Mining is carried out using conventional open pit techniques with a carbon-in-pulp processing plant. There are currently five open pits. The main pit oxide resource recently completed mining however mining is currently occurring in the satellite orebodies FE3 and FE4 southeast of the main pit.
The pit slopes have been engineered to industry standards of stability for the range of lithologies present at Sadiola, following risk management principles. Grade control is effected by drilling 10 metre long vertical holes on a 10 metre by 5 metre grid. Ore is transported to the ore stockpile located one kilometre from the pit and waste is disposed of in dumps adjacent to the pit.
Approximately 90% of ore is stockpiled before processing. The ore stockpiling facility is located between the pit and the process plant and its purpose is twofold. Primarily, the area allows stockpiles of ore with differing oxide and sulphide mineralogy, gold grades, hardness, viscosity levels to be laid down separately. Ore is reclaimed from the stockpiles and fed into the process plant on a blended basis contributing to the efficiency of the process plant and maximising gold recovery. The second function of the stockpile is to provide a reserve of ore to sustain feed when pit operations are affected by external factors such as heavy rains.
Most of the ore is delivered from the pit to a stockpile/reclaim area, adjacent to the processing plant site. The ore blend is reclaimed from the stockpile and fed to two parallel mineral sizers, a type of crusher designed to handle the softer ores that are found at the Sadiola Gold Mine. The ore passes to surge bins located ahead of the two SAG mills. A single regrind mill is incorporated, serving both circuits, to further grind the coarse fraction contained in the output from the SAG mills.
The discharge from the mills is fed to cyclones, the overflow from which goes to the leach circuit where the pulp is subject to cyanide leaching while the underflow goes to the regrind mills. Following leaching, the pulp is fed to CIP adsorption tanks where the gold is absorbed onto activated carbon. This ‘‘loaded’’ carbon is stripped of its gold and the gold bearing solution is pumped to storage tanks. The stripped carbon is regenerated in an oil fired kiln and then reused. After leaching, the barren slurry after removal of the gold is pumped to the tailings dam 3 kilometres southeast of the process plant for final disposal. The gold is recovered from the solution by electroplating onto stainless steel wool cathodes. The cathodes are washed and the gold bearing sludge dried and placed in an induction furnace for smelting to produce gold bullion.
In 2002, the Sadiola plant was modified to increase the recovery on the sulphidic saprolite ore from approximately 65% to 75%. In 2008 a gravity circuit was commissioned to treat a portion of the cyclone underflow in the grinding circuit. The circuit has allowed for improved recovery on high grade oxide ores from the satellite pits that contain a significant coarser “nuggety” gold fraction.