes tarnish brown. HCl, Neg. KCN, Neg. (Some specimens very slowly browned; rubs clean.) FeCU, Neg. HgCU, Neg. KOH, Neg.

Hardness, Low. 2-2.5. Brittle. Gray powder when scratched.

Description. C. — Lead-gray. Str. — Grayish black.

B.B. Gives azure-blue copper chloride flame with HCl (IV, 6, 6). With KI & S flux shows both lead and bismuth (IV, 3 and 10). Fus. — Galena White Dognacskaiie Cu, Bi, and S (Very Rare)

Microchem. HNOj, Quickly effervesces and turns iridescent to black; rubs to gray, roughened surface. Fumes tarnish. HCl, Neg. Fumes tarnish brown; rubs to pale brown. KCN, Neg. FeClj, Neg. HgCU, Neg. KOH, Neg.

Hardness, Low. Very Sectile. Gray powder when scratched.

Description. C. — Gray, tarnishing on exposure to the air.

B.B. Same as Emplectite. Galena White Boulangerite 3PbS.Sb2S3 (Very Rare)

Microchem. HNO3, Effervesces and blackens; washes to etched struc- ture. Fumes tarnish light brown. Other reagents negative.

Hardness, Low. 2.5-3. Sectile, but slightly brittle. Gray powder when scratched.

Description. C. — Bluish lead-gray. Str. — Black. Occurs fibrous, granu- lar, or compact.

B.B. Like Jameson ite. Galena White Horsfordite CueSb (Very Rare)

Microchem. HNO3, Slightly effervesces and quickly blackens; rubs to faint gray. HCl, Practically negative; some specimens turn very slowly faint brown and rub to very faint gray. KCN, Neg. FeCls, Neg. HgCls, Tarnishes a brown rim which rubs clean. KOH, Slowly tarnished faintly.

Hardness, Low. Very Sectile. Gray powder when scratched.

Description. C. — Silver-white. Occurs massive.

B.B. Reacts for antimony and copper. Fus. — 1.5.

HN03 HCl

Determinative Tables Kcn

Med. FeCl,-N

Creamy White Sulvanile CusVS (Very Rare)

Microchem. HNO3, Neg. Fumes tarnish; rubs clean. HCl, Neg.

Fumes tarnish; rubs clean. KCN, Neg. Fumes tarnish; rubs clean.

FeCla, Neg. HgCU, Neg. KOH Neg. Hardness, Medium. 3.5. Brittle. Gray powder when scratched Description. C. — Bronze-yellow. Occurs massive. (South Australia.) B.B. Roasted and reduced with sodium carbonate and borax yields cop-

per.buttons. Gives vanadium bead with the fluxes (IV, 27, a).

Galena White Guarite See page 83.

Galena White Hessite AgjTe

Microchem. HNO3, Slowly tarnishes iridescent to brown ; rubs to rough- ened surface. (Sometimes slowly effervesces.) HCl, Tarnishes irides- cent; rubs faint or clean. (Sometimes nearly negative.) KCN, Slowly tarnishes. FeCls, Tarnishes iridescent; rubs faint to clean. HClj, Tarnishes brown; rubs clean. KOH, Very slowly tarnishes slightly; rubs faint.

Hardness, Low. 2.5-3. Quite sectile.

Description. C. — Steel-gray. Str. — Gray. Occurs crystalline, massive, etc.

B.B. Coat and flame are not decisive. Shows tellurium with concen- trated HjSOi. Reduced with sodium carbonate, yields silver buttons. Fus.— 1.

Beown Pyrolusite See page 101.

HNO, HCl DETERMINATIVE TABLES KCN

Low FeCla

Creamy White Dyscrasite AgaSb, AgsSb, etc. (Very Rare) Microchein. HNOs, Tarnishes and develops differential etching. HCl,

Slowly tarnishes with development of differential etching. KCN,

Slowly and faintly etches differentially. FeCU, Differential iridescent

tarnish. HgClj, Tarnishes to brownish iridescence with structure;

rubs same. Fumes tarnish light brown. KOH, Neg. Hardness, Low. 3.5-4. Exceedingly sectile. Description. C. — Silver-white, sometihies tarnishing yellow or blackish.

Str. — Silver-gray. B.B. Easily fuses to a globule, coating the charcoal with white antimony

trioxide, and finally leaving a globule of pure silver. Soluble in nitric

acid. Fus. — 1.5.

Grayish White Argentite AgjS

Microchem. HNO3, Slowly tarnishes light brown; rubs clean. Fumes tarnish brown. HCl, Sometimes slowly tarnishes faint brown, but often almost negative. KCN, Tarnishes brown; rubs to faint gray. Fumes tarnish brown. FeCla, Slowly brown to iridescent; rubs to very faint iridescence. HgCU, Tarnishes brown; rubs to pale brown. KOH, Neg. Blackened by short exposure to unscreened strong elec- tric arc light.

Hardness, Low. 2-2.5. Exceedingly sectile. Black powder when scratched.

Description. C. — Lead-gray. Str. — Shining gray. Common in many silver deposits and also occurs in disseminated small crystals in silver bearing lead minerals, etc.

B.B. Fuses with intumescence in the O.F. on charcoal, emitting sulphur dioxide odor and a globule of pure silver. Fus. — 1.5.

Grayish White Stromeyerite (Ag,Cu)2S (Very Rare)

Microchem. HNO3, Tarnishes slightly with etching; rubs to rough gray. Fumes tarnish. HCl, Slowly very faint brown. (Sometimes prac- tically negative.) Fumes tarnish. KCN, Tarnishes brown; rubs to faint gray. FeCU; Quickly tarnishes brown or iridescent with struc- ture; rubs to brownish iridescence. HgCU, Tarnishes brown; rubs to pale yellowish. KOH, Neg.

Hardness, Low. 2.5-3. Very sectile. Black powder when scratched.

Description. C. and Str. — Dark steel-gray. Prismatic, massive, com- pact.

B.B. Fuses in the O. F. on charcoal to a semi-malleable globule, which reacts for copper (IV, 6) and cupelled with lead yields a silver button. Soluble in nitric acid. Fus. — 1.5.

Grayish White Jalpaite SAgjS.CuaS? (Very Rare)

Microchem. HNOa, Acid has no effect, but the fumes tarnish slowly brown; rubs clean. HCl, Acid turns green and surface is slightly roughened, but the reaction often appears negative. KCN, Tarnishes brown very slowly; rubs clean. FeClj, Tarnishes and rubs to faint greenish iridescence. HgCh, Tarnishes brown; rubs to faint spot. Fumes tarnish. KOH, Neg.

Hardness, Low. Specimen from Tres Puntas, Chili is brittle and has a blood red powder when scratched. Internal reflection seen with in- clined light is blood red.

Description. C. Blackish lead-gray.

B.B. Like stromeyerite.

Hno, Mci Determinative Tables Kcn

Low

FeCl3-N

Bluish White Brongniardiie* PbS.Ag2S.Sb2S3? (Very Rare)

Microchem. HNO3, Slowly tarnishes pale brown; rubs clean. HCl, Slowly tarnishes faint brown; rubs clean. KCN, Slowly tarnishes faint brown; rubs clean. FeCU, Neg. KOH, Tarnishes iridescent; rubs to clean etched surface.

Hardness, Low. 3 + .

Description. C. and Str. — Grayish black. Massive.

B.B. On charcoal, decrepitates, fuses easily, and gives off sulphur dioxide vapors. Upon roasting yields an impure globule of silver and a yellow coating of lead oxide. In the closed tube yields a faint orange sub- limate. In the open tube, fuses, and yields a sublimate of white anti- mony trioxide. Fus. — 1.

HNO, HCl DETERMINATIVE TABLES KCN-N

High FeCL-N

Gray Psilomelane HMnOs?

Microchem. HNO3, Acid tarnishes faintly; fumes strongly. Rubs

nearly clean. HCl, Tarnishes and rubs faint brown. KCN, Nee.

FeCU, Neg. HgClj, Neg. KOH, Neg. Hardness, High. 5-6. Brittle. Description. C. — Iron-blacli. Str. — Shining brownish black. Massive,

botroidal, reniform, and stalactitic. B.B. Infusible. In the closed tube yields water. Yields a green bead

with sodium carbonate (IV, 11, a). Soluble in HCl with evolution of

chlorine. May contain enough iron to become magnetic when roasted.

HNO, HCl

Determinative Tables Kcn-N

Med. FeCl,

Grayish White Tenorite CuO (Very Rare)

Microchetn. HNO3, Acid without effect, but fumes tarnish; washes clean. HCl, Tarnishes and deposits a mass of white acicular crystals; rubs to faint gray. Fumes tarnish. KCN, Neg. FeCU, Tarnishes pale brown very slowly; rubs clean. HgClj, Neg. KOH, Neg.

Hardness, Medium. 3-4. Slightly brittle.

Description. C. — Iron-gray to black. Str. — Black. Occurs massive, crusted, in minute crystals, and scales. Found in oxidation zone in some Cu deposits.

B.B. Like cuprite (page 33).

HNOs HCl DETERMINATIVE TABLES KCN-N

Med. FeCla -N

Gray Cuprodescloizile (Pb, Zn, Cu)4V209.H20? (Very Rare) Microchem. HNO3, Blackens; rubs to roughened surface. Fumes

tarnish brown. HCl, Tarnishes with structure, acid turning yellow;

rubs to slightly roughened surface. Fumes tarnish. KCN, Neg.

FeCl,, Neg. HgCU, Neg. KOH, Neg. Hardness, Medium. 3.5. Brittle. Reddish yellow powder when

scratched. Internal reflection as seen by inclined light is greenish or

yellowish brown, but maj' not always be noticeable. Description. C. — Dull green to greenish black or yellowish brown.

Usually in crusts or reniform masses with mammillary surface and

columnar structure. B.B. In the closed tube yields water. Will test for constituents m the

formula above as well as for arsenic and other imourities. (See Chap.

Iv.)

Gratish White Tenorite See page 73. Gray Sphalerite See page 94.

Grayish White Aguilariie AgjS.AgjSe (Very Rare)

Microchem. HNO3, Slowly tarnishes brown ; rubs clean. Fumes tarnish. HCl, Acid without effect, but fumes often tarnish brown; rubs to faint brown. KCN, Neg. FeCU, Slowly tarnishes iridescent; rubs to faint iridescence. HgClj, Tarnishes brown to iridescent; rubs to iridescence. KOH, Neg.

Hardness, Low. 2.5. Extremely sectile.

Description. C. — Iron-black. Str. — Black.

B.B. On charcoal yields a white coat with metallic-like luster, also a selenium odor and blue flame. Heated slowly in the open tube yields metallic silver. Fus. — 1.

HNOa

HCl DETERMINATIVE TABLES KCN-N

Low Feci,

PuRPiJ) Umangite* CusSej (Very Rare)

Microchem. HNO3. Turns blue; rubs same. HCl, Same as HNOj.- KCN, Neg. FeCla, Same as HNO3. KOH, Slowly tarnishes brown; rubs blue.

Hardness, Low. 3.

Description. C. — Cherry-red, tarnishing to violet-blue. Str. — Black. Massive.

B.B. Roasted and reduced with sodium carbonate on charcoal, yields copper buttons. Also yields a white coat with metallic-like luster, a selenium odor, and colors the flame blue (IV, 17, a). Fus. — 1.5. White Clausthalite* PbSe (Very Rare)

Microchem. HNO3, Forms brick-red coating; rubs off to brown surface. HCl, Slowly tarnishes brown; rubs clean. KCN, Neg. FeCls, Slowly tarnishes, forming bluish and yellowish coating. KOH, Neg.

Hardness, Low. 2.5-3.

Description. C. — Lead-gray. Str. — Black. Granular masses; cubic cleavage.

B.B. Decrepitates in the closed tube. Gives all tests for lead and sel- enium. (See Chap. IV, 10 and 17.) Fus. — 2. Galena White Galena PbS

Microchem. HNO3, Quickly blackens; rubs black, with rough surface. (In some specimens shows effervescence.) HCL Tarnishes brown; rubs to gray. Fumes tarnish. KCN, Neg. FeCls, Tarnishes brown to iridescent; rubs brown. HgCU, Neg. KOH, Neg.

Hardness, Low. 2.5-2.75. Sectile, but slightly brittle. Gray powder.

Description. C. and Str. — Pure lead-gray. Perfect cubic cleavage.

B.B. Yields all tests for lead (IV, 10). Fus.— 2. Galena White Lillianite* 3PbS.Bi2S3 (Very Rare)

Microchem. HNO3, Quickly tarnishes iridescent; rubs clean. HCl, Slowly tarnishes pale brown; rubs clean. Fumes tarnish. KCN, Neg. FeCIs, Slowly tarnishes iridescent; rubs clean. KOH, Neg.

Hardness, Low.

Description. C. — Steel-gray. Str. — . Massive, also crystalline.

B.B. With KI & S flux shows both lead and bismuth (IV, 3 and 10). Fus.— 1-1.5. Grayish White Teallite* PbSnS2 (Very Rare)

Microchem. HNO3, Tarnishes brown to iridescent; rubs clean. HCl, Slowly tarnishes light brown ; rubs clean. Fumes tarnish. KCN, Neg. FeCU, Slowly tarnishes faint brown. KOH, Same as FeClj.

Hardness, Low. 1-2.

Description. C. — Blackish gray. Str. — Black. Thin flexible folia. Perfect basal cleavage.

B.B. Yields all tests for lead and tin. (See Chap. IV.) Grayish White Cylindrite PbuSbjSnsSji (Very Rare)

Microchem. HNO3, Slowly tarnishes brown; rubs to iridescence. Fumes tarnish iridescent. HCl, Acid is without effect, but fumes tarnish brown; rubs to very faint gray. KCN, Neg. FeCU, Tarnishes brown ; rubs to very faint brown. HgClj, Neg. KOH, Tarnishes brown to iridescent; rubs to faint gray.

Hardness, Low. 2.5-3. Very sectile. Gray powder when scratched.

Description. C — Blackish gray. Str. — Black. Massive; also in cylin- drical forms separating into distinct shells under pressure.

B.B. See Chapter IV for tests for antimony, tin, and lead. Fus. — 1.5.

Creamy White Native Silver See page 43.

White Native Antimony See page 98.

HNO, HCl DETERMINATIVE TABLES KCN-N

Low FeClj-N

Galena White Meneghinite* 4PbS.Sb2S3 (Very Rare)

Microchem. HNO3, Quickly tarnishes and blackens; rubs to gray, rough

surface. HCl, Very slowly faint brown to almost negative. KCN,

Neg. FeCls, Neg. HgCU, Neg. KOH, Tarnishes very slowly. Hardness, Low. 2.5. Brittle. Gray powder when scratched. Description. C— Blackish gray. Str. — Black. Pinacoidal cleavage.

Slender prismatic crystals; also massive, fibrous, and compact. B.B. Decrepitates and fuses very easily. Yields antimony flame and

coat on charcoal (IV, a). With KI & S flux yields lemon-yellow lead

iodide coat (IV, 10 a). Fus. — 1.

Galena White Geocronite 5PbS.Sb2S3 (Very Rare) Microchem. Same as Meneghinite. Except KOH is negative. Hardness, Low. 2.5. Brittle. Gray powder when scratched. Description. C. and Str. — Light lead-gray to grayish blue. Usually

massive, granular, or earthy. B.B. Like Meneghinite.

Grayish White Franckeite PbsSnjSbjSia (Very Rare)

Microchem. HNO3, Tarnishes brown, then iridescent; rubs faint irides- cent. HCl, Usually tarnishes faint brown. Fumes tarnish slightly. KCN, Neg. FeCla, Neg. HgCl,, Neg. KOH, Practically negative, but sometimes faintly tarnishes and rubs clean.

Hardness, Low. 2.75. Extremely sectile. Gray powder when scratched.

Description. C. — Blackish gray. Str. — Black. One perfect cleavage. Massive.

B.B. See Chapter IV for tests for lead, tin, antimony, etc. Fus. — 1.

White Eucairite See page 97.

Grayish White Cylindrite See page 77.

,Omh

Hno,

HCl-N DETERMINATIVE TABLES KCN

Med. FeCl,

Grayish White Poltbasite See page 87.

Grayish (Brownish) White Freibergite (Cu, Ae)8Sb2S7'

Microchem. HNO3, Slowly tarnishes brown to iridescent; rubs pale. Fumes tarnish brown. HCl, Neg. KCN, Tarnishes brown to irides- cent; rubs same. FeCla, Neg. HgCU, Neg. KOH, Neg. Hardness, Medium. 3-4. Description. Similar to tetrahedrite. B.B. like tetrahedrite, but contains silver.

