DIAMOND PAGE — Diavik JV to evaluate diamonds

The Diavik Diamond joint venture in the Northwest Territories has begun processing an underground bulk sample of more than 3,000 tonnes of kimberlite material.

The material was extracted from pipe A-418 and from large-diameter core (LDC) holes drilled in pipes A-154 South, A-21 and A-10. The underground headings were 145 metres below lake level.

Diavik Diamond Mines, a subsidiary of London-based Rio Tinto (RTP-N) (formerly RTZ-CRA), has a 60% interest in the project and acts as operator.

The remainder is held by Aber Resources (ABZ-T), which retains the right to market its share of production.

The project, now in the prefeasibility stage, is 250 km northeast of Yellowknife, in vicinity of Lac de Gras. About 300 km southwest of the town is the pilot plant, which, to date, has processed 1,490 tonnes, yielding 4,217 carats of rough diamonds.

Unlike the relatively homogeneous pipe A-154 South, pipe A-418 displays internal variation in both rock character and grade. So far, the bulk sample has been found to grade an average of 2.8 carats per tonne.

Both Aber and Diavik Diamond Mines believe the higher-grade section constitutes a large part of the upper portion of the pipe.

The pipes contain an estimated resource of 36 million tonnes of kimberlite, calculated to a depth of 400 metres. All four have undergone mini-bulk sampling by LDC drilling to establish an estimated grade of diamonds per tonne.

Pipe A-154 South has a resource of 12 million tonnes grading 4.2 carats. A sample representing half of the close to 12,800 carats recovered from the 2,900-Tonne bulk sample yielded a value of US$67 per carat. Based on these values, the partners infer the entire sample has an average value of US$63 per carat.

The diamonds will be evaluated in Antwerp, Belgium, by mid-June. Results will be released prior to Aber’s annual general meeting, on June 25 in Toronto.

The prefeasibility stage has a 2-year budget of $80 million and will be completed in the autumn.