Gold metallurgy - Processes

In most cases, gold metallurgy is based on solution mining and extraction from gold solutions, followed by metal refining. However, pre-treatment operations based on mineralogical phase separations are often carried out to increase the grades of raw ore by eliminating sterile or troublesome phases prior to metallurgy (§ 1). Concentrates are then processed by hydro or pyrometallurgy. Amalgamation, a very old technique, is now only used in small-scale operations. It is responsible for serious pollution and mercury poisoning.

In most cases, hydrometallurgy consists of cyanide solution treatment of raw ores in heaps or stirred reactors, with gold extraction by cementation or adsorption on activated carbon. The gold is then re-extracted and refined (§ 2).

Effluents and tailings are detoxified (§ 5 and 6). Contrary to popular belief, hydrometallurgy based on cyanidation is not a source of danger, as the control and destruction of cyanides is a constant concern for the operator. Proven methods do exist, but they need to be implemented without interruption during operation and after it has ceased.

The properties, economics and resources of gold were the subject of dossier [M 4 730] and the equipment and costs of extraction will be the subject of another dossier in this treatise.