Tag Archives: Karowe

WEC Projects looks to nature for Lucara Karowe sewage treatment plant

Diamond mining, Environmental, Mining services, Water management, , , , , ,

WEC Projects has secured a R3 million ($187,460) contract to supply a new sewage treatment plant for the expansion of Lucara Diamond’s Karowe diamond mine in Botswana.

The mine, near the village of Letlhakane in the eastern Kalahari Basin region of Botswana, is planning to cease open-pit activities by 2026 after which it will continue mining underground, extending its operational life to around 2040. More than 1,000 m above sea level, the mine operates in a region where temperatures average 35°C and water is scarce; so much so that the Government of Botswana has legislated mandatory water saving requirements for industry.

WEC Projects installed the original treatment plant in 2012 and will integrate the new system into the existing facility, increasing throughput from 100 cu.m/d to 150 cu.m/d to meet the requirements of an increase in the number of staff at the mine. While the treatment plant itself is a fairly standard installation, the mine requested a variation to the original project scope – a man-made natural reed bed wetland system that will provide a “polishing” phase to the treatment process, using natural organisms and filtration processes to further clean the wastewater, WEC Projects said.

Wayne Taljaard, Managing Director of WEC Projects, said: “This is a particularly unique feature for a mine as usually such reed bed wetlands are built for much larger installations such as municipal sewage treatment. The government’s mandate for water conservation has forced companies in Botswana to apply creative thinking to overcome the challenge of operating in an arid country.”

The main sewage treatment facility will consist of a WEC Projects Model A treatment plant, an extended aeration system using conventional activated sludge to process the sewage. The wastewater passes through a mechanical screen which removes solids and is then treated by a biological reactor which integrates anoxic, aerobic and clarification zones.

After treatment, the water will enter the reed bed wetland area where it will percolate through the reed bed allowing microorganisms to breakdown contaminants such as sulphur, heavy metals and chlorine. The water produced by this process, while not for human consumption, will be reused by the mine for applications such as irrigation and dust suppression, according to the company.

To create the wetland, a shallow dam will be built, its bottom to be filled with gravel and reeds planted. The water from the treatment plant will feed into the wetland area where nature will be left to take its course.

Taljaard added: “The reed bed solution offers a number of advantages for the mine as the effluent will be relatively odourless and is flexible enough to cope with fluctuations in input. It also requires little maintenance once it is up and running and will ensure that the mine remains within the constructs of the law.”

UMS gearing up for shaft sinking work at Karowe Underground

Diamond mining, Mine shafts and equipment, Mineral project development, Mining services, , , , , , , , , , ,

With a team comprising some of the most experienced professionals in shaft sinking, United Mining Services (UMS) says it is gearing up for the pre-sinking of two shafts for the Karowe Underground Mine Expansion Project (UGP) in Botswana.

Following the completion of the feasibility study for the Karowe UGP, UMS was appointed by Lucara Botswana Pty Ltd and JDS Energy & Mining Inc in October 2019 to engineer and design the shaft sinking of the production shaft (8.5 m in diameter), and the ventilation shaft (6 m diameter), both reaching a depth of approximately 750 m below surface.

Fully commissioned in 2012, Karowe is an open-pit diamond mine with operations until 2026. The UGP will extend Karowe’s mine life to at least 2040. At the end of 2020, Karowe’s total probable reserve stood at 53.9 Mt containing 7.4 Mct including stockpiles.

According to Lucara, the Karowe mine remains one of the best producing mines of high quality plus-10.8 ct diamonds, having yielded five of the 10 largest diamonds in recorded history. It is also the only mine to have recovered three diamonds greater than 1,000 ct.

Dr Pieter Louw, Group Executive Project Services at UMS and UMS’ Project Manager, says the company’s wealth of knowledge and expertise in shaft sinking played a key role in securing the contract, and that the company is bringing in the heavyweights in the industry for the project.

Louw, himself, has a long history in underground mining and shaft sinking, having worked for major players in the mining and engineering sectors. He was involved in the De Beers Venetia Underground Project feasibility study, as well as a number of other feasibility projects for mines that are now in development or have already started production.

Louw explains that the two shafts at Karowe will be blind sunk using conventional drill and blast techniques. The production and ventilation shafts will both have equipment installed to pre-sink to a shaft depth of 100 m, if required, to accommodate the main sink shaft equipment. The pre-sink phase also allows the sinking process to commence as soon as possible while the main sink infrastructure is being fabricated and installed.