HNO, HCl-N DETERMINATIVE TABLES KCN

Med. FeClj-N

Pinkish White Luzonite CU3ASS4 (Very Rare)

Microchem. HNO3, Very slowly tarnishes faintly; washes clean. Fumes tarnish slightly. HCl, Neg. KCN, Slowly tarnishes. FeCl,, Neg. HgCU, Neg. KOH, Neg. Hardness, Medium. 3.5. Brittle. Gray or black powder when scratched. Description. C. — Dark reddish steel-gray. Str. — Black. Massive. B.B. Like enargite.

Brownish White Enargite CujAsS4

Microchem. HNO3, Very slowly tarnishes faint brown: rubs clean. Fumes slowly tarnish faint brown. HCl, Neg. KCN, Sometimes re- acts very faintly, but quickly darkens some specimens, rubbing to a rough etched surface. FeCls, Neg. HgClj, Slowly tarnishes brown; rubs clean. KOH, Neg.

Hardness, Medium. 3. Brittle. Gray powder when scratched.

Description. C. and Str. — Grayish to iron-black. Often seen with pris- matic planes vertically striated ; also massive or disseminated. Colum- nar cleavage.

B.B. In the closed tube decrepitates, yielding a sublimate of sulphur. At a higher temperature it fuses and yields a sublimate of arsenic sul- phide (IV, 2, c). Roasted and reduced with sodium carbonate, yields a malleable copper button.

Pinkish White Famatinite CujSbS,

Microchem. HNOs Very slowly tarnishes brown; rubs to brown. Fumes tarnish famtly. HCl. Neg. KCN, Slowly tarnishes brown with etching ; rubs to pale etched surface. (Some specimens are prac- tically negative.) FeCU, Neg. HgCU, Neg. KOH, Neg.

Hardness, Medium. 3.5. Brittle. Gray powder when scratched.

Description. C. — Gray with tinge of copper-red. Str. — Black.

B.B. In the closed tube decrepitates, yielding sublimate of sulphur, and on higher heating, a sublimate of antimony sulphide (IVjl, c). Re- duced with fluxes, yields metallic copper and, when moistened with HCl, yields a blue copper chloride flame (IV, 6). Fus. — 1-1.5.

Galena White Guejarite Cu2Sb4S7 (Very Rare)

Microchem. HNOs, Tarnishes dark; rubs to gray. HCl, Neg. (Some specimens tarnish very faintly and rub clean.) KCN, Slowly tarnishes brown; rubs to a faint brown. FeClj, Neg. HgCU, Tarnishes faint brown; rubs clean. KOH, Quickly tarnishes; rubs to deeply etched surface.

Hardness, Medium. 3.5. Sectile, but slightly brittle. Gray powder when scratched.

Description. C. — Steel-gray with tinge of blue. Str. — Black. Prismatic crystals. Good pinacoidal cleavage.

B.B. Like Famatmite.

Yellow

Chalcopyrite

See page 117,

Grayish White

Tennantite

See page 117,

Grayish White

Tetrahedrite

See page 117,

Creamy White

Sulvanite

See page 65.

HNOs HCl-N DETERMINATIVE TABLES KCN

Low FeCl,

Grayish (Greenish) White Pearcite AgsAsSe (Very Rare)

Microchem. HNO3, Acid without effect, but fumes tarnish and wash clean. HCl, Neg. KCN, Quickly blackens; rubs to gray, roughened surface. FeCU, famishes iridescent; rubs to very faint gray. (Some- times rubs clean.) HgCU, Tarnishes brown; rubs to iridescent brown. KOH, Neg.

Hardness, Low. 3. Sectile.

Description. C and Str. — Black. Tabular crystals and massive.

B.B. Yields arsenic odor and white coat on charcoal (IV, 2, a). Roasted and reduced with sodium carbonate jdelds silver buttons. Fus. — 1.

Bluish White Polyargyrite See page 109.

Grayish White Argentite See page 67.

Grayish White Jalpaite See page 67.

Grayish White Polybasite See page 87.

HNO, HCl-K DETERMINATIVE TABLES KCN

Low FeCU-N

Galena White Stibnite Sb2S3

Microchem. HNO3, Tarnishes dark brown; rubs to gray. HCl, Neg.

KCN, Dissolves, bleaches, and roughens surface, but does not tarnish.

FeClj, Neg. HgCU, Neg. KOH, Tarnishes brown and shows yellow

coating; rubs to roughened surface often showing patches of yellow. Hardness, Low. 2. Slightly brittle. Gray powder when scratched. Description. C. and Str. — Lead-gray. Crystals are long prisms with

striations parallel to elongation. Highly perfect "b" pinacoidal

cleavage. B.B. Yields antimony flame and coat on charcoal (IV, 1, a). When

pure volatilizes entirely. Fus. — 1.

Galena White Kebmesite Sb2S20

Microchem. HNO3, Tarnishes light brown; rubs pale brown. HCl, Neg. KCN, Slowly tarnishes pale brown; rubs faint. FeCla, Neg. HgCU, Neg. (?). KOH, Tarnishes iridescent and is coated with yellow; rubs clean.

Hardness, Low. 1-1.5. Very sectile. Red powder when scratched.

Internal reflection as seen by inclined light is red.

Description. C. — Cherry-red. Str. — Brownish-red. Usually in needle- like crystals.

B.B. In the closed tube blackens, fuses, and at first yields a white sub- limate of antimony trioxide; after strongly heating yields the usual black or dark red antimony sublimate in closed tube. Otherwise like stibnite. Fus. — 1.

Gbatish White Polybasite AgaSbSj

Microchem. HNO3, Some specimens practically negative. Others

tarnish very slowly; rubs to faint gray etched surface. HCl, Neg.

KCN, Develops scratches and tarnishes dark brown ; rubs to gray etched

surface. FeCU, Practically negative, but some specimens tarnish faint

brown; wash clean. HgClj, Quickly tarnishes brown to black; rubs

to faint brown. KOH, Neg. Hardness, Low. 2-3. Sectile, but slightly brittle. Gray powder when

scratched. Internal reflection as seen by inclined is red. (Not

always detected.) Description. C. — Iron-black, in thin splinters cherry-red. Str. — Black. B.B. On charcoal fuses with spirting to a globule, yielding antimony

flame and coat (IV, 1, a). Reduced with sodium carbonate yields

silver (IV, 18, a). Fus.— 1.

Galena White Ldvingstonite See page 111.

HNO, HCl-N DETERMINATIVE TABLES KCN-N

High FeCla

White Chloanthite NiAsz

Microchem. HNO3, Slowly tarnishes faint brown; rubs to pale gray. Fumes tarnish. HCl, Neg. KCN, Neg. FeCla, Slowly tarnishes faint brown, but is often almost negative. HgClj, Neg. KOH, Neg.

Hardness, High. 5.5-6. Brittle. Gray powder when scratched.

Description. C. — Tin-white. Str. — Gray-black.

B.B. Fuses easily to a globule and yields an arsenic odor and perhaps a white arsenic coat on charcoal. Yields a red precipitate with dimethyl glyoxime (IV, 14, 6). Gives a cobalt reaction with borax usually due to impurities of that element. Fus. — -2.

White Rammehhergite NiAsj (Very Rare) Like chloanthite in all properties except crystal system.

White Gebsdorpfite NiAsS

Microchem. HNO3, Tarnishes brown, then black; rubs to rough gray surface. Fumes tarnish brown and develop structure. HCI, Mineral unaffected, but acid turns bright yellow. KCN, Neg. FeClj, Slowly tarnishes faint brown. (Sometimes practically negative.) HgCU, Tarnishes brown; rubs clean. KOH, Neg.

Hardness, 5.5. Brittle.

Description. C. — Silver-white, tarnishing to gray. Str. — Grayish black. Good cubic cleavage.

B.B. Decrepitates in the closed tube and yields a yellowish brown sub- Umate (IV, 2, c). Otherwise like chloanthite.

HNO, HCl-N DETERMINATIVE TABLES KCN-N

High FeCU-N

White Ldllingite FeAs2 (Very Rare)

Microchem. HNOj, Slowly tarnished faint brown. Fumes tarnish.

HCl, Neg KCN, Neg. Fed,, Neg. HgCl,, Neg. KOH, Neg. Hardness, High. 5-5.5. Brittle. Description. C. — Silver-white. Str. — Black. B.B. Fuses to strongly magnetic globule in R.F. on charcoal. Gives

arsenic coat and odor; also sublimate and mirror in open and closed

tube respectively. Fus. — 2.

White Ulmannite* NiSbS (Very Rare)

Microchem. HNOj, Tarnishes brown to iridescent; rubs to iridescent

gray. HCl, Neg. KCN, Neg. FeClj, Neg. KOH, Neg. Hardness, High. 5-5.5. Brittle. Description. C.-Silver-gray. Str. — Graj'ish black. Perfect cubic

cleavage. B.B. On charcoal in the R.F. fuses easily to a globule, boils, and yields

an antimony coat (IV, 1, a). Yields a red precipitate with dimethyl

glyoxime (IV, 14, 6). Fus. — 1.5.

Creamy Whte Linnanle C03S4 (Very Rare)

Microchem. HNO3, Tarnishes very faint brown. Fumes tarnish brown very slowly. HCl, Neg. KCN, Neg. FeCla, Neg. HgClj, Tar- nishes iridescent brown. KOH, Neg.

Hardness, High. 5.5. Brittle.

Description. C. — Pale steel-gray, tarnishing copper-red. Str. — Black. Imperfect cubic cleavage.

B.B. On charcoal fuses to a magnetic globule. The roasted mineral yields, with the fluxes reactions for nickel, cobalt, and iron usually. Fus.— 2.

Pinkish White Glaucodot (Co,Fe)AsS (Rare)

Microchem. HNO3, Slowly tarnishes; rubs to rough gray surface. HCl,

Neg. KCN, Neg. FeCla, Neg. HgCU, Neg. KOH, Neg. Hardness, High. 5. Brittle. Description. C. — Gray. Str. — Black. Usually prismatic crystals or

massive. B.B. Yields arsenic odor and coat on charcoal, etc. (IV, 2). In the

R.F. fuses to a feebly magnetic globule, black on the surface, but a

light bronze in color when freshly fractured. Fus. — 2-3.

Creau Hawchecornile (Ni,Co)7(S.Sb.Bi)8 (Very Rare)

Microchem. HNO3, Very slowly tarnishes brown; rubs to very pale

brown. Fumes tarnish slightly. HCl, Neg. KCN, Neg. FeCls,

Neg. HeCU, Slowly tarnishes brown; rubs clean. KOH, Neg. Hardness, High to medium. 5. Very Brittle. Steel-gray powder when

scratched. Description. C. — Light bronze-yellow. Str. — Black. B.B. Yields common reactions for constituents indicated in formula.

(See Chapter IV.)

White Gersdorffite See page 89.

White Chloanthite See page 89.

White Willy amite See page 57.

Creamt White Pyrite See page 57.

Cream Pyrrhotite See page 95.

TKAaXO

HNOa HCl-N DETERMINATIVE TABLES KCN-N

Med. FeCl,

Pink Breithauplite NiSb (Very Rare) Microchem. HNOj, Blackens; rubs to dark gray. HCl, Neg. KCN,

Neg. FeClj, Tarnishes; rubs to clean-pitted surface. KOH, Neg. Ife.rdness, Medium to high. 5.5.? Brittle. Reddish-brown powder

when scratched. Description. C. — Light copper-red. Str. — Reddish brown. B.B. Yields antimony flame and coat on charcoal and with dimethyl

glyoxime gives a red precipitate. (IV, 14, b). Fus. — 1.5-2.

Grayish White Bournonite (PbCu2)3Sb2S(i (Rare)

Microchem. HNO3, Fumes usually tarnish slowly; rubs clean. HCl,

Nee. KCN, Neg. FeCl,, Neg. HgClj, Tarnishes faintly at edge

of drop; rubs to very faint brown. KOH, Neg. Hardness, Medium to low. 2.5-3. Slightly brittle. Description. C. — Steel-gray. Str. — Black. B.B. In the closed tube decrepitates and gives a dark red sublimate.

Yields antimony flame and coat on charcoal; with continued heating,

yielding a lead coat. Residue reduced with sodium carbonate yielM

copper buttons. Fus. — 1. Gratish White Styhtypite 3(Cu2Ag2Fe)S.Sb2S3 (Very Rare) Microchem. HNO3, Tarnishes brown very slowly; rubs faint or clean.

Fumes tarnish. HCl, Neg. KCN, Neg. FeCl,, Neg. HgClj, Neg.

KOH, Neg. Hardness, Medium. 3. Brittle. Description. C. and Str. — Iron-black.

B.B. Decrepitates and fuses easily, yielding a steel-gray, magnetic glob- ule. Also tests for constituents in formula. Fus. — -1.5. Grayish White Stannite SnCu2FeS4 (Very Rare)

Microchem. HNO3, Tarnishes brown to iridescent; rubs to very famt

brown. HCl, Neg. KCN, Neg. FeClj, Neg. HgClj, Neg. KOH,

Neg. Hardness, Medium. 4. Brittle.

Description. C. — Steel-gray. Str. — Black. Massive, granulur, or dis- seminated. B.B. In the closed tube decrepitates, giving a faint sublimate only.

See Chapter IV for tests for constituents of the mineral. Grayish White Crookesite* (CuTlAg)2Se (Very Rare)

Microchem. HNO3, Slowly tarnishes faint brown; rubs clean. Fumes

tarnish. HCl, Neg. KCN, Neg. FeCl,, Neg. KOH, Neg. Hardness, Medium to low. 2.5-3. Brittle. Description. C. — Lead-gray. Str. — Black. Massive, compact. B.B. Fuses easily to greenish black, shining enamel, coloring flame blue.

Roasted and reduced with sodium carbonate yields copper and silver.

(IV, 6, and 18.) Fus.— 1. Grayish White Hauerite MnSj (Very Rare)

Microchem. HNO3, Fumes tarnish brown very slowly; washes clean.

HCl, Neg. KCN, Neg. FeCU, Neg. HgCU, Neg. KOH, Neg. Hardness, Medium. 4. Brittle. Brick-red powder when scratched. Description. C. — -Brownish black. Str. — Reddish brown. B.B. Roasted mineral yields green bead with sodium carbonate. Fus.

—3. Gray Sphalerite ZnS

Microchem. HNO3, Tarnishes faintly brown: rubs clean. HCl, Neg.

KCN, Neg. FeCls, Neg. HgCU, Neg. KOH, Neg. Hardness, Medium. 3.5-4. Brittle. Yellow or brown powder when

scratched. Internal reflection as seen by inclined light is yellow or brown. Description. C. — Shades of yellow, brown to black. Str. — Pale to

colorless. Perfect dodecahedral cleavage. B.B. Nearly infusible. Reduced with soda on charcoal yields white

zinc oxide coat, which when moistened with cobalt nitrate sol. and

again heated in the O.F. becomes green (IV, 29, a). Wurtzite is like sphalerite physically and microchemically.

Yellow Chalcopyrite See page 117.

Creamy White Sulvaniie See page 65.

Pinkish White Famatinite See page 83.

Gbat Voltzile See page 116.

HNOs

HCl-N DETERMINATIVE TABLES KCN-N

Med. FeClj-N Pale Yellow Millerite NiS (Rare,

Microchem. HNO3, Acid is without effect, but fumes tarnish brown;

rubs to very faint brown. HCl, Neg. KCN, Neg. FeCls, Neg.

HeCU, Tarnishes brown; rubs clean. KOH, Neg. Hardness, Medium. 3-3.5. Brittle. Grayish yellow powder when

scratched. Description. C. — Bronze-yellow. Str. — Greenish black. Commonly

occurs as hair-like crystals or botryoidal crusts. At least two perfect

cleavages. B.B. On charcoal in the R.F. the roasted mineral gives a coherent

metallic mass, slightly magnetic. As well as yielding reactions for

nickel, most varieties also show copper, cobalt, and iron. Fus. — 2. Cream Pyrrhotite FeS(S)x

Microchem. HNO3, Tarnishes very slowly faint brown; almost negative;

rubs clean. Fumes tarnish brown. HCl, Neg. (Fumes sometimes

tarnish faintly.) KCN, Neg. Fed,, Neg. HgClj, Neg. KOH,

Slowly tarnishes brownish or iridescent; rubs to brownish iridescence. Hardness, Medium. 3.5-4.5. Brittle.

Description. C. — Bronze-yellow. Str. — Grayish-black. Usually mas- sive or disseminated. Naturally magnetic. B.B. In the R. F. on charcoal blackens and becomes strongly magnetic.

