Pretium Resources Inc.: Brucejack Mine ramp-up advances

by Keith Powell
Interior of Brucejack Mine building.

— Photo courtesy Pretivm

Pretium Resources Inc. (TSX:PVG) (NYSE:PVG) (“Pretivm” or the “Company”) is pleased to report that the ramp-up continues to advance at the high-grade gold Brucejack Mine, and the mine remains on track to reach steady state production mid-to-late 2018.  Additionally, an exploration drill program has been initiated underground to test for a porphyry source and evaluate the potential extension of the Valley of the Kings deposit to the east.

Optimizing Operations

To improve access and build stope inventory the rate of underground development has been increased to 700 meters per month, up from 420 meters originally envisioned in the Brucejack Feasibility Study. A third long-hole drill is now on site to serve as a back-up drill and will also be utilized to increase the rate of underground production to build stope inventory, which is expected to increase to 10 to 12 stopes with a range of grades by mid-year.  The availability of stopes representing a range of grades, including multiple higher grade stopes, will allow mining operations to optimize stope blending and provide alternative stopes with comparable grades for mining in the event of operational issues with any stopes. The increased stope inventory is expected to improve the management of production grades as the ramp-up continues.

Operational Grade Control

The grade control program is underway and is currently being integrated into the mining process. The grade control program, which comprises sampling and drilling, is designed to refine stope dimensions, reduce dilution and optimize grade.

Stope Ring Sampling

As part of the grade control program, grade is estimated on a ring-by ring basis to refine the shape of the long-hole stope prior to mining. Long-hole drill cuttings are selectively collected from each ring within a stope and split to a smaller sample size. The reduced sample is then assayed. Assayed data from each of the rings is then fed back into the short-term mine planning cycle to refine stope dimensions.

The upgraded and modified underground sample splitting station is now functional. The sample splitting station is used to further validate the sampling process.

Reverse Circulation Drilling

Another component of the grade control program, reverse circulation (RC) drilling to optimize stope definition, has commenced on a trial basis. The RC drill will cross-cut the stopes drilling 5-meter to 7.5-meter centers to refine stope location and dimensions prior to mining. The RC drilling will provide a larger sample per meter and is expected to be faster and more cost effective than core drilling, which has been used for infill drilling to date.

Exploration Drilling for Porphyry Source

An exploration drill program has been initiated to test for a porphyry source and evaluate the potential extension of the Valley of the Kings to the east. The drill program will follow-up on the success of the 2015 regional grass-roots exploration drill program. High-grade gold was intersected in the Flow Dome Zone, located approximately 500 meters east of the Brucejack Mine, confirming the presence of either a new stockwork zone or an extension of the Valley of the Kings deposit (see news release dated October 8, 2015). A drill has been set up underground on the eastern edge of the 1200-meter Level of the Valley of the Kings development. Two drill holes, each 1,600 meters long will serve to provide a continuum of information from the Valley of the Kings to the Flow Dome Zone. The drilling will also test below the Flow Dome Zone where structural geology combined with a geophysical anomaly suggests a potential porphyry source.

Lyle Morgenthaler, B.A.Sc., P.Eng., Chief Mine Engineer, Pretium Resources Inc. is the Qualified Person (“QP”) responsible for Brucejack Mine development. Warwick Board, Ph.D., P.Geo, Pr.Sci.Nat., Vice President, Geology and Chief Geologist, Pretium Resources Inc. is the Qualified Person (“QP”) responsible for the Brucejack Mine exploration drilling.

About Pretivm

Pretivm is ramping-up gold production at the high-grade underground Brucejack mine in northern British Columbia. 

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