Diavik mine a hive of activity

Diavik Diamond Mines, a unit of Rio Tinto (RTP-N) and 60%-owner of the Diavik diamond mine, and its 40% joint venture partner Aber Diamond Mines (ABZ-T) are beginning construction of a second dike at Diavik mine, 300 km northeast of Yellowknife, NWT.

The dike represents the first phase of development of the A418 open pit. Construction is expected to take about two-and-a-half years and cost about US$190 million.

The A418 pipe contains an estimated proven and probable open pit and underground reserve of 8.7 million tonnes grading 3.2 carats of diamonds per tonne.

During the first quarter of this year, the mine produced about 1.75 million carats of diamonds. Production was from the A154 North and A154 South pipes.

At the end of last year, proven and probable reserves at Diavik totalled 29.8 million tonnes grading 3.2 carats per tonne, or 95.6 million carats of diamonds. These reserves are contained within three kimberlite pipes (A154 South, A154 North and A418).

A154 South accounted for almost half of this reserve with proven and probable open pit and underground reserves of 10.5 million tonnes grading 4.5 carats per tonne, or 46.7 million carats of diamonds.

Previously the A21 kimberlite was also listed in the reserves, but now it is considered to contain an indicated resource of 4.3 million tonnes grading 3.1 carats per tonne. More drilling is planned to test this resource.

At the end of last year A154 North had a proven and probable open pit and underground reserve of 10.6 million tonnes grading 2 carats per tonne.

Last year the underground resource of the A154 North pipe became a reserve following the valuation of a large parcel of diamonds at US$82 per carat (an earlier sample used in the feasibility study had been valued at US$33 per carat).

Diavik is generally a fly-in operation, but it is accessible for about ten weeks via a seasonal ice road. From the end of February until early April the company used this road to transport 2,770 loads of supplies up to the mine site. In addition to fuel, explosives and general freight, heavy equipment including cranes, boats and dredges were delivered.

Almost one quarter of the supplies were slated for dike construction and underground development. The company is beginning ramp development to sample several of the kimberlites at depth and test ground and water conditions prior to underground mining.

Diavik has awarded the construction and engineering contracts for the A418 dike to the same contractors who built the dike around the A154 pipe (joint venture companies Lac de Gras Constructors, and Nishi-Khon SNC Lavalin).

Diavik employs about 750 people, about 70% of whom live in the north.