Fus.— 2.5-3. Cream Chalmersite CuFezSs (Very Rare)

Microchem. HNO3, Fumes tarnish slightly; washes clean. HCl, Neg.

KCN, Neg. FeCla, Neg. HgCU, Neg. KOH, Neg. Hardness, Medium. 3.5. Slightly brittle. Description. C. — Pale yellow. Str. — Grayish or greenish black.

Strongly, though variably magnetic. B.B. In the R.F. on charcoal fuses to a strongly magnetic globule. Well

roasted and reduced with sodium carbonate on charcoal yields cop- per (IV, 6, a). Creamy White Pentlandite (Fe,Ni)S (Rare)

Microchem. HNO3, Slowly tarnishes very faint brown; rubs to very

faint brown. HCl, Neg. KCN, Neg. FeCl,, Neg. HgCl,, Neg.

KOH, Neg. Hardness, Medium. 3.5-4. Brittle. Description. C. — Light bronze-yellow. Str. — Bronze. Non-magnetic.

Massive. B.B. Fuses readily to a magnetic globule on charcoal and yields a red

precipitate with dimethyl glyoxime (IV, 14, b). Fus. — 2. Creamy White Wittichenite CujBiSj . (Very Rare)

Microchem. HNO3, Tarnishes light brown; rubs to gray. Fumes

tarnish. HCl, Neg. KCN, Neg. FeCU, Neg. HgClj, Neg. KOH,

Slowly tarnishes famt brown; rubs clean. Hardness, 3.5. Slightly brittle. Description. C. — Steel-gray. Str. — Black. B.B. On charcoal fuses easily, at first throwing out sparks, and yielding

a bismuth oxide coat (IV, 3, a). The roasted material, moistened with

HCl yields a strong blue copper chloride flame. Fus.- — 1. Galena White Andorite PbAgSb.-.Sn (Very Rare)

Microchem. HNO3, Slowly tarnishes brown or iridescent; rubs faint or

clean. Fumes tarnish slowly. HCl, Neg. KCN, Neg. FeCls, Neg.

HgCl2, Neg. KOH, Slowly tarnishes to pale brown; rubs to faint

brownish iridescence. Hardness, Medium to low. Brittle. Description. C. — Steel-gray. Str. — Black. B.B. Shows lead and antimony as in bournonite, but when cupelled

yields silver. Fus. — 1. Grayish White Tennantite See page 117.

White Native Antimony Sb

Microchem. HNO3, Tarnishes brownish or iridescent; rubs same. HCl, Neg. (Sometimes appears to tarnish very faintly.) KCN, Nee. FeCla, Tarnishes slowly brown; rubs to pale brown. HgCls, Slowly tarnishes faintly brown; rubs nearly clean. KOH, Neg.

Hardness, Low. 3.3-5. Very brittle.

Description. C. and Str. — Tm-white. Perfect cleavage.

B.B. On charcoal yields a white coat in both R.F. and O.F.; with inter- mittent blowing the globule is finally crusted over with prismatic crystals of antimony trioxide.

Creamy White Native Silver See page 43.

Galena White Plagionite See page 43.

Grayish White Aguilarite See page 76.

HNOa

HCl-N DETERMINATIVE TABLES KCN-N

Low FeCls

White Berzelianite CujSe (Very Rare)

Microchem. HNO3, Tarnishes iridescent; rubs to iridescent greenish

gray. HCl, Neg. KCN, Neg. FeCU, Tarnishes very brown;

rubs clean. HgCU, Tarnishes very Ught brown; rubs clean. KOH,

Neg. Hardness, Low. Very sectile. Description. C. — Silver-white, soon tarnishing. Str. — Shining. Occurs

in thin dendritic crusts and disseminated. B.B. In the open tube gives a red sublimate of selenium, with white

crystals of selenium dioxide. On charcoal yields white coat, selenium

odor, and blue flame; with soda in R.F. gives metallic copper. Fus. —

White Eucairite CusSe.AgjSe (Very Rare)

Microchem. HNO3, Tarnishes black and shows orange coating; rubs to

rough gray. Fumes tarnish slightly. HCl, Neg. KCN, Neg. FeCls,

Practically negative. (Sometimes tarnishes very slowly faint brown.)

HgCU, Neg. KOH, Neg. Hardness, Low. 2.5. Very sectile.

Description. C. — Silver-gray. Str. — Shining. Massive and granular. B.B. Like berzelianite except that silver is shown on reduction. Creamy White Kalgoorlile HgAuzAgeTee? (Very Rare)

Microchem. HNO3, Very slowly tarnishes faint brown; rubs almost

clean. HCl, Neg. KCN, Neg. FeCU, Tarnishes iridescent; rubs to

rough brownish surface. HgCl, Neg. KOH, Neg. Hardness, Ijow. Sectile, but slightly brittle. Description. C. and Str. — Iron-black. Occurs massive.

B.B. Yields tellurium flame and coat on charcoal (IV, 20, a). Roasted

and reduced with sodium carbonate yields gold and silver. With soda

in a closed tube gives metallic mercury. Grayish White Peizite (Ag, Au)2Te (Very Rare)

Microchem. HNO3, Tarnishes brown to black; rubs gray. (Some

specimens effervesce.) HCl, Neg. KCN, Neg. FeCl3, Tarnishes

brown; rubs clean. HgCU, Tarnishes light brown; rubs faint. KOH,

Neg. Hardness, Low. 2.5-3. Very sectile.

Description. C. — Iron-black. Str. — Gray. Granular to compact. B.B. Yields a bright green tellurium flame and white coat on charcoal

(IV, 20, a). Roasted and reduced with soda on charcoal yields gold

and silver button. Fus. — 1.5. Grayish White Coloradoite HgTe (Very Rare)

Microchem. HNO3, Slowly tarnishes iridescent; rubs clean. HCl, Neg.

KCN, Neg. FeCla, Tarnishes very faint brown; rubs clean. HgCli,

Neg. KOH, Neg. Hardness, Low. 3. Very sectile.

Description. C. — Iron-black. Str. — Black. Massive; granular. B.B. Easily volatile on charcoal. In the closed tube slightly decrepi- tates, fuses and yields metallic mercury, also tellurium oxide in drops,

and next to the assay metallic tellurium. Fus. — 1. Grayish White Molybdenite M0S2.

Microchem. HNO3, Slowly very faint tarnish; rubs clean. Fumes

tarnish faint. (Reaction is often practically negative.) HCl, Neg.

KCN. Neg. FeCls, Practically negative, but sometimes tarnishes very

faint brown; washes clean. HgCU, Neg. KOH, Neg. Hardness, Low. 1-1.5. Very sectile. Description. C. — Lead-gray to bluish black. Str. — Bluish gray. Marks

gaper. Laminae are flexible, but inelastic. Perfect basal cleavage. . Infusible, but yields a green flame, also a white coat in O.F. on charcoal (IV, 13).

Gai£NA White Galenobismulite* PbBijS4 (Very Rare)

Microchem. HNO3, Tarnishes brown to black; rubs same. HCl, Neg.

KCN, Neg. FeCls, Neg. KOH, Neg. Hardness, Low. 3-4.

Description. C. — Lead-gray to tin-white. Str. — Grayish black. B.B. With KI & S flux shows both lead and bismuth (IV, 3, and 10). Galena White Beegerite* PbBi2S9 (Very Rare)

Microchem. HNOs, Tarnishes; rubs to faint gray. Fumes tarnish.

HCl, Neg. KCN, Neg. FeCU, Neg. KOH, Neg. Hardness, Low.

Description. C. — Gray. Str. — Grayish black. B.B. Like galenobismutite. Galena White Freieslebenile (Pb,Ag2)6Sb4Sii (Very Rare) Microchem. HNO3, Tarnishes dark; rubs to rough gray. One fairly

reliable specimen of this mineral was negative with HNO3. HCl,

Neg. KCN, Neg. FeCl,, Neg. ifgCl,, Neg. KOH, Neg. Hardness, Low. 2-2.5. Brittle.

Description. C. — Steel-gray. Str. — Black. Vertically striated prisms. B.B. Yields antimony flame and coat on charcoal (IV, 1, a). With

KI & S flux shows lead (IV, 10, a). Reduced with soda and cupelled

shows silver. Fus. — 1. Galena White Nagyagite Au2PbioSb2Te6Si5? (Very Rare) Microchem. HNO3, Slowly tarnishes iridescent; rubs gray. HCl, Neg.

KCN, Neg. FeCl,, Neg. HgCU, Neg. KOH, Neg. Hardness, Low. 1-1.5. Description. C— Gray. Str. — Black. One perfect clea.vage. Thin

laminae are flexible. Tabular crystals ; also granular massive. B.B. Complex, but yields tests for constituents of formula. (See

Chap. IVT) Creamy White Sylvanite AuAgTcj (Very Rare)

Microchem. HNO3, Tarnishes brown; rubs to deep brown, sometimes

developing cleavage. HCl, Neg. KCN, Neg. FeCls, Neg. HgCli,

Neg. KOH, Neg. Hardness, Low. 1.5-2. Slightly brittle. Description. C. — Yellowish steel-gray. Str. — Gray. Perfect pinacoidal

cleavage. Usually crystalline. B.B. Yields bright green tellurium flame and coat on charcoal (IV, 20,

a). Roasted and reduced with soda yields both gold and silver.

Fus.— 1. Creamy White Guanajuaiile Bi2Se3 (Very Rare)

Microchem. HNO3, Quickly tarnishes iridescent; rubs practically clean.

Fumes tarnish brown. HCl, Neg. KCN, Neg. FeCU, Neg. HgClj,

Slowly tarnishes brown; rubs clean. KOH, Neg. Hardness, Low. 2.5-3.5. Sectile to slightly brittle. Description. C. — Bluish gray. Str. — Black. B.B. Yields blue selenium flame, odor, and coat on charcoal. (IV, 17, o).

With KI & S flux yields a brick-red bismuth iodide coat (IV, 3).

Fus.— 1.5.

HNO, HCl-N DETERMINATIVE TABLES KCN-N

Low FeCl,-N

Paie Brown Stembergite* AgFejSj? (Very Hare)

Microchem. HNO3, Tarnishes iridescent; rubs gray. HCl, Neg. KCN, Neg. FeCU, Neg. KOH, Tarnishes brown; rubs clean.

Hardness, Low. 1-1.5.

Description. C. — Bronze. Str. — Black. Perfect basal cleavage. Lam- inse are flexible, like tin-foil. Marks paper. Tabular crystals.

B.B. Roasted on charcoal becomes magnetic and the surface of the glob- ule shows separated metallic silver. Fus. — 1.5. Galena White Lengenbachite Pb(AgCu)2As4Si3 (Very Rare)

Microchem. HNO3, Practically negative, but sometimes tarnishes slightly; rubs to faint gray. HCl, Neg! KCN, Neg. FeClj, Neg. HgCl,, Neg. KOH, Neg.

Hardness, Low. Brittle.

Description. C. — Steel-gray. Str. — Brownish. Marks paper.

B.B. Yields arsenic odor and coat on coal (IV, 2, a). See Chapter IV. Galena White Rathite Pb(As,Sb)S? (Very Rare)

Microchem. HNO3, Very slowly tarnishes brown; rubs to faint gray. Sometimes practically negative. HCl, Neg. KCN, Neg. FeCls, Neg. HgCU, Neg. KOH, Tarnishes brown; rubs to faint gray.

Hardness, Low. Brittle.

Description. C. — Blackish lead-gray. Str. — Reddish brown. Prismatic cryst.

B.B. Yields common tests for constituents in formula. (Chap. IV). Galena White Jordanite* PbiAsjSi (Very Rare)

Microchem. HNO3, Tarnishes slightly; rubs clean. HCl, Neg. KCN, Neg. FeCl,, Neg. KOH, Neg.

Hardness, Low. 3. Brittle.

Description. C. — Lead-gray. Str. — Black. Six sided crystals.

B.B. Decrepitates strongly yielding arsenic odor and white coat on char- coal; also a yellow lead oxide coat near the assay. Fus. — 1. Galena White Guitermanite* SPbS.AsjSs? (Very Rare)

Microchem. HNO3, Quickly tarnishes iridescent; rubs clean. HCl, Neg. KCN, Neg. FeCl,, Neg. KOH, Neg.

Hardness, Low. 3.

Description. C— Bluish gray. Str. — Black. Massive, compact.

B.B. Like jordanite. Galena White Epiboulangerite* Pb3Sb2S (Very Rare)

Microchem. HNO3, Tarnishes black; rubs to gray. Sometimes shows small white crystals after rubbing. HCl, Neg. (Fumes sometimes tarnish slightly.) KCN, Neg. FeCl,, Neg. KOH, Neg.

Hardness, Low.

Description. C. — Dark bluish gray. Str. — Black. Striated prismatic needles.

B.B. Yields antimony flame and coat on charcoal (IV, 1, a) ; also yellow lead oxide coat near the assay. Fus. — 1.

White Eucairite See page 97.

White Berzellianite See page 97.

Creamy White Emplectite See page 63.

Galena White Stibnite See page 87.

Galena White Geocronite See page 79.

Grayish White Crookesite See page 94.

Grayish White Regnolite See page 119.

Grayish White Jamesonite See page 62.

Galena White Andorite See page 95.

HNOi-N HCl

Determinative Tables Kcn

Low FeCl,

Grayish White Stephanite Ag6SbS4

Microchem. HNO3, Neg. HCl, Fumes slowly tarnish brown to irides- cent; rubs clean. KCN, Quickly tarnishes brown; rubs pale brown, developing cracks. FeCls, Slowly gives a speckled surface; rubs clean. HgClj, Quickly tarnishes brown; rubs to brown. KOH, Slowly tar- nishes deep brown; rubs clean.

Hardness, Low. 2-2.5. Slightly sectile to brittle.

Description. C. and Str. — Iron-black.

B.B. In the closed tube decrepitates and fuses, after long heating giving faint antimony sublimate. On charcoal fuses easily with spirting, yielding a white coat which may become red with oxidized silver. Roasted and reduced with soda yields silver button.

Brown Pyrolusite Mn02

Microchem. HNOj, Practically negative. (Faintly tarnishes and dis- solves in two or three minutes.) HCl, Tarnishes slowly; rubs pale. KCN, VAith 20 per cent, solution almost negative, but rapidly tarnishes with very dilute solution and is noticeable usually after washing. FeCU, Tarnishes dark brown; rubs pale. HgClj, Neg. KOH, Neg.

Hardness, Low (Variable).

Description. C. — Dark steel-gray to iron-black. Str. — Black. Soils fingers.

B.B. Infusible. Yields manganese reactions with the fluxes. Evolves chlorine when treated with HCl.

Grayish White Jalpaile See page 67.

Bluish White Proustite See page 109.

Hno,-N

Determinative Tables Kcn-N

Med. FeCls-N

Gbatish White (Creamy) Delafossite CuO, FcjOs? (Very Rare)

Microchem. HNOj, Neg. HCl, Tarnishes slightly and acid turns yel- lowish-green; rubs to etched surface. KCN, Neg. FeClj, Neg. HgCU, Neg. KOH, Neg.

Hardness, Medium. 2.5. Brittle.

Description. C. — -Dark gray. Str. — Blackish gray. Cleavable into laminse. Occurs in small crystalline plates.

B.B. Fusible with difficulty, coloring the flame green. Easily soluble in HCl.

HNOrN HCl-N DETERMINATIVE TABLES KCN

Med. Feci,

Grayish White Poltbasite See page 87.

Hno,-K

HCl-N DETERMINATIVE TABLES KCN

Med. FeCls- N

Yellow Chalcopyrite See page 117.

Brownish White Enargite See page 83.

Gbatish White Pyraroybite See page 111.

HNC-N HCl-N DETERMINATIVE TABLES KCN

Low FeCI,

Bluish White Proustite AgaAsSs

Microchem. HNO3, Neg. HCl, Neg. Fumes sometimes tarnish faintly; rubs clean. KCN, Slowly tarnishes brown, developing scratches; rubs to faint brown. FeCla, Slowly tarnishes faintly; rubs clean. HgCU, Slowly tarnishes brown; rubs to brownish irides- cence. KOH, Quickly tarnishes black ; rubs to pale brown.

Hardness, Low. 2.5. Slightly brittle. Blood-red powder when scratched.

Internal reflection as seen by inclined light is bright red.

Description. — C. and Str. — Scarlet. Commonly as elongated crystals.

B.B. Yields arsenic odor and white coat on charcoal. Prolonged heating in the O.F. or reduction with soda in the R.F. yields silver. Fus. — 1.

Bluish White PolyargyrUe* AgziSbaSu (Very Rare)

Microchem. HNO3, Neg. Fumes often tarnish slightly; rubs clean.