The new underground mine’s production shaft will have an A-frame type headgear, which will hoist 21-t payload skips, and will have a single drum auxiliary winder for people movement, and a man/material winder with counterweight and a big cage to service the underground.

UMS has refurbished four winders, which will be going to the mine for shaft sinking, including two stage winders and two Kibble winders. The company also purchased and refurbished Scotch derrick winder cranes for the pre-sink.

Louw says that UMS is in the process of mobilising up to 170 people to site for the pre-sink, which is expected to commence at the end of August and will take between eight and 12 months to achieve changeover ready for the start of the main sink. The main sink will take another two years after that, ready for mine development to commence in 2024, and full underground operations in 2026.

To make sinking safer, Louw says that UMS has adopted different sinking methodologies and equipment to be used at Karowe.

“In the past, we used to sink with cactus grabs which needed people in the bottom,” Louw said. “We are now using vertical shaft muckers and are buying state-of-the-art jumbo drill rigs to drill at the bottom. We’re doing inline work as opposed to concurrent work with people working at the bottom.”

He adds that, as part of its safety management plan, UMS has established a training centre on site at Karowe that facilitates inductions and training of local operators on the various equipment. The company is constructing a mock-up training tower on the surface to train operators on vertical shaft muckers and will have a similar training simulator for excavator operators.

Louw says UMS is fully established in Botswana and has partnered with Botswana Investment and Trade Centre to ensure that the project work permits run smoothly. Furthermore, the UMS design engineers are registered with the Botswana certification boards and can sign off all engineering designs and drawings for the project.

UMS to start pre-sinking work at Lucara’s Karowe Underground Expansion project

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Lucara Diamond Corp’s Karowe Underground Expansion project (UGP) in Botswana is moving ahead with mobilisation of shaft sinking teams commencing late in June, and pre-sinking activities scheduled in the September quarter.

The Karowe UGP, which is expected to extend the operation’s mine life to 2040, is in a fully-financed position, with the latest schedule expected to see underground production hit full production by the end of 2026.

The 2019 feasibility study for the project envisaged life of mine production of 7.8 Mct, a payback period of 2.8 years and an after-tax NPV (5% discount) of $718 million; all from $514 million in pre-production capital.

COVID-19 delays have pushed the project off the original schedule – both in terms of timeline and cost – but the company says it is now making headway towards a 2026 start to underground production.

Lucara said no “material variances” between the 2019 feasibility study and the current execution plan have resulted, despite the delays.

“Rather, during this period in 2020 and 2021, all critical path items were addressed and a concerted effort was placed on detailed design, engineering and procurement which have helped to significantly de-risk the project,” it said.

Out of the total capital budget, the company has spent $51.4 million on project execution activities through 2020 until the end of June 2021, including shaft and geotechnical engineering, procurement of long lead time and essential shaft sinking items, surface infrastructure and construction activities, bulk power supply power line engineering and procurement.

Mobilisation of the shaft pre-sink team has commenced with shaft pre-sinking on track to commence in the middle of the current quarter.

Detailed engineering and design of the underground infrastructure and layouts will commence this quarter and are expected to be competed in the September quarter of 2022, with no major changes from the 2019 study plan anticipated.

Underground mine development is scheduled to commence in the second half of 2024 with underground production ramp up starting in 2026. Full production is scheduled for the end of 2026.

At the same time, open-pit mining operations have been adjusted to limit the risk of production shortfalls during the ramp up of the underground mine operations commencing in the first half of 2026. The open-pit mine is expected to terminate in mid-2026, Lucara said.

Access to the underground mine will be via two vertical shafts, the production and ventilation shafts. The shafts will be concrete lined with the production shaft acting as the main air intake and the ventilation shaft as the exhaust.

The number of shaft stations and nominal elevations remain the same as the feasibility study, with the planned depth of the production shaft still at around 767 m. The final planned depth of the ventilation shaft has, however, increased marginally to 733 m, from 716 m.

A 7,200 t/d shaft operation using long hole shrinkage (LHS) mining will provide an additional 13 years of mine life to the Karowe operation after a five-year construction period. The 767-m-deep production shaft will be equipped with two 21 t skips for production hoisting and a service cage for man and material movement through the mine. This shaft will also serve as the main fresh air intake to the mine.

The pre-sink construction contract and shaft sinking equipment procurement were awarded to UMS Botswana and UMS South Africa, respectively. METS International Ltd, a subsidiary of UMS, was awarded the shaft engineering contract.

