Ekati Diamond Mine, Northwest Territories, Canada

Ekati diamond mine, near Lac de Gras in Canada’s Northwest Territories, is about 300km north east of Yellowknife. It is a joint venture between BHP Billiton Diamonds Inc (80%) and geologists Charles E Fipke and Dr Stewart E Blusson (10% each), BHP Billiton having bought out Dia Met Minerals’ holding in mid-2001.

A 500km seasonal ice road is rebuilt every year by Robinson's Trucking to supply the northern mining operations, including Ekati. The only other transport is by air from Yellowknife.

GEOLOGY AND RESERVES

Lac de Gras kimberlites are similar to those of South Africa and Russia, with all the kimberlite pipes being overlain by small lakes.

As of mid-2000, Ekati had proven and probable reserves of 60.3Mt at 0.9ct/t. By mid-2003, reserve addition through exploration had virtually equalled production to date, with reserves standing at 59.0Mt grading 1.0ct/t. As of end-2005, the measured open cut resource at Ekati (core and buffer) stood at 42.5Mt grading 0.8ct/t; the S/P resources at 2.6Mt with 2.6ct/t and underground ore at 6.8Mt at 1.5ct/t. The proved core reserves were 16.5Mt (0.4ct/t) open cut, 2.7Mt (1.4ct/t) S/P, and 3.4Mt (1.0ct/t) underground ore.

MINE PLAN

To date, 150 kimberlite bodies have been discovered within the project's concession area, although most of these do not carry economic diamond concentrations. The current mining plan is focusing on open-pit mining from the Panda, Koala, Fox, Beartooth, Pigeon, Sable and Misery orebodies, with subsequent underground production from Panda and Koala. The project is expected to have a life of 25 years or beyond.

Open-pit mining started on the Panda pipe and Koala, Misery and Fox have subsequently been developed sequentially. Each lake is being drained and shovel-and-truck, open-pit mining developed, with some 35–40Mt/y of waste rock being excavated from the pits. The ore feeds a central 18,000t/d-capacity processing plant. The 3.4km Panda Diversion Channel diverts water around the Panda and Koala Lakes into Kodiak Lake.

Mining equipment includes four Driltech D90KS blasthole drills, two Demag H655SO diesel-hydraulic shovels, ten Caterpillar D10R bulldozers, a Cat 994 loader, a Cat 5120 hydraulic excavator, four Cat 992 loaders and other support equipment. 13 240t Cat haul trucks, three 170t Cat 793 haul trucks and 11 100t Cat 777D haul trucks carry waste and ore from the pits.

DIAMOND RECOVERY

In the process plant, a gyratory primary crusher reduces ore to minus 300mm, coarse ore being stockpiled in a 20,000t-capacity storage building. A hot water-flushed cone crusher reduces the ore to 75mm before a high pressure roll crusher reduces it to minus 25mm. Primary and secondary scrubbers and degritting and sanding sections remove fine waste material for disposal. Heavy-medium separation (HMS) using slurried water and ground ferrosilicon separates a diamond concentrate from the crushed ore. Finally, X-ray fluorescence sorters are used to extract the diamonds from the HMS concentrate.

UNDERGROUND EXPANSION

Development of the US$182m Panda underground project should provide some 4.7 Mct/y over a six-year life from 4.6Mt of ore. The underground mine was completed early in 2006, on time, on budget and will produce around 2,600t/d of ore. Panda underground will provide around 40% of Ekati's output by value.

In June 2006, BHP Billiton announced approval of a second underground mine, Koala, intended to contribute 3,300t/d of ore by mid-2009, following start-up late in 2007.

PRODUCTION, SALES AND MARKETING

In late 2002, BHP Billiton ended the agreement by which De Beers bought 35% of Ekati’s output, with the remaining 65% being marketed independently, and will now market all Ekati's output. All mine production is sorted and valued at Yellowknife prior to shipment for sale.

The mine treated 5.6Mt of ore during 2003 to yield 6.96Mct of diamonds. The tonnage treated during 2004 was considerably lower, at 4.5Mt, and lower again in the year ending June 2006, when 4.3Mt ore was processed to yield 2.56Mct.

ENVIRONMENT

Environmental awareness is an integral part of staff training. Water use, waste management and land use and rehabilitation are carefully monitored. To date 314ha of tundra habitat have been used for construction of the mine and 611ha of the total lease area of 10,960ha has been affected by the operation. Rehabilitation is an on-going, long-term aim.