HCl, Neg. KCN. Quickly tarnishes brown; rubs clean. FeCU,

Tarnishes dark or iridescent; rubs clean. KOH, Neg. Hardness, Low. 2.5. Very sectile. Description. C. — Iron-black to grayish black. Str. — Black. Cubic

cleavage. B.B. Fuses easily on charcoal to a black globule, giving antimony flame

and coat, and finally a brittle globule of silver. Fus. — 1.

Grayish White Cerargyrite AgCl

Microchem. HNO3, Neg. HCl, Neg. KCN, Quickly tarnishes to red- dish brown; washes to dark solution pit. FeCU, Quickly tarnishes dark brown; rubs same. HgCU, Neg. KOH, Slowly tarnishes; rubs pale.

Hardness, Low. 1-1.5. Highly sectile.

Description. C. — Pearl-gray, various. Str. — WaxUke.

B.B. Fuses in closed tube without decomposition. On charcoal gives a globule of metallic silver.

Grayish White Bromyrite ' AgBr (Very Rare)

Microchem. HNO3, Neg. HCl, Neg. KCN, Tarnishes slightly; rubs

nearly clean. FeCU, Tarnishes dark gray to brown ; rubs same. HgCU,

Slight tarnish? KOH, Tarnishes rapidly and forms whitish coating. Hardness, Low. Sectile. Description. C. — Bright yellow to grass or oUve green. Str. — Yellowish

green. No cleavage. B.B. On charcoal emits bromine vapors and yields a globule of metallic

silver. In the closed tube reacts Uke cerargyrite.

EmbolUe, Ag(Cl, Br), and iodobromite, 2AgCl.2AgBr.AgI, are intermediate between cerargyrite, bromyrite and iodyrite in all chemical and physical properties as well as in composition. The differences in color on the polished surface are usually enough to distinguish between any two that may be present together, and the difference in the rates of reaction with any of the active reagents easily brings out contrasts between them.

Grayish White Jalpaite See page 67.

Grayish White PearcUe See page 86.

Bluish Wsite Miargyrite AgSbSj (Very Rare) Microchem. Like pyrargyrite.

Hardness, Low. 2-2.5. Brittle. Cherry-red powder when scratched. Internal reflection as seen by inclined light is deep red. Description. C. — Iron-black to steel-gray. Str. — Cherry-red. B.B. On charcoal fuses quietly, giving a white antimony coat and a

gray bead, which after continued treatment in the O.F. leaves a bright

globule of silver. Fus. — 1.

Grayish White Argyrodite AgeGeSs? (Very Rare)

Microchem. HNO3, Neg. HCl, Neg. KCN, Tarnishes brown, devel- oping scratches; rubs to very faintly etched surface. FeClj, Neg. HgClj, Tarnishes brownish iridescent; rubs to iridescence. KOH, Neg.

Hardness, Low. 2.5. Brittle.

Description. C. — Steel-gray on a fresh fracture, with a tinge of reddish violet. Str. — Grayish black.

B.B. In the closed tube yields a brilliant black sublimate; in the open tube fumes of sulphur dioxide. On charcoal fuses to a bead, giving near the assay a faint white sublimate; after long heating, an orange- yellow sublimate and a silver globule. Fus. — 1.5.

Grayish White Orpiment AsjSs

Microchem. HNO3, Neg. HCl, Neg. KCN, Tarnishes dark quickly ; rubs nearly same. FeClj, Neg. HgClj, Yellow coat, rubs clean. KOH, Quickly tarnishes black.

Hardness, Low. 1.5-2. Sectile. Lemon-yellow powder when scratched.

Internal reflection as seen by inclined light is yellow.

Description. C. — Lemon-yellow. Str. — Pale yellow. Usually in foli- ated or columnar masses. Perfect pinacoidal cleavage.

B.B. On charcoal fuses and volatilizes entirely, yielding arsenic odor. In the closed tube, fuses, volatilizes, and gives a dark yellow sublimate. Fus.— L

Grayish White lodyrile Agl (Very Rare)

Microchem. HNO3, Neg. HCl, Neg. KCN, Quickly dissolves and tarnishes to dark surface; rubs to gray, etched surface. FeCU, Neg. HgClj, Tarnishes brownish to iridescent; rubs same or slightly lighter.. KOH, Very slowly yields slight tarnish.

Hardness, Low. Sectile. Internal reflection seen by incUned light is yel- lowish to brownish.

Description. C. — Yellow to yellowish green, sometimes brownish. Str. — Yellow. Perfect C cleavage.

B.B. In the closed tube fuses and assumes a deep yellow color, but re- sumes its yellow color on cooling. On charcoal gives fumes of iodine and a globule of metallic silver.

Hno,-N Hci-N Determinative Tables Kcn

Low FeClrN

Blue Covellite CuS

Microchem. HNO3, Neg. HCl, Neg. KCN, Quickly tarnishes purple ;

rubs to grayish, deeply etched surface. FeCls, Neg. HgClj, Neg.

KOH, Neg. Hardness, Low. 1.5-2. Slightly brittle. Description. C — Deep indigo-blue. Str. — Gray to black. Perfect

basal cleavage; flexible in thin leaves. Common in smaller quantities

as a secondary mineral in nearly all copper deposits. B.B. On charcoal bums with a blue flame, fusing to a globule which

reacts like chalcocite (IV, 6). Fusi — 2.5.

Yellow Native Gold Au

Microchem. HNO3, Neg. HCl, Neg. KCN, Slowly blackens; rubs to brownish, rough surface. FeCls, Neg. (?). HgCla, Neg. KOH, Neg. Hardness, Low. 2.5-3. Sectile. Yellow powder when scratched. Description. C and Str. — Gold-yellow. B.B. Fuses easily to yellow button. Not acted on by any of the fluxes.

Galena White Ldvingslonite HgSbiSr (Very Rare)

Microchem. HNO3, Neg. (?) HCl, Neg. KCN, Slowly tarnishes

grayish. FeCU, Neg. HgCU, Tarnishes to brownish iridescence; rubs

same. KOH, Neg. Hardness, Low. 2. Red powder when scratched. Internal reflection as seen by inclined light is deep red. Description. C. — -Lead-gray. Str. — Red. Usually in slender prismatic

crystals. B.B. Roasted on charcoal is completely volatile. Yields antimony

flame and coat (IV, 1, a). With soda in the closed tube yields mercury

(IV, 12, a). Fus.— 1.

Bluish White Onofrite Hg(SSe) (Very Rare)

Microchem. HNO3, Neg. HCl, Neg. KCN, Faintly tarnishes brown or bluish, differentially; rubs to faint brown. FeCU, Neg. HgCU, Neg. KOH, Neg. Hardness, Low. 2.5. Sectile to slightly brittle. Some flakes show yellow internal reflection as seen by inclined light. Description. C and Str. — -Blackish gray. Massive; fine granular. B.B. In the closed tube decrepitates and gives sublimates of sulphur and mercury (IV, 12, a). On charcoal gives copious fumes with selen- ium odor and a sublimate with metallic-like luster which touched by the R.F. disappears, coloring the flame azure-blue.

Gbatish White Pyrarqtrite Ag3SbS3

Microchem. HNO3, Neg. HCl, Neg. KCN, Tarnishes pale brown slowly; rubs to faint gray surface showing structure. FeCU, Neg. HgClj, Slowly tarnishes light brown; rubs clean. KOH, Tarnishes black; rubs to speckled yellowish gray surface. Hardness, Low. 2.5. Brittle. Blood-red powder when scratched. Internal reflection as seen by inclined light is brilliant red. Description. C. — Black to grayish black. Str. — Purplish red. B.B. On charcoal fuses with spirting to a globule, coats the coal white, and the assay is converted into silver sulphide, which, treated in the O.F., or with soda in the R.F., gives a globule of silver. Fus. — 1. Bluish White Proustite See page 109. (Very Rare)

Grayish White Polybasite See page 87.

HNOa-N HCl-N DETERMINATIVE TABLES KCN-N

High Feci,

Gray Uraninite Uranate of U,Pb, etc. (Very Rare)

Microchem. HNO,, Neg. HCl, Neg. KCN Neg. FeCU, Slowly

tarnishes to still darker brownish gray; rubs same. HgClj, Neg.

KOH, Neg. Hardness, High. 5.5. Brittle. Description. C. — Pitch-black to greenish. Str. — Greenish brown to

black. Usually massive and botryoidal. B.B. Infusible. In the R.F. gives a green bead with both borax and

salt of phosphorous (IV, 26, a). Many impurities are always present

and any or all may yield reactions.

Grayish White Wolframite (FeMn)W04

Microchem. Negative with all reagents.

Hardness, High. 5-6.5. Brittle.

Description. C. — Dark brown to nearly black. Str. — Reddish or brownish to nearly black. Perfect pinacoidal cleavage. Crystals commonly tabular, bladed, columnar, etc.

B.B. Fuses to a magnetic globule with a crystalline surface. With soda yields a green manganate bead (IV, 11, a). For tests for tungsten, see IV, 25. Fus.— 3.

(Note. Hubnerite, MnW04, and Ferberite, FeW04, differ from Wol- framite only in color.)

Gray Cassiterite SnOj

Microchem. Negative with all reagents. Hardness, High. 6-7.

Description. C. — Brown to black; variable. Str. — Light. B.B. Infusible. Reduced with soda and borax on charcoal yields metal- lic tin buttons.

Gray (Variable) Limonite 2FesO,.3HjO(?)

Microchem. Negative with all reagents.

Hardness, High. 5-5.5. Brittle. Yellow powder when scratched.

Internal reflection as seen by inclined light is often reddish brown.

Description. C. — Ocher-yellow to brownish black. Str. — Yellowish brown. Never crystallized. Usually botryoidal, concretionary, mas- sive, earthy, etc.

B.B. Infusible. Yields water when heated in the closed tube. Other- wise like hematite.

(Note. — Gothite, FejOs.HjO, and Turgite, 2Fe20s.H20, behave chemically like Limonite, but Turgite is very much lighter in color.)

Gray Chromite FeCr204

Microchem. Negative with all reagents.

Hardness, High. 5.5.

Description. C. — Iron-black to brownish black; various. Str. — Brown.

Commonlv massive; fine granular to compact. B.B. Infusible in O.F., but in R.F. is slightly rounded on edges and

becomes magnetic. For tests for chromium see IV, 4.

Grayish White Rare Earths

Columbite, Tantalite, Samarskite, etc., are all chemically inert with the reagents used and are indistinguishable on polished sections.

Grayish White Manganese Oxides

Manganite, MnjOs.HjO, Hausmannite, MnO.MujOa, and Braunite, SMnjOj.MnSiOj, are all chemically inert with the reagents used.

U4

HNOs-N HCl-N DETERMINATIVE TABLES KCN-N

High FeCl,-N White Sperrylite PtAsj (Very Rare)

Microchem. HNO,, Neg. HCl, Neg. KCN, Neg. FeCU, Neg.

HgClj, Neg. KOH, Neg. Hardness, High. 6-7. Brittle. Description. C. — Tin-white. Str. — Black. In minute isometric

crystals. B.B. Decrepitates slightly. Unchanged in the closed tube. Yields white arsenic trioxide sublimate in the open tube. Dropped on red- hot platinum foil, melts, gives off arsenic trioxide fumes,] and deposits porous platinum on the foil. Fus. — 2. Pinkish White Cobaltite CoAsS

Microchem. HNO3, Neg. HCl, Neg. KCN, Neg. (Sometimes slowly

faint tarnish rubs clean.) FeCU, Neg. HgClj, Neg. KOH, Neg. Hardness, High. 5.5. Brittle. Description. C. — Silver-white, inclined to pinkish. Str. — Grayish black.

Good cubic cleavage. Often in cubic crystals. B.B. Unaltered in the closed tube. On charcoal yields an arsenic coat and fuses to a magnetic globule. When well roasted it yields a blue bead with borax. Fus. — 2-3. Creamy White Hematite Fe20j Microchem. Negative with all reagents. Hardness, High. 5.6-6.5. Brittle. Brownish red to gray powder when

scratched. Description. C. — Reddish brown, steel-gray, to iron-black. Str. —

Cherry-red. B.B. Infusible. On charcoal in R. F. becomes magnetic. Grayish White Magnetite Fe304 Microchem. Negative with all reagents. Hardness, High. 5.5-6.5. Brittle.

Description. C. — Iron-black. Str. — Black. Naturally strongly mag- netic. B.B. Nearly infusible. In the O.F. loses its magnetism. With the fluxes reacts like hematite. Grayish White Ilmemte FeTiOj Microchem. Negative with all reagents. Hardness, High. 5-6. Brittle.

Description. C. — Iron-black. Str. — Black to brownish. B.B. Infusible in O.F., but slightly rounded on edges in hottest R.F. For wet test for titanium see (IV, 24, 6 and c). Grayish White Rutile TiOj

Microchem. Negative with all reagents.

Hardness, High. 6-6.5.

Internal reflection as seen by inclined light sometimes is reddish.

Description. C. — Reddish brown to nearly black. Str. — Pale brown.

Occurs usually in prismatic crystals. Knee-like twins. B.B. Infusible. Yields bead and wet tests for titanium (IV, 24). Grayish White Franklinite (FeZnMn)0.(FeMn)203 (Very Rare) Microchem. Negative with all reagents. Hardness, High. 5.5-6.6. Brittle. Description. C. — Iron-black. Str. — Very dark brown. B.B. Infusible. With soda gives a green manganate bead and on char- coal a coating of zinc oxide (IV, 29). (Note. — Chalcophanite (Mn,Zn)0.2Mn02.2HjO, is also grayish white and behaves chemically like Franklinite.) White LoUingite See page 91.

Gray VoUzUe ZntSO (Very Rare)

Microchem. Negative with all reagents. (HNO3, fumes sometimes

tarnish very faintly.)

Hardness, Medium. 4-4.5.

Internal reflection as seen by inclined light is reddish yellow or brown.

Description. C — Dirty rose-red, yellowish, or brownish. Str. — Light.

Occurs thin curved, lamellar, etc. B.B. Nearly infusible. Reduced with soda on charcoal yields white

zinc oxide coat, which when moistened with cobalt nitrate solution and

again heated in the O.F. becomes green (IV, 29, a)

Gbat Erythrozineite* (MnZn)S (Very Rare) Microchem. Negative with all reagents. Hardness, Medium to low.

Description. C — Red. Str. — Pale yellow. Occurs in thin plates. B.B. Yields green manganate bead with soda. Also usual tests for zinc.

HNOa-N HCl-N DETERMINATIVE TABLES KCN-N

Med. FeCh-N Yellow Chalcopyrite CuFeSs

Microchem. HNOj, Neg. (Sometimes tarnishes brown; rubs faint. Fumes also tarnish in such cases.) HCl, Neg. KCN, Ne. (Rarely tarnishes iridescent with development of scratches.) FeCls, Neg. HeCU, Neg. KOH, Neg. Hardness, Medium. 3.5-4. Brittle. Description. C. — Brass-yellow. Str. — Greenish.

B.B. On charcoal fuses to a magnetic globule in R. F. Decrepitates in closed tube and gives sulphur sublimate. Roasted and reduced with soda, yields copper buttons. Fus. — 2. Galena White Chalcostibite* CuSbS2 (Very Rare) Microchem. Negative with all reagents. Hardness, Medium. 3-4. Brittle.

Description. C. — Blackish gray. Str. — Black. Perfect basal cleavage. B.B. Yields antimony flame and coat on charcoal. Reduced with soda gives a globule of metallic copper. Fus. — 1.5. Galena White Berlhierite FeSb2S4 (Verv Rare)

Microchem. HNO3, Neg. HCl, Neg. KCN, Neg. FeCls, Neg.

KOH, Slowly tarnishes brownish; rubs faint or clean. Hardness, Medium to low. 2-3. Description. C. — Steel-gray. Str. — Black. Elongated prisms or

fibrous massive. B.B. Fuses easily, yielding an antimony flame and coat on charcoal, and a magnetic residue. Fus. — 2. Grayish White Baumhauerite PbiAssSu (Very Rare)

Microchem. HNO3, Neg. (Sometimes tarnishes along cracks; rubs clean.) HCl, Neg. KCN, Neg. (Sometimes tarnishes along cracks.) FeCls, Neg. HgCU, Slowly tarnishes brown; rubs to pale brown. KOH, Tarnishes iridescent; rubs clean. Hardness, Medium to low. 3. Brittle. Internal reflection as seen by inclined light is often red. Description. C. — Lead-gray. Str. — Brown. One perfect cleavage. B.B. Yields arsenic odor and coat on charcoal; lead coat near the assay. With KI & S flux gives lemon-yellow lead iodide coat (IV, 10, a). Grayish (Brownish) White Tetrahedrite CusSbjS?

