MINING IN CHILE — La Coipa mine posts record output

Output at La Coipa, an open-pit gold and silver mine in northern Chile, has continued to expand.

Production in 1993 — 8 million grams gold (258,200 oz.) and 413.7 million grams silver (13.3 million oz.) — increased by more than 30% from the previous year.

Joint-venture partners Placer Dome (TSE) and TVX Gold (TSE) brought the mine on stream at 1,000 tonnes per day in July, 1989. Two years later, daily output was boosted to 15,000 tonnes.

La Coipa consists of four orebodies, including a new deposit defined last year.

Proven and probable minable reserves at the end of 1993 totaled 63.3 million tonnes grading 1.3 grams gold and 76.5 grams silver per tonne. The overall stripping ratio is 1.7-to-1 and the cutoff grade is variable. An “elevated” cutoff of 1.5 grams gold equivalent was used last year and, for 1994, this has been lowered to 1.2 grams. (Material grading below 1.2 grams and above the economic cutoff of 1 gram is stockpiled for potential processing later in the mine life.)

The mill consists of circuits for semi-autogenous grinding, crusher grinding, leaching and filtering, as well as a Merrill-Crowe plant and refinery. Gold recoveries averaged 84.9% last year while silver recoveries were 73.8%. By all accounts the operation has been extremely successful, having never reported a yearly loss.

The cash cost per tonne milled in 1993 stood at US$19, or US$142 per gold-equivalent ounce — unchanged from 1992.

By comparison, in 1989 and 1990, when the mine was originally producing only 1,000 tonnes per day, the production cost per tonne was US$42 and US$51, respectively. These figures equate to a per-ounce cost of US$179 and US$153, respectively.