Diavik sampling confirms grade

A consistent grade of 4.53 carats per tonne is reported from sampling of the A-154 South pipe at the Diavik diamond project in the Northwest Territories. To date, processing has been completed on just under one-quarter of a 3,000-tonne underground bulk sample.

Situated near Lac de Gras, the project is held 60% by Kennecott Canada, a wholly owned subsidiary of London-based RTZ, and 40% by Aber Resources (TSE).

The partners report that 2,987.6 carats have thus far been recovered from 659.6 tonnes, and that the largest gem-quality diamond weighs 4.83 carats, up from the previously reported 4.05 carats. The largest stone recovered weighs 14.75 carats.

Separate from the 659.6 tonnes is the initial 46.5-tonne sample, taken from the first two rounds of advancement into the kimberlite. The sample was diluted with a substantial proportion of wall rock and grout cement, and yielded 85 carats for a grade of 1.85 carats per tonne.

The remaining 2,300 tonnes of the bulk sample is being processed at Kennecott’s recovery plant in Yellowknife and at the BHP-Dia Met Koala plant.

The objective of the bulk-sampling program is to recover a representative 10,000 carats for valuation, a key factor in the economics of any diamond project. Diamonds recovered in a 1995 large-diameter drill program were valued at US$58.17 per carat, about half the value of diamonds from the best pipes at the nearby BHP Minerals project.

The A-154 South pipe hosts a drill-inferred resource of 8.4 million tonnes to a depth of 250 metres, and Aber believes the pipe could contain as much as 20 million tonnes if projected to a depth of 650 metres. The bulk sample was taken at a depth of 155 metres. Both the bulk sampling and previous surface drilling are proving the grade to be consistent throughout the pipe.

In the meantime, the partners are devising plans for a 3,000-tonne program of underground bulk sampling on the A-418 pipe, to be carried out later this year. Kennecott recently began developing an underground ramp towards A-418 and anticipates it will reach the pipe by late summer or early fall. The A-418 pipe lies just offshore, 700 metres southwest of A-154 South.

A further six large-diameter drill holes were completed on the A-418 pipe. In total, nine holes recovered 63 tonnes of sample. As previously reported, the first three holes yielded 83.1 carats from 19.1 tonnes for a grade of 4.3 carats per tonne. The largest gem-quality diamond recovered weighs 2.2 carats.

Aber believes A-418 could contain 15-20 million tonnes to a depth of 650 metres.

Large-diameter drilling was also carried out on the A-154 North and A-21 kimberlite pipes. A total of eight holes recovered 56 tonnes from A-154 North, which lies 300 metres northeast of A-154 South.

In 1995, two large-diameter holes yielded 28.6 carats from 12.9 tonnes of kimberlite material, giving A-154 North a preliminary grade of 2.2 carats per tonne. The pipe is estimated to contain 5.3 million tonnes to a depth of 250 metres; moreover, it is believed to have the potential to host 15 million tonnes to a depth of 650 metres.

The A-21 pipe lies 4.4 km southwest of A-154 South. Drilling was limited to only one large-diameter hole, which recovered 8.5 tonnes of material.

Delineation drilling is continuing.

The large-diameter drill core from pipes A-154 North and A-21 will be analyzed following the processing of the A-154 South underground bulk sample.

Aber has 35.5 million shares outstanding, with 37.9 million fully diluted.