The company explained: “Detailed design and engineering work on the production and ventilation shafts is now 90% complete, and has resulted in the following changes to the 2019 feasibility study: i) production shaft diameter has increased from 8 m to 8.5 m, ii) ventilation shaft permanent headframe, hoists and internal conveyances have been removed, iii) parallel pre-sinking of both shafts, iv) ventilation fans and coolers to be located on surface, v) in-shaft grouting of water strikes changed from grout curtain installation from surface, vi) planned development of an additional sublevel to assist in drilling of drawbells, and vii) removal of 670L de-watering galleries.”

Increased schedule time related to shaft sinking has been a result of the increased production shaft diameter, time allowances for in-shaft grouting during sinking operations planned at known water strike horizons, holing through all shaft stations between shafts and additional ground support for underground stations/level breakouts, the company said.

UMS is in the process of mobilising crews to Karowe to initiate pre-sink works. Pre-sinking of the two shafts will run in parallel and start with mobile cranes and then transition to Scott Derrick cranes with the final depth of pre-sink at around 40 m below surface.

With the exception of an additional sublevel (340L) to assist with drill and blast of drawbells, the design, layout and infrastructure of the underground mine all remain aligned with the 2019 feasibility study, the company noted.

Temporary power for shaft sinking is required until such time as the upgrade bulk power supply infrastructure is commissioned in the December quarter of 2022. A three-phased ramp up of the generator capacity is planned to support the increasing power requirements related to the shaft sinking activities.

A power supply and services contract for the temporary generators has been signed with Aggreko International Projects Ltd. Mobilisation has been initiated with the generator pad established. Commissioning of Phase 1 is scheduled during the September quarter to support the start of pre-sink activities.

The Karowe UGP is targeting the substantial resources remaining below the economic extents of the open pit in the South Lobe.

The LHS method is planned to systematically drill and blast the entire lobe on a vertical retreat basis. In LHS, a significant proportion of the blasted muck is left in the stope during blasting and stoping to stabilise the host rock with only the swell extracted during the drill and blast phase. Mucking will take place from draw points from the 310L extraction level. Once the column is fully blasted, the stope will be drawn empty by mucking the draw points.

The bottom-up approach of the LHS mining method takes advantage of the higher value EM/PK(S) kimberlite unit at depth in the South Lobe at Karowe, and balances high initial capital costs with low operating costs while de-risking the project with respect to the geotechnical and hydrogeological aspects of the host rocks, according to Lucara.

A revised project cost and schedule has been developed that captures the detailed engineering and design work through 2020 until May 2021, incorporating all changes, improvements, and COVID-19 related delays. Overall capital expenditures, including contingency, have increased marginally by some 4%, to $534 million, driven by the increase to the production shaft diameter and additional mine development.

The schedule to 75% of full production has increased by 1.3 years, driven mainly by COVID-19-related delays to commence the shaft pre-sinking and additional planned time for shaft station break-outs and ground support, Lucara added.

During 2020, Lucara negotiated and signed a self-build agreement with the Botswana Power Corp (BPC) for the construction of two substations and a 29-km-long 132 kV transmission line from BPC’s newly established Letlhakane substation to the Karowe mine. The planned route follows an existing regional 400 kV line and then runs parallel to the existing 11 kV transmission line currently supplying bulk power to the Karowe mine.

The new power infrastructure will provide the required power for the current open pit, processing plant and the underground mine expansion. Commissioning of and handover to BPC is scheduled for the December quarter of 2022. Construction of substations is scheduled to commence this quarter and power line construction in the March quarter of 2022, the company said.

JDS Energy & Mining Inc is the engineering procurement and construction manager for the execution of the Karowe UGP and is currently building up the on-site project team in conjunction with Lucara’s owners team and working in close cooperation with the Karowe Diamond Mine operations team.

Lucara recovers second plus-300 ct diamond of 2021 at Karowe mine

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

Lucara Diamond Corp has announced another recovery of significance from its 100% owned Karowe Mine, in Botswana, with its TOMRA X-ray Transmission (XRT) sensor-based ore sorting units, again, helping the miner recover and keep the diamond intact.

A magnificent unbroken Type IIa 378 ct gem quality top white diamond was recently recovered from milling of ore sourced from the M/PK(S) unit of the South Lobe, Lucara reported. This recovery is the second plus-300 ct gem quality diamond to be recovered this year from direct milling of the M/PK(S) unit, a further testament to the strong resource and process circuit performance at Karowe, the company said.

