Cominco Res. advances garnet project

The remnants of a gold-dredging operation that ceased production about 70 years ago are providing Cominco Resources International (TSE) with the makings of a new mining operation.

The company is working toward a production decision for a garnet mine, based on reserves of 30 million tonnes grading 4% garnet, contained in the tailings from the former dredging operation. Mining costs are expected to be low, as the tailings are loose, free of clay, easy to dig and have no overburden cover.

Garnet is used as an air-blasting abrasive and for water-jet cutting purposes. It is also used in water filtration systems to improve market quality. Consumption is reported to be on the rise as garnet is continuing to replace silica sands and copper slags for environmental reasons. Cominco Resources’ Alder property is in Madison Cty., 60 miles from Butte, Mont. The tonnage calculation is based on past production records, while the garnet content was determined from 13 test pits and 19 large-diameter holes. A pilot plant recently treated 7,000 tonnes of ore and produced 250 tonnes of garnet concentrate, which was tested successfully in the marketplace. An updated feasibility study forecasts initial production of 9,000 tonnes of garnet per year. As markets expand, output could be increased to 40,000 tonnes per year, with additional processing facilities.

Capital costs for the full project (40,000 tonnes annually) would be about US$6.5 million. Processing would entail simple gravity concentration, screening and drying, with no crushing or grinding required. Cominco Resources already has a network for marketing of abrasives through a joint venture with Cominco (TSE), whereby subsidiaries of both companies produce and market nickel slag abrasives at Riddle, Ore.