Following the native metal, the tellurides are the most important gold minerals. The tellurides include calaverite and krennerite which contain about 40 percent gold, and sylvanite and hessite with about 25 percent.
The Kalgoorlie, Australian, ores contain free gold and tellurides which occur in Pre-Cambrian rock consisting essentially of schists and quartz-dolerite-greenstones. Auriferous pyrite is also present and the gold is occasionally associated with chalcopyrite, tetrahedrite and arsenopyrite.
The gold in the pyrite is finely divided and requires grinding to about 75 percent passing 200 mesh. The ground product is floated and the concentrate, after cyanidation and filtration, is roasted and recyanided. Flotation tailings are also cyanided.
The ores of the Emperor Mine in Fiji contain gold associated with the telluride minerals sylvanite and hessite. A chemical oxidation step is used in place of roasting to liberate the gold for cyanidation.
Gold with Copper Minerals
Gold is often associated with chalcopyrite in porphyry deposits. When recovered into the copper concentrate, it travels through the smelter and to the refinery where it reports with the anode slimes from electrolytic refining and is subsequently recovered as gold bullion. Gold losses in copper concentrating are about the same as for copper, but are negligible in smelting and refining. Gold occurring in pyrite associated with chalco-pyrite can sometimes be separated by flotation into an auriferous pyritic concentrate for cyanidation as at Benguet Exploration. At the Itogon Suyoc, Palidan Mill, the auriferous pyrite and chalcopyrite are recovered into a bulk flotation concentrate which is then separated into two flotation products; a pyrite concentrate for cyanidation of the gold and a copper concentrate for shipment to a smelter.
At San Manuel, Arizona, the gold follows the molybdenite and this concentrate is treated by a standard type of cyanidation flowsheet.
Gold with Lead and Zinc Minerals
Gold occurring with lead-zinc sulfide ores or copper-lead-zinc ores usually is recovered into the flotation concentrates and shipped to a smelter where gold recovery is high, particularly at lead smelters. Occasionally, free gold may be recovered by amalgamating the concentrate from a jig in the grinding circuit. Gold contained in the flotation tailing is recovered by cyanidation as any residual galena or sphalerite is not harmful to cyanidation.
The Kalgoorlie, Australian, ores contain free gold and tellurides which occur in Pre-Cambrian rock consisting essentially of schists and quartz-dolerite-greenstones. Auriferous pyrite is also present and the gold is occasionally associated with chalcopyrite, tetrahedrite and arsenopyrite.
The gold in the pyrite is finely divided and requires grinding to about 75 percent passing 200 mesh. The ground product is floated and the concentrate, after cyanidation and filtration, is roasted and recyanided. Flotation tailings are also cyanided.
The ores of the Emperor Mine in Fiji contain gold associated with the telluride minerals sylvanite and hessite. A chemical oxidation step is used in place of roasting to liberate the gold for cyanidation.
Gold with Copper Minerals
Gold is often associated with chalcopyrite in porphyry deposits. When recovered into the copper concentrate, it travels through the smelter and to the refinery where it reports with the anode slimes from electrolytic refining and is subsequently recovered as gold bullion. Gold losses in copper concentrating are about the same as for copper, but are negligible in smelting and refining. Gold occurring in pyrite associated with chalco-pyrite can sometimes be separated by flotation into an auriferous pyritic concentrate for cyanidation as at Benguet Exploration. At the Itogon Suyoc, Palidan Mill, the auriferous pyrite and chalcopyrite are recovered into a bulk flotation concentrate which is then separated into two flotation products; a pyrite concentrate for cyanidation of the gold and a copper concentrate for shipment to a smelter.
At San Manuel, Arizona, the gold follows the molybdenite and this concentrate is treated by a standard type of cyanidation flowsheet.
Gold with Lead and Zinc Minerals
Gold occurring with lead-zinc sulfide ores or copper-lead-zinc ores usually is recovered into the flotation concentrates and shipped to a smelter where gold recovery is high, particularly at lead smelters. Occasionally, free gold may be recovered by amalgamating the concentrate from a jig in the grinding circuit. Gold contained in the flotation tailing is recovered by cyanidation as any residual galena or sphalerite is not harmful to cyanidation.
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