Mining
Goldex uses an innovative but simple, high-volume bulk mining method. There are three large, contiguous stopes, which are mined via longhole open stoping techniques. The stopes are blasted from Level 76 (760 metres below surface) upward, with the broken ore (muck) drawn out from Level 76. An underground crusher on Level 77 reduces the ore size before it is hoisted to surface in Shaft No.2. Extraction, underground crushing and hoisting average 6,900 tonnes per day, and will increase to 8,000 tonnes per day by late 2011. The mining method requires that the majority of the muck be temporarily left in the stopes to avoid the cost of backfilling, while reducing dilution due to sloughing of the walls. Production blasting is expected to be completed in 2012, while the broken ore will be extracted through 2017. All the muck will eventually be removed and processed, leaving the stopes empty.
Processing
Goldex processing facilities include grinding, a gravity circuit to recover coarse gold, sulphide flotation and a concentrate-handling facility.
The two-stage grinding circuit comprises a semi-autogenous grinding (SAG) mill and a ball mill. The grinding target is to reduce 80% of the ore to a diameter of 106 microns or less. Most of the ground ore is fed to the gravity circuit which recovers about two-thirds of the gold, which is then smelted on site to form doré bars. Flotation recovers the remainder, producing a gold-bearing pyrite concentrate.
The pyrite concentrate is thickened and trucked to LaRonde. There the concentrate is fed to a dedicated cyanide leach circuit, producing a gold-bearing pregnant solution. This joins the stream of similar material from LaRonde ore and is processed through the Merrill-Crowe circuit in the LaRonde plant to recover precious metals, which are smelted into doré bars.
An average gold recovery of 92.1% is targeted for the Goldex ore.
The pyrite concentrate tails from Goldex are disposed of with the LaRonde tails.
Goldex Mine Milling Flowsheet