Abstract: A bio-leaching method is provided for recovering metal from a metal containing ore. The ore is subjected to contact with a microorganism selective to the oxidation of sulfur. A sulfur containing compound is mixed with the microorganism before, during or after contact with the ore to systemically form sulfuric acid to leach the metal from the ore. The ore is in the form of a slurry, a heap, a charge in a vat and is bioleached for a time sufficient to dissolve the metal in the ore and form a metal-rich leachate and an ore residue. The metal can then be extracted from the metal-rich leachate. The metal containing ore may contain base metals, precious metals, or platinum group metals. Upon formation of the metal-rich leachate, the ore residue may be further processed to recover any precious metals or platinum group metals that may be present.

Abstract: A process for recovering precious or base metals from particulate refractory sulfide materials comprises: a) contacting the sulfide material with an aqueous solution containing a thermotolerant bacteria culture capable of promoting oxidation of the sulfide material at a temperature in the range from 25.degree. to 55.degree. C., b) separating the oxidized residue from the aqueous liquid, and, c) treating the oxidized residue and/or the aqueous liquid to recover metal. In this context, a thermotolerant bacterium is one which has an optimum growth temperature of 40.degree. to 45.degree. C., and an operating temperature of 25.degree. to 55.degree. C.