Feasibility Study and Technical Report - Pretivm

• a belt conveyor, 914 mm wide by 97.7 m long, to feed the SAG mill feed surgebin• a mill feed surge bin with a live capacity of 2,500 t• four belt feeders, 920 mm wide by 6,25 m long• three local dust collection systems.Each of the crushed ore transfer points will be equipped with a dust collection system tocontrol fugitive dust that is generated while transporting the crushed material.PRIMARY GRINDING, CLASSIFICATION AND PRIMARY GRAVITY CONCENTRATIONA SAG mill/ball mill (SAB) circuit is proposed for primary grinding. The circuit will beequipped with a centrifugal gravity concentrator to recover gold/silver nugget grains thatare liberated or partially liberated from their host minerals.The primary grinding circuit will consist of a SAG mill and a ball mill in a closed circuit withclassifying hydrocyclones and a centrifugal gravity concentrator. Grinding will beconducted as a wet process at a nominal rate of 122 t/h of ore.The grinding/gravity concentration circuit will include:• one SAG mill, 5,790 mm diameter by 2,950 mm long (19 ft by 9.7 ft) (EGL),driven by a 1,300 kW variable frequency drive (VFD)• one ball mill, 3,960 mm diameter by 7,260 mm long (13 ft by 23.8 ft) (EGL),powered by a 1,600 kW fixed speed drive• two hydrocyclone feed slurry pumps• four 500 mm hydrocyclones• one centrifugal gravity concentrator• one particle size analyzer• one online sampler.The crushed ore from the surge bin will be reclaimed onto the belt conveyor that feedsthe ore to the SAG mill. The SAG mill will be equipped with 40 mm pebble ports todischarge the fine fraction from the SAG mill. The SAG mill discharge will be screened bya trommel screen that is integrated with the SAG mill. The trommel screen will have anopening of 9.5 mm (slot wide). The oversize from the trommel screen will be transportedby three 500 mm-wide belt conveyors back to the SAG mill feed conveyor. The screenundersize will discharge by gravity to the hydrocyclone feed pump box in the grindingcircuit.The ball mill will be operated in closed circuit with hydrocyclones and a centrifugal gravityconcentrator. The product from the ball mill will be discharged into the hydrocyclone feedpump box where the ball mill discharge will be combined with the SAG mill trommelscreen undersize slurry and the gravity concentration tailings. The blended slurry in thePretium Resources Inc. 17-7 1291990200-REP-R0012-02Feasibility Study and Technical Report on the BrucejackProject, Stewart, BC