THE DIAMOND PAGE — Diavik bulk sampling nears completion

The processing of a 3,000-tonne underground bulk sample from the A-154 South pipe at the Diavik diamond project is about two-thirds completed.

To date, an overall grade of 4.67 carats per tonne is reported for 1,905 tonnes of processed kimberlite. Gem-quality diamonds weighing up to 6.02 carats have been recovered.

Situated at Lac de Gras in the Northwest Territories, the Diavik project is a joint venture held 60% by Kennecott Canada and 40% by Aber Resources (ABZ-T).

The overall grade excludes the first two rounds of advance into the A-154 South pipe, which were diluted with a substantial amount of wall rock and grout cement. The initial 46-tonne sample yielded 85 carats for a grade of 1.85 carats per tonne.

The objective of the bulk-sampling program is to recover a minimum 10,000 carats to determine a representative average carat value of the diamonds.

CRA Diamonds of Perth, Western Australia, recently completed an evaluation of diamonds recovered from the first 705 tonnes of the A-154 South bulk sample.

A total weight of 3,070 carats was valued at an average US$58 per carat, which is almost unchanged from a previous estimate of US$58.17 per carat for a 255.6-carat parcel recovered in the 1995 large-diameter drilling.

CRA valued those diamonds weighing greater than 0.66 carat, while using an inferred valuation for the smaller stones based on the previous valuation of the 255.6-carat package. The 1995 value of the smaller stones was adjusted to reflect the current value.

Based on the current grade of 4.67 carats per tonne and an average value of US$58 per carat, the overall value of the A-154 South pipe stands at US$271 per tonne, ranking it among the world’s highest-grade diamond deposits.

The A-154 South pipe contains a drill-inferred resource of 8.4 million tonnes to a depth of 250 metres, with the potential to host 20 million tonnes to a depth of 650 metres.

Aber Vice-president Jordan Ethans expects the average carat value will increase somewhat, as a number of the larger diamonds, including the 6.02-carat stone, have yet to be evaluated.

In preparation for a 3,000-tonne bulk-sampling program on the nearby A-418 pipe, the processing of a 44-tonne, large-diameter-drilling mini-bulk sample is under way. A previous 19.1 tonnes of sample yielded 83.1 carats for a grade of 4.3 carats.

A 600-metre-long decline, currently being driven to the A-418, has been advanced a distance of 354 metres to date.