Extraction of gold from an Indian low-grade refractory gold ore through physical beneficiation and thiourea leaching

The work carried out on the processing of a low-grade and refractory gold ore using thiourea is presented. Direct leaching of the “as-received” ore with thiourea has yielded only 16% gold extraction. Starting with ore containing 1.4 g/t of gold, it has been possible to generate a sulphide concentrate with 6.1 g/t of gold by physical beneficiation of the ore through froth flotation. Thiourea leaching of this flotation concentrate after pressure, pre-oxidation has resulted in gold extraction of 98%, with an overall gold recovery of 74%. Pressure oxidation was found to be slightly superior to roasting for the pre-oxidation of the refractory gold ore/concentrate.