Engineering & Mining Journal

MAR 2017

Engineering and Mining Journal - Whether the market is copper, gold, nickel, iron ore, lead/zinc, PGM, diamonds or other commodities, E&MJ takes the lead in projecting trends, following development and reporting on the most efficient operating pr

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NEWS-LEADING DEVELOPMENTS 4 E&MJ • MARCH 2017 Pretium's Brucejack Mine Nearing Startup in Northwest British Columbia Pretium Resources reported that commis- sioning is under way at its high-grade, un- derground Brucejack gold mine in north- west British Columbia and that the mine will reach commercial production before year-end 2017. Brucejack is scheduled to produce an average of 504,000 ounces per year (oz/y) of gold over its first eight years of operation and a mine-life average of 404,000 oz/y over 18 years. Capital cost to complete the Brucejack project is now estimated at $811.1 mil- lion. The feasibility study for the project, completed in June 2014 and updated in December 2016, considers only the pro- ject's Valley of the Kings deposit, which hosts proven and probable reserves of 6.9 million oz of gold in 13.6 million metric tons (mt) grading 15.7 grams/mt gold. The study describes a path to produc- tion for a 2,700-mt/d underground mine. Stopes will be mined using a combination of longitudinal and transverse mining, de- pending on zone width and orientation. Cemented paste tailings will be prepared in a paste plant on surface near the mill and pumped underground for distribution to the stopes. As of early February, underground devel- opment was well advanced, with 11 stopes crosscut on two levels in preparation for long-hole drilling. Crosscutting of a further four stopes was in progress. Long-hole drills were being mobilized, with long-hole drill- ing expected to begin in the second week of March. Construction of underground infra- structure, including the crusher, conveyor and transfer tower, was ongoing. Construction was also ongoing on the Valley of the Kings portal building. The portal will serve as the primary access point to convey gold ore from the under- ground crusher to the mill. Also as of early February, all major mill components had been delivered to site and assembly and installation was in prog- ress. Processing will be based on conven- tional gravity concentration and sulphide flotation. Gravity concentrate will be re- fined on-site to produce gold-silver doré. Flotation concentrate will be trucked to Terrace, British Columbia, where it will be loaded in bulk form into rail cars for ship- ping to a smelter in eastern Canada. The 330-person Brucejack camp, which includes the mine dry, offices, rec- reation facilities, dining hall and kitchen, had been commissioned and was fully op- erational in early February. The Brucejack project is located ap- proximately 950 kilometers (km) north- west of Vancouver and 65 km north of Stewart, British Columbia. Construction of the 57-km transmission line to the site was nearing completion in early February. All towers were in place, and the first 42 km of the line had been energized. The final 15-km section was 90% complete. An additional six 2-megawatt (MW) diesel generators along with the proj- ect's initial 5 MW of diesel power are lo- cated on-site and will provide sufficient power to maintain full mill and under- ground production in the event of any grid power interruption. Barrick Offers Update on Gold Projects Barrick Gold reported progress on proj- ects with the potential to contribute up to 1.1 million ounces (oz) of gold produc- tion at Cortez, Goldrush, Lagunas Norte and Turquoise Ridge. The company also initiated a prefeasibility study to evaluate the construction of an underground mine at Lama, on the Argentinean side of the Pascua-Lama project. Optimization work in Chile remains under way. All of Barrick's projects must pass a rigorous, independent peer review process led by its evaluations team. The projects are measured against a 15% rate of return, using a long-term gold price of $1,200/oz, the company said. Once they are deemed worthy, they are ranked, prioritized, and sequenced to optimize capital spending over time, allowing the company to antici- pate and plan for funding requirements. The Cortez Underground Expansion project will develop underground mining into Deep South area, below currently permitted levels. The Deep South project, located within the Lower Zone of the Cor- tez Hills underground mine, remains on track to contribute average underground production of more than 300,000 oz/y between 2022 and 2026. Development of the range-front twin declines that will provide access to the lower zone of the mine began in the fourth quarter of 2016. For the first time, the mine is using a roadheader to bore the tunnels rather than traditional drill- and-blast techniques. The expansion will enable the company to access approxi- The Valley of the Kings portal building will serve as the primary access point to convey gold ore from the under- ground crusher to the mill.

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