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AIM-listed diamond company Stellar Diamonds has recovered a 55 carat diamond from trial mining at its 75% owned, 5 ha Baoulé kimberlite pipe in Guinea.

Recovery of the diamond confirms the presence of large stones in the pipe, further supported with the continued recovery of high quality gems of up to 12 carats.

“We are extremely encouraged to have recovered this 55 carat stone as it confirms that the Baoulé pipe is a possible source of the large diamonds which have been mined in alluvial deposits downstream of the Baoulé pipe for many years, several of which have been +100 carats in size,” says Stellar Diamonds chief executive Karl Smithson.

“We will carefully examine the stone which appears to have a ‘boart’ exterior and a potentially better quality diamond on the interior.”

“With approximately 63% of our trial mining and processing at Baoulé now complete, subject to the company having sufficient working capital, we are currently on track to finalise the trial mining and processing of 100 000 t in Q3 and look forward to providing further updates in due course.”

Trial mining production and processing

Trial mining of the Baoulé kimberlite pipe resumed in late November 2015 after the rainy season, with stripping and mining of the western lobe.

Extraction of the kimberlite commenced in December 2015 and processing of the material continues on a double shift basis (16 hours per day). The kimberlite material remains predominantly weathered, with increasing amounts of friable harder primary kimberlite at depth.

The overall objective of the trial mining exercise is to extract and process up to 100 000 t of kimberlite in order to determine with confidence the diamond grade and ultimate value of the pipe. The company remains on track to achieve this objective, having processed over 63 000 dry tonnes of kimberlite thus far.

Diamond results

A total of 8 043 carats have been recovered to date from Baoulé at a +1.25 mm cut off, giving an average grade of 12.7 cpht. This grade is slightly lower than previously reported average grade of 13.5 cpht due to an average lower grade for the west lobe (11 cpht) as compared to the east lobe (13 cpht).

This seems to be a consequence of fewer smaller stones in the -7 sieve fraction and thus should not impact negatively on the gross diamond value.

A total of 610 stones greater than 1 carat have been yielded including numerous gem diamonds of up to 12 carats in size.

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