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OF

GOLD EXTRACTION:

A TEXT-BOOK FOR THE USE OF MINING STUDENTS,

METALLURGISTS, AND CYANIDE OPERATORS.

BY

JAMES PARK,

PROFESSOR OF MINING AND DIRECTOR OF OTAGO UNIVERSITY SCHOOL OF MINES ;
FELLOW OF THE GEOLOGICAL SOCIETY OF LONDON ; MEMBER OF THE AMERICAN
INSTITUTE OF MINING ENGINEERS; MEMBER OF THE INSTITUTE OF
MINING AND METALLURGY, LONDON ; LATE SUPERINTENDENT,
NEW ZEALAND GOVERNMENT METALLURGICAL WORKS,

THAMES GOLDFIELD,

FOURTH ENGLISH EDITION. REVISED AND ENLARGED.
(The First English Edition was revised and enlarged from the Third Edition

published in New Zealand.]

With frontispiece, Plates and illustrations.

(Authorized Text-book, Australian Schools of Mines.,

LONDON:
CHARLES GRIFFIN & COMPANY, LIMITED,

EXETER STREET, STRAND.

1906.

[All Rights Reserved.]

1906

SOME PRESS OPINIONS OF

THIS BOOK

Mining Journal :

"Mr Park's book deserves to be ranked as amongst the best of the existing treatises on this subject. may safely and advantageously be recommended to

students.” Nature :

"A sound and practical knowledge of 'The Cyanide Process of Gold Extraction' can be obtained from the volume."

Engineer :

“ Both in text and illustration it is an excellent

example of what a technical manual should be." Camborne School of Mines Magazine :

A first-rate text book on the subject.... one which

every mining student ought to possess.' Chemical Trade Journal :

“This eminently practical work .... one of the best technological treatises we have had occasion to notice in these columns. ... There is no better

work.” Chemical News:

We can strongly recommend this book to all those

engaged in gold and silver mining." New Zealand Times :

“To all engaged in mining and metallurgical work, whether in laboratory or at gold extraction works,

Mr Park's book will be invaluable." Otago Daily Tintes:--:

“This is an extremelyóvalsiahle text-book .... the çlearness of style and fucidity of expression commend {t to-&ny interested reader."

GB

PREFACE TO THE FOURTH ENGLISH

EDITION.

The exhaustion of the last edition has enabled the author to revise the text and add much new matter relating to recent improvements in cyanide practice in different parts of the globe.

The principles underlying the treatment of silicious silver ore carrying more or less gold is dealt with more fully than in former editions. The weak point in the present treatment of these ores is the low extraction of the silver. At the current price of silver this is perhaps not of much moment with ores in which the chief value lies in the gold contents; but in the case of low-grade silver ores carrying from 1 to 3 dwt. of gold, and from 10 to 20 oz. of silver, per ton, the subject is one of increasing concern to the mine owner. The difference between an extraction of 50 per cent. and 85 per cent. of the silver may represent the sole margin of profit in a low-grade venture.

The dissolution of gold in a clean pyritic ore seldom presents serious chemical difficulties. From such an ore the bulk of the gold is extracted by plate-amalgamation, leaving only the more finely-divided gold to be extracted by cyanide from the tailings. The treatment of argentiferous gold ores, such as those of New Zealand, South Dakota, and Mexico, is a much more difficult matter, involving not only the direct cyaniding of all the crushed material, but the solving of chemical problems not met with in the treatment of ordinary gold ores.

The dissolution of silver sulphides liberates a corresponding

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amount of sulphur, which at once forms alkaline sulphides and sulphocyanides, both causing loss of cyanide and free oxygen, the former being especially injurious in that it retards the progress of dissolution and prevents a satisfactory extraction of the silver.

The use of a desulphurizing agent will be found to give increased extractions of both the gold and silver, besides effecting a saving of cyanide, and a lessening of the time required for dissolution. It should, however, be remembered that to obtain the highest extractions from the majority of dry silver ores finegrinding is a necessity; and fine-grinding does not necessarily mean sliming. It is hopeless to expect a desulphurizer to increase the extraction when the values are enveloped in grains of silica. The economic limit of fine-grinding must be determined for each ore by actual experiment.

For the successful treatment of pyritic concentrates finegrinding is a necessity, and here also the use of a desulphurizer will be beneficial, more especially when followed by thorough aeration, or the addition of an oxidizing agent.

Fine-grinding by tube-mills is now in successful operation in Western Australia, New South Wales, New Zealand, and Mexico, and in the past two years much additional experience has been gained in the successful running of these machines. The re. spective merits of grinding pans and tube-mills is still an open question, and is probably incapable of solution. Each machine possesses certain distinctive features which will enable it to assert a superiority in the grinding of an ore suited to its peculiar capacity. Thus on some Kalgoorlie ores the tube-mill may

show the higher efficiency, while on Rand ore the pan may possess a decided superiority. This also is a matter for actual experiment.

One of the most notable advances in the metallurgy of gold in recent years is the introduction of the Rose process for the refining of gold and impure bullion. Its use should reduce the cost and labour of refining cyanide bullion.

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