Feasibility Study and Technical Report - Pretivm

In 2012 and 2013, most of the flotation tests were conducted at a natural slurry pH thatwas developed from the previous test programs. The tests that were conducted at anelevated pH (10.5) adjusted by lime with 3418A and A208 as collectors did not show asignificant influence of slurry pH on metal recoveries.The 2009 to 2010 test program investigated the effect of flotation reagents and slurrypH on metallurgical performance. Figure 13.8 shows the test results of the Bridge Zonecomposite sample. It appears that the reagents and slurry pH have an insignificant effecton gold recovery.Figure 13.8 Effect of Reagent and Slurry pH on Gold Recovery (2009 to 2010)Note:Test F27 was conducted at a higher pH; the other tests were conducted at a natural pH.CLEANER FLOTATION TEST WORKIn the early stages of the 2012 test program, a master composite labelled as CompositeBJ-A, was used to study the metallurgical responses to the cleaner flotation. Twodifferent cleaner procedures were tested: one procedure upgraded the rougher andscavenger concentrates separately after regrinding, and the other procedure upgradedthe combined rougher and scavenger concentrate. On average, both cleaner proceduresproduced similar results. Test results from the combined concentrate are shown inFigure 13.9 and Figure 13.10. The results indicate that upgrading efficiencies are goodfor gold and silver. Gold appears to have better cleaner efficiency than silver.Pretium Resources Inc. 13-18 1291990200-REP-R0012-02Feasibility Study and Technical Report on the BrucejackProject, Stewart, BC