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EKATI DIAMOND MINE, 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 for Ekati and for Echo Bay mine's Lupin
operation. 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. All kimberlite pipes are overlain by small
lakes. Five kimberlite pipes are being developed in the core zone
with two more undergoing feasibility studies – Beartooth and
Pigeon. Four more pipes are currently being bulk sampled –
three from the core zone and one from the buffer zone.
As of June 2000, Ekati had proven reserves of
40.2Mt at an average grade of 1.0ct/t and probable reserves of 20.1Mt
at an average grade of 0.8 ct/t. This gives a total reserve of 60.3Mt
at 0.9ct/t. At breakdown of the six operating open pits gives reserves
of:
Panda - 4.5 Mt at 1.1 ct/t
Misery - 4.7 Mt at 2.3 ct/t
Koala - 8.8 Mt at 0.8 ct/t
Fox - 7.9 Mt at 0.3 ct/t
Sable - 12.0 Mt at 0.8 ct/t
Koala North - 0.2 Mt at 0.7 ct/t
In addition, there are underground-mineable resources at Panda,
Koala and Koala North.
MINE PLAN
Initial open-pit mining will be extended underground where necessary.
To date, 121 kimberlite bodies have been discovered: 36 pipes within
the buffer zone and 85 within the core zone. The project is expected
to have a life of 25 years or beyond.
Open-pit mining started on the Panda pipe and
Koala, Misery, Fox and Sable 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 Driltech D90K2 blasthole
drills, a Demag H655SP diesel hydraulic shovel, Caterpillar D10R
bulldozers, a Cat 994 loader, a Cat 5130 hydraulic backhoe, Cat
992 loaders and other support equipment. Eight 218t Cat 793C haul
trucks and four 90t 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.
EXPLORATION
Recent exploration has focused on three pipes.
Gazelle produced a sample grade of 0.59ct/t valued at $15.12/ct.
Phoenix graded 1.41ct/t with a value of $24.78/ct. Piranha produced
a sample grade of 2.33ct/t with a value of $29.72/ct.
PRODUCTION, SALES AND MARKETING
De Beers currently buys 35% of Ekati’s output
under a three-year agreement, the remaining 65% being marketed independently.
All mine production is sorted and valued at Yellowknife prior to
shipment for sale.
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