Tag Archives: Eira Thomas

TOMRA XRT units help recover unbroken 998 ct diamond at Lucara’s Karowe mine

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TOMRA’s COM XRT 2.0/1200 ore sorters have aided Lucara Diamond’s Karowe diamond operations, in Botswana, once again, recovering an unbroken 998 ct high white clivage diamond from the 100%-owned mine.

The diamond, measuring 67 x 49 x 45 mm, was recovered from direct milling of ore sourced from the EM/PK(S) unit of the South Lobe, and follows a series of significant diamond recoveries during this recent production run, including several top quality clivage and gem-quality stones of 273 ct, 105 ct, 83 ct, 73 ct, and 69 ct in weight.

“The EM/PK(S) forms an important economic driver for the proposed underground mine at Karowe and continues to produce large gem-quality diamonds in line with expectations, a further testament to the strong resource performance at Karowe,” the company said.

Last year, a feasibility study showed the company could double the mine life of Karowe by establishing an underground mine for $514 million in pre-production capital.

The 998 ct diamond (pictured) was recovered in the MDR (Mega Diamond Recovery) XRT circuit that allows for diamond recovery post primary crushing and prior to milling. The MDR circuit has, in the past, treated material in the size range between 50-120 mm. This latest recovery represents the second plus-500 ct diamond recovered from this circuit in 2020, Lucara noted.

Year to date, Karowe has produced 31 diamonds greater than 100 ct, including 10 diamonds greater than 200 ct comprising of the 549 ct Sethunya, and the 998 ct diamond.

Eira Thomas, Lucara CEO, said: “Lucara is extremely pleased with the continued recovery of large high-quality diamonds from the South Lobe of the Karowe mine. To recover two plus-500 ct diamonds in 10 months along with the many other high-quality diamonds across all the size ranges is a testament to the unique aspect of the resource at Karowe and the mine’s ability to recover these large and rare diamonds.

“Operations at Karowe have continued through 2020 and operational challenges, due to COVID-19 restrictions, have been met with professionalism by the team. We look forward to a safe finish to 2020 and continued success at Karowe as we remain focussed on strong operations to ensure maximum resource performance.”

Lucara and TOMRA continue to recover rare diamonds at Karowe

Comminution of minerals, Diamond mining, Mine operation news, Mineral processing, Mining equipment, Mining services, , , ,

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.”

Lucara looks to go underground at Karowe following feasibility study

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Lucara Diamond Corp looks like having a combined open pit and underground future at its Karowe diamond mine, in Botswana, after a feasibility study showed the company could double the mine life of the operation for $514 million in pre-production capital.

Already one of the world’s most prolific producers of large, high value type IIA diamonds and the only diamond mine in recorded history to have produced two +1,000 ct diamonds, Karowe’s existing open pit and underground expansion showed off life of mine production of 7.8 Mct to 2040, a payback period of 2.8 years and an after-tax NPV (5% discount) of $718 million.

Eira Thomas, President and CEO, said: “Lucara is highly encouraged by the results of the Karowe Underground feasibility study which has outlined a much larger economic opportunity than first envisaged in the 2017 PEA and represents an exciting, world class growth project for our Company.

“Diamond deposits are rare and getting rarer. In this context, we are extending a mine that is in a class of its own, having produced 15 diamonds in excess of 300 carats, including 2 greater than 1,000 carats in just seven years of production.  Further, we have sold 10 diamonds for in excess of $10 million each, including the record-setting 813 ct Constellation which sold for $63.1 million.”

A significant portion of the cost to expand the mine underground can be funded from cash flow, according to Thomas, and the investment is expected to be paid back in under three years, as the underground expansion allows Lucara to exploit the highest value part of the orebody first and generate more than $5.25 billion in gross revenue, she added.

The Karowe mine has produced 2.5 Mct since 2012 and generated $1.5 billion in revenue. The FS looks to double the mine life from the original mine design of 2010 and add net cash flow of $1.22 billion and gross revenue of $5.25 billion.

The long hole shrinkage (LHS) underground bulk mining method has been selected for the underground deposit, which should provide early access to higher value ore, allows for a short pay back period of 2.8 years and low operating costs of $28.43 per tonne processed, according to the company.

On the basis of a construction start in mid-2020, ore from underground mining is expected to seamlessly integrate into current operations providing mill feed starting in 2023 with a ramp up to 2.7 Mt/y to the processing plant by 2026, and the opportunity to increase throughput.

Current production rates will be maintained through the underground ramp up period.

The Underground is designed to access the South lobe kimberlite resource below the current planned bottom of the open pit (which is expected to be at approximately 700 m above sea level (masl), to a depth of 310 masl.  Access to the South Lobe underground will be via two vertical shafts (production and ventilation) of approximately 765 m and 715 m deep, respectively.

The study identified key focus areas of hydrogeology, geotechnical constraints of the kimberlite and host rocks, which have been addressed through an intensive set of work programs and data collection that commenced during the PEA completed in November 2017 and were substantially updated and augmented by the FS study, the company said.

TOMRA XRT technology recovers massive diamond at Lucara’s Karowe mine

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Lucara Diamond Corp claims to have found and recovered one of the largest diamonds in recorded history at its Karowe operation in Botswana.

The 1,758 ct diamond was recovered through Lucara’s X-ray Transmission (XRT) circuit, commissioned in April 2015 by TOMRA Sorting Mining.

Lucara said it is the largest diamond recovered in Botswana, and the largest diamond to be mined at Karowe to date. It comes on top of the 1,111 ct diamond the company recovered in 2015.

“Weighing close to 352 g and measuring 83 mm x 62 mm x 46 mm, the diamond has been characterised as near gem of variable quality, including domains of high-quality white gem,” Lucara said.

Since commissioning of the XRT circuit in 2015, a total of 12 diamonds in excess of 300 ct have been recovered at Karowe, including two greater than 1,000 ct, from a total production of around 1.4 Mct. Of the 12 plus-300 ct diamonds recovered, 50% were categorised as gem quality with 11 sold to date generating revenue in excess of $158 million, Lucara said.

Geoffrey Madderson, Diamond Segment Manager for TOMRA Sorting Mining, said: “As the largest diamond ever recovered by a mechanical process, it reinforces the unparalleled value XRT offers kimberlite and diamond mining companies. Lucara’s innovative strategy, in combination with TOMRA’s world-class sensor technology, has once again proved an enormous success.”

Eira Thomas, Lucara’s CEO, said: “Lucara’s technologically-advanced, XRT diamond recovery circuit has once again delivered historic results. Karowe has now produced two diamonds greater than 1,000 ct in just four years, affirming the coarse nature of the resource and the likelihood of recovering additional, large, high quality diamonds in the future, particularly as we mine deeper in the orebody and gain access to the geologically favourable EM/PK(S) unit, the source of both of our record breaking, plus-1,000 ct diamonds.”