Feasibility Study and Technical Report - Pretivm

The dried tabling concentrate will be calcined and then mixed with flux, which consists ofborax (Na2B4O2), sodium nitrate (NaNO3), silica (SiO2), and fluorspar (CaF2). Theconcentrate and flux mixture will be charged into a 175 kW induction furnace and meltedat approximately 1,150°C. The metal melt and slag will be poured into bar molds in acascade-casting arrangement. The gold doré will be weighed, sampled, and stored in thevault prior to being shipped to refiners.The slag from the melting will be crushed by a jaw crusher and ground by a rod mill on abatch basis. The ground slag will be pumped to the fine gravity concentrate stock binand tabled to recover gold-silver alloy grains entrained in the slag. The table tailings willbe sent to the concentrate thickener to be blended with the flotation concentrate.A wet scrubbing system will be installed for ventilating and cleaning the off-gas generatedduring the drying, calcination, mixing, melting, and slag crushing operations. Theequipment used for these processes will be equipped with hooks. Sufficient ventilationwill be provided in the gold room to protect the operators. All clothes, gloves, and othersafety equipment necessary for high-temperature protection, will be provided to theoperators working in the secure area.CONCENTRATE HANDLINGThe concentrate from the third cleaner flotation will be thickened, filtered, and baggedprior to being transported to off-site smelter(s). The concentrate handling facility willhave the following equipment:• one 5 m diameter high-rate thickener• two slurry pumps• one concentrate filter feed stock tank (4,000 mm diameter by 5,000 mm high)• one 75 m 2 pressure filter• one bagging system.The final flotation concentrate will be pumped to the concentrate thickener. Flocculantwill be added to the thickener feed well to aid the settling process. The thickenedconcentrate will be pumped to the concentrate stock tank. The underflow density of thethickener will be approximately 65% solids. The concentrate stock tank will be anagitated tank, which serves as the feed tank for the concentrate filter. A plate-frame typepress filter will be used for further concentrate dewatering. The filter press will reducethe moisture content of the thickener underflow to approximately 10 to 12%. The filterpress solids will be discharged onto a conveyor that transports the filter cake to thebagging system feed surge bin. The filter cake will then be bagged in 2 t bags andstacked prior to being loaded into containers for shipping. The bagged concentrate willbe transported by Tracked Vehicles to the Knipple Transfer Station, then to Terrace, BC,where the concentrate will be transported in bulk by rail to a smelter in eastern Canada.The plant will provide sufficient on-site storage capacity for up to 10 days of production inthe event of unexpected transportation disruption. Additional secured storage will alsobe provided at the Knipple Transfer Station.Pretium Resources Inc. 17-11 1291990200-REP-R0012-02Feasibility Study and Technical Report on the BrucejackProject, Stewart, BC