DESCRIPTION: Flotation followed by cyanidation of flotation concentrates. In this flowsheet the flotation concentrates produced are reground and treated by cyanidation leaching.
ORE TREATED: Sulphide ores wherein base metal values are negligible (such as pyrite) but with good gold and silver values, or in cases where increased returns can be secured from the marketing of a gold and silver bullion over and above the returns that could be secured from marketing the flotation concentrate.
ADVANTAGES: Where adaptable, a plant using this flowsheet can be built for about sixty per cent of a straight cyanide plant. The production economics of either are the same, as the precious metals are produced in bullion form. Lower operating costs often result by removing the mineral values in a flotation concentrate, which is a small part of the tonnage of ore treated, regrinding this concentrate and cyaniding this reduced tonnage. In a number of cases where the gold is closely held in arsenopyrite or combined in tellurides the flotation concentrate is roasted prior to cyanide treatment. In these cases there have been tremendous savings in plant investment and operating costs by confining this treatment to small tonnage of concentrates.
PROCESSING COMMENTS: This flowsheet shows a continuous cyanide treatment plant for the concentrates. Where less than 12 to 15 tons per day of concentrates are recovered, simple batch plants are used with great success, with capacities as low as 1 ton per day. The step of regrinding the concentrates can be eliminated in some cases.