Imagine finding diamonds in your trash. That's what happened when Lucara Diamond Corp. salvaged a 375 carat gem quality diamond from a pile of old tailings at its prolific Karowe mine in Botswana. When cut and polished, this diamond rough should yield polished diamonds roughly 175 carats.
Tailings are the residue of the diamond-bearing ore that was processed during an original mining operation.
The company revisited the tailings because they were generated prior to the 2015 implementation of its advanced XRT diamond sorters, which were designed to identify and preserve high value diamonds of 100 carats or larger. Older, less sophisticated sorting devices often mistakenly damaged, pulverized or passed through large diamonds as worthless tailings.
The new XRT sorters have the ability to detect the carbon signature of rocky material coming down a conveyor belt so the diamond-bearing ore can be picked out and preserved. The machines can be calibrated to extract valuable material based on X-ray luminescence, atomic density and transparency.
The 375 carat rough diamond was just one of nine 100 plus carat diamonds recovered from the re-processing of old material.
Lucara also reported strong results from the processing of new material, including the discovery of a 123 carat diamond from Lucara's South Lobe (see photo, above). Year to date, the mining company has recovered 22 diamonds larger than 100 carats, including six of 200 carats or more. You might wonder how large diamonds like can be lost in the first place. When you think about the millions of tons of dirt that must be moved to find even one diamond you can imagine how a few diamonds can "slip through the cracks".
Lucara's Karowe Mine is famous for yielding many of the world's largest diamonds, including the 1,109 carat Lesedi La Rona, the 813 carat Constellation and the recently recovered 1,758 carat Sewelô.
Credit: Image courtesy of Lucara.