The mineralization at Musselwhite can be classified as an Iron Formation hosted gold deposit. Typically, gold in these deposits occurs in cross-cutting quartz veins and veinlets or as fine disseminations associated with pyrite, pyrrhotite, and arsenopyrite hosted in iron formations and adjacent rocks within volcanic or sedimentary sequences (McMillan 1996).

Mesothermal veins.
Mineralization is predominantly hosted within meta-chemical sediments (banded iron formations) and in particular within garnet-magnetite-grunerite facies meta-banded iron formations (locally termed the Northern Iron Formation). The location of mineralization is controlled by the intersection of shear zones and folded meta-banded iron formations. These geological controls result in mineralized shoots, which plunge at approximately 15 degrees to grid north, have a down dip extent of up to 150 metres, down plunge continuation in excess of 1.5 kilometres, and across-lithology width of up to 10 metres. Mineralized zones are characterized by abundant pyrrhotite, quartz flooding and, rarely, visible gold.

The mine site consists of a potable water treatment plant, crushing plant, mill and tailings complex, tailings thickener facility, groundwater interception system, conveying system, shop/warehouse and other ancillary facilities.

The milling facility uses two-stage crushing to reduce the ore and conventional gold extraction techniques to concentrate the gold. The tailings or residue from this process is washed with incoming tailings reclaim water in thickeners to recover cyanide. Residual cyanide is treated by an INCO SO2 cyanide destruct system prior to being pumped to the tailings thickener plant (installed in 2010) which is located in the Tailings Management Area (TMA) approximately 3 km west of the plant site.

The use of cyanide begins with the grinding area, which uses re-circulated cyanide bearing solution from the counter current decantation (CCD) wash circuit as process water within the grinding mills, Knelson concentrators, Delkor linear screen and pump boxes. The grinding circuit classified product reports to the grinding thickener and thickened underflow slurry is pumped to the leaching circuit. After the slurry reports to the leaching circuit, the control system (via an automatic titrator) adds make-up cyanide to the first of four leach tanks using sodium cyanide solution at approx. 19 w/w%. In rare cases, operators also add make-up cyanide to “leach tank #3” as required. The leach pulp is transferred from tank to tank via gravity with approximately 7.5 hours retention per tank with 4 tanks in series. The purpose of these tanks is for the dissolution of gold. The leached pulp then flows to the carbon-in-pulp (CIP) circuit for gold adsorption using activated carbon. The CIP circuit utilizes six tanks with a nominal retention time of 0.8 hour per tank allowing the slurry to flow by gravity through in-tank or interstage agitated screens. The CIP tails report to an activated carbon safety screen and tails are pumped to the CCD thickeners for cyanide recovery. Interstage screens retain the activated carbon within the CIP tanks, which advances carbon counter current to the slurry via vertical pumps within the tanks, operating on an operator initiated timed basis. Loaded carbon from the first tank (CIP #1) is scalped from the slurry over a screen and forwarded to the elution circuit to remove the gold. This elution step produces a concentrated solution of gold that is sent to the electrowinning circuit for gold recovery. The barren solution from electrowinning is recycled for reuse in the elution circuit. There is however a small bleed of weak cyanide solution from the elution/electrowinning circuit to either the leach tank(s) or alternatively the CIP #4 tank.