Precious Metals

Cyanide Leaching Platinum Catalytic Converter Chemistry

Previous research by the U.S. Bureau of Mines showed that autoclave cyanide leaching of used automobile exhaust catalysts for recovery of platinum group metals (PGM) was technically feasible. This work involves a more detailed investigation of the chemistry of the dissolution of PGM in cyanide solutions. The PGM species in solution were identified by ultraviolet … Read more

Scrap Silver Recovery

The Bureau of Mines undertook a study of recovery of precious metal values from surplus and obsolete electronic gear as a part of its continuing effort to achieve maximum use and conservation of natural resources. During the early phase of the study it was learned that some military aircraft contained significant quantities of silver as … Read more

Precipitate Refining Method

This cyanide precipitate is unique in that it is apt to vary widely in composition in the course of very short periods of time, and a method of refining and melting that would prove highly satisfactory at one cleanup would yield almost a hopeless “mess” at a second. Table I gives a general conception of … Read more

Platinum Alloys with Tungsten & Molybdenum

Metallurgical research has discovered many an alloy possessing properties not combined in any single metal, and progress still consists chiefly in the investigation and utilization of alloys. In the case of iron, the demands of automobiles, high-speed machines and high-duty engines have led to the production of special iron alloys which will meet any reasonable … Read more

How to Assay & Evaluate a Gold Bar: Bullion Purity Determination

The Bureau of the Mint of the United States Treasury maintains offices for the purchase of gold-bullion, and this paper describes an investigation to establish the reasonable differences in the assay-results at the various institutions which may be commercially allowable in the settlements between them. Beginning with the comparative assay of proof-gold at the Philadelphia … Read more

Laboratory Gold Ore Chlorination Testing Procedure

Experience has shown how difficult it is to obtain information regarding laboratory tests in connection with the chlorination-process for the extraction of gold from its ores, and I therefore present the following method, somewhat in detail, for the benefit of those who may desire to pursue research work in this field. The ore chosen was … Read more

Refining Base Metal Bullion & By-Product Treatment (Pb, Cu, Zn) Bars

Here is a short account of the treatment of the base bullion for the recovery of lead, silver, and gold, and for the treatment of by-products. Appended is a short description of the chief facilities of plant which have been adopted to overcome the main difficulties in the refining of lead. The difficulty of obtaining fair samples … Read more

Gold Leaching of Pyrite Concentrate

The ore consisted of quartz, in which, above the 250-ft. level, the iron-minerals were largely oxidized and some free gold was visible; below that level few traces of oxidation occurred, and pyrite constituted the principal mineralizer in the quartz, together with occasional pockets of galena and a few eccentric specks of covellite. The 20-stamp mill … Read more

Bromine Cyanide Gold Leaching: Cyanogen Bromide

Although the bromo-cyanide or Diehl process for the extraction of gold from its ores is used on several of the Kalgoorlie mines, very little information has been published on the original process, and no details are available from the various mines now using it. The following description of the process as carried on at the … Read more

Gold Ore Deposits

The volcanic source of gold deposits is also most clearly indicated in the Cripple Creek district, Colorado, where the deposits of commercial grade are either within a complex volcanic neck or extend for only short distances into the surrounding rocks. It is true that similar mineralization has taken place for considerable distances from the neck, … Read more