Feasibility Study and Technical Report - Pretivm

The gold and silver minerals responded well to the flotation concentration. The reagentscheme screening tests showed that the addition of collector 3418A would improve therecovery of the precious metals and reduce concentrate mass pull. The test work alsoindicated that the addition of lime, to increase slurry pH from 8.1 to 10.5, couldsubstantially reduce the concentrate weight from 6.8 to 1.5%.Similar metallurgical performances were produced from the West Zone samples and theR8 Zone samples. However, the test results appeared to indicate that the R8mineralization might require finer primary grinding.Using a combined process of gravity separation and flotation, CESL projected the overallgold and silver recoveries to be approximately 89% and 83% for the West Zonemineralization, and 88% and 85% for the R8 Zone. The projections for the blend of thetwo zones are detailed in Table 13.3.Table 13.3Metallurgical Performance ProjectionProductsMassRecovery(%)Grade(g/t)Recovery(%)Au Ag Au AgGravity Concentrate 0.2 1,139.0 3,966.0 22.5 1.1Flotation Concentrate 4.5 143.4 12,665.0 66.4 82.4Tailings 95.3 1.2 119.7 11.1 16.5Head 100.0 9.3 777.6 100.0 100.0Source: CESL – Blend (1990)13.3 2009 TO 2013 TEST WORKInspectorate−previously Process Research Associates Ltd. (PRA)−carried out preliminarymetallurgical test work investigating the metallurgical performance of the Brucejackmineralization from 2009 to early 2011. During 2012 and 2013, Inspectorateconducted further comprehensive metallurgical test work on the VOK Zone and WestZone mineralization; this test work was conducted to optimize process conditions,improve metallurgical performance, and support the feasibility study. These testprograms were conducted under the supervision of Frank Wright, P.Eng., a metallurgistcontracted by Pretivm.13.3.1 SAMPLE DESCRIPTIONThe samples used for the test work beginning in 2009 were generated from numerousdiameter drill core intervals that were produced from various geological explorationprograms. Drillhole distribution is presented in Figure 10.3.Pretium Resources Inc. 13-3 1291990200-REP-R0012-02Feasibility Study and Technical Report on the BrucejackProject, Stewart, BC