Feasibility Study and Technical Report - Pretivm

Year Program ID Laboratory ** Gravity Flotation Grindability Cyanidation Others2010-2011 1004608 Inspectorate √ √ √ √ -2009-2010 0906609 Inspectorate √ √ √ √ -Before 1990 * - Various √ √ √ √ √Notes:*From Feasibility Study Sulphurets Property by CESL**Hazen = Hazen Research Inc.; Inspectorate = Exploration & Metallurgical Testing InspectorateAmerica Corporation; Met-Solve = Met-Solve Laboratories Inc.; Knelson = FLSmidth Knelson;Pocock = Pocock Industrial Inc.; JZM = Joe Zhou Mineralogy Ltd.13.2 HISTORICAL TEST WORKHistorical test work used composite samples collected from the West Zone and the R8Zone. The feasibility study prepared in 1990 indicated that the Brucejack mineralizationconsists of apparently erratic veins and lenses containing metallic gold (native gold) andmetallic silver (native silver), together with a variety of sulphide minerals in a quartz-richenvironment, within a zone of altered volcanic rocks . Gold occurs as a range of relativelycoarse grains (40 to 100 µm) to fine grains (less than 40 µm) locked in either pyrite orquartz gangue. Silver occurs in small amounts in metallic form, while most silver isintimately associated with, or a component of, various sulphide minerals. The majorminerals in the samples are listed in Table 13.2.Table 13.2MineralMineralogical AssessmentContent(%)Pyrite 9.7Sphalerite 0.5Tetrahedrite 0.1Jalpaite 0.1Ruby Silver 0.05Galena 0.05ChalcopyriteNative GoldNative SilverTraceTraceTraceGangues 89.5Source: CESL (1990)Metallurgical testing included gravity separation, flotation, cyanidation, and roasting pretreatment.The test work indicated that gravity separation would recover a significant portion of thecontained gold. Cyanide leaching on the gravity tailings produced good overall goldrecoveries, but poor silver recoveries (less than 40%). As reported in the 1990 feasibilitystudy, it was indicated that the poor silver recoveries were attributed to the silveroccurrence in the form of relatively insoluble silver sulphides such as tetrahedrite andproustite.Pretium Resources Inc. 13-2 1291990200-REP-R0012-02Feasibility Study and Technical Report on the BrucejackProject, Stewart, BC