Feasibility Study and Technical Report - Pretivm

Based on the findings of the preliminary test work, Inspectorate conducted further testingusing a combination of flotation, gravity concentration, and cyanidation to recover goldand silver from the Brucejack mineralization. There were three different processcombinations:• primary grind, gravity concentration, rougher/scavenger flotation, and regrind onthe flotation concentrate, followed by cyanidation on the reground concentrate(Flowsheet A)• primary grind, rougher/scavenger flotation, regrind on the flotation concentrate,and gravity concentration on the reground concentrate, followed by cyanideleaching on gravity tailings (Flowsheet B)• primary grind, gravity concentration, rougher/scavenger flotation, regrind on theflotation concentrate, gravity concentration on the reground concentrate,followed by cyanide leaching on the gravity tailings, and intensive leaching onthe panning tailings (Flowsheet C).Test results for the three different process combinations are presented in Table 13.26 toTable 13.28.As shown in Table 13.26, the flotation and gravity concentration recovered approximately94% of the gold from the BZ sample, and 97% of the gold from the R8 and GH samples.The gold leach extraction rates from the flotation concentrates were higher than 91% forthe BZ and R8 samples. Compared to the other two samples, the GH sample showed alower gold cyanide extraction at approximately 84% on average.Table 13.26Test Results - Gravity Concentration, Flotation and Cyanide Leach CombinedFlowsheet (Flowsheet A) (2009 to 2010)Test ID/Sample IDPrimary Grind/Regrind SizesGrade (g/t) Recovery/Extraction * (%)Au Ag Au AgGF35/Composite BZGravity Concentrate P80 131 µm 685 428 17.0 4.4Flotation Concentrate - 18.6 45.2 77.1 77.3Leach on Flotation Concentrate P90