Vancouver — The erratic nature of the mineralization will make underground mining a challenge at Orphan Boy Resources’ (ORS-V) Willa gold-silver-copper deposit in southern British Columbia.
The Willa property is situated in the Goldstream River region near the town of Silverton in the Slocan Mountains.
Independent firm, Hatch lays out a plan for two phases of mining the seven mineralized zones at Willa. Hatch’s recent mine development and operating plan relies on a geological block model which was part of a preliminary assessment technical report completed in March 2003 by Geospectrum Engineering, then updated in January 2005.
Hatch concedes, “The erratic nature of the mineralization within the Willa deposit host breccia has created a challenge in designing an underground mine plan that maximizes metal recovery without excessive development costs, particularly as the gold cutoff grade is raised.”
Willa contains a measured resource of 487,989 tonnes grading 6.77 grams gold, 0.97% copper and 11.59 grams silver, plus an indicated resource of 292,457 tonnes at 5.31 grams gold, 0.65% copper and 11.94 grams silver.
Total resources, including inferred, are pegged at 996,623 tonnes grading 6.3 grams gold, 0.79% copper and 10.77 gram silver per tonne, at a 3.5-gram gold cutoff.
The Hatch study, which factors in mining grades, recovery, dilution and timing of the work, was intended to assist with the project’s cash flow predictions.
Hatch used a 3-gram gold cutoff to design the seven stope envelopes for the mine which will employ long-hole stoping methods. Four stopes are slated for mining during the first phase with the remainder to be mined in the second phase.
The first phase material comprises 259,000 tonnes averaging 5.4 grams gold, 12.9 grams silver and 0.71% copper. Another 216,000 tonnes of 3.9 gram gold, 11.5 gram silver and 0.91% copper will be mined as part of the second phase.
Hatch’s mine plan would result in production of some 71,700 oz. gold, 187,000 oz. silver and 8.37 million lbs. copper from Willa.
Orphan Boy is awaiting the final feasibility report before deciding if and when to put Willa into production. Geospectrum plans to apply capital and operating costs to Hatch’s mine plan and incorporate these into the project’s final feasibility study.
Orphan Boy’s previous feasibility studies had proposed mining Willa at the daily rate of 500 tonnes and trucking the ore to its wholly-owned Goldstream mill for processing into a gold-enriched copper concentrate. The mill operated from 1983 to 1984 and from 1991 to 1996.
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