BULGARIA – Dundee Precious Metals of Toronto says recent metallurgical testing proves that metal recoveries at the Chelopech gold-copper-silver mine can be boosted to more than 90%. A preliminary economic assessment of a method of recovering pyrite indicates that up to an additional 85,000 oz of gold could be recovered annual. That represents a recovery jump to 90% from 55% for gold.
The Chelopech underground mine 70 km east of Sofia currently produces a copper concentrate. Recovery rates of metals to the concentrate are 55% for gold, 85% for copper and 42% for silver. The remaining metals are associated with the pyrite fraction of the ore that is rejected during flotation. Treating the pyrite tails in a pressure oxidation circuit (autoclave) will produce a product containing 30 to 60 g/t Au and 25 to 27 g/t Ag. Copper and silver that remain in the acid solution after oxidation can be recovered through precipitation during neutralization.
Dundee puts the total capital expenditure for pyrite treatment at $202 million. The concentrator would be updated by mid-2012 at a cost of $22 million. The first pressure oxidation circuit costing $65 million (plus $28 million contingency) would begin production in 2016. The second costing $67 million ($20 million contingency) would begin production in 2017. The cash cost per ounce of gold (net of by-product credits) is estimated to be $615/oz.
Go to DundeePrecious.com to learn more about the Chelopech mine.