Feasibility Study and Technical Report - Pretivm

In general, there was a reduction in gold and silver recoveries when there was anincrease in the grind size. However, the effect of the primary grind size on the overallmetal recoveries was insignificant, especially when the grind size was finer than 80%passing 60 to 80 µm. A grind size of 80% passing 74 µm was selected for the variabilityand locked cycle tests.In the 2013 test program, the master composite samples generated from the upperzone and lower zone of the VOK deposit (labeled as MU and ML composites) were testedfor their metallurgical response to three different grind sizes ranging from 80% passingbetween 79 µm to 114 µm. No significant difference was noted in gold and silverrecoveries when the primary grind size changed.In the 2010 to 2011 testing program, similar tests were conducted to assess the effectof primary grind size on gold and silver recoveries. The test results, shown in Figure 13.3and Figure 13.4 appear to indicate that a finer grind size produces better metal recovery.Figure 13.3 Effect of Primary Grind Size on Gold Recovery (2010 to 2011)Pretium Resources Inc. 13-14 1291990200-REP-R0012-02Feasibility Study and Technical Report on the BrucejackProject, Stewart, BC