Feasibility Study and Technical Report - Pretivm

Table 1.2West Zone Mineral Resource Estimated Based on a Cut‐off Grade of 5 g/tAuEq – April 2012 (1)(4)(5)CategoryTonnes(Mt)Gold(g/t)Silver(g/t)Contained (3)Gold(Moz)Silver(Moz)Measured 2.4 5.85 347 0.5 26.8Indicated 2.5 5.86 190 0.5 15.1M+I 4.9 5.85 267 0.9 41.9Inferred (2) 4.0 6.44 82 0.8 10.6Note: (1), (2), (3), and (4) See footnotes to Table 1.1.1.5 MINERAL PROCESSING AND METALLURGICAL TESTING1.5.1 METALLURGICAL TESTINGSeveral metallurgical test programs were carried out to investigate the metallurgicalperformance of the mineralization. The main test work was completed from 2009 toearly 2013. The samples tested were generated from various drilling programs. Themetallurgical test programs conducted on the Brucejack mineralization included headsample characteristics, gravity concentration, gold/silver bulk flotation, cyanidation andthe determination of various process related parameters. The early test work focused ondeveloping the flowsheet for gravity concentration, bulk flotation, and flotationconcentrate cyanidation. The test work also studied the metallurgical responses of thesamples to the gravity concentration flowsheet for gravity concentration followed bywhole ore leaching. The later test work concentrated on the gravity-flotationconcentration flowsheet.In general, the VOK Zone and West Zone mineralization is moderately hard. The mineralsamples tested responded well to the conventional combined gravity and flotationflowsheet. The gold in the mineralization was amenable to centrifugal gravityconcentration. On average, 40 to 50% of the gold in the samples were recovered by thegravity concentration. The flotation tests results indicated that bulk flotation caneffectively recover the gold remained in the gravity concentration tailings usingpotassium amyl xanthate (PAX) as a collector at the natural pH. Two stages of cleanerflotation would significantly upgrade rougher flotation concentrate. The gold in themineralization showed better metallurgical performance, compared to silver. On average,approximately 96 to 97% of the gold and 91 to 92% of the silver were recovered to thegravity concentrate and bulk flotation concentrate at the grind size of 80% passingapproximately 70 to 80 µm. There was a significant variation in metallurgicalperformances among the samples tested. This may be a result of the nugget gold effect.Cyanide leach tests were also conducted to investigate the gold and silver extractionsfrom various samples, including head samples, flotation concentrates, flotation tailingsand gravity concentrates. In general, most of the sample responded reasonably well todirect cyanidation, excluding a few of samples containing higher contents of graphitePretium Resources Inc. 1-6 1291990200-REP-R0012-02Feasibility Study and Technical Report on the BrucejackProject, Stewart, BC