Sigma has 10-year life after reserves change

Having already completed new ore reserve calculations at Campbell Red Lake Mines, (N.M., Jan 26/87), the Dome Mines group reports a reserve recalculation has also been done for Sigma Mines (Quebec).

The change is part of a move by Dome to adopt the general industry practice of reporting proven and probable reserves. Up to now, the company at its mines has been calculating reserves as only proven ore, which can be mined without additional development costs.

As a result of the change, for instance, reserves at Campbell Red Lake’s gold mine near Red Lake, Ont., were boosted to 7,597,000 tons grading 0.608 oz gold per ton, from 2 million tons of a similar grade.

The new calculation at Sigma puts proven and probable reserves in place, including dilution, at 4,902,940 tons, at an average grade of 0.139. That breaks down into 1,640,779 tons of proven reserves at an average grade of 0.163 oz, and 3,262,16l tons of probable reserves at 0.127 oz.

Under the previous reporting method, proven Sigma reserves (as at Dec 31, 1985), were 978,000 tons, at 0.194, equivalent to about two years of future production.

The new reserve calculation gives Sigma the equivalent of 10 years of future production at current milling rates.

Henry Brehaut, president of Sigma and of parent Dome Mines, tells The Northern Miner a similar recalculation for the Dome mine itself, at Timmins, Ont., will be completed later this year. “There’s a lot of work still to be done on this,” he said.