Pretium Plans Major Mine Production Increase at Brucejack

Brucejack in northwest British Columbia produced more than 82,200 oz of gold in the third quarter of 2017.
Pretium Resources has submitted an application to British Columbia’s ministries of Energy, Mines and Petroleum Resources and of Environment and Climate Change Strategy to increase mine production at its Brucejack mine in northwest British Columbia from 2,700 metric tons per day (mt/d) to 3,800 mt/d. The application, submitted in December, reflects an increase to an average of 1.387 million mt/y from 990,000 mt/y. The approval process is expected to take six to 12 months.

Engineering is under way to assess required mill capacity upgrades. Based on preliminary engineering, the capital cost to increase mill capacity is estimated to be less than $25 million and will be updated when the engineering process is complete.

The Brucejack mine reached commercial production on July 7, after pouring its first gold on June 30. During the three months ended September 30, the mine produced 82,203 ounces (oz) of gold and 83,233 oz of silver from low-grade stockpiles, development muck, and stope ore.

In July, the mill feed was predominantly from low-grade stockpiles and development muck. As the mine rampup progressed through the quarter, more stope ore was fed directly to the mill, which improved production results.

Brucejack is an underground mine located approximately 950 km northwest of Vancouver and 65 km north of Stewart, British Columbia. Mine design at startup called for production of an average of 504,000 oz/y of gold over its first eight years of operation and a mine-life average of 404,000 oz/y over 18 years. All-in sustaining costs of production are estimated at $445/oz.

Stopes are mined using a combination of longitudinal and transverse mining, depending on zone width and orientation. Ore is processed using a combination of conventional sulphide flotation and gravity concentration to recover gold and silver. Brucejack’s gold reserves are currently estimated at 8.7 million oz at a life-ofmine grade of 14.1 g/mt (16.1 g/mt in years 1 to 10).

As featured in Womp 2018 Vol 02 -