THE DIAMOND PAGE — Sampling proceeds on Aber’s A-418 pipe

A decline driven into the A-418 pipe at the Diavik diamond project in the Lac de Gras area of the Northwest Territories has encountered kimberlite much sooner than anticipated.

The 529-metre-long decline was driven from the bend in the main A-154 South decline to a depth of 150 metres.

The A-418 kimberlite is the second pipe to have been advanced to the underground bulk-sampling stage at the Diavik project, which is held 60% by operator Kennecott Canada and 40% by Aber Resources (ABZ-T).

To date, about 1,000 tonnes of a planned 3,000-tonne bulk sample have been mined from the pipe, representing an advancement of 70 metres. The material is being stored at surface until it can be transported early next year, via winter ice road, to Kennecott’s diamond recovery plant in Yellowknife.

Based on 61.8 tonnes of kimberlite recovered from nine previous large-diameter drill holes, the A-418 averages a grade of 4.02 carats per tonne. Drilling to date has outlined a resource of 5.8 million tonnes to a 250-metre depth. Aber estimates A-418 could contain 15-20 million tonnes to a depth of 650 metres. Preliminary diamond evaluations by Australia-based RTZ-CRA are pending.

The A-418 pipe lies 750 metres southwest of A-154 South.

Meanwhile, the processing of eight additional large-diameter holes from the A-154 North pipe is complete. In all, 71.72 tonnes of kimberlite recovered from 10 holes yielded 156.81 carats for a grade of 2.19 carats per tonne. The diamonds ranged in weight from 0.013 to 2.77 carats, with the largest gem-quality diamond weighing 2.27 carats. An initial evaluation will be carried out by RTZ-CRA.

Eight of the drill holes bottomed in kimberlite, with the deepest hole reaching a depth of 458 metres. A-154 North is estimated to contain a resource of 5.3 million tonnes to a 250-metre depth. It is believed to have the potential to host 15 million tonnes to a depth of 650 metres.

Processing of the remaining 800 tonnes of underground bulk sample from the A-154 South pipe has resumed. To date, a total of 1,905 tonnes has been processed, yielding a grade of 4.67 carats per tonne. Gem-quality diamonds weighing up to 6.02 carats have been recovered.

A 3,070-carat parcel of diamonds recovered from the first 705 tonnes was valued at an average US$58 per carat. Several of the larger stones have yet to be evaluated, including the 6.02-carat diamond.

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

The final processing of one large-diameter hole from the A-21 pipe, which is 5 km south of the A-154 South pipe, is nearing completion. The hole recovered 8.5 tonnes of kimberlite. Previous delineation drilling recovered 300 macrodiamonds and 789 micros from 1.4 tonnes of sample core.

A more extensive program of large-diameter drilling is scheduled for the winter of 1997.

Initially the joint-venture partners had budgeted $23.5 million to evaluate the A-154 South pipe. The budget has been expanded to $80 million to include the evaluation of the A-418, A-154 North and A-21 pipes by the end of next year. To date, 41 kimberlite pipes have been discovered on the Diavik property, 15 of which are diamond-bearing.

Aber has 36 million shares outstanding, or about 38 million fully diluted.