Recent progress in mineralogical investigations related to gold recovery

CIM Bulletin, Vol. 82, No. 931, 1989

William Petruk, Process Mineralogy Section, Mineral Processing Laboratory, Mineral Sciences Laboratories, CANMET-EMR

Mineralogical investigations in connection with gold metallurgy are usually performed to find the reason for poor recoveries by cyanidation or by other leaching techniques. Poor recoveries most commonly are obtained when (1) native gold is encapsulated in an insoluble mineral as "invisible gold"; (2) native gold is coated with a precipitate; (3) gold-bearing products are insoluble in cyanide solutions; (4) carbonaceous material in the ore adsorbs gold; and (5) associated minerals decompose and consume cyanide. Samples of refractory material quite often have low gold tenors. It is difficult to find the gold-bearing minerals in such samples with an optical microscope because the probability of finding trace minerals in samples is small. The probability decreases with decreasing grain size of the gold-bearing mineral and with decreasing gold tenor of the sample. Techniques have been developed to increase the success rate of finding gold grains; some are (1) concentrating heavy minerals; (2) preparing special polished sections; (3) searching with an image analyzer; and (4) dissolving associate silicate and sulphide minerals.
Keywords: Gold, Refractory gold, "Invisible gold", Alloys, Mineralogy, Recovery