Sand Processing

Cutting edge tech helps recover huge diamond

The unbroken 1758-carat diamond, weighing in at 352 grams, was recovered at Karowe Mine by TOMRA XRT sensor technology, commissioned by Lucara Diamond Corp.

Since introducing the TOMRA XRT technology as the primary recovery tool to the mine in 2015, Lucara has recovered two diamonds greater than 1000 carats.

TOMRA sorting technology has detected four of the top 10 largest diamonds in the world to date.

“As the largest diamond ever recovered by a mechanical process, it reinforces the unparalleled value XRT offers kimberlite and diamond mining companies,” the diamond segment manager for TOMRA Sorting Mining Geoffrey Madderson said.

“Lucara’s innovative strategy in combination with TOMRA’s world-class sensor technology has once again proved an enormous success.”

TOMRA’s new multi-channel laser sorting solution enables the operator to define and apply a greater number of sorting criteria, which enables separating with much greater precision.

The laser identification technology consists of a multi-channel laser scanning system with high resolution imaging, and cutting-edge colour and textural selectivity. Multiple material characteristics such as brightness, colour, size, shape and surface texture are processed simultaneously.

Quartz processing

For quartz, the scattering effect of multiple lasers can be used to distinguish a rock containing quartz from its identically coloured neighbours.

A pure or non-contaminated quartz rock now registers as a glowing crystal, while a similar looking piece of quartzite, sandstone or other rock types, exhibit no visible scattering at all and simply remain dark.

Conventional approaches have involved the use of colour sorters. However, sorting based on colour alone tends to reject rock material that, though it may be iron-stained on the surface, still contains an acceptably low percentage of iron.

Rejecting such iron-stained material causes significant loss of yield, thereby necessitating additional mining to maintain production levels. Also, as quarrying material is mined out, product specifications may become increasingly difficult to achieve as lower quality areas of the deposit are encountered.

“TOMRA’s new laser sorting solution is unlocking untapped opportunities within the market and offers our clients an innovative and cost-efficient solution which increases the lifespan of their deposits,” product manager at TOMRA Sorting Mining Ines Hartwig said.

“Analysing results from tests and practical trials at several installations, we have demonstrated that we can achieve higher recovery, better quality and more consistent sorting of quartz material with laser sorting than with other sensor technologies.

“But other segments could also benefit from this technology – any application in which a crystalline structure helps to separate the valued material from the waste can also be targeted,” he said.

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