West Africa-focused diamond-mining and exploration company Stellar Diamonds has started exploration drilling of 20 holes – a total of 3 000 m – on the Droujba kimberlite pipe, in Guinea, which has grades of up to 200 cpht, the company reports.
“Over the next few months, we will be defining the geological model of the pipe to a depth of 150 m and collecting representative samples for microdiamond analysis by the Saskatchewan Research Council laboratory, in Canada,” says Stellar Diamonds CEO Karl Smithson.
The results of this work will enable the company to model and forecast the macrodiamond (commercial) grade of the pipe, which, if positive, will give it the incentive to undertake a larger-scale bulk sample of the kimberlite pipe to more accurately determine the diamond grade and value.
Stellar has signed a contract with drilling contractor E-Global Drilling Corporation, a subsidiary company of contract diamond driller Energold Drilling Corporation, for a minimum 3 000-m diamond drilling programme for the Droujba kimberlite pipe. The EGII rig can drill cores of 56,1 mm in diameter to depths of 400 m.
Stellar Diamonds plans a series of angled and strategically positioned drill holes to model the Droujba pipe to a depth of 150 m. Further, a number of high- priority geophysical targets will be drilled to determine if they represent undiscovered kimberlites within the Droujba kimberlite cluster.
“Kimberlite core, representing the main internal facies of the pipe, will be sampled in batches of 200 kg and consigned to the Saskatchewan Research Council laboratory for microdiamond analysis. Based on these results, an independent diamond consultant will be retained to under- take diamond grade model- ling work with the objective of forecasting the potential commercial diamond grade of the Droujba pipe,” Smithson says.
The pipe was discovered in the early 1960s by the Russian Aid Mission, which mapped and drilled the pipe and determined it to be about 120 m × 80 m in size, or 1 ha. The Russians mined the kimberlite down to a depth of 20 m before the kimberlite became too hard to mine and process with the technology then available. In 1964, the Russian Aid Mission left Guinea and the pipe has remained undeveloped since. Diamond grades as high as 200 cpht were reported by the Russians, though there is no information on diamond quality.
A series of ground magnetic, electromagnetic and gravity sur- veys were previously undertaken by Stellar and diamond-focused UK explorer West African Diamonds.