Both the 378 ct and the 341 ct diamonds recovered this year came from the Coarse XRT circuit, Lucara said.

Eira Thomas, Lucara’s CEO, said: “The 378 ct joins a rare and special lineage of exceptional, high value diamonds recovered at Karowe and continues to highlight the wonderful diamond potential of Botswana. Continued and consistent recovery of large diamonds, such as the 378 ct and 341 ct stones, comes at a critical time and provides continued strength and additional foundation to the opportunity to finance and build the underground expansion at Karowe that will see mining continue for at least another 13 years after the open pit ceases operations in 2026.

“We look forward to a safe, productive and busy 2021.”

A 2019 feasibility study looking at a combined open pit and underground future at Karowe showed the company could double the mine life of the operation for $514 million in pre-production capital by developing an underground deposit.

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.”

TOMRA takes XRT ore sorting testing virtual in face of COVID-19 restrictions

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TOMRA Sorting Mining is bringing ore sorting testing capabilities to its stay-at-home mining customers though the development of virtual testing facilities that enable them to take informed purchasing decisions for their processing plants, regardless of location.

This is the latest action in the company’s plan to provide its customers the support they need to take their business forward in the face of current COVID-19-related restrictions.

“Ensuring business continuity at this time is of paramount importance for mining operations,” TOMRA Mining said. “This includes taking forward ongoing investment projects in sorting equipment to improve their efficiency and the quality of their product.”

TOMRA Mining is leveraging digital technology to help customers identify the best sorting solution for their mine by offering them remote access to its Test Center in Wedel, Germany, a facility that has capabilities for all applications, according to the company.

“TOMRA’s temporary Virtual Demonstration and Test Solution will enable mining companies to test the sorting solutions on their samples without leaving their office,” the company said. “They will just need to book a session with their TOMRA sales representative and ship a sample of their minerals to the Test Center, which will conduct the test.”

Once testing is complete, mining customers will receive a video of their material being sorted and be able to discuss the results with a TOMRA sales person and the Test Center’s experts via video call, the company said. “With their support, they will be able to make a decision on the following steps and take the project forward without delay,” it added.

Albert du Preez (pictured), Senior Vice President and Head of TOMRA Sorting Mining, said: “At TOMRA, we work closely with our customers to devise the solution that is perfect for their operation. The visit to one of our test centres can be an important step in this process, as it enables them to work out with our teams the best combination of technologies and develop the flowsheet for their ore sorting plant.

“With this virtual solution, we are able to provide this support, taking our Test Center to our customers’ office so they can make an informed decision on an important investment. This means that they are able to take their business forward in the current situation.”

TOMRA’s test centres play a key role in the company’s collaborative approach to supporting customers with their ore sorting requirements, according to the company. Based on the tests conducted on TOMRA equipment with material from the customer’s mine, the centre can provide an initial feasibility study and detailed reports on the machine’s performance with the sample. With this information and the advice of the centre’s experts, the customer can proceed with their investment with confidence, the company says.

The opportunity for the customer to see first-hand the equipment at work on their sample and discuss the options with TOMRA’s team provides important added value, according to the company.

This was the experience of John Armstrong, VP Mineral Resources at Lucara Diamonds, who visited the Test Center in Wedel when researching a solution for the diamond mine in Karowe, Botswana.

“We gained a lot of confidence in the people at TOMRA, in the technology that they were presenting to us, and the possible solution that it provided to the Karowe mine…We could also see that they had already gone down the road of the next step in X-ray Transmission (XRT) technology, so they were not just focused on one particular module to present to us, but they were working on different modules.

“That helped alleviate some of our concerns about the robustness of the platform and the technology itself, which ultimately led us to use TOMRA as the solution.”

Lucara has since gone on to recover some of the largest diamonds in history with the TOMRA XRT system that was installed following this visit to the Test Center.

In addition to developing this Virtual and Demonstration and Test Solution in reaction to the COVID-19 outbreak, TOMRA has increased stocks of critical components to ensure its ability to fulfil current and future orders, and to ensure the supply of spare parts without disruption.

And the company is leveraging digital technology not only to take the expertise of its test centres to customers, but also by using its remote service and training tools to support their equipment while respecting social distancing safety measures, it said.

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

Diamond mining, Mineral project development, Mining project news, , ,

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.”