Lucara Diamond Corp, which owns the Karowe diamond mine, has TOMRA and its XRT ore sorting technology to thank for a lot of its recent success recovering high value diamonds at the Botswana operation.
In production since 2012, the mine is recognised as one of the foremost producers of very large, high-quality Type IIA diamonds in excess of 10.8 ct.
Historic recoveries include the 1,109 ct Lesedi La Rona – the second-largest gem quality diamond ever found – and the 813 ct Constellation diamond. This success at Karowe has recently continued, with rare gem quality blue and pink diamonds recovered in September.
Initial work on the mine was carried out by previous owners in the 1970s with the technology available at the time, which had its limitations.
Eira Thomas, CEO of Lucara, said: “What we realised in looking at the diamonds that resulted from that work is that many of them were actually broken.
“When production started, it became apparent that the diamond population was quite coarse, and that necessitated a re-think on how we could adjust or optimise flow sheet focused on diamond value preservation. That was our real focus and goal in starting the conversation with TOMRA, about how can we do this better, how can we actually get diamonds out of our mineralised ore in a more efficient way and in a way that actually maximises the value of those diamonds and minimises the damage of those goods.”
The AK6 Kimberlite, found in Karowe, presents a difficult challenge, as John Armstrong, Vice President, Technical Services for Lucara, explained: “It has a very high DMS yield, in that up to 10% to 15% of the material that would go into the plant would report as a heavy-metal concentrate, making it a very difficult orebody to process in a traditional diamond processing scenario.
“We undertook a series of testing campaigns and investigations to explore alternative technologies. We elected to go with TOMRA as our partner in moving forward in getting this technology to the mine into part of the circuit that hadn’t been envisioned previously.”
TOMRA’s solution delivered very quickly, exceeding all expectations: “When we put in the large diamond recovery circuit in 2015, it was within two weeks of making this investment, which was somewhere around $30-35 million, that we recovered those two exceptionally large diamonds, so in this case it was under two weeks we’d already had two times our return on that investment,” Thomas said.
Thomas said while Lucara felt TOMRA’s technology was the best on offer, its collaborative approach and willingness to work with Lucara stood out.
“We weren’t entirely certain what the solution was going to be, we just felt that by working with a team of experts that understood the problem and had technology that could help us, we could together come up with a solution that made sense. And, I think, that was the big opportunity for us as we sought in working with TOMRA.”
Thomas added: “I think the Lesedi and The Constellation recoveries really did open up a lot of eyes, and I think it opened a lot of minds to the idea that technology can and will make a big difference to not only existing diamond mining operations, but future mining opportunities, and it’s a great testament to the efforts that we’ve made in collaboration with TOMRA to really get out and tell the story.”