Modern Mining: Featured News

In its latest update on its BK16 kimberlite project in Botswana, Tsodilo Resources, listed on the TSX-V, says that the treatment of the samples generated by the company’s Large Diameter Drill (LDD) programme is underway and will be completed early in April. The samples are being processed in Tsodilo’s refurbished DMS plant near the town of Letlhakane.

The BK16 project is located within the Orapa Kimberlite Field (OKF) which hosts 83 known kimberlite bodies, eleven of which have been or are currently being mined. The diamondiferous BK16 pipe is approximately 6 hectares in size at surface and is known to contain rare and valuable Type IIa diamonds.

Tsodilo DMS 1

Tsodilo's DMS plant - located near letlhakane - has been fully refurbished.

The pipe was discovered by De Beers in the 1970s using soil sampling techniques, airborne magnetics, and ground magnetic surveys. This work was followed up by some drilling and the sinking of a shallow shaft to 36 m in the central part of the pipe. Initial indications were that the kimberlite was diamondiferous but of low grade and no further work was done by De Beers.

Over the period 1994 to 2010, several companies held the prospecting rights over the area containing the BK16 kimberlite and various forms of surveying and sampling were employed in an attempt to ascertain whether BK16 was economically viable.

Tsodilo believes that much of the above described sampling was done in the upper part of the kimberlite which is characterised by a basalt breccia. Like several of the other Orapa kimberlites, this upper zone of basalt diluted kimberlite is of low grade but the underlying ‘cleaner’ kimberlite is known to be of higher grade.

Tsodilo’s Large Diameter Drilling programme, including collaring of the holes, was executed between July and October 2017, and including the Kalahari cover sediments a total of 3 150 m was drilled. Excluding the cover sediments, 2 008,6 tonnes of kimberlite was extracted. A 1 mm screening unit attached to the drill removed the fines resulting in 1 441,5 tonnes of +1 mm of kimberlite for processing through the DMS plant. The kimberlite was sampled every 12 m down each LDD hole subdividing the 1 441,5 tonnes into 243 individual samples for treatment.

The LDD programme was contracted to De Wet Drilling, which used its Elephant drill rig. This rig has a direct hydraulic pullback of 120 tonnes and a rotational torque of 100 000 Nm.

Tsodilo’s DMS plant was purchased in March 2015 by Tsodilo’s subsidiary, Newdico, from the original owner, De Beers Botswana Prospecting Ltd. The plant was built for De Beers in Kimberley, South Africa, and later transported and installed just outside Letlhakane to evaluate the AK6 kimberlite (now the Karowe mine). It was used over several years for the feasibility study of AK6.

The plant has been extensively refurbished by Tsodilo and was commissioned in January this year using the historic tailings material to test the plant. The facility consists of a scrubbing unit, jaw and cone crushers, screening units, a DMS cyclone and a DMS concentrate cage to collect and secure the DMS concentrate.

To date (13 March), 724,7 tons have been processed through the plant representing 141 samples out of a total of 243 or 61 % of the tonnage. These 141 samples have generated 2 778,6 kg of concentrate translating to a DMS yield of 0,38 %.

Tsodilo anticipates that the treatment of the LDD samples through the DMS plant will be completed in the first week of April. The treatment of the tailings material of BK16 will then resume.

The second consignment of 71 drums of concentrate has been securely moved to Tsodilo’s final recovery area at its secure complex in Maun, where it installed a Polus-M X-ray sorter from Bourevestnik, Inc in January this year. Numerous diamonds were recovered during the setup, calibration and instruction period.

The sorter has been set up to treat dry DMS concentrate in the size range of -8 +3 mm and -3 +1 mm. To date, it has treated 32 LDD samples and produced cumulatively 7,0 kg of concentrate in the 1 to 3 mm size range and 0,6 kg of the 3 to 8 mm size material. The material in the 8 to 12 mm size range for these 32 LDD samples has a combined weight of 43,6 kg.

The X-ray sorted concentrates will be hand sorted in the Maun secure sorting facility by a third-party sorter. The -12 +8 mm material will also be hand-sorted in Maun. The recovered diamonds will be transported to the Diamond Technology Park in Gaborone for acid cleaning and valuation. The company is exploring avenues to obtain the use of a larger Bourevestnik machine to treat the plus 8 mm fraction.

The sorter operation concept is based on the use of diamonds’ property of luminescence under X-ray impact and on the difference of those properties with diamonds and associate luminescent minerals.

Photos courtesy of Tsodilo Resources.

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