Microchem. HNOj, Neg. (Fumes sometimes tarnish faint brown; rubs clean.) HCl, Neg. KCN, Neg. FeCla, Neg. HgCh, Neg. KOH, Neg. Hardness, Medium. 3-4.5. Very brittle. Description. C. — Gray to black. Str. — Brown to black. B.B. Reacts for copper, antimony, arsenic, silver, and often mercury, etc. Almost impossible to distinguish between tetrahedrite and tennantite. Fus. — 1.5. Grayish (Greenish) White Tennantite CusAsjS?

Like tetrahedrite into which it grades chemically. Pale Yellow Millerite See page 95.

Cream Pyrrhotite See page 95.

Cream Chalmersite See page 95.

Creamy White Pentlandite See page 95. Grayish White Bournonite See page 94.

Grayish White Cinnabar HgS

Microchem. Negative with all reagents used.

Hardness, Low. 2-2.5. Slightly sectile. Carmine-red powder when

scratched. Internal reflection as seen by inclined light is carmine-red. Description. C. — Cochineal-red, inclining to brownish and lead gray.

Perfect prismatic cleavage. B.B. On charcoal entirely volatile when pure. In closed tube alone

gives a black sublimate of mercuric sulphide, but with soda, one of

metallic mercury. Fus. — 1.5.

Grayish White Metacinnabarite HgS (Very Rare)

Microchem. Negative with all reagents used. (HNO sometimes

tarnishes faintly.) Hardness, Low. 3. Slightly brittle. Description. C. — Grayish black. Str. — Black. B.B. Like cinnabar.

Grayish White Patronite VS4(?) (Very Rare)

Microchem. HNO3, Neg. HCl, Neg. KCN, Neg. FeCl,, Neg.

HeCla, Neg. KOH, Tarnishes iridescent; rubs to paler iridescence. Hardness. Very low. Sectile. Description. C. — Bluish black. Str. — Bluish gray. Occurs massive

and amorphous. B.B. Gives test for vanadium with S. Ph. bead. Also wet tests.

Gray Lorandite* TlAsSj (Very Rare)

Microchem. HNO3, Neg. HCl, Neg. KCN, Neg. FeCU, Neg.

KOH, Quickly develops coating of orange; rubs clean to rough surface. Hardness, Low. 2-2.5. Dark red powder when scratched. Internal reflection as seen by inclined light is orange-red. Description. C. — Carmine-red, often tarnishes gray on the surface.

Str. — Cherry-red. Perfect pinacoidal cleavage yielding flexible lamellee. B.B. For tests for the rare element thallium see Chapter IV, 21.

Galena White Freieslebenite See page 98.

Galena White Berthierite See page 117.

Galena White Lengenbachite See page 99.

Galena White Rathite See page 99.

Grayish White Baumhauerite See page 117.

Grayish White Molybdenite See page 97.

Gray Erythrozincite See page 116.

HNOa-N HCI-N DETERMINATIVE TABLES KCN-N

Low FeCU-N

Galena White Dufrenoysile Pb2Ad2Sj (Very Rare)

Microchem. HNO3, Neg. HCl, Neg. KCN, Neg. FeCU, Neg.

HgCU, Neg. KOH, Tarnishes iridescent and darkens; rubs to faint

gray, etched surface. Hardness, Low. 3. Brittle. Description. C — Blackish gray. Str. — Reddish brown. Perfect basal

cleavage. B.B. On charcoal decrepitates, fuses, and yields a globule of lead which

gives trace of silver on cupellation. Also gives arsenic coat on charcoal.

Pus.— 1. Galena White MatUdite* AgBiSj (Very Rare) Microchem. Negative with all reagents used. Hardness, Low. Description. C — Gray. Str. — Light gray. Often as slender striated

prisnirf. B.B. Fuses easily on charcoal, giving a coating of bismuth oxide and on

long heating a globule of silver. Galena White Lehrbachite PbSe + HgSe Microchem. Negative with all reagents used. Hardness, Low. Quite brittle. Description. C. — Lead-gray to iron-black. Occurs massive, granular,

etc. B.B. On charcoal yields to a strong odor of selenium and partly fuses.

In the closed tube gives a lustrous metallic gray sublimate of mercury

selenide, with sodium carbonate a sublimate consisting of globules of

mercury. Bluish White Tiemannite HgSe (Very Rare) Microchem. Negative with all reagents used. Hardness, Low. 2.5. Sectile to slightly brittle. Description. C — Blackish gray. Str. — Black. B.B. Decrepitates in the closed tube and when pure entirely sublimes,

giving a black sublimate with the upper edge reddish brown. On char- coal yields selenium odor and blue flame and deposits a white coat with

a metallic-like luster. Bluish White Vrbaite* TlAsjSbSj (Very Rare)

Microchem. HNO,, Neg. HCl, Neg. KCN, Neg. FeCh, Neg.

KOH, Tarnishes iridescent; rubs to gray. Hardness, Low. Internal reflection by inclined light is red. Yellowish

red powder when scratched. Description. C. — Gray-black. Str. — Light yellowish red. Bluish White StUtzite* AgjTe? (Very Rare) Microchem. Negative with all reagents used. Hardness, Low. Description. C. — Lead-gray with reddish tinge. Str. — Blackish lead-

B.B. Easily fusible to a dark bead from which a silver globule is obtained by reduction with soda. Yields tellurium oxide in the open tube. (IV, 20, c). Grayish White Regnolile CU7AS2S12 (Very Rare)

Microchem. Negative with all reagent used. (HNO3 fumes sometimes

tarnish faint brown; rubs clean.) Hardness, Low.

Resembles tetrahedrite and tennatite very closely. Grayish White Seligmannite CuPbAsSj (Very Rare)

Microchem. HNO3, Neg. HCl, Neg. KCN, Neg. FeCU, Neg.

HgCU, Neg. KOH, Slowly tarnishes to iridescence; rubs clean. Hardness, Low. Sectile to slightly brittle. Description. C. — Blackish gray. Str. — Brownish black. B.B. Like boumonite except tests for arsenic instead of antimony.

Chapter Iv

Supplementary Tests

Tabulated Properties Of Ore Minerals

Some few of the opaque minerals when viewed on a polished surface with vertical illumination show colors other than shades of white or gray. The following table will often be helpful in immediately identifjdng these minerals.

Table 7

Ckilor

Mineral

Formula

Page

Purple

Umangile

CujSe,

Purple

Rickardite

CuiTe,

Blue

Covellite

CuS

m

Yellow

Chalcopyrite

CuFeSj

Yellow

Gold

Au

Pale yellow

MiLLERITE

NiS

Cream

(Pyrite)

FeSs

Cream

(Marcasite)

FeSj

Cream

Pyrrhotite

FeS(S).

Cream

Pbntlanmte

(FeNi)S

Cream

Chalmersite

CuFesSa

Cream

Whitneyile

Cu,As

Cream

Maucherite

NiaAss

Cream

Haucheeornile

(NiCo),(Bi,S,Sb),

Cream

Sulvanite

CusVS,

Creamy pink

Niccolite

NiAa

Coppery pink

Copper

Cu

Coppery pink

Breithauptite

NiSb

Brown

Bornite

CujFeS*

When the vertical illumination is cut out and the light from some strong source is allowed to strike the polished surface at an incUnation, a number of the ore minerals reveal more or less brilhantly colored internal reflections. These colors are quite characteristic of certain minerals and should always be observed in the course of an identification. Table 8 lists those minerals in which such colors are commonly seen.

Supplementary Tests

Table 8

Color of internal

Mineral

Formula

Page

reflection

Red

Baumhaueriie

PbiAseS,,

Red

Cinnabar

HgS

Red

Cuprite

CujO

Red

Jalpaite

SAgjS.CujS

Red

Kermesite

SbjSjO

Red

Livingslonite

HgSbiS,

Red

Miargyrite

AgSbSj

Red

Polybasite

Ag,SbS.

Red

Proustite

AgsAsSj

Red

Pyrargtrite

AgaSbSa

Red

(Rutile?)

TiOj

Red

Vrbaite

TlAsjSbSs

Reddish brown

Limonite

2Fe203.3H20

Reddish brown

Hiibnerite

MnWO,

Brown or yellow

(Cassiterite?)

SnOj

Brown or yellow

Sphalerite

ZnS

Brown or reddish yellow Voltziie

ZuiSiO

Brownish or greenish

Cuprodescloizite

(PbZnCu)4V20,.H20

Olive green

Alabandite

MnS

Orange red

Lorandite

TlAsSj

Orange

Realgar

AsS

Yellow

iOnofrite'!)

Hg(SSe)

Yellow

Orpiment

AbS,

When the polished surface of an ore mineral is deeply scratched or gouged with a sharp needle a powder is usually produced, and although this is gray or black in the majority of minerals, a few yield a powder or scratch with distinct colors as seen under the microscope with vertical illumination. This property may often be used as a valuable aid in mineral identification. The minerals giving powders of characteristic colors in this way are grouped in Table 9 which follows :

122 Microscopic Examination Of The Ore Minerals

Table 9

Color of powder

Mineral

Formula

Page

Carmen red

Cinnabar

HgS

Blood red

Cuprite

CujO

Blood red

Jalpaite

SAgjS.CujS?

Blood red

Proustite

AgaAsSs

Blood red

Pyrargyrite

AgsSbSa

Bed

Kermesite

SbjSjO

Red

Living stonite

HgSbiS,

Red

Lorandite

TlAsS,

Red

Miargyrite

AgSbS,

Reddish brown

Hauerile

MnS,

Reddish brown

Hematite

FejOs

Reddish brown

Regnolite

Cu7As2S12

Pink

Copper

Cu

Golden brown

Bornite

CujFeSi

Brown to yellow

Sphalerite

ZnS

Orange

Realgar

AsS

Reddish yellow

Cuprodescloizite

(PbZnCu)4VjO,.H20

Yellow

Chromite

FeCrOi

Yellow

Gold

Au

Hi

Yellow

Limonite

2Fe203.3H20

Yellow

Orpiment

As2S3

Olive-green

Alabandite

Supplementary Tests

Table 10. — Classification According to Electrical Conductivity,

Measured with Two Dry Cells with Voltmeter, and using

Sharp's No. 9 Sewing Needles for Terminals

Electrical conductivity

equal to or greater than

copper, voltmeter reads 150

Average voltmeter readings

Apparently non-conductors, voltmeter reads 0

Arsenic (native)

147 Onofrite

Aikinite

Algodonite

145 LoUingite

Alabandite

Antimony (native)

142 Petzite

Andorite

Bismuth (native)

142 Bxjrnite

Argyrodite

Calaverite

142 Tiemannite

Baumhauerite

Chalcopyrrhotite

140 Clausthalite

Boulangerite

Chloanthite

137 Arsenopyrite

Bournonite

Coloradorite

137 Eucairite

Brongniardite

Copper (native)

135 Chalcocite

Cassiterite

Covellite

130 Metacinnabarite

Chromite

Dyscrasite

130 Ploydymite

Cinnabar

Gersdorffite

126 Kalgoorlite

Cuprite

Glaucodot

126 Altaite

Cuprodescloiaite

Harrisite

124 Chalcopyrite

Cylindrite

Hauchecornite

120 Galena

Delafossite

Hessite

120 Stutzite

Dufrenoysite

Huntilite

120 Luzonite

Emplectitc

Kallilite

120 Tennantite

Franklinite

Krennerite

120 Aguilarite

Geocronite

Linnseite

109 Steinmannite

Hauerite

Magnetite

85 Berzellianite

Horsfordite

Maucherite

SO Naumannite

Jalpaite

Melonite

70 Nagyagite

Jordanite

Millerite

57 Polytelite

Kermesite

Mohawkite

55 Stromeyerite

Legenbachite

Niccolite

~50 Pearceite

Limonite

Pentlandite

37 Cobaltite

Lorandite

Pyrrhotite

25 Guanajuatite

Matildite

Rammelsbergite

15 Chivatite

Meneghinite

Safflorite

15 Enargite

Miargyrite

Silver (native)

12 Marcasite

Orpiment

Skuttcrudite

7 Regnolite

Plafeionite

Smaltite

7 Lillian ite

Polyargyrite

Stcrnbergite

7 Rezbanyite

Proustite

Sylvanite

7 Pyrite

Pyrargyrite

Tellurium (native)

7 Ilmenite

Rathite

Ullmannite

5 Psilomelane

Realgar

Whitneyite

6 Jamesonite

Rutile

Willyamite

3 Plenargyrite

Seligmannite

3 Chalmersite

Semseyite

3 Famatinite

Sphalerite

3 Cosalite

Stephanite

2 Bismuthinite

Stibnite

2 Argentite

Sulvanite

2 Stannite

Tenorite

1 Stylotypite

Tetrahedrite

1 Teallite

Uraninite

1 Frankeite

Voltzite

1 Polybasite

Wittichenite

1 Molybdenite

Wurtiite

1 Hematite

124 Microscopic Examination Of The Ore Minerals

50 per cent. Au-

50 per cent. Cu

to 60 per cent.

Au-40percent.Cu

(Pyrite) Smaltite Cobaltite Pyrolusite

fed 3 ago .

Sg

(Famatinite)

Arsenopyrite

Millerite

Covellite

(Hessite)

Metacinnabarite

Coloradoite

(Enargite)

Pyrite

Is

g O

b

O

ta

iJ

1'

30 per cent. Au-70

percent. Cu to 40

per cent. Au-60

per cent. Cu

Linnaeite

(Magnetite)

Gersdorffite

Hessite

Enargite

(Pyrite)

Famatinite

LoUingite

Luzonite

Lehrbachite

Psilomelane

20 per cent. Au -80

per cent. Cu to 30

per cent. Au-70

percent. Cu

Chloanthite

Bornite

Chalcocite

Galena

Tetradymite

Dyscrasite

Magnetite

Marcasite

Nagyagite

Native silver

Stromeyerite

Maucherite

Tennantite

Tellurium

Ps H O

10 percent. Au- 90 per cent. Cu to 20 per cent.Au -80 per cent. Cu

"o o

1— 1

S

5 percent. Au-95

percent. Cu to 10

per cent. Au-90

percent. Cu

Pyrrhotite (Domeykite)

Between 3 per

cent. Au-95 per

cent. Cu and 100

per cent. Cu

ia

Potential Less

than 100 per

cent. Cu

o

Supplementary Tests

Tests for the Elements'

1. Antimony, Sb

Antimony Minerals

Minera Formula

Andorite PbAgSbsSe

Berlhierite FeSbjSi

Boulangerile PbsSbjSs

' BOURNONITE (Cu2Pb)3Sb8S

Breilhauptite NiSb

Brongniardite PbAgjSbzSs

Chalcoslibile CuSbSj

Cylindriie Pb6Sb2Sn6S2i

Dyscrasite AgeSb, etc.

Epiboulangerite Pb3Sb2S8

Famatinite Cu3SbS4

Franckeite Pb6Sn2Sb2Si2

Freibergite (CuAg)8Sb2S7

Freieslebenite (Pb,Ag2)6Sb4Sii

Geocronite Pb6Sb2Sg

Guejarite Cu2Sb4S7

Hauchecornite (NiCo)7(BiSbS)8

Horsfordile CuSb

Jamesonite Pb2Sb2S5

Kallilite Ni(SbBi)8

Kermesite Sb2S20

Litnngstonile RgSbiSy

Meneghinite Pb4Sb2S7

Miargyrite AgSbS2

Nagyagite Au2PbioSb2Te8Sij

Plagionite PbsSbsSi?

Polyargyrite Ag24Sb2Sis

Polybasite AggSbSe

Pyrargyrite AgsSbSa

Ralhite Pb(As,Sb), S

Semseyite PbySbeSie

Stephanite AgiSbSi

Stibnite Sb2S3

Stylolypite 3(Cu2Ag2Fe)S.Sb2S3

Tetrahedrite Cu8Sb2S7

Ullmannite NiSbS

VrbaiU TlAsjSbSs

Willyamite (CoNi)SbS

Zinkenile PbSb284

Page

' Reference has been made to standard works on mineralogy and blow- pipe analysis by A. H. Phillips, Moses and Parsons, Brush and Pen- field, etc.

126 Microscopic Examination Of The Ore Minerals

(a) Coat on Charcoal. — Antimony minerals, when heated on charcoal in the O.F. yield a white oxide coat which settles fairly near the assay. This coat is volatile and may be completely driven off with either flame. The powdered mineral, when fused with KI & S flux on charcoal, yields a faint yellow coat

(6) Flame Test. — When the above coat is quickly volatiUzed in the O.F. the flame is colored a pale yellowish-green. (Arsenic coat colors the flame faint violet.)

