Manual of assaying gold, silver, lead, copper

Front matter

THE LIBRARY

OF

DEPARTMENT OF GEOLOGY

Preface

Besides the above, and other printed sources referred to in their proper places, I wish to publicly thank the following gentlemen who have very kindly aided me in my work with valuable information: Mr. S. A. Reed, Irwin, Colo.; Mr. A. H. Low, Assayer of the Boston and Colorado Smelting Works, Argo, Colo.; Mr. C. Boyer, Assayer of the U. S. Branch Mint, Denver, Colo.; Mr. M. G. Nixon, Engineer, and Mr. R. G- Coates, both of Chicago.

In conclusion, I trust that all those who are willing to aid me in the preparation of an improved edition of this book will at once communicate with me.

WALTER LEE BROWN,

Analytical and Consulting Chemist and Assayer, 105 Metropolitan Block, Chicago, 111.

Preface To The Second Edition

So many words of praise, both from the press and private individuals, greeted the first edition of this work, that I feel encouraged to put forth a second and greatly improved edition, which will not contain the faults that have been pointed out to me as existing in the first.

The salient features of the new-comer are increase in matter from 318 to 488 pages; the stating of all charges in assay tons, grammes, and grains; detailed charges in the scorification process; full notes on the colors and appearances of the scorifiers(with a colored plate)and cupels after work; the expansion of the crucible process from nine to almost ninety pages; more complete articles on the assay of gold and silver bullion, and the volumetric analysis of copper ores; and, finally, the issuance of the book in flexible covers.

For the idea of the oxidizing powers of ores which I have

PREFACE.

developed in the notes on the crucible process, I am indebted to Aaron's Assaying.

Whatever appears in this edition extracted from the following authorities is given with the Ju II and written permission of the authors, editors, or owners of the copyright, as the case may be: Mitchell's Manual of Assaying, Kustel's Roasting of Gold and Silver Ores, Aaron's Assaying, Chapman's Furnace Assay, and Hank's Fourth Annual Report as the State Mineralogist of California.

Besides for that which I have incorporated from the above-mentioned sources, I wish to give thanks to the following gentlemen: to Mr. J. C.Jackson, my successor in business in Chicago, for illustrations of a permanent furnace, and particularly for the neat and characteristic frontispiece; to Mr. F. E. Fielding, Assayer, Virginia City, Nev., for valuable notes on the assay of gold bullion and volumetric analysis of copper ores; and to Mr. G. H. Ellis, for the careful working out of the qualitative schemes.

WALTER LEE BROWN.

NOTES TO THE THIRD EDITION.

This edition differs from the previous one only in the correction of a few typographical errors; in the revision (and reduction) of the prices of a number of articles listed in the assayer's outfit on pages 439-441, and some minor alterations in the descriptions of apparatus and re-agents.

It has been a matter of gratification to both publisher and author that at least one-fourth of the second edition has been sold in England, Germany, and Australasia, and this without making any special effort to effect its sale in foreign countries.

WALTER LEE BROWN.

PREFACE.

NOTES TO THE FOURTH EDITION.

In the course of time, all books, and especially technical works, become more and more obsolete, unless they keep pace with the improvements and progress of the age. So with this little work, it must be fully up to the times. Consequently the section on apparatus has been thoroughly revised, all matter, both illustrative and descriptive, representing apparatus not now commonly used, has been expunged, and new forms have been added. We have also reason to believe that the illustrations to this work have been considered as among its most important features, so that their number has been increased from ninety-four to one hundred and thirtytwo.

Amongst the methods, some of those on " Lead Ores" have been re-written in accordance with the results of recent investigations. In the appendix, chapters have been added on the "Tin Assay," on "Gold and Silver Ores and Minerals," and a short chapter on the "Determination of the Specific Gravity of Minerals."

To fit the Manual for the English market, where many copies of the previous editions have found a welcome, the pecuniary values of apparatus, etc., which have heretofore been given only in American dollars and cents, will now be found additionally in their English equivalents.

There has in general been a sharp revision, making good many little omissions, adding clearer explanations, and so on, all tending to bring this book a little nearer to that plane of perfection which we all seek.

January, 1892. WALTER LEE BROWN.

NOTES TO THE FIFTH EDITION.

Some changes will be observed in the chapter on apparatus, notably the insertion of the new "Ball Balance," "Kellogg Bunsen Vapor Lamp," the improved " Bosworth Crusher," etc.

