PEA Supports Renewed Mining at Sleeper Property
Metal Mining Consultants (MMC) conducted the Sleeper PEA. The study’s basecase scenario assumes open-pit mining and a 30,000-mt/d heap-leach facility having throughput capacity of about 11 million mt/y. Production would average 102,000 oz/y of gold and 105,000 oz/y of silver for seven years, with an additional 37,850 oz of gold and 30,500 oz of silver recovered during final leaching.
The gold grade would average 0.47 g/mt over the first three years and 0.41 g/mt over the life of the mine. Initial capital is estimated at $175 million, with a payback period of 2.7 years. Projected lifeof- mine all-in capital, operating, and sustaining costs are estimated at $869/gold equivalent oz.
The PEA assumed $1,250/oz gold and $16/oz silver prices. Processing facilities would be based on standard cyanide heap leaching, with a carbon-in-column and adsorption-desorption recovery plant. The plant would produce a doré product for direct sale to a regional refinery.
Existing infrastructure at the Sleeper mine site would require upgrades; however, the basic components remain in place. The site is currently connected to the regional electrical grid; however, a substantial capacity upgrade would be required. Existing shop and office buildings are located on top of mineable material and would require removal and reconstruction.
In addition to the base-case scenario, MCC also evaluated a combined heapleach and bio-oxidation scenario to test its economic viability and to guide future metallurgical testing and trade-off analysis during prefeasibility. This opportunity would result in a 14-year operation incorporating a much larger pit supplying 50,000 mt/d to a standard heap-leach processing operation for 11 years. A 10,000- mt/d bio-oxidation plant would commence operation in year nine followed by standard heap leaching of this mineralized material. Life-of-mine production would total 1.7 million oz of gold and 3.2 million oz of silver. Total capital and sustaining costs would increase to $373 million.