(c) Closed Tube Reaction. — Most minerals containing both antimony and sulphur, when heated in the closed tube, yield a black sublimate when hot, which becomes reddish-brown upon cooling.

(d) Open Tube Reaction. — Minerals containing antimony and sulphur, when heated in the open tube, yield dense white fumes which settle along the lower half of the tube. This sublimate is volatile and can be entirely driven off.

2. Arsenic, As Arsenic Minerals

Mineral

Formula

'' Arsenic

As

Arsenopyrite

FeAsS

Baumhauerite

PbiAseSi,

Chloanthite

NiAs2

Cobaltite

CoAsS

Domeykite

CunAs

Dufrenoysite

PbjAszSs

Enargite

CusAsS,

V Gersdorffite

NiAsS

(CoFe)AsS

Guilermamle

PbsAsjSe

.lordanile

Pb,As2S,

Lengenbachile

Pb6(AgCuhAs4Si,

' Lollingite

FeAs2

Lorandite

TlAsSj

Luzonile

CusAsS,

Maucherite

NisAsj

Niccolite

NiAs

Orpiment

As2S5

Pearcite

AgoAsSe

Proustite

AgsAsSa

Rammelsbergite

NiAs2

Rathite

Pb(AsSb)S

Realgar

AsS

Page

S3

Mineral

Formula

Regnolite

CuyASjSi!

Safflorile

C0As2

Seligmannite

CuPbAsSs

Smaltite

CoAsj

Sperrylite

PtAsj

Tennantite

Cu8As2S7

Vrbaite

TlAsoSbSs

Whitneyite

CusAs

Supplementary Tests 127

Page

(a) Coat on Charcoal. — Arsenic minerals, when heated on charcoal in the O.F. yield a white oxide coat which settles at a distance from the assay. (Beyond the antimony coat.) This coat is extremely volatile in either flame and, with the R.F. especially, strong characteristic garlic-hke odors are given off.

(6) Flame Test. — -When arsenic minerals are heated on char- coal in the R.F. the flame is colored a faint violet. (Antimony yields a pale, yellowish green flame.)

(c) Closed Tube Reaction. — Fusible arsenic minerals mixed with coal dust are placed in the bottom of a narrow closed tube and covered with a small spHnter of charcoal. First heat the coal to glowing and then the mineral and coal dust mixture. Any arsenic present, reduced in passing over the hot carbon, deposits as a mirror on the cold walls of the tube. The mirror may be tested by breaking off the bottom of the tube and heat- ing in the Bunsen flame. The characteristic garlic-like odor of arsenic can now be detected as the fumes escape from the mouth of the tube. These fumes also impart a faint violet tinge to the flame if allowed to escape in it. Most arsenic minerals when heated in the closed tube without a flux yield a sublimate which is dark red when hot and reddish-yellow when cold.

(d) Open Tube Reactions. — Arsenic minerals, when very slowly heated in the open tube, yield a ring of white crystals which are very volatile and may be completely driven off from the tube upon heating. No arsenic odor is usually noticed in this test.

3. Bismuth, Bi

Bismuth Minerals .

Mineral

Formula

Aikinite

PbCuBiSa

Beegerite

PbeBijS,

yBismuth 7 Bismuthinite

Bi

BijS,

Chilenite

AgeBi

Chiviatite

PbiBiSu

/ Cosalite

PbjBijSs

Dognacskaiie

Cu, Bi, and S

Emplectite

CuBiSj

Guanajualile

BijSes

Hauchecomite

(NiCo),(BiSSb),

Kallilite

Ni(SbBi)S

Lillianite

PbsBizSe

Malildite

AgBiSj

Rezbanyite

PbiBiioSis

Tapalpaite

3Ag2(STe).Bi2(STe),

X Tetradymite

Bi2(Te,S)3

Wiltichenite

CusBiS,

128 Microscopic Examination Of The Ore Minerals

Page

(a) Coat on Charcoal. — Bismuth minerals, finely powdered and mixed with 2 or 3 parts of sodium carbonate, when heated in the R.F., yield metallic globules which are brittle instead of malleable (as in the case of lead). If the heating is continued, oxide forms and volatilizes, depositing a yellow coat close to the assay. This coat is very similar to that of lead and is best distinguished from it by means of the iodide reaction. The above coat moistened with hydriodic acid and heated gently in the O.F., or the powdered mineral mixed with 2 or 3 parts of KI & S flux and similarly heated, yields a brick-red bismuth iodide coat at some distance from the assay, inside of which there is often a yellow oxide coat.

4. Chromium, Cr

Chromite FeCr204 Page 114

(a) Bead Tests. — The bead tests for chromium, as for most other elements are only satisfactory when other substances do not interfere. The colors of the borax and S.Ph. beads are given in Table 17, page 149.

(6) Wet Test. — Fuse the finely ground chromium mineral mixed with 4 parts sodium carbonate and 2 parts of potassium nitrate

Supplementary Tests

on a platinum wire. The fusion is dissolved in 2 or 3 c.c. of water, acidified with acetic acid, and filtered if the solution is not clear. If 2 or 3 drops of lead acetate are now added, anj* chro- mium present will be precipitated as yellow lead chromate. This may be filtered off and tested as in (a).

Page

(a) Bead Tests. — Cobalt minerals, when dissolved in S.Ph. or borax, after roasting on charcoal, yield a deep blue bead in all flames. This test is quite sensitive, but if very large amounts of copper or nickel are present the borax bead should be taken from the wire and reduced beside tin on charcoal. The copper and nickel are absorbed by the tin and the bead will remain blue.

5. Cobalt, Co

Cobalt Minerals

Minera

Formula

Cobaltite

CoAsS

Glaucodot

(CoFe)AsS

Hmichecornile

(NiCo)7(BiSSb)(

Linnceite

C03S,

,X Safflorite

CoAsj

y Smaltite

CoAss

tWillyamite

(CoNi)SbS

6. Copper, Cu

Copper Minerals

Mineral

Formula

Aikinite

PbCuBiS,

Berzelianile

CuaSe

Bornite

CusFeS,

Bournonite

(PbCu2)3Sb2S4

Chalcocite

Cu2S

Chalcopyrite

CuFeSj

Chalcostibile

CuSbSj

Chalmersite

CuFejSa

Copper

Cu

Covellite

CuS

Crookesite

(CuTlAg)2Se

Cuprite

CuaO

Cuprodescloizite

(PbZnCu)4V20,.H20

Delafossite

CuO,re203

Dognacskaile

Cu, Bi, and S

Domeykite

CusAs

EmplecHte

CuBiSj

Enargite

CujAsS,

Page

130 Microscopic Examination Of The Ore Minerals

Mineral Formula Page

Eueairite Cu2Se.Ag2Se 97

Famatinite Cu3SbS4 83

FreibergiU (CuAg)sSb2S7 82

Guejarite CuaSbiS? 83

Horsfordite CueSb 63

Jalpaite . Cu2S.3Ag2S 67

Lengenbachite Pb6(AgCu)2AsSu 99

Luzonite CU3ASS4 83

Regnolite CU7AS2S12 119

Rickardile CuiTes 35

Seligmannile CuPbAsSj 119

Slannite SnCu2FeS4 94

Stromeyerite (Ag,Cu)2S 67

StyloUjpile 3(Cu2Ag2Fe)S.Sb2S, 94

Sulvanite CusVSi 65

Tennantite CU8AS2S7 117

Tenorite CuO 73

Tetrahedrite Cu8Sb2S7 117

Umangite Cu3Se2 77

Whitneyite CugAs 33

Wittichenite CuaBiSa 95

(a) Reduction on Charcoal. — Copper minerals, roasted in O.F. on charcoal, then finely ground and mixed with two or three parts of sodium carbonate and borax, when treated in a strong R.F. on charcoal, yield malleable copper buttons. It may some- times be necessary to crush and wash the charge in the mortar to obtain the buttons if small.

(b) Flame Tests. — Copper minerals heated in O.F. on charcoal; moistened with HCl and then reheated in the R.F., yield a brilliant azure-blue copper chloride flame, which may be tinged with the green flame of copper oxide. This azure-blue flame is very sensi- tive and will detect a fraction of 1 per cent, of copper. Copper oxide and a few copper minerals when powdered and heated directly in the O.F. yield an emerald-green flame.

(c) Bead Tests. — Copper minerals, when roasted in O.F. on charcoal, and dissolved in S.Ph. or borax, yield a green bead while hot, which becomes blue when cold. In the R.F. if much oxide is present, the cold bead in reflected light is an opaque red due to cuprous oxide, CuaO.

(d) Wet Test.- — Copper salts color all acid solutions blue or green. With an excess of ammonium hydroxide the solution turns deep blue. Iron, if present, may be held in solution by adding tartaric acid before introducing the ammonia.

SUPPLEMENTARY TESTS 7. Germanium, Ge

Argyrodit* AgeGeSs Page 110

(a) Coat on Charcoal. — Argyrodite, when heated in the R.F. and O.F. on charcoal, yields a glazy white coat near the assay, which assumes a yellowish color at a distance from it.

8. Gold, Au

Gold Minerals

Mineral

Formula

Calavebite

AgAuTej

Gold

Au

Kalgoorlite

HgAuAgeTee

Krennerite

AgAuTej

Nagyagite

AujPbioSbjTeeSi

Petzite

(AgAu)2Te

Sylvanite

AgAuTej

Page

Gold is usually present in such small amounts that ordinary blowpipe methods are not of much value in detecting it. It is present as a major constituent only in the tellurides, and reducing these minerals with sodium carbonate on charcoal in the R.F. jdelds a malleable button containing gold and silver. After dis- solving with nitric acid the black residue is ignited and turns gold yellow.

9. Iron, Fe

Iron Mineeam

Mineral

Formula

Page

Arsenopyrite

FeAsS

Berthierite

FeSbjS,

Bornite

CusFeS*

Chalcopyrite

CuFeSz

Chalmersite

CuFejS,

Chromite

FeCrjO,

Delafossite

CuO.FejOa

Ferberile

FeWOi

Glaucodot

(CoFe)AsS

Gothite

FejOj.HaO

Franklinite

(FeZnMn)0.(FeMn)20s

Hematite

Ilmenite

FeTiO.,

Limonite

2FejO,.3H20

132 Microscopic Examination Of The Ore Minerals

Mineral

Formula

Lollingiie

FeAs2

Magnetite

Marcasite

FeSj

Pentlandits

(FeNi)S

Pyrite

FeSj

Pyrrhotite

FeS(S)x

Stannite

SnCujFeS*

Slernbergite

AgFesSa

Slylolypite

3(Cu2Ag2Fe)S.Sb2S,

Turgile

2Fe203.H20

Wolframite

(FeMn)W04

Page

(a) Magnetic Test. — Iron minerals when treated on charcoal in the R.F. become magnetic after cooling. Cobalt and Nickel also become magnetic when so treated and, when their presence is suspected, may be tested for as on pages 129 and 135.

(6) Bead Tests. — The colors obtained upon dissolving iron minerals after roasting in S.Ph. or borax are not very satisfactory and should not be depended upon alone for identifications. For these tests see Table 17, page 149.

(c) Wet Test. — When ammonium hydroxide is added in excess to a solution obtained by boiling any iron mineral in nitric acid, a heavy precipitate of reddish-brown ferric hydroxide is thrown down. In this way iron may be quantitatively separated from the solution. The precipitate filtered off may be tested in the S.Ph. or borax bead or it may be ignited on charcoal and tested for magnetism.

Mineral Aikinite AUaite Andorite Baumhauerite Beegerile Boulangerile

Bournonitb

Brongniardite

Chivialile

Clausthalite

Cosalite

Cuprodescloizite

10. Lead, Pb

Lead Minerals Formula PbCuBiSs PbTe PbAgSbsS,

Pb4AS6Sl3

PbeBizS,

PbsSbaSe

(PbCu2)3Sb2S6

PbAgjSbjSs

PbBijSu

PbSe

PbzBiaSs

(PbZnCiOiVoOs.HjO

Page

Supplementary Tests

Mineral

Formula

Page

Cylindrite

PbsSbjSnsSji

Dufrenoysiie

PbjAsjSs

Epiboulangerite

PbaSbSs

Franckeite

PbsSnjSbjSn

Freieslebenite

(PbAg2)5Sb,Su

Galena

PbS

Geocronite

PbeSbjSs

Guilermanite

PbsAsjSe

Jamesonite

PbjSbiSs

Jordanite

PbAszSj

Lehrbachite

PbSe + HgSe

Lengenbachite

Pb,(AgCu)2As,S,3

Lillianite

PbaBijSe

Meneghinite

PbiSbjS,

Nagyagite

AuaPb.oSbaTeeSu

Naumannite

(Ag2Pb)Se

Plagionite

PbsSbsSiT

Rathite

Pb(As,Sb),S

Rezbanyite

PbiBi.oSi,

Seligmannite

CuPbAsSa

Semseyite

PbiSbeSie

Teallite

PbSnSj

Uraninite

Uranate of U, Pb, Th, etc.

Zinhenile

PbSbjS,

(a) Coat on Charcoal. — Lead minerals when slowly heated on charcoal yield a volatile yellow oxide coat which deposits close to the assay. (If much sulphur is present and the heating is rapid, a white coat similar to the antimony coat is formed — this does not occur when the heating is done slowly.) This yellow coat, moistened with hydriodic acid and heated gently in the O.F., or the powdered mineral mixed with 2 or 3 parts of KI & S flux and similarly heated, yields a lemon-yellow lead iodide coat. (Similarly treated, Bismuth yields a brick-red coat.)

{h) Reduction on Charcoal. — Lead minerals powdered and roasted in a very small O.F., then mixed with 4 parts sodium carbonate, 1 part borax, and 1 part charcoal dust, and treated with the R.F. on charcoal, yield soft, highly malleable metallic lead buttons. (Bismuth buttons are brittle.)

(c) Wet Test. — Sulphuric acid added to a nitric acid solution of lead minerals, brings down a white powdery precipitate of lead sulphate. This, when filtered off, may be tested on charcoal as in (a) and (6).

134 MICROSCOPIC EXAMINATION OF THE ORE MINERALS 11. Manganese, Mn

Manganese Minerals

Mineral

Formula

Alabandite

MnS

Braunite

SMnOs.MnSiO, (MnZn)S

ErylhrozincUe

Franklinite

(FeZnMn)0.(FeMn)20,

Hauerite

. MnSj

Hatjsmannite

MnO.MnjOa

Hiibnerite

MnWOi

Manganite

MnOa.HjO

PsiLOMELANE

HMnO,

Pyrolusite

MnOs

Wolframite

(FeMn)W04

(a) Sodium Carbonate and Niter Bead. — Any manganese mineral and any mineral containing as much as 0.1 per cent, of manganese will give a decisive test with this method, which, moreover, is not interfered with by the presence of any other substances. The finely powdered mineral, after roasting on charcoal, is fused with sodium carbonate on a platinum wire in the O.F. and again fused with a small grain of potassium nitrate in the O.F. The resulting bead will be green to dark blue, de- pending upon the amount of manganese present.

(b) Common Bead Tests. — Manganese imparts characteristic colors to the borax bead, and to a lesser extent, to the S.Ph. bead. See Table 17, page 149, for these colors.

12. Mercury, Hg

Mercury Minerals

Mineral

Formula

Cinnabar

HgS

Coloradoite

HgTe

Kalgoorlite

HgAujAgeTee

Lehrbachite

PbSe + HgSe

Livingstonite

HgSbiS:

Metacinnabarite

HgS -

Onofrile

Hg(SSe)

Tiemannite

HgSe

Page

(a) Closed Tube Reaction. — Mercury minerals, powdered and mixed with 3 parts sodium carbonate, placed in a closed tube w ith a little sodium carbonate on top of the charge, and heated, yield a gray sublimate of metalUc mercury globules on the walls of the tube. The common mercury mineral, cinnabar (and

Supplementary Tests 135

metacinnabarite) when heated alone in the closed tube, yields a black sublimate on the cold walls of the tube.

(6) Open Tube Reaction. — Mercury minerals, when heated very slowly in the open tube, yield a gray sublimate of metallic mercury.

13. Molybdenum, Mo Molybdenite M0S2

(a) Coat on Charcoal. — Molybdenite, strongly heated in the O.F. on charcoal, yields a volatile oxide coat which is yellowish while hot and white when cold. If this coat is touched in- stantaneously with the R.F. it turns deep blue. Close about the assay a non-volatile film of copper-red M0O2 may sometimes be seen.