The subject matter of the entire book has been critically examined for errors, misstatements or other flaws, so that this addition may be as acceptable to the public as have been its predecessors.

March, 1894. * WALTER LEE BROWN.

PREFACE.

NOTES FOR THE SIXTH EDITION.

The alterations in this edition consist chiefly of corrections of a few persistent errors, the removal of the frontispiece to page 480, changes in the descriptions of apparatus, and some slight revisions.

October i, 1896. WALTER LEE BROWN.

NOTES TO THE SEVENTH EDITION.

The introduction has been re-written and brought strictly up to date. The chapter on apparatus has again been "overhauled," some old appliances stricken out, and newer ones admitted.

November 1. 1897. WALTER LEE BROWN.

NOTES TO THE EIGHTH EDITION.

The " List of Useful Books More or Less Connected with Assaying," on page 472, has been thoroughly revised, giving data of latest editions, with insertions covering works which have been published since the list first appeared. As to errors, mathematical and other, careful search has revealed many, which are now, however, corrected.

Credit is here given, for the first time, to Dr. Charles F. Chandler, of the School of Mines, Columbia University, New York City, for the devising and putting into use, of the "Assay ton" weights described on pages 66-70. This invaluable system, now in universal use, was first described by him in the American Supplement to the Chemical News, Vol. V, No. 2 (26), August, 1869, page 113, the weights having been, at that time, three years in use at the School of Mines. It is with sincere pleasure that I give this recognition, deserved if delayed.

January, 1899. WALTER LEE BROWN.

PREFACE.

NOTES TO THE NINTH EDITION.

To this edition has been added "Appendix B," consisting of three articles by George H. Ellis, Chemist and Assayer, Chicago, on these subjects:

I. Laboratory Tests in Connection with the Cyanide

Process.

II. Estimation of Copper by the Iodide Method. III. Volumetric Estimation of Lead by the Molybdate Method.

The first of these is especially timely, owing to the now extended usage of the cyanide process in the metallurgy of gold and silver; and Mr. Ellis's carefully worked out and practical methods will be found to be very valuable.

As usual, a few more past errors have been corrected, and some obscure passages cleared up — the road to perfection is beset with many brambles!

WALTER LEE BROWN.

NOTES TO THE TENTH EDITION.

Again errors, chiefly minor, have been corrected. Where there was a lack of clearness in a few places, this fault has been removed. Some cross references have been added. A few charges have been improved. Important alterations have been made in "Gold and Silver Ores," page 308 in the appendix, on the "Volumetric Analysis of Copper Ores," pages 358 to 361 inclusive; and in "Amalgamation Assay," page 369. But still more vital are three new articles in Appendix B: IV. Copper in Gold and Silver Ores. V. Chlorination Test of Ores.

VI. Technical Estimation of Zinc.

For all of the preceding I am indebted to Mr. George H. Ellis, who has become practically my collaborateur in this work- WALTER LEE BROWN.

Chapter I. Apparatus Used In Assaying

IMPLEMENTS FOR PULVERIZING, SAMPLING, ETC., - - 20

SCALES AND BALANCES, 42

WEIGHTS, 65

FURNACES, 70

FURNACE TOOLS, 98

APPARATUS USED IN THE FURNACE, ... 108

APPARATUS OF GLASS AND PORCELAIN, - - - - 118

MISCELLANEOUS APPARATUS, 124

Chapter II. Re-agents Used In Assaying

DRY RE-AGENTS FOR ASSAYING, 141

WET RE-AGENTS FOR ASSAYING, .... 155

RE-AGENTS FOR ANALYSIS, 158

MISCELLANEOUS, .... ... 166

Chapter III. Testing Of Re Agents

I. TESTING OF LITHARGE FOR SILVER, - - - 168 II. TESTING OF GRANULATED LEAD FOR SILVER, - 172

III. TESTING OF SHEET LEAD FOR SILVER,- - 174

IV. DETERMINATION OF THE REDUCING POWERS OF

REDUCING AGENTS, - - - - - 175

V. DETERMINATION OF THE OXIDIZING POWER OF

NITRE (NITRATE OF POTASH), - - - 176

IO CONTENTS.

