Feasibility Study and Technical Report - Pretivm

Figure 13.4 Effect of Primary Grind Size on Silver Recovery (2010 to 2011)Gold and silver recoveries from the Galena Hill Zone sample and the West Zone samplewere higher than the Bridge Zone sample. At a grind size of 80% passing 143 µm, thegold recoveries of the Galena Hill Zone sample and the West Zone sample wereapproximately 97% and 95%, respectively.Silver recoveries are lower than gold recoveries for the Galena Hill Zone and the WestZone samples. However, for the Bridge Zone sample, the difference in gold and silverrecoveries is much smaller.The 2009 to 2010 test program investigated the relationship between metal recoveryand primary grind size as well. Figure 13.5 shows that gold recovery improves when theprimary grind size is finer than 70 µm. The improvement becomes much less significantat a grind size between 80% passing 70 µm and 80% passing 125 µm. The test resultsalso indicate that gold recovery increases with concentrate mass pull, in particular whenthe mass pull is less than 15 to 20%.Pretium Resources Inc. 13-15 1291990200-REP-R0012-02Feasibility Study and Technical Report on the BrucejackProject, Stewart, BC