Feasibility Study and Technical Report - Pretivm

EquipmentFeed toGravity(t/h)CirculationLoadTreated(%)ConcentratingCycle Time(min)GravityRecovery(% total Au)GravityConcentrate(kg/d)(g/t)XD30 80 21 20 48 2,520 9,796QS40 140 37 30 55 2,976 9,5282 x QS40 280 74 30 63 5,952 5,4082 x QS48 365 97 30 65 6,240 5,363Centrifugal gravity concentrate upgrading by acacia reactor, assuming gold is present as electrumXD20 40 11 15 39 1,920 10,490XD30 80 21 20 50 2,520 10,116QS40 140 37 30 57 2,976 9,8342 x QS40 280 74 30 65 5,952 5,5672 x QS48 365 97 30 67 6,240 5,511Centrifugal gravity concentrate upgrading by tabling, assuming gold is present as electrumXD20 40 11 15 32 1,920 8,451XD30 80 21 20 42 2,520 8,528QS40 140 37 30 49 2,976 8,5032 x QS40 280 74 30 57 5,952 4,9542 x QS48 365 97 30 60 6,240 4,956Met-Solve also conducted GRG and intensive leach tests, as well as gravity concentrationcircuit simulations to estimate the recoveries of gold and silver from the mineralization.Table 13.21 summarizes the test results, which show:• The sample had a high GRG value of 80.7%, which is in agreement with the testresults produced by Knelson.• The extractions from the centrifugal concentrates by intensive leach were 99.2%for gold and 92.2% for silver.• The intensive cyanide leach option on the gravity concentrate is predicted tohave better overall gold and silver recovery than the concentrate tablingprocess.Table 13.21Gravity Separation Test ResultsElementsHead GradeCalculated(g/t)Gravity ConcentrationThree- stage FalconRecovery (%)IntensiveCN LeachGravityUpgrading TableGold 18.7 80.7 99.2 61.1Silver 63 33.7 92.2 42.5Pretium Resources Inc. 13-29 1291990200-REP-R0012-02Feasibility Study and Technical Report on the BrucejackProject, Stewart, BC