The Snap Lake diamond mine covers an area of 500 ha and is located some 220 km northeast of Yellowknife in Northwest Territories, Canada.
In 1995, Winspear Resources Ltd began its regional diamond exploration program and succeeded to discover a diamondiferous kimberlitic dike in 1997. De Beers bought the company in 2000 and continued work to further study and delineate the deposit.
Snap Lake is the first completely underground Canadian diamond mine and at the same time it is the first De Beers mine located outside of Africa.
The remote diamond mine is supplied by means of a winter road in February and March and by air all year round.
The deposit consists of a northwest striking 2.7 m thick diamondiferous kimberlite dike, which dips approximately 15° to the east and underlies part of the Snap Lake. The underground mine employs a modified room and pillar mining method. Low profile trackless equipment is used to access small underground spaces. The ore is crushed underground and conveyed to an on-site process plant.
Diamonds are sorted and then a value is assigned to them at De Beers Yellowknife valuation facility. They are subsequently shipped to London for final sorting and sale by De Beers' sales and distribution arm: the Diamond Trading Company (DTC).
The mine reached commercial production in early 2008 with planned full production capacity of 3,150 tpd. At an average recoverable ore grade of 1.2 cpt it is expected to produce about 1.4 million carats per year.
The mine was officially opened on July 25, 2008. Mine life is estimated to be close to 20 years.
The Canadian Arctic region situated above the boreal tree line is often referred as the Barrenlands or the Arctic tundra. Frozen soil or permafrost prevents tree growth and favors low growing plants such as lichens, moss and heath. The soil is frozen for most of the year because of harsh and windy winter conditions (minus 28 to minus 50 degree Celsius). During the short summer season the top layer of soil melts creating bogs and marshes. Caribou, bears, musk ox, foxes and hares populate these Arctic lands.
Up to 20 hours of light per day are expected over the summer which is in stark contrast with the thick continuous dark that lays down over everything during the frigid winter months, a time when Northern Lights (Aurora Borealis) put up a free celestial show.
The 1991 discovery of diamonds in Northwest Territories triggered the greatest mineral staking rush in the Canadian history. The Ekati and Diavik diamond mines were the first diamond mines to be opened in the territory.
The newer Snap Lake diamond mine is located 220 km northeast of Yellowknife, the capital city of the territory. For 6 to 8 weeks per year the site is accessible via an ice road from Yellowknife. The road is open mostly during the months of February and March. In 2006, the Canadian Arctic experienced one of the warmest winters on record which cut the ice road season short and made necessary for materials and supplies to be delivered by air. The site boasts an all-year round airstrips able to accommodate big transport planes - Boeing 737 and Hercules C-130.
Geology & Mineralization
The Snap Lake claims are situated in the southern part of the Archean Slave Province and are underlain by turbiditic meta-sedimentary rocks of the Yellowknife Group intruded by granitic rocks of Archean age. These rocks were subsequently cut by major Proterozoic faults and diabase dikes.
The region is dominated by the Snap-Crackle system (a series of faults trending east-northeast), which is possibly correlated with another important fault system: the Camsell Lake - Enemy Lake system.
The Snap Lake deposit is characterized by a series of sub parallel diamondiferous kimberlite sheets/dikes that are continuous and shallow dipping. Their emplacement is considered to have been controlled by the presence of a series of stacked low angle pre-existent faults that provided planes of weaknesses for the low on volatiles and water kimberlitic melt.
The deposit consists of a NW striking kimberlite dike which dips approximately 15° to the east and underlies the NW peninsula of Snap Lake, part of the lake and on the north shore of Snap Lake. The true thickness of the dike is approximately 2.7 m. The dike remains open down-dip and in both directions along strike however kimberlite intersections in the north part of the dike range from 0.2 - 0.8 m in thickness.
The 2005 opening of the Yellowknife-Snap Lake winter road marked the beginning of the construction for the $975 million underground mining project.
Mining is done by using a modified room and pillar method. Some paste and fill operations will also be done to better control ground movement and to allow remnant mining of pillars.
Detailed orebody delineation is carried out by using a hardrock borehole radar surveying system provided by GeoMole.
Because of the flat lying low dipping and relatively thin ore body mining has to deal with small spaces that are also characterized by low overhead clearance. These facts obliged De Beers to use a fleet of low profile trackless mining equipment in addition to regular light vehicles.
Other equipment used in the underground includes jumbo drills, scoops and mechanized roof bolters.
Ore is hauled to an underground high pressure roll crusher; the resulting crushed kimberlites are conveyed to surface through a special dedicated tunnel.
The mine commenced full scale production in 2007 and it is expected to produce 1.1 million tones per year at a recoverable grade of 1.2 carats per tonne.
Mine life was estimated at about 20 years.
The 1.1 Mt/y plant separates waste from diamonds by employing an already classic gravitational process and very few chemicals.
The crushed ore is scrubbed and screened to the desired fraction prior of being mixed with ferrosilicon and pumped through cyclones to create a heavy mineral concentrate. Water and ferrosilicon are recovered and recycled.
The heavy mineral concentrate contains diamonds that are automatically separated from waste by using X-ray systems that are part of the recovery modules.
Part of the processed rock is being dewatered, mixed with cement and pumped back in the underground where it will fill mining voids. Tailings would be deposited in the North Pile containment area.
Process plant diamonds are sorted first and then shipped to company's Yellowknife valuation facility where they are valued for royalty purposes.
As a result of a 2004 agreement with the local government De Beers will provide 10% of diamond production by value to local cutters and polishers. The rest of the diamonds are being sent to London to De Beers' Diamond Trading Company, its international sales and distribution arm.
The plant began recovering diamonds in August 2007 is envisaged to recover some 1.4 million carats per year.
Environment & Community
The mine site's location in the middle of the Canadian Barren Land, far and away from any human settlement, combined with the fact that mining is taking place underground - Snap Lake didn't have to be drained - and the fact that diamond processing is an environmentally friendly process is definitely going to minimize its environmental footprint.
A comprehensive EIA has been approved by the government and local communities - e.g. caribou migration it is not to be impeded by road construction or mining operations.
At Snap Lake, De Beers has in place an important Environment Management Policy, and most important ongoing monitoring and regular independent audits are taking place on a regular basis. These have already won the company a cherished ISO 14001 certification for its environment stewardship during the planning and construction of the mine.
De Beers also ratified an environmental agreement with the local and federal governments and major local Aboriginal communities to establish the Snap Lake Environmental Monitoring Agency. The agency involves local communities in monitoring the company's environmental performance.
In full operation the mine will employ about 560 workers of which 260 will be working on site at any given time on a two-week rotations schedule. All efforts have been made to make sure that 60% of the workforce is represented by Northwestern Territory residents.
Different agreements have been signed with the local government and Aboriginal groups all having the purpose of making sure that the local population will derive benefits from mining operations - training, employment, business opportunities and financial benefits.