Global prepares for bulk sample

Global Diamond Resources (GDRS-O) plans to begin underground bulk sampling at the Montrose kimberlite pipe in South Africa.

The California-based explorer completed 30 large-diameter, vertical drill holes. Each measured 10 inches in diameter and was drilled to a depth of 100 metres as part of a 222-ton bulk sample, results from which are pending.

Global Diamond is processing the drill cuttings hole by hole to produce heavy mineral concentrates in various size ranges. To date, the work has resulted in 19 diamonds with a total weight of 2.6 carats, the largest being 0.43 carat. Most of the stones appear to be gem quality, says Global Diamond’s chairman, Johann de Villiers.

Results of the drilling and mini-bulk sample will determine the location for a larger bulk sample. Collection of this 5,000-ton sample is to begin in January 1999 and last eight months. The cost of the work is pegged at US$1 million.

To date, Global has delineated 9 million tonnes of kimberlite material at the Montrose pipe to a depth of 400 metres. The bulk sample is expected to determine the grade of the material; de Villiers expects it should come close to 15 carats per 100 tonnes, which would be similar to grades recorded early in the century. The Montrose pipe, which covers 4 ha, is 8 km north of the famous Premier mine of De Beers Consolidated Mines.