A re-thinking of the style of mineralization at
The open-pit measured and indicated resource at Sigma now stands at 28.3 million tonnes grading 2.19 grams per tonne (or 2 million contained ounces), based on a cutoff grade of 0.5 gram gold. At a 1-gram cutoff, the resource declines to 18 million tonnes grading 3.05 grams (1.8 million contained ounces).
As late as December 1999, McWatters had estimated Sigma’s open-pit resources to be only 3.8 million tonnes at 3.28 grams gold. However, the company says it had a breakthrough last year when it discovered that sub-horizontal gold-bearing veins occur in predictable patterns exterior to the better-known vertical vein systems.
McWatters says its new estimate is based on mapping, drilling and ongoing mining of the open pits. Consultanting firm Geostat International has confirmed the grade through geostatistical work.
McWatters will release a new reserve figure for Sigma by the end of February.
Consulting firm John Tully & Associates has been auditing McWatters’ reserves and resources since the end of 1999.
McWatters is also considering applying the Sigma model to its nearby Lamaque open pits.
McWatters recently reported its year-end production results: in 1999, the company fell slightly short of its 170,000-oz. goal by producing 168,534 oz. gold at a cash operating cost of US$227 per oz., compared with 169,255 oz. at US$255 in 1998.
Last year’s production came from: the underground Kiena mine, which produced 86,602 oz. at a US$212-per-oz. cash operating cost; the underground operations at Sigma-Lamaque, which produced 28,067 oz. gold at a cost of US$349 per oz.; and the open-pit operations at Sigma-Lamaque, which produced 53,865 oz. gold at US$188 per oz.
McWatters’ fourth quarter was highlighted by the performance of the Sigma-Lamaque open-pit operations, which produced 15,605 oz. gold at a cash operating cost of US$153 per oz., compared with 3,619 oz. at US$314 in the corresponding period of 1998.
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