Bioleach Test Facility for B.C. Gold Project

A 60,000-gallon biological leach test facility will be built by Congress Operating Corp. and Giant Bay Resources (TSE) near Gold Bridge, B.C. The plant, which is expected to be in production this fall, is designed for the treatment of refractory gold concentrate from the Congress property near Gold Bridge.

The Congress gold project is a 50/50 joint venture between Levon Resources (TSE) and Veronex Resources (VSE) through the Congress Operating Corporation, managed by Levon.

Levon is currently exploring the Congress property with the objective of placing in sight sufficient reserves to justify a production rate of 250 tons per day, drawn from several of nine known gold zones. Geologic reserves are currently estimated at 670,000 tons of ore grading 0.24 oz gold per ton.

Louis Wolfin, president of Levon, says an initial test will leach some 600 tons of concentrate to determine if biological leaching is the optimum oxidation choice for the refractory Congress ores, as has been indicated in laboratory tests to date. The company believes bioleaching has many advantages over roasting or pressure oxidation, the primary alternatives for treatment of refractory ores. In particular, the company says, the process can virtually eliminate the air pollution hazards associated with other treatments while maintaining high recoveries. Bioleach lab tests on Congress ores to date have achieved gold recoveries of 90%-94%, the company reports.

The refractory nature of some ores is due to the gold and/or silver grains being locked inside sulphide crystals which prevent cyanide from reaching the precious metals. Giant Bay’s bacterial oxidation processes make use of various strains of sulphide-oxidizing bacteria to convert the sulphides to sulphates, and in the process make the gold and silver available for cyanidation and subsequent recovery. The process can also be used to treat other sulphide ores such as cobalt, copper and platinum ores.

Giant Bay’s process was first successfully tested at Giant Yellowknife’s Salmita mine in the Northwest Territories where, as a result of bioleaching, recoveries on a 300-ton sample were increased from about 65% to 96%. The Congress prototype will be considerably larger, employing a tank with about 10 times the capacity of those used in the Salmita operation.