(6) Bead Tests. — After roasting on charcoal, molybdenite imparts characteristic colors to the S.Ph. and borax beads. See Table 17, on page 149.

Page

(a) Bead Tests. — For the colors imparted by nickel to the borax and S.Ph. beads see Table 17, page 149. Iron, cobalt, and copper, etc. will often entirely obscure the nickel color. It may often be detected in the presence of these elements by the following procedure: The mineral is fused to a globule and most of the arsenic, antimony, or sulphur roasted off. A piece of borax twice the size of the globule is placed beside it on the charcoal and heated in the O.F. for a short time, and the color of the bead observed. Iron, cobalt, nickel, and copper oxidize in

14. Nickel, Ni

Nickel Minerals

Mineral

Formula

Briethauptite

NiSb

Chloanthite

NiAsj

Gersdorffitb

NiAsS

Hauchecorniie

(NiCo),(BiSbS)8

Kallilile

Ni(SbBi)S

Maucherile

NijAsz

Meloniie

NisTea

MiLLERITB

NiS

Niccolite

NiAs

Pentlandite

(FeNi)S

Polydymite

Ni,S5

Rammelsbergile

NiAs2

Ullmannile

NiSbS

WiUyamite

(CoNi)SbS

136 Microscopic Examination Of The Ore Minerals

the order named, and if successive charges of borax are each treated briefly in the O.F. beside the globule, each element will in turn impart its color to the bead. The amount of each present may be roughly estimated from the number of fresh charges of borax required to absorb it. For example, if it takes two or three beads to remove the cobalt it is present only as a minor constituent and after the cobalt blue has disappeared, the borax will be colored reddish brown by any nickel present. Even with this procedure the results are not always satisfactory, in which case the following wet reaction must be resorted to.

(b) Wet Test. — The powdered mineral is dissolved in 4 or 5 c.c. of nitric acid, an equal amount of tartaric acid is added, and ammonium hydroxide to excess. The tartaric acid holds the iron in solution. The liquid may be filtered if not clear and then made neutral or very slightly acid with HCl. If 3 or 4 drops of a 1 per cent, solution of dimethyl glyoxime in alcohol are now added, any nickel present will be thrown down as a brilliant red precipitate. This precipitate, when filtered off, may be tested for nickel in the beads as in (a). This test is very sensitive and is not interfered with by other elements provided the iron is held in solution by sufficient tartaric acid.

15. Oxygen, O

Oxygen Minerals

Mineral

Formula

Page

Cassitbbite

SnOi

Chromite

FeCrjO,

Cuprite

CusO

Cuprodescloizite

(PbZnCu)4V209.H,0

Delafossite

CuO.FeOs

Franklinile

(FeZnMn)0.(FeMn)203

Ferberite

FeW04

Hematite

FejOs

Hubnerite

MnWOi

Ilmemte

FeTiOs

Kermesite

SbjSjO

Limonite

2Fe203.3H80

Magnetite

FbsOa

Psilomelane

HiMnOs

Pyrolusite

MnOj

Rutile

TiOj

Tenobitb

CuO

Uranninile

Uranate of U, Pb, Th, etc.

Voltzite

Wolframite

(FeMn)W04

Supplementary Tests 137

Oxygen usually cannot be directly tested for in the minerals, but its presence is inferred from a knowledge of the character and behavior before the blowpipe of the other constituents.

16. Platinum, Pt

Native Platinum Pt Sperrylile PtAsa

Platinum is usually recognized from its physical properties and insolubility in acids. If present it is collected in the re- duction and cupellation for silver and gold. (See page 139.) If the button so obtained, or the residue after parting with nitric acid, is dissolved in aqua regia, evaporated nearly to dryness, a little hydrochloric acid added, and again almost evaporated, diluted with a little water, and concentrated ammonium chloride added, a precipitate of yellow ammonium platinic chloride is thrown down. Platinum tests are usually delicate operations and the standard references on qualitative analysis should be consulted.

17. Selenium, Se

Selenium Minerals

Mineral Formula Page

Aguilarite AgjS.AgaSe 76

Berzelianite CujSe 97

Clausthalite PbSe 77

Crookesite (CuTlAg)2Se 94

Eucairite CuaSe.AgaSe 97

Guanajuatite BijSes 98

Lehrbachite PbSe + HgSe 119

Naumannile (Ag2Pb)Se 43

Onofrite Hg(SSe) 111

Tiemannite HgSe 119

Umangile CusScj 77

(a) Coat on Charcoal. — Selenium minerals, when heated on charcoal, yield a white oxide coat with a metallic-like luster, sometimes reddish at the edges.

(6) Flame Test. — When the above coat is heated in the R.F. the flame is colored an intense azure-blue and a disagreeable characteristic odor is given off. This odor has been likened to that of horse radish, but really must be experienced in order to be recognized. It is noticed when even very small amounts of selenium are present.

138 Microscopic Examination Of The Ore Minerals

(c) Closed Tube Reaction. — Some selenium minerals, when heated in the closed tube, yield fused brownish red globules of selenium on the walls of the tube.

(d) Open Tube Reaction. — Selenium minerals, when heated in the open tube, yield colorless globules of selenous oxide, which crystallize and whiten when cold. The characteristic azure-blue color will be obtained if the volatile oxide fumes are allowed to escape into the Bunsen flame.

18. Silver, Ag

Mineral Aguilarite Andorite Argentite Argyrodite Brongniardite Calaverite Cerargyrite Chilenite Crookesite

Eucairite

Freieslebenite

Freibergiie

Hessite

Jalpaite

Kalgoorlite

Lengenbachite

Matildite

Miargyriie

Naumannite

Pearciie

Petzite

Polyargyrile

Polybasite

Proustite

Pyrargybite

saver

Stephanite

Sternbergite

Stromeyerite

Slutzite

Stylotypite

SyUmnite

Silver Minerals

Formula Ag2S.Ag2Se

PbAgSbsS,

AgjS

AgeGeSs

PbAgjSbjSs

AgAuTej

AgCl

AgeBi

(CuTlAg)2Se

AgeSb, etc.

CuaSe.AgjSe

(PbAg2)6Sb4Sn

(CuAg)sSb2S7

AgjTe

SAgjS.CujS

HgAusAgeTee

Pb6(AgCu)2As4Si,

AgBiSa

AgSbSa

(Ag2Pb)Se

AggAsSe

(AgAu)2Te

Ag24Sb2Sl6

AgaSbSa AgsAsSs AgaSbSs

Ag

AgShSt

AgFejSs

(AgCu)2S

Ag,Te

3(Cu2Ag2Fe)S.Sb2S,

AuAgTej

Page

Supplementary Tests 139

(a) Reduction on Charcoal.— Silver minerals, when powdered and well roasted in O.F., then mixed with 3 or 4 parts of sodium carbonate and fused on charcoal in the R.F., yield metallic silver, which should be collected as much as possible into one button.. If the button is not bright it should be heated beside borax on charcoal in the O.F. The base metals are oxidized first and dis- solve in the borax, leaving a bright, malleable silver button, which may be further tested by dissolving in nitric acid and pre- cipitating the silver as white silver chloride by adding hydro- chloric acid. This silver chloride precipitate, when filtered off is insoluble in hot water, while a similar lead precipitate is dis- solved by boiling water. Mercurous mercury also yields a white chloride precipitate which is blackened by ammonium hy- droxide, but mercury should not be found in a button treated as in the above case.

When the suspected silver mineral occurs in very small amount and cannot be separated, conclusive tests can be applied provid- ing the microscope reveals no other mineral likely to contain silver. The powdered sample is mixed with an equal volume each of pure test lead and borax glass, and fused and reduced by the R.F. in a deep cavity on charcoal. Manipulate the assay to collect the lead in a single button. The O.F. is now applied to oxidize impurities of arsenic, antimony, etc., and continued until the globule boils freely. It is now allowed to cool and is freed of slag by hammering into a small cube. A cupel is now prepared by compacting dry bone ash in a cavity in charcoal about a centimeter in diameter and one-half centimeter deep. The agate pestle is conveniently used in this operation and by finishing up with a twirling motion the cupel will have a hard, smooth, concave surface. Any loose bone ash is blown off and the cupel is strongly ignited in the O.F. to drive off all moisture. The button is now placed on the cupel and fused in the R.F. for a few moments; then the O.F. is applied and continued without in- terruption until all the lead is oxidized and absorbed by the bone ash, the end point being marked by a distinct change in color and brightening of the button. If very little silver is present the bead will appear to disappear entirely, but the spot should always be carefully examined with the lens. The residual button will contain any silver, gold, or metals of the platinum group present in the sample. If the bead is treated with a few drops of nitric acid and hydrochloric acid added to the liquid, any

140 Microscopic Examination Of The Ore Minerals

silver present will be thrown down as insoluble white silver chloride.

19. Sjilphur, S

Sulphur is present in most metallic ores and tests for the ele- ment seldom aid determinations in mineragraphic work.

(a) Roasting on Charcoal. — Sulphur in sulphides, heated on charcoal in the O.F., yields sulphur dioxide fumes which are rec- ognized by their odor.

(6) Sodium Carbonate Test. — Powdered sulphide, fused with about 3 parts of sodium carbonate, when placed on a bright silver coin and moistened with a little water, stain the coin brown or black. (Since very faint reactions are sometimes due to the sulphur in the gas used, the fusion may be made in a closed tube in cases of doubt.)

20. Tellurium, Te

Tellurium Minerals

Mineral

Formula

AUaile

PbTe

Calaverite

AgAuTej

Coloradoite

HgTe

Hessite

Ag,Te

Kalgoorlite

HgAujAgeTe,

Kbennebite

Ag.-VuTes

Melonite

NisTes

Nagyagite

Au2PbioSb2Te6Si5

Petzite

(AgAu)2Te

Rickardite

CuiTes

Stutzite

Ag.Te

Sylvanite

AuAgTej

Tellurium

Te

Telradymile

Bi2(Te,S)3

Page

(a) Coat on Charcoal. — Tellurium minerals, when heated on charcoal in the R.F., yield a white oxide coat resembling the antimony coat, which also colors the flame pale greenish.

(6) Closed Tube Reaction. — Tellurium minerals, fused in the closed tube with 3 parts of sodium carbonate and some charcoal dust, when dissolved in water after cooling, yield a reddish violet colored solution which gives a gray tellurium precipitate if poured out and exposed to the air.

21. ThaUium, Tl

Thallium Minerals

Mineral

Formula

Crookesile

(CuTlAg)2Se

Lorandile

Tiass2

Vrbaite

TIAszSbSs

Supplementary Tests 141

(c) Open Tube Reaction. — Tellurium minerals, when heated in the open tube, yield heavy white oxide fumes which condense close to the heated portion of the tube. This sublimate is vola- tilized with difficulty and fuses to yellow globules which become colorless on cooling.

(d) Sulphuric Add Test. — Tellurium minerals, powdered and heated in a test tube with 2 or 3 c.c. of concentrated sulphuric acid, yield a reddish violet solution which gives a precipitate as in (6) when cooled and diluted with a little water.

Page

(a) Coat on Charcoal and Flame. — Thallium minerals, when heated on charcoal in the R.F., yield a white oxide coat and color the flame bright green. This coat moistened with hydriodic acid and heated gently in the O.F., or the powdered mineral mixed with 2 or 3 parts of KI & S flux and similarly heated, yields a lemon-yellow coat very similar to that of lead. The bright green flame, however, will serve to distinguish it from lead.

22. Thorium and the Rare Earths

These rare elements which occur in uraninite, columbite, tan- talite, samarskite, etc., are detected by somewhat complicated wet methods. For their application reference should be had to complete works on analytical chemistry.

Page

(a) Reduction Test and Coat on Charcoal. — Tin minerals, pow-. dered and roasted, then mixed with 4 parts sodium carbonate, 1 part borax, and 1 part charcoal dust, and treated with the R.F.

23. Tin, Sn

Tin Minerals

Mineral

Formula

Cassitebite

SnOz

Cylindrile

PbeSbjSneS,,

Franckeite

PbiSbjSnaSi,

Stannite

SnCujFeS,

Teallite

PbSnSs

142 Microscopic Examination Of The Ore Minerals

on charcoal, yield white malleable metallic tin globules which give a white insoluble precipitate on heating in a test tube with nitric acid. (The charge should not be heated long after reduc- tion as metallic tin is easily volatile.) An oxide coat is usually formed very near the assay. This coat, which is yellow while hot and white when cold, is very like the zinc coat, and like it, is volatilized with difficulty. If the tin coat is moistened with cobalt nitrate solution and heated in the O.F. it turns blue or bluish green when cold. (A zinc coat similarly treated is grass green.)

24. Titanium, Ti

Titanium Minerals

Mineral

Formula

nmenite

FeTiOa

Rutile

TiOz

Page

(a) Bead Tests. — The bead reactions for titanium are not very decisive and are interfered with by other elements. They will be found in Table 17, page 149.

(b) Wet Test with Metallic Tin. — A charge containing not less than 3 per cent, titanium may be treated as follows: The finely powdered mineral mixed with 6 parts of sodium carbonate and a little borax is strongly fused on charcoal. The fusion is dis- solved in 2 or 3 c.c. of concentrated hydrochloric acid, granu- lated tin added and the solution heated. The liquid takes on a violet color especially upon standing a few minutes.

(c) Hydrogen Peroxide Test. — For charges containing only a very small amount of titanium the fusion is carried out as directed in the foregoing paragraph, but is boiled in a test tube with 2 or 3 c.c. of dilute sulphuric acid. When dissolved, dilute with about 10 c.c. water and add about 2 c.c. hydrogen peroxide, which turns the solution yellow to orange depending on the amount of titanium present.

26. Tungsten, W

Tungsten Minerals

Mineral

Formula

Page

Ferberite

FeWO,

Hiihneriie

MnWO,

Tungstenite

Ws2

Wolframite

(FeMn)WO,

Supplementary Tests 143

(a) Bead Tests. — The bead colors for tungsten will be found in Table 17, page 149.

(6) Wet Test. — Tungstates, dissolved in the S.Ph. bead, then reduced beside tin on charcoal, powdered, and boiled with 1 or 2 c.c. of dilute hydrochloric acid and a little granulated tin, yield a characteristic blue solution.

26. Uranium, U

Uraninite Uranate of U, Pb, Th, etc. Page 113

(a) Bead Tests. — The colors which uranium gives when dis- solved in the S.Ph. bead usually serve to identify it. See Table 17, page 149.

(6) Wet Test. — The powdered mineral is fused with sodium carbonate and dissolved in hydrochloric acid, nearly neutralized with ammonium hydroxide, a solution of sodium carbonate added imtil precipitation is complete, then half as much more. Let stand and filter. Acidify the filtrate with hydrochloric acid, boil to expel CO2, and add an excess of ammonium hydroxide. The precipitate of yellow ammonium urinate may be filtered off and tested in the S.Ph. bead as in (o).

27. Vanadium, V Vanadium Minerals

Mineral Formula Page

Cuprodesclointe (PbZnCu)4V209.H80 75

Patronite \S, 118

Sulvanite CusVSj 65

(a) Bead Tests. — Vanadium minerals yield characteristic colors with the beads, especially S.Ph. See Table 17, page 149.

(6) Wet Test. — The well roasted vanadium mineral is fused with 4 parts of sodium carbonate and 2 parts of potassium nitrate, the fusion is powdered and dissolved in boiling water and the insoluble residue filtered off. The alkali vanadate formed will be found in the filtrate, which is acidified with acetic acid and lead acetate added. A light yellow precipitate of lead vanadate is formed and turns white on standing. (Lead chromate so formed is of a brighter yellow color.) The precipitate may be filtered off and tested in the S.Ph. bead as in (a).

144 Microscopic Examination Of The Ore Minerals

28. Water, HjO

Minerals Yielding Water

Mineral

Formula

Page

CuprodescloizUe

(PbZnCu)4V20,.H20

Gothite

FeaOs.HjO

Limonite

2Fe203.3H20

PsiLOMELANE

H.MnOs

Turgite

2Fe203.H20

When a powdered hydrated mineral is heated in the closed tube, water of crystallization is expelled and condenses upon the cold walls of the tube.

29. Zinc, Zn

Zinc Minerals

Mineral

Formula

Page

Cuprodescloizite

(FbZnCiOiVjOs.HjO

ErythrozineUe

(ZnMn)S

Franklinite

(FeZnMn)0.(FeM)203

Sphalerite

ZnS

VolUite

ZnsSiO

Wurtzite

ZnS

(a) Coat on Charcoal. — Zinc minerals, when intensely heated in the R.F. on charcoal, yield a zinc oxide coat which deposits close to the assay. This coat is pale yellow while hot and white when cold. It is non-volatile in the O.F. and difficultly volatile in the R.F. When the powdered zinc mineral is fused with an equal part of sodium carbonate and a little charcoal dust the coat is usually heavier and more satisfactory. This coat, if moistened with cobalt nitrate solution and heated in the O.F. turns grass-green, at least in spots. (The tin oxide coat similarly treated is blue or bluish green.)

