Written on December 3, 2013 at 8:00 pm, by Scott
|Commodity||Zinc, Copper, Lead, Gold, Silver|
|Location||British Columbia, Canada
Nearest Landmark: CAMPBELL RIVER
Distance: 90 Km SW from the nearest Landmark
Latitude: 49° 35′ (North)
Longitude: 125° 36′ (West)
|Owners||Nyrstar – 100%|
|Production||15 kt zinc, 1.6 kt copper, 0.4 kt lead, 5.1 koz gold, 220 koz silver in concentrate (2011)|
|Deposit Type||Volcanogenic hosted massive sulphide (VHMS|
|Reserves & Resources||N.A.|
|Mining Method||Drift and fill|
|Processing Method||Grinding, gravity separation, flotation|
|Mine Life||To 2012|
|Mining Equipment||Electric-hydraulic jumbos, diesel powered scoop trams|
|Processing equipment||Underground crusher, Ball & rod mills, Outokumpu OK8 flotation cells, 7 ft. diameter
column cells (2), Larox pressure filters, Knelson gravity circuit
|Contact Information||c/o Spit Rd
P.O. Box 8000
Campbell River, British Columbia
Canada V9W 5E2Phone:+ (250) 287-9271
Fax:+ (250) 287-7123
|Last updated: July 9, 2012|
Myra Falls is an underground zinc mine located in Strathcona – Westmin Provincial Park on Vancouver Island, British Columbia, Canada. The property consists of claims, mining leases, and 23 crown granted claims, covering 3,629 hectares. The H-W and Lynx orebodies are part of the property.
Operations consist of 2 underground mines: the H-W mine and the Battle mine and are located approximately 1.8 km NW of the H-W mine. The original Myra Falls mill was constructed in 1966. The H-W mine commenced production in 1985 and a new mill was built at that time.
Mining operations are carried out using bulk-mining methods. A single production shaft at the 700 m level services both mines. Ore is processed through a modern 4,000 tpd mill facility. Zinc and copper/precious metals concentrates which are transported 90 km by truck to the port at Campbell River on the east coast of Vancouver Island for shipment overseas.
Myra Falls is an underground mining operation that produces zinc, copper, gold and silver. The mine occupies 3,600 hectares of land on the surface. However, underground there are more than 240km in drifts, shafts and stopes between the two separate mines.
Myra Falls is located within Strathcona – Westmin Provincial Park on Vancouver Island, British Columbia, Canada in an area designated with a Class B park status. The various ecosystems within the park support many large mammals, birds and amphibians as well as spawning beds for trout and char. Although the mine controls 3,600 hectares (36 square km) of land, it impacts only 170 hectares (1.7 square km) and obeys current regulations that are in place to protect the park and minimize the operation’s impact.
Geology & Mineralization
Volcanic hosted massive sulfide (VHMS) deposits on Vancouver Island, including those at Myra Falls, are hosted by ancient island arc systems of the Paleozoic Sicker Group. The Sicker Group is exposed on Vancouver Island in several fault-bounded uplifts. At Myra Falls, the Devonian to Mississippian aged Sicker Group volcanic rocks are conformably overlain by limestone of the Permian aged Buttle Lake Formation. In order of decreasing age, the Sicker Group comprises the basement Price Formation andesite, Myra Formation felsic to mafic volcanic rocks, Thelwood Formation mafic fine-grained volcaniclastic rocks, Flower Ridge Formation mafic breccias and sills, and Buttle Lake limestone. Sulfide mineralogy at Myra Falls is typical of most VHMS deposits. The common sulfide minerals present in order of decreasing abundance are pyrite, sphalerite, chalcopyrite, and galena. Less common sulfides are pyrrhotite, arsenopyrite and the copper-rich sulfides bornite, renierite, and anilite. The VHMS deposits are hosted by the Myra Formation and are associated with two rhyolite horizons, the atdepth H-W Horizon and the near-surface Lynx-Myra-Price (L-M-P) Horizon.
Mining & Operation
Electric-hydraulic jumbos bore holes into the rock for blasting, which is done every day, producing 360 tonnes of ore. Muck is removed by diesel powered scoop trams and hauled to an underground crusher. After crushing, the ore is hoisted to the surface. There, it is moved on conveyor belts another 1km to the mill.
The mine does not have a waste rock dump as the mined waste rock is left in the underground.
The crushed ore enters the mill where it enters one of several ball and rod mills that grind it with water into sand size particles. The slurry is piped to froth flotation cells which produce separate copper and zinc concentrates. The mill, which was built in 1985, processes 1.4 million tons of ore every year. In 1992 a gravity circuit that used a BC-made Knelson concentrator was added to the mill to better recover the gold.
The Myra Falls concentrator is a fully automated plant. The rod mill/ ball mill circuit has a capacity of 4,000 tpd milling capacity. The flotation circuit uses Outokumpu OK8 flotation cells and two 7 ft. diameter column cells. Concentrate is filtered with Larox pressure filters. The plant produces copper, zinc and gold concentrate.
Coarser tailings are mixed with cement and pumped back in the mine being used to back-fill the mined out mining works. In 2012, the company developed a formal tailings storage facility closure plan as it had reached capacity.
Other facilities include a headframe and hoist building which houses compressors, a hydraulic backfill plant, and concentrate loadout facility in Campbell River.
Myra Falls uses a series of six special settling ponds, called polishing ponds, to clarify and purify the water that comes from the mine, mill, and the tailings pond. These waters contain dissolved metals and mill reagents, and are acidic. Sensors detect the pH level and help the environmental engineers decide how much lime or CO2 to add to the water.
Flocculating agents are added to cause the solids to settle out. Floating pumps move this solid material, or sludge, out of the ponds into the tailings area, leaving the water neutral and cleaner than before. It is tested daily to ensure it is safe for fish and fish habitat before being released into the environment. Most of the water, however, is pumped back into the mill to be used again.
Lime and flocculating agents are added to produce clear, clean and neutral water, which is tested daily for toxicity to ensure it is safe for fish and fish habitat before it is released into the environment.
On a daily basis, copper and zinc concentrates are trucked 90km to the company’s Discovery Terminal, a deep-sea port in Campbell River. The terminal has a storage capacity of 40,000 mt and ship loading capacity of 500 mt/hr. Once a month concentrate is shipped overseas to smelters in Japan and Korea.
Environment & Community
The Myra Falls mine is relatively unique in that it is surrounded by a Class A park and the boundary of its mineral claims fall entirely within the Strathcona-Westmin Class B Park. All mining activities, and the eventual reclamation and rehabilitation of the site, fall under a park-use permit. Constant monitoring ensures that environmental concerns and public safety are an integral part of the continuing mine program. It is interesting to note that not only are recreational activities not impeded by mining activities, but mine tours have become an important attraction for park visitors.
Myra Falls is currently conducting trials on soil cover systems to prevent future acid rock drainage from their ponds and old waste rock dumps. So far, the best material for the job is one made from a mixture of mine tailings and the sludge from their polishing ponds.