Mining

Access to LaRonde’s underground mining operation is through the 2.2-kilometre-deep Penna Shaft, believed to be the deepest single-lift shaft in the Western Hemisphere.

Since 2006, we have been sinking an 835-metre internal shaft (Shaft No.4) just 50 metres from the Penna Shaft to access deeper ore, as part of the LaRonde Extension project.

Two mining methods are used – longitudinal retreat with cemented backfill, and transverse open stoping with cemented and unconsolidated backfill. Daily tonnages come from various mining horizons between 98 level and 242 level, with more than 40% from below 215 level (more than 2 kilometres below surface).

Processing

The LaRonde processing plant has a daily capacity of 7,200 tonnes of ore, and has been expanded five times since it opened in 1988. In 1999, several modifications were made including the addition of a new coarse ore handling system, a new semi-autogenous (SAG) grinding mill, and a zinc flotation circuit, and capacity increases to the copper flotation and precious metals circuits.

Since 2008, gold-bearing sulphide concentrate from the Goldex mine has been trucked to LaRonde for treatment in a dedicated, 150-tonne-per-day cyanidation facility. The treated concentrate is then processed through LaRonde’s existing Merrill-Crowe circuit, and the recovered gold is consolidated with precious metals from the LaRonde mine.

A 1,500-tonne-per-day processing facility dedicated to treating the ore trucked from the nearby Lapa mine began operation in 2009. The concentrates from Lapa’s gravity and leach circuits are sent to the LaRonde refinery to produce doré bars.

A biological water treatment plant was put into service in 2004 to address the build-up of thiocyanate which was causing toxicity problems in the tailings ponds at LaRonde. This was the result of the high sulphide content of the LaRonde ore and 90% recirculation of the process water. The plant uses bacteria to oxidize and destroy thiocyanate, and removes phosphate from the water before it is released to the environment. After a series of adjustments, the effluent has remained non-toxic since 2006.