07 Jun 2015

In April 2013, Debswana management board approved the implementation of Yellow Diamonds Project through a P73. 2 million capital to deal with the yellowish brown colour found in a significant portion of diamonds.

The Grease Plant project manager, Mr Omphile Ntabeni told journalists during a media visit in Orapa recently that the construction of the project commenced in September 2013 at Orapa’s No. 2 Plant and was completed in June 2014.

The objective of the project was to install and commission a grease recovery plant to recover diamonds present in x-ray sorter rejects stream, he said, adding that regular performance audits identified that about two to three per cent of free diamonds were not being recovered in the X-ray diamond sorting machines.

He said the diamonds were sent for analysis and it was confirmed that they were of very low Luminescence Intensity (LI), noting that it was not possible to optimise current X-ray sorters to recover the LI Diamonds.

Mr Ntabeni said alternative technologies were considered including grease recovery, but the test work confirmed grease technology to be a suitable ‘scavenger’ to recover the diamonds in the X-ray sorter rejects stream.

He highlighted that grease separated diamonds from other material based on their strong affinity for oils rather than water. He noted that most of the material found with diamonds had a strong affinity for water.

The diamond surface he said needed to be scrubbed to eliminate pockets of water hence the need for scrubbing or milling prior to grease recovery. He added that grease recovery technology had matured relatively easy to operate and maintain.

Mr Ntabeni stated that 350 000 carats were recovered per annum. ENDS