Precious metals scavenging at Equity Silver Mines Limited

CIM Bulletin, Vol. 79, No. 891, 1986

P.B. MARCHANT Director of Research and Project Development, Coastech Research Inc. Vancouver, British Columbia

Considerable gold and silver values are lost to flotation tailing from both the Southern Tail orebody and the Main Zone orebody. The underlying mineralogical assemblage of the two ore types is quite different. This paper describes the research strategy employed to determine an economical method to scavenge gold and silver from flotation tailing. Much of the unrecovered gold in the Southern Tail ore is associated with arsenopyrite while silver losses are probably as unliberated tetrahedrite and minor silver-bearing sulphosalts. Processing alternatives tested include bulk sulphide recovery by flotation and gravity, selective pyrite-arsenopyrite separation, cyanidation, and oxidation pretreatments such as pressure leaching and bioleaching to enhance cyanidation response. Gold losses in the Main Zone ore are more closely associated with silver-bearing minerals, pyrite, and siliceous gangue and consequently respond more readily to conventional tank cyanidation. The 5 300 t/d carbon-in-leach circuit to treat Main Zone flotation tailing is described in detail.
Keywords: Milling, Mineral processing, Precious metals, Scavenging, Gold, Silver, Flotation tailings, Cyanidation, Bioleaching, Pressure leaching.