Overview -

Keywords   Canada   diamonds   open pit

The Diavik diamond mine is located about 300 km northeast of Yellowknife, Northwest Territory, Canada, and 30 km from the Ekati Mine. The mine consists of 4 kimberlite pipes beneath Lac de Gras. Dikes had to be built around the diamondiferous pipes to drain the water above them.

The open pit mine was commissioned in 2003 and reached full production in 2004. Underground production will begin in 2009, and will grow to replace open pit mining by 2012. The expected mine life is 16 to 22 years. Diavik is the most profitable mine in Canada.

The property consists of a total of 267,917 hectares (661,755 acres) of prospective lands surrounding the mine site which comprises five mining leases with a total area of 2,470.5 ha.

Ownership Summary  Name: Rio Tinto    Interest: 60%    Note: public  Name: Harry Winston Diamond Corporation    Interest: 40%    Note: public Reference: 14 Mar 2008

Total employment is 700. Employees work two week rotation on a fly in / fly out basis.

Diavik is an unincorporated joint venture between Rio Tinto (60%) and Harry Winston (40%).

Location - The Diavik Diamond Mine is located on a 20 square kilometre island, informally called East Island, in Lac de Gras, approximately 300 kilometres by air northeast of Yellowknife, capital of Canada's Northwest Territories. The Arctic Circle is located 220 kilometres north of the mine.

In winter an ice road is operated jointly by a number of mines. From February to April and during this period all the heavy hauling is done.

Aboriginal people named the lake for quartz veins resembling caribou fat. Lac de Gras is 60 kilometres long, and averages 16 kilometres wide. The lake averages 12 metres deep, and has a maximum depth of 56 metres. Aquatic productivity is low due to low nutrients, low light during winter, eight months of ice, and low water temperatures. Lac de Gras has a 4,000 square kilometre drainage area. The headwaters of the Coppermine River flowing 520 kilometres from western Lac de Gras to the Arctic Ocean.

The mine is surrounded by rolling tundra. The area has numerous lakes, bedrock outcrops and glacial deposits of boulders, till, and eskers. Permafrost occurs within 1-2 metres of the surface. Vegetation includes dwarf birch, northern Labrador tea, blueberry, mountain cranberry, and bearberry, with willow, sphagnum moss, and sedge tussocks dominating wet lowlands.

Lac de Gras contains lake trout, cisco, whitefish, arctic grayling, burbot, longnose sucker, and slimy sculpin are among fish species.

Location Summary Nearest Landmark: YELLOWKNIFE Distance from Landmark: 300km Direction from Landmark: NE Latitude: 64 deg 30 min N Longitude: 110 deg 20 min W Satellite Image: <click to view>

Animals in the region include, grizzly bears, wolves, foxes, arctic hare, ground squirrels, and wolverines. In spring and fall, portions of the Bathurst caribou herd migrate through the region. There are 84 bird species and 16 mammal species as migrant or permanent residents.

Temperatures range from an average of 10°C in July to -31°C in January. There are 22 hours of daylight per day in June and 2 hours a day in December.

Property - The Diavik Diamond Mine was discovered in Precambrian rocks of the Slave Geological Province. Known to host deposits of gold, copper, zinc, nickel, and now diamonds, this ancient rock is among the world's oldest and was formed about 2.7 to 2.5 billion years ago. The Slave Geological Province has produced much of the North's mineral wealth.

Granitic rocks predominantly underlie the area, and have been intruded into slightly older meta-sedimentary rocks, originally deposited as sandstone and shale.

Pleistocene continental glaciation and retreat has left a thin, discontinuous mantle of sandy and bouldery basal and ablation tills and ice contact deposits such as eskers in the area.