Chapter I. Gold And Silver Ores

OCCURRENCE, • - - - 181

1. PREPARATION OF THE SAMPLE, - - -185

II. SCORIFICATION PROCESS, .... I95

a. Preparation of Charge, 197; b. Scorification, 208; c. Cupellation, 214; d. Weighing the Gold and Silver Bead, 223; e. Parting, 224; /. Inquartation, 228; g. Weighing the Gold Residue, 229 ; //. Calculations, 230. III. CRUCIBLE PROCESS, - - ... 231

Preliminary, 231; Roasting, 273; Methods of the Crucible Assay, 278; Preparation of the Charge, 281 ; Running the Crucibles in the Fire, 287; General Charges, 290; Special Charges and Directions, 296.

Chapter II. Copper Ores

OCCURRENCE, , o

I. METHOD FOR NATIVE COPPER, - . - 320 II. METHOD FOR OXIDES AND CARBONATES OF

COPPER, . . 32I

III. METHODS FOR SULPHIDES OF COPPER, ; 321

Chapter III. Lead Ores

OCCURRENCE, - ....

ASSAY, - . .

* 326

I. METHODS FOR GALENA, - - ... ,26 II. METHODS FOR OXIDES AND CARBONATES, . 334

CONTENTS.

APPENDIX "A."

Section I. Special Methods

I. ASSAYING OF THE VARIOUS MINERALS CON- TAINED IN AN ORE, 341

II. ASSAYING OF ORES CONTAINING FREE GOLD

OR FREE SILVER, 343

III. ANALYSIS OF COPPER ORES, .... 347

IV. AMALGAMATION ASSAY OR LABORATORY MILL

RUN, - 365 V. PAN TEST FOR GOLD ( " PANNING " ), - - 369 VI. CHLORINATION ASSAY OF GOLD ORES, - - 378 VII. CHLORINATION TEST FOR SILVER, ... 381 VIII. THE ASSAY OF GOLD AND SILVER BULLION, - 383 IX. THE ASSAY OF BASE BULLION, - ... 418 X. QUALITATIVE TESTS; CARBONATES, SULPHATES, SULPHIDES, TELLURIDES, COPPER, IRON, LEAD, MANGANESE, SILVER, - 422 XI. BRIEF SCHEME FOR SILICA, IRON, AND MANGA- NESE, - - 427

XII. DETERMINATION OF MOISTURE IN AN ORE, - 429

XIII. DETERMINATION OF SULPHUR IN PYRITES, - 430

XIV. THE ASSAY OF TIN ORES, - - - 431 XV. GOLD AND SILVER ORES AND MINERALS, - - 434

XVI. DETERMINATION OF SPECIFIC GRAVITY OF MIN- ERALS, - - - - - - ' - - 459

Section II. Lists And References

LIST OF THE PRINCIPAL GOLD MINERALS FOUND IN

THE UNITED STATES, 461

MINERALS LIKELY TO CARRY GOLD, - 462

LIST OF THE PRINCIPAL SILVER MINERALS FOUND IN

THE UNITED STATES, ...... 462

1 2 CONTENTS.

MINERALS LIKELY TO CARRY SILVER, - - - 465

LIST OF THE PRINCIPAL COPPER MINERALS FOUND IN

THE UNITED STATES, ----- - 466

LIST OF THE PRINCIPAL LEAD MINERALS FOUND IN

THE UNITED STATES, - 469

LIST OF USEFUL BOOKS ON SUBJECTS MORE OR LESS

CONNECTED WITH ASSAYING, 472

PLAN FOR ASSAY LABORATORY, 485

FORM FOR CERTIFICATE OF ASSAY, - , 486

OUTFIT, ASSAYING, - - - - - - 487

OUTFIT, BLOW-PIPE, - - 489

Section III. Tables

MULTIPLICATION TABLE FOR GOLD AND SILVER, - 491

TABLE OF VALUES OF GOLD AND SILVER, - - - 492 TABLES OF WEIGHTS: AVOIRDUPOIS; TROY; APOTHE- CARIES'; FRENCH OR METRIC SYSTEM, - - - 493 EQUIVALENTS OF SOME OF THE ENGLISH AND FRENCH

WEIGHTS, . . . ^ ASSAY TON EQUIVALENTS IN GRAMMES, TROY GRAINS AND TROY OUNCES,

APPENDIX "B."

I. LABORATORY TESTS IN CONNECTION WITH THE

CYANIDE PROCESS,

I. ESTIMATION OF COPPER BY THE IODIDE METHOD c,4

III. VOLUMETRIC ESTIMATION OF LEAD BY THE MOLYB- DATE ME_THOD,

IV. COPPER IN GOLD AND SILVER ORES, - -

V. CHLORINATION TEST OF ORES, ....

VI. TECHNICAL ESTIMATION OF ZINC, -

Introduction

In our present state of knowledge we believe matter to be either one element, or to be composed of two or more elements, or original, simple, substances which can not be further resolved or split up into other kinds of matter.