Supplementary Tests 145

Tables Of Important Chemical And Blowpipe Reactions

Table 12. — Microchemical Reactions'"

From W. L. WHITEHEAD'S condensation of the complete tables of microchemical tests on the opaque minerals found in the second volume of " Behrens-Kley Mikrochemische Analyse," Kley, P. D. C 1915, pp. 109-130.

Metal

Reagent

Precipitate

Remarks

Arsenic

Silver nitrate

Lemon yellow

Solution in HCl. Arse- nic must be as arsenite

Antimony

Cesium chloride

Hexagonal plates

Bismuth

Cesium chloride

Rhombic plates

Cobalt

Ammonium mercuric

Dark blue prisms

Neutral or slightly acid

sulphocyanate

(acetic) solution

Copper

Potassium ferrocyanide

Amorphous red brown

Acetic acid solution

Gold

Thallium nitrate

Citron yellow needles

Solution must be strong and neutral

Iron

Lead

Potassium iodide

Bright yellow hex.

Slightly acid (nitric) so-

plates

lution

Manganese . .

Potassium chromatc

Yellow brown crystals

Solution neutral

Mercury

Potassium iodide

Mercuric-vermilion Merc urous -amorphous bright yellow

Reagent added solid

Nickel

Dimethyl glyoxime

Acicular magenta col- ored

In ammoniacal solution

Selenium

Potassium iodide

Powdery brown red

HCl solution of sele- nates

Silver

Hydrochloric acid

Amorphous white sol- utlein

Nitric acid solution

Sulphur

Calcium acetate

White needles of CaSO*

Nitric acid solutions of sulphides give sul- phates

Tellurium. . . .

Cesium chloride

Citron yellow octahedra

HCl solution of tellu- rium dioxide

Tin

Interfering elements numerous

cubes

Titanium. . . .

Rubidium chloride

Hex. and octagonal

Reagent added to solu-

plates

tion of sodium fluro- titanate

Uranium

Sodium acetate

Tetrahedrons light yel-

Weak acetic acid solu-

low

tion

Vanadium . .

Silver nitrate

Pointed yellow grains

Acid solution pyrovan- adate

Zinc.

White feathery crystals in crosses and aggre-

sulphocyanate

gates

Table 13. — Standard Fusibilities

Fusibility

Standard

Character of fusion

Stibnite Chalcopyrite Pyrite (Actinolite)

(Orthoclase)

Large fragments fuse in the yellow flame Small fragments fuse in the yellow flame Coarse fragments globular in the O.F. Coarse edges rounded in the O.F. No opaque

representatives of this class Needle-like fragments become globular in the

O.F. A few nearly infusible opaque minerals

belong here

146 Microscopic Examination Of The Ore Minerals

Table 14. — Heating on Charcoal (With or without fluxes)

Sublimate, reduction, etc.

Element

Remarks

White sublimate at a consider- able distance from the assay. Very volatile

White sublimate nearer the assay than the above. Vola- tile

White sublimate with metal- lic-like luster. Very volatile. Sometimes reddish at the edges

White sublimate like anti- mony. Volatile

Sublimate near the assay which is pale yellow when hot, white when cold. Not volatile in the O.F.

Sublimate which is pale yellow when hot, white when cold. Copper-red close to the assay

Sublimate which is faint yel- low to white when hot, white when cold. Not volatile in the O.F.

Sublimate which is yellow when hot, pale yellow when cold. Volatile in the O.F. and R.F.

Sublimate close to assay which is deep yellow when hot, pale yellow when cold. Volatile in O.F. and R.F.

Sublimate which is deep yel- low when hot, pale yellow when cold. Volatile in the O.F. and R.F.

Reduction with soda yields brittle gray button as well as coat

Arsenic

Antimony

Selenium

Tellurium

Zinc

Molybdenum

Tin

{Sulphur and Lead)

Lead

Bismuth

Antimony

Often yields strong garlic odor

The sublimate touched with the R.F. imparts an azure- blue color to the flame

The sublimate touched with the R.F. volatilizes and colors the flame green

This sublimate moistened with cobalt nitrate solution and ignited becomes green

The sublimate if touched in- stantaneously with the R.F. becomes azure-blue

The sublimate moistened with cobalt nitrate solution and ignited becomes bluish- green

This sublimate resembles the antimony coat and forms when galena or other lead sulphides are heated very quickly and intensely

This sublimate moistened with HI and ignited forms lemon-yellow lead iodide coat

This sublimate moistened with HI and ignited forms a brick-red bismuth iodide coat.

SUPPLEMENTARY TESTS Table li.— Continued

Sublimate, reduction, etc.

Element

Hemarlcs

Reduction with soda yields

gray infusible particles as

well as coat Reduction with soda yields

malleable white button as

well as coat. Reduction with soda yields

gray malleable button as well

as coat Reduction with soda yields

reddish white brittle button

as well as coat Reduction with soda yields

malleable buttons, but no

coat Reduction with soda yields

gray magnetic particles, but

no coat

Molybdenum

Tin

Lead

Bismuth

Copper, Silver, or Gold

Iron, Cobalt, or Nickel

Table 15. — Sublimates in the Closed Tube

Nature of sublimate

Element

Remarks

Mirror-like; collects in glob-

Mercury

Mercury minerals fused with

ules

sodium carbonate

Black; turns red when rubbed

Mercury

Cinnabar alone in closed tube

Mirror-like; does not collect

Arsenic and

Arsenic minerals fused with

in globules

Tellurium

charcoal dust

Deep red when hot; reddish

Arsenic

The sulpharsenides heated

yellow when cold

alone in closed tube

Black when hot; reddish

Antimxmy

Some sulphantimonides alone

brown when cold

in closed tube

Red when hot; yellow, cold.

Sulphur

Many sulphides

White if in small amount

Red to black; becomes red

Selenium

Selenides

when rubbed.

148 MICROSCOPIC EXAMINATION OF THE ORE MINERALS Table 16. — Reactions in the Open Tube

Natiire of sublimate, etc.

Element

Remarks

Dense fumes, depositing white

Antimony

All sulphantimonides

powder mostly on under side

of the tube. Pale yellow

while hot, white when cold.

Non-volatile and infusible

White, volatile, and crystal-

Arsenic

Sulpharsenides, etc.

line sublimate

White, non-volatile sublimate.

Tellurium

fusible to colorless or pale

yellow globules

White, non-volatile sublimate,

Lead

Sulphides containing lead

fusible to yellow globules;

white when cold

White, non-volatile sublimate

Bismuth

Sulphides containing bismuth

which is infusible

White, volatile, and crystal-

Selenium

line sublimate. Often shows

some red at distance from the

assay

Crystalline sublimate near the

Molybdenum

assay; yellow while hot,

white when cold

Volatile metallic mirror of

Mercury

Globules will unite when

gray globules

rubbed

Supplementary Tests 149

Table 17. — Bead Reactions with Borax and Salt op Phosphorus

Borax

Salt of phosphorus

Element

O.F.

R.F.

O.F.

R.F.

Hot. yellow to red;

Green

Hot, yellow to

Dirty brownish

Iron

cold, yellow to

red; cold, yel-

or greenish

colorless

low to colorless

Hot, yellow; cold,

Brown

Yellowish green

Fine green

Molybdenum

colorless

to colorless

Hot, pale yellow;

Yellow to brown

Yellow to color-

Hot, dirty blue;

Tungsten

cold, colorless

less

cold, fine blue

Hot, pale yellow;

Grayish to

Pale yellow to

Hot, yellow;

Titanium

cold, colorless

brown

colorless

cold, violet

Hot, yellow; cold.

Colorless

Hot, yellow;

Colorless

Cerium

pale yellow

cold, colorless

Hot, yellow; cold,

Fine green

Fine green

Fine green

Chromium

yellowish green

Hot, yellow; cold,

Fine green

Yellow

Fine green

Vanadium

yellow to colorless

Hot, orange; colt

Green

Greenish yellow

Fine green

Uranium

yellow

Hot, green; cold.

Colorless to

Green to blue

Colorless to

Copper

blue

opaque red

opaque red

Blue

Blue

Blue

Blue

Cobalt

Hot, violet; cold.

Opaque gray

Reddish yellow

Reddish yellow

Nickel

reddish brown

Hot. violet; cold.

Colorless

Violet

Colorless

Manganese

reddish violet

Index

Abbreviations, table of, 22 Aguilarite, 76 Aikinite, 63 , Alabandite, 41 Altaite, 43

Alundum, use in grinding and polish- ing, 2 Andorite, 95 Antimony, native, 96

tests for the elements, 126

table of minerals, 125 Argentite, 67 Argyrodite, 110 Arsenic, native, 59

table of minerals, 126

tests for the element, 127 Arsenopyrite, 57

Bastin, E. S., 7 Baumhauerite, 117 Bead colors, table of, 149 Beegerite, 98 Berthierite, 117 Berzelianite, 97 Berzelius, J. J., vii Bismiuth, native, 43

tests for the element, 128

table of minerals, 128 Bismuthinite, 62 Bornite, 53 Bottles, reagent, 5, 7 Boulangerite, 63 Bournonite, 94 Braunite, 114 Breithauptite, 93 Brittleness, testing for, 7 Bromyrite, 109 Brongniardite, 69

Calaverite, 61

Calf skin, use in polishing, 3 Campbell, William, vii Cassiterite, 114

Cerargyrite, 109

Chalcocite, 51

Chalcophanite, 115

Chalcopyrite, 117

Chalcostibite, 117

Chalmersite, 95

Chamot, E. M., 11

Chilenite, 35

Chiviatite, 63

Chloanthite, 89

Chromic oxide, use in polishing, 3

Chromite, 114

Chromium, tests for the element, 128

Cinnabar, 118

Clausthalite, 77

Closed tube, sublimates in, 147

Coats on charcoal, table of, 146

Cobalt, tests for the element, 129 table of minerals, 129

Cobaltite, 115

Color filters, need for, 13 exposure factors for, 17 range of transmission, 14

Color of internal reflection of min- erals, 121

Color of mineral powders, 122

Coloradoite, 97

Colored minerals with vertical illu- mination, 120

Conductivity, electrical; method of testing, 8 table of mineral conductivity,

Copper, native, 51

table of minerals, 129 tests for the element, 130

Cosalite, 59

Covellite, 111

Crookesite, 94

Cuprite, 33

Cuprodescloizite, 76

Cylindrite, 77

Index

Delafossite, 103 Determinative tables, 33

outline of, 23

use of, 20, 21 Dognacskaite, 63 Domeykite, 35 Dufrenoysite, 119 Dyscrasite, 67

Electrodes, standard copper and gold, 10

Electrolysis on polished surface, 9

Electro-potential of minerals, table of, 124 method of testing, 10

Embolite, 109

Emplectite, 63

Enargite, 83

Epiboulangerite, 99

Erythrozincite, 116

Eucairite, 97

Exposure, method of determining, factors for color filter, 17 factors for magnification, 17 factors for numerical aperture,

factors for source of light, 16 graphical solution of, 18

Famatinite, 83

Ferberite, 114

Ferro-type plate, non-sticking solu- tion for, 19

Field preparation of polished sec- tion, 4

Filter, color, 13, 14

factors for exposure, 17

Finder, use under miroscope, 6

Focusing for photography, 14

Franckeite, 79

Franklinite, 116

Freibergite, 82

Freieslebenite, 98

Fusibilies, standard, 145

Galena, 77 Galenobismutite, 98 Geocronite, 79

Germanium, tests for the element,

Gersdorfiite, 89 Glass wheel, use in grinding, 2 Glaucodot, 91 Gold, native, 111

table of minerals, 131 Gothite, 114 Graton, L. C, x Grinding, methods employed. 2 Guanajuatite, 98 Guejarite, 83 Guitermanite, 99

Hardness, testing for, 7 Hauchecornite, 91 Hauerite, 94 Hausmannite, 114 Hematite, 115 Hessite, 66 Horsfordite, 63 Hubnerite, 114 Huntilite, 33

Illumination, exposure factors for, 16

Ilmenite, 115

lodobromite, 109

lodyrite, 110

Internal reflection, table of colors,

Iron, tests for the element, 132 table of minerals, 131

Jalpaite, 67 Jamesonite, 62 Jordanite, 99

Kalgoorlite, 97 Kallilite, 57 Kermesite, 87 Krennerite, 63

Lead, tests for the element, 133

table of minerals, 132 Lehrbachite, 119 Lengenbachite, 99 Leveling cup, 5, 6 Light, exposure factors for, 16

Index

Lillianite, 77 Limonite, 114 Lindgren, Waldemar, x Linen, use in polishing, 3 Linnaeite, 91 Livings tonite, 111 Lollingite, 91 Lorandite, 118 Luzonite, 83

Magnetite, 115

Magnification curves for Leitz micro- scope, 16

exposure factors for, 17 Manganese, tests for the element,

table of minerals, 134 Manganite, 114 Marcasite, 57 Matildite, 119 Maucherite, 55 Mees, C. E. Kenneth, 13 Melonite, 61 Meneghinite, 79 Mercury, tests for the element, 134

table of minerals, 134 Metacinnabarite, 118 Miargyrite, 110 Microchemical qualitative reactions,

Microscopes, Sauveur and Boyles- ton, 4, 6

Leitz, 12 Millerite, 95

Mineragraphy, definition, x Molybdenite, 97 Molybdenum, tests for the element,

Mounting, modelling clay for, 6 Murdoch, Joseph, vii, ix

Nagyagite, 98

Naumannite, 43

Needle, testing, 7

Niccolite, 55

Nickel, tests for the element, 135

table of minerals, 135 Numerical aperture, exposure factors for, 16

Onofrite, 111

Open tube, reactions in, 148

Orpiment, 110

Oxygen, table of minerals, 136

Patronite, 118

Pearoite, 85

Pentlandite, 95

Petzite, 97

Photomicrography, 12

Plagionite, 43

Platinum, tests for the element, 137

Polishing, method employed, 2

Polyargyrite, 109

Polybasite, 87

Polydymite, 57

Potential, electrical, method of test- ing, 10 table of electro-potential of minerals, 124

Printing paper, 19

Proustite, 109

Psilomelane, 71

Pyrargyrite, 111

Pyrite, 57

Pyrolusite, 101

Pyrrhotite, 95

Qualitative microchemical tests, 145

Rammelsbergite, 89

Rare earths, 114

Rathite, 99

Reactions, features to be observed, 8

Reagents, method of applying, 7

table of, 11 Realgar, 62

Reduction on charcoal, 146 Regnolite, 119 Rezbanyite, 61 Rickardite, 35 Rutile, 116

Safiiorite, 55

Sectility, testing for, 7

Selenium, tests for the element, 137

table of minerals, 137 Seligmannite, 119 Semseyite, 45

Index

Silver, native, 43

table of minerals, 138 tests for the element, 139

Smaltite, 55

Sperrylite, 115

Sphalerite, 94-

Stannite, 94

Stephanite, 101

Sternbergite, 99

Stibnite, 87

Stromeyerite, 67

Stutzite, 119

Stylotypite, 94

Sublimates, in the closed tube, 147 in the open tube, 148

Sulphur, tests for the element, 140

Sulvanite, 65

Sylvanite, 98

Tapalpaite, 43

Teallite, 77

Tellurium, native, 61

table of minerals, 140 tests for the element, 140

Temiskamite, 55

Tennantite, 117

Tenorite, 73

Tetradymite, 61

Tetrahedrite, 117

Thallium, tests for the element, 141 table of minerals, 141

Thorium, tests for the element, 141

Tiemannite, 119

Tin, tests for the element, 141

table of minerals, 141 Titanium, tests for the element, 142

table of minerals, 142 Tungsten, tests for the element, 143

table of minerals, 142 Tungstenite, 62 Turgite, 114

UUmannite, 91

Umangite, 77

Uraninite, 113

Uranium, tests for the element, 143

Vanadium, tests for the element, 143

table of minerals, 143 VoHzite, 116 Vrbaite, 119

Water, tests for, 144

table of minerals, 144 Whitehead, W. L., x, 1 Whitneyite, 33 Willyamite, 57 Wittichenite, 95 Wolframite, 114 Wratten M plate, 13 Wurtzite, 94

Zinc, tests for the element, 144

table of minerals, 144 Zinkenite, 62

QE Davy, William Myron 367 Microscopic examina- D38 tion

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