Myra Falls zinccopper-gold (lead-silver) mineral deposits are comprised of complex metal-zoned Volcanic Hosted Massive Sulphide deposits. The principal sulphide minerals are sphalerite, pyrite and chalcopyrite with minor galena, bornite, and tennantite. Myra Falls mine produces copper, lead, zinc, and gold concentrates with silver in concentrate. There is strong geological continuity of the mineralization as demonstrated in the extensive diamond drilling and underground development.

Current underground mining methods utilized at Myra Falls depend on orebody geometry and include drift and fill, cut and fill, drift, and sublevel longhole open stoping. Some surface mining is still conducted within the Lynx open pit. Hydraulic backfilling uses pyritic mill cycloned tailings. Approximately 55% of the tailings are pumped underground for this purpose.

The mill and concentrator have a capacity of 1.4 M tonnes per year. At surface, the muck is transported by a 1.4 km long conveyor belt. This belt discharges into a 3,600 tonne coarse ore bin at the concentrator. Secondary and tertiary cone crushing and screening reduces the mill feed to less than 16 mm x 28 mm size. Two 3,500 tonne fine ore bins receive this crushed material.

The concentrator has two parallel grinding and rougher circuits, each capable of treating 2,000 tonnes per day. Rod mill discharge is pumped to a pair of Krebs D20LB cyclones. Cyclone underflow is ball mill feed and is 80% to 85% solids. Product from the grinding circuit is 75% to 80% passing –200 mesh. Cyclone underflow is then passed through a Knelson gold concentrator that recovers coarse free gold. Gold and silver recoveries are about 53% and 77% respectively.

The resultant mill slurry is then processed first by two Cu rougher flotation circuits producing a Cu final concentrate which repo ........