JOHANNESBURG (miningweekly.com) – Trial mining at the 5 ha Baoulé kimberlite pipe, in Guinea, has yielded a total of 5 087 ct to date, at an average grade of 13.5 ct per hundred tons (cpht), Aim-listed Stellar Diamonds said on Monday.

The West Africa-focused company noted that the first sale of 733 gem-quality carats from Baoulé, last month, realised $195 000 at an average value of $266/ct.

“Good progress continues to be made from trial mining. Our objective is to produce 15 000 ct from this exercise to enable us to determine the grade, value and presence of large stones in the pipe, with a view to using this information to consider a decision to advance Baoulé to commercial-scale mining,” CE Karl Smithson commented.

“It is pleasing that we have achieved our maiden revenues following the first diamond sale from Baoulé, as well as other Stellar projects. We are currently planning the next export and sale of Baoulé goods and remain committed to targeting additional diamond sales throughout 2015,” he added.

To expand the Baoulé pit area in preparation for the second 3 m cut, mining progressed towards the eastern and southern margin of the pipe where a lower-grade contact breccia was recently encountered, reducing the average grade to 13.5 cpht at a 1.2 5 mm cutoff.

This resulted in fewer carats being produced than anticipated at this point in time, but mining and processing of the second cut was expected to see a return to higher grades, based on the results realised from the first cut of the lobe.

Simultaneous to this mining, stripping of the western lobe of the pipe started in advance of the rainy season. Overburden and ground disturbed by diamond diggers was currently being stripped to access the uncontaminated kimberlite in preparation for bulk sampling.

The company further noted that the processing plant was running at a steady state average capacity of 50 t/h over a double shift of 16 hours.

The kimberlite material remained predominantly weathered; however, some harder blocks of kimberlite were being encountered. Since these blocks were too hard to scrub, but were also too soft to efficiently crush, it was sent to an oversize stockpile, where they were broken down with an excavator, prior to being re-fed into the plant, to ensure maximum diamond liberation and integrity of results.