BHP Diamonds has uncovered two additional kimberlite pipes at the Ekati mine property in the Northwest Territories, bringing the total to 138.
The latest pipes were discovered during a spring drilling campaign. One of them, dubbed Impala, returned a significant number of microdiamonds. Impala was targeted on the basis of a proprietary airborne gravity gradiometer survey flown over the Ekati claims late in the summer of 2000. The pipe occupies about 2-3 ha and lies in the outlying Buffer zone claims.
An aggregate 277.9 kg of sample collected from the Impala discovery hole yielded 72 macrodiamonds and 111 micros weighing a total of 0.382 carat. (A macro is defined as exceeding 0.5 mm in at least one dimension.)
The Buffer zone claims surround the Core group of claims, which centre on the Ekati diamond mine. Ownership of the inner Core block, which comprises 1,800 sq. km and contains all of the pipes in the current mine plan, is held 80% by BHP Diamonds, a member of the
The outlying Buffer zone covers 2,040 sq. km and is owned 58.8% by BHP, 31.2% by
Additional drilling was completed on the promising Lynx pipe early in the second quarter. The Lynx pipe has a surface area of just 0.6 ha and lies in the Buffer zone, under a small lake 3 km southwest of Misery, the second pipe slated to be mined at Ekati. Misery contains a proven and probable open-pit reserve of 5.4 million tonnes grading 3.3 carats per tonne at US$34 per carat. Misery’s stones are the lowest in value taken from the six pipes that comprise the current mine plan. At the end of 2000, proven and probable reserves at Ekati stood at 60.3 million tonnes grading 0.9 carat per tonne, equivalent to 54.3 million carats. The diamonds range in estimated value from US$34 per carat for the Misery pipe to US$168 per carat for Panda.
The Misery pipe is 29 km south of the main processing plant.
Based on results from the 2001 drilling, BHP estimates that the Lynx pipe contains a measured and indicated resource of 1.4 million tonnes of kimberlite. A 168.5-tonne mini-bulk sample collected last year by reverse-circulation (RC) drilling returned 140.74 carats of diamonds, giving a preliminary grade of 0.83 carat per tonne. Three Antwerp, Belgium-based diamond dealers evaluated the parcel at US$139 per carat.
BHP has collected a further 173.3 tonnes of bulk sample from the Lynx pipe for on-site processing this summer. In addition, RC drilling was completed earlier this year on the Fox pipe in the Core zone. Results from a 172.6-tonne bulk sample will be used to update the reserve classification, which stands at 16 million tonnes of proven and probable ore grading 0.3 carat per tonne at US$129 per carat.
Ekati production for the quarter ended June 30, 2001, was 837,000 carats of diamonds, up 15% from the corresponding period last year and 14% higher than in the March 2001 quarter. The increase is due to a combination of higher throughput and higher ore grade. Higher recoveries of low-value diamonds were also recorded during the period. Production to date has come solely from the Panda pipe.
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