Modern Mining March 2015

DIAMONDS

increasing tenfold, yielding in the region of 240 000 carats a year.” The first results of the trial mining were reported early in January this year, with Stellar announcing the recovery of 2 145 car- ats, including a total of 138 stones greater than 1 carat with the biggest being a 9,2 carat dia- mond. Gem and near gem diamonds accounted for approximately 60 % of the diamond popula- tion recovered. The average grade was 14,6 cpht (at a +1,25 mm cut-off), slightly higher than the 13 cpht anticipated based on the historical exploration and sampling work. The first parcel of diamonds has been exported to Antwerp and will probably have been sold by the time this article is in print. Stellar anticipates the export and sale of diamonds every two to three months during 2015. The trial mining is being carried out using a smallish fleet of mining equipment consisting of several 45-t excavators working in conjunc- tion with 25-t and 30-t articulated dump trucks. The processing plant is an amalgam of a 100 t/h DMS plant from the Mandala project and a 5 t/h bulk sampling plant from Droujba. Stellar retained ADP Metco to reconstruct the plants and combine them into a fully integrated kim- berlite processing facility (able to handle both weathered and fresh material) with primary and secondary crushing and final recovery via Flow Sort machines. “We’re currently running the plant at a throughput of approximately 50 wet tonnes per hour on a 2 x 8-hour shift basis,” remarks Smithson. “This is only half its capacity, so we do have a lot of flexibility in terms of increasing the mining and processing rate if we deem it necessary. After some initial modifications post

commissioning, the plant is now working very well and is efficiently treating a wide variety of ore types.” According to Smithson, the staff and labour complement at Baoulé now numbers around 70 people. This includes five expats, one of them being Stellar’s Chief Operating Officer, Rowan Carr. Like Smithson, he is a geologist who spent much of his earlier career with De Beers, gain- ing experience in many of Africa’s diamond mining countries, including South Africa, Botswana, Angola, the DRC and the Central African Republic. As Smithson says, “Most of our permanent staff are out in the field and we have only a tiny head office establishment in London.” Turning to the Tongo Dyke-1 project in Sierra Leone, Smithson says Stellar’s inten- tion is to fast track it into production over the

Processing plant at the Tongo kimberlite dyke project in Sierra Leone.

Bench stope mining from surface to 40 m depth will be used to get Tongo into early production.

March 2015  MODERN MINING  27