HISTORY OF CIP

Gold is the only metal which has the combination of lustre, easy workability and virtual indestructibility and also rarity. This means ways are continually being sought to identify new feed sources and improve the recovery of existing and new processes. From ancient times, as far back as 4,000 B.C., gravity concentration has played an important part in the recovery of gold, especially from alluvial deposits. In the 1890s, MacArthur and the Forrest Brothers of Glasgow, U.K., introduced the cyanide process for the dissolution of gold and its subsequent precipitation by means of zinc. This enhanced the recovery of gold from stamp milling and amalgamation by allowing the recovery of fine gold in stamp tailings. Over the years, the basic system of cyanidation and zinc cementation has been developed into a highly efficient process that is used worldwide for the recovery of gold.

Activated charcoal was used as a means of recovering gold from solution in the 1880s, especially in chlorination plants in Australia. Two factors probably retarded the development of carbon instead of zinc-based processes during these years. Firstly, there was no satisfactory procedure for the elution of carbon to allow its recycling and, secondly, the development of the Merrill-Crowe process for zinc cementation discouraged any further work on the use of carbon.

Two major factors have led to the re-introduction of carbon for gold cyanide processes. Firstly, the availability of granules of hard activated carbon developed for use in the Second World War and, secondly, the development of an elution method for carbon, thereby allowing it to be recycled. J. B. Zadra developed the elution process at the request of the Getchell mine, in Nevada, but it was first applied to the slimes fraction at Cripple Creek in 1961 and subsequently to the slimes fraction at the Homestake mine in South Dakota. The successful application of carbon-in-pulp at the Homestake mine, employing the Zadra process, has been used by a number of other similarly successful plants throughout the world. The preceding is from a paper entitled “Review of Feed Sources and Preparation for Gold Carbon-in-Pulp Processes.” Its author, K. G. Thomas, is vice-president of metallurgy for American Barrick Resources Corp.