These elements are from sixty-three to say eighty-six in number, accordingly as we accept more or less of the doubtful ones. Certain of them have what we may term a commercial importance, listed as follows, the metals being in italics.

Aluminium.

Hydrogen.

Platinum.

Antimony.

Iodine.

Potassium.

Arsenic.

Iridium.

Selenium.

Barium.

Iron.

Silicon.

Bismuth.

Lead.

Silver.

Boron.

Lithium.

Sodium.

Bromine.

Magnesium.

Strontium.

Cadmium.

Manganese.

Sulphur.

Calcium.

Mercury.

Tin.

Carbon.

Molybdenum.

Titanium.

1 1.

Chlorine.

Nickel.

Tungsten.

Chromiztm.

Nitrogen.

Uranium.

'3-

Cobalt.

Oxygen.

Vanadium.

Copper.

3°-

Palladium.

Z,inc.

Fluorine.

Phosphorus,

Zirconium.

1 6.

Gold.

, 4 I NT ROD UC TION.

Some of the above are valuable in themselves, as well as in combination, others only in modified forms.

The remainder of the accepted elements having no practical value and being of interest only to the investigators in theoretical chemistry, are :

2. Cerium. Beryllium. 13. Scandium.

Niobriiim. 8. Lanthanum. 15. Tellurium.

4. Gallium. 9. Osmium. 16. Thallium.

5. Germanium. 10. Rhodium. 17. Thorium.

1 1 . Rubidium.

Besides the 63 above classed, there are some two dozen so-claimed elements of greater or lesser rarity, whose existence is not satisfactorily proven to all, so that while they remain on the field of research, they are not universally adopted. They are :

1. Actinium. 9. Helium. 17. Philippium.

2. Argon. 10. Holmium. 18. Praseodymium.

4. Decipium. 12. Ilmenium. 20. Terbium.

5. Didymium. 13. Mosandrium.2\. Thulium.

6. Erbium. 14. Neodymium. 22. Ytterbium.

7. Gadolinium. 15. Neptunium. 23. Yttrium.

8. Gnomium. 16. Norwegium.

A fourth list, in . this connection, can be formed of those supposed elements which have been shown not \o exist. While of no actual value, it yet makes an interesting finale :

INT ROD UC TION. I 5

1. Austrium. 6. Gadenium. 10. Polymnestum.

3. Comesium. 8. Lavcesium. 12. Uralium.

4. Dysprosium. 9. Neobium. 13. Vesbium.

5. Erebodium.

In order to ascertain the value of an ore, it is necessary to determine the percentage of the metal or metals which it contains.

This is the first thing to be done — an after consideration is the question of the presence of other ingredients which may injuriously affect the value of the ore or product.

There are two general methods, known respectively as assaying and analysis, whereby we may test an ore to learn its composition.

A comprehensive definition of assaying is to call it that branch of exact science which enables us to find out of what a substance is composed^ and the proportions, by means of dry re-agents and heat.

On the other hand, analysis is that branch which effects the same results mainly by the use of wet re-agents, with or without the aid of heat.

The above definitions have been strongly objected to by some who claim, and with reason, that an assay, which means an essay or trial, is as appropriate as the name of a test by use of wet re-agents, as of one by means of fire only. Others claim that the term assay applies only to such examinations as deter-

INTRODUCTION.

mine the one element of value in the material examined, whatever the means used. But in spite of these arguments, common usage must prevail. An "assay "in the minds of those who most commonly require or make such a test, means a determination by fire, hence, the terms assaying or analysis, as defined above, will continue to be employed throughout this work, in opposition to the distinction into wet assays and dry or fire assays.

The greater number of the processes given in this little book come under the former heading, while analysis proper is employed in only a few cases.

The following metals are sought for in ores by assaying : antimony, bismuth, cobalt, copper, gold, iron, lead, nickel, platinum, silver, tin, and zinc.

It is the object of this manual to 'treat only of gold, silver, copper and lead. For information concerning the assaying of the remaining metals just mentioned, the student must seek it either among the processes described in the appendix, or look for them among the various works on assaying listed on pages 480-482.

PART I.

APPARATUS AND RE-AGENTS.

MANUAL OF ASSAYING.

PART I.

APPARATUS AND RE-AGENTS.