Reserves Summary Name: Diavik Commodity: Diamond Class: Proven + Probable Tonnage: 21.9 Mt Grade: 3.5 carats/t Note: containing 77.1 million carats Reference: 31 dec 07

Kimberlites were formed by volcanic surface eruptions and near surface injections of kimberlite magma and volcaniclastic debris into the granitic country rocks and into mid Cretaceous to Tertiary mudstones that once covered the Archean basement. The kimberlite pipes at the Diavik Diamond Mine are volcanic cores injected into the much older, granitic and meta-sedimentary rocks a mere 55 million years ago.

Relatively fresh, often charred -- but not petrified -- wood that is found only in China today, has been encountered in drill core at depths up to 400 metres. Reflecting a much warmer climate at that time, the coniferous trees were uprooted and incorporated into the pipes by the tremendous force of the explosion that brought diamondiferous magma to the surface.

Deposit Summary Deposit Type: Kimberlite pipe Primary Commodity: Diamond

Diavik has located 64 kimberlites of which four were considered part of the initial feasibility study: A-154 South, A-154 North, A-418 and A-21. The company's mineral holdings cover nearly 240,000 hectares.

Operation - Diavik's mine plan includes mining of three diamond-bearing ore bodies commonly called kimberlite pipes. A combination of open pit and underground mining methods will be used. Underground production will begin in 2009, and will grow to replace open pit mining by 2012. The underground mining will use a combination of underhand cut-and-fill mining and blast-hole stoping depending on the rock stability encountered in actual production. Ore processing is expected to be approximately 2 million tonnes annually.

Diavik's mining equipment includes:

11 - Komatsu 830E haul trucks, each with a 218 tonne payload
2 - Hitachi EX 3600 excavators, each with a 20m3 bucket and a 35 tonne payload
1 - LeTourneau front-end loader, with a 20m3 bucket and a 35 tonne payload

Mine Production Summary  Mine - Diavik    Capacity: Not Known     Rate: Not Known  Reference: 31 December 2007

3 - D75EX Driltech blasthole drills
4 - Komatsu HD785 haul trucks, each with a 90 tonne payload

Assorted support equipment includes:

5 bulldozers, 1 wheeldozer, 2 graders, 1 backhoe, and 2 loaders.

Process - At full capacity, the mine is expected to process approximately 2 million tonnes of kimberlite ore annually.

Separating diamonds from waste rock is a non-chemical, largely gravity-based process. A loader adjacent to the processing plan feeds stockpiled ore into the run-of-mine building. Ore is crushed, scrubbed, and screened to the desired fraction, which is material larger than one millimetre and smaller than 25 millimetres.

Ore is processed through various circuits within the plant. Material is mixed with ferrosilicon -- a fine-grained, heavy, magnetic sand -- and pumped through cyclones to create a heavy mineral concentrate.

Waste kimberlite goes to the processed kimberlite containment area for permanent storage. Heavy mineral concentrate, which contains diamond, garnet, diopside, olivine and spinel, is conveyed to the recovery process. Ferrosilicone and water are recycled.

Processing Summary  Facility - Diavik    Capacity: 2.0 Mt/y    Rate: 1.95 Mt/y  Product    Commodity: Diamond    Quantity: 11.9 Mcts    Cost: Unknown     Note: 2007 production Reference: 31 December 2007

In the recovery building, diamonds are separated from waste minerals using X-rays. Diamonds fluoresce under this kind of light, and photo-electric sensors direct strategically placed air blasts to blow the diamonds off the conveyor belt into diamond collection receptacles.

Diamonds are shipped to the Diavik product splitting facility in Yellowknife. They are cleaned, divided between the joint venture partners, and undergo government royalty evaluation.

Environment and Community -

Diavik has achieved ISO 14001 certification for its environmental management system. Key elements are protection of wildlife, especially caribou, and protection of water and fish habitat.

When the mine closes the dikes surrounding the mine will be opened and the lake will be as it was before mining.

On an ongoing basis rock piles are created to replicate the landforms that existed before mining.

Diavik has committed to 66% northern employment and 40% aboriginal employment.