Ekati Diamond Mine, North-West Territories, Canada
Ekati diamond mine, near Lac de Gras in Canada's North-West Territories, is about 300km north east of Yellowknife. It is a joint venture between BHP Billiton Diamonds (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
In November 2011, BHP Billiton announced its plan to sell its stake in the Ekati mine as part of its business restructuring strategy. Investec, an asset management firm, estimated the stake to be worth about $300-500m.
Ekati diamond mine was discovered in 1991. Diamond production formally commenced in October 1998 and the first million tonnes production was achieved by 1999. In late 2010, a 78-carat diamond was discovered from the mine. It was the first time in 12 years of production that a diamond of such a significant gem quality was discovered. Ekati has an average annual production of 3Mct of rough diamonds. It has been, however, declining.
Ekati diamond mine 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. The measured open cut resource at Ekati (core and buffer) are 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.
Ekati mine plan
To date, 156 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. Ekati has a mine-life up to 2019.
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 35-40Mtpa 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.
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.
Development of the $182m Panda underground project should provide some 4.7mct/y over a six-year life from 4.6mt of ore. The underground mine was completed early in 2006, on time, on budget and produces around 2,600t/d of ore. Panda underground provides around 40% of Ekati's output by value.
In June 2006, BHP Billiton announced approval of a second underground mine, Koala. Official production from Koala underground mine was started in December 2007. The Koala mine, which has a production life of 11 years, is expected to produce about 9.8Mct of diamond.
In June 2011, BHP Billiton planned a $400m expansion of the Misery open-pit project. The mining operations are expected to start in late 2015 and have a mine-life of two years.
Production, sales and marketing
The mining processes consist of excavation, cleaning and diamond separation. The mine employs about 800 full-time staff and 700 contractors.
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 now markets 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.
The mine has produced about 45Mct of diamonds out of six open pits between 1998 and 2009. The Ekati mine diamonds are sold under Aurias brand name and genuineness is verified through CanadaMark service.
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.
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.