A heap consisting of 800 tons of a rich-in-pyrite copper sulphide ore containing also gold finely disseminated in sulphides was leached by means of acidophilic chemolithotrophic bacteria to solubilize the copper and to liberate the gold from the sulphide matrix. Sixty eight per cent of the copper was leached from the ore within approximately 9 months. The degree of sulphide oxidation at the end of this period reached about 54%. The copper was precipitated from the pregnant heap effluents by cementation with metallic iron. The pretreated ore was then leached by solutions containing amino acids of microbial origin and thiosulphate ions to solubilize the gold. 70.1% of the gold was leached in this way within 30 days. The pregnant gold-bearing heap effluents were treated by cementation with metallic zinc to precipitate the gold.
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