The Influence of Roasting Temperature Upon Gold Extraction by Cyanidation from Refractory Gold Ores

CIM Bulletin, 1952


The results of this investigation indicate that the gold in the cyanide tailing of refractory gold calcines is occluded in fused particles formed during roasting. This conclusion was reached following microscopic examination of calcines produced at various furnace temperatures with different atmospheres, and a comparison with calcines produced by decomposing samples of completely sulphated concentrate under conditions such that the maximum particle temperature varied between 650°C. and 1,100°C. This comparison showed that the particle temperature during a normal roast may be several hundred degrees higher than the furnace atmosphere, or that the fusion is associated with a low melting (950°C.) eutectic mixture of FeO and FeS. Because of the unavoidable particle fusion during a furnace roast, and because low particle temperatures are essential for gold extraction by cyanidation, aqueous medium oxidation under high oxygen pressures was studied. Gold recovery from calcines produced by this means was over 98 per cent compared with a maximum of 80 per cent from furnace calcines.
Keywords: arsenic, eutectic, gold extraction, iron oxide, solid solution, Calcine, Concentrate, Concentrates, Cyanidation, Furnaces, Gold, particles, Roasting, Temperature