Tag Archives: diamonds

De Beers diamond XRF technology optimises sorting at emerald mine

Diamond mining, Gem stone mining, Mineral processing, Mining project news, Mining services, , , , , , , , , ,

De Beers Group Technology has adapted one of its X-ray fluorescence (XRF) diamond sorting range of machines to create “a secure and efficient sorting solution for emeralds”, it says.

According to De Beers Group Technology head, Gordon Taylor, the company’s sorting technologies have been applied to a range of minerals apart from diamonds, and these include gemstones like rubies to lower value commodities like manganese and coal.

“We are always on the look-out for new applications for our sorting equipment, which also employ X-ray luminescence, X-ray transmission, laser, magnetics and ultra-violet technologies,” Taylor said.

“So, we were excited by the opportunity to collaborate with Magnum Mining and Exploration on their Gravelotte emerald project in Limpopo province.”

In its trial mining and processing phase, Gravelotte has been gathering data to confirm the historic grades previously recovered at the project. In operation for much of the 20th century, total recorded production from this area was estimated at nearly 113 Mct. It was reportedly the world’s largest emerald mine of its type in the 1960s, employing over 400 sorters, De Beers said.

General Manager of Operations at Gravelotte, Wessel Marais, said the traditional manual method of sorting carried an associated security risk and led to less than optimal recoveries.

“Various mechanical sorting options are available on the market today,” Marais said, “and Magnum approached De Beers Group Technology to determine whether their diamond sorting technology could be adapted to emerald sorting.”

He says testing of samples provided by Magnum came out with successful results.

“This led to Magnum leasing an XRF machine from De Beers Group Technology for the duration of our trial mining, and the results to date have been very encouraging,” he says. “With the machines now deployed in the operational environment, research and development work is continuing in conjunction with De Beers Group Technology to refine the process.”

Taylor noted that constructive collaboration with customers is often an important element in extending the application of De Beers Group Technology’s equipment.

“On this project, we were able to conduct some fundamental investigation on the properties of emeralds to guide us in developing the most effective solution,” he said.

The De Beers Group Technology emerald sorting machine can make a potentially significant contribution to the success of the Gravelotte operation, according to De Beers, with its high recoveries combined with excellent processing security. The project aims to reach a target of around 3 Mct/y as its initial production rate.

Before the run-of-mine material reaches the De Beers Group Technology XRF machine, it is crushed to -30 mm and put through a trommel screen for cleaning and further size reduction. After material containing emeralds is ejected from the material stream by the sorter, it is further sorted by hand and graded.

“De Beers Group Technology is constantly pushing the boundaries where our equipment can be applied and has had significant successes in non-diamond commodities. Whether removing the value product or the waste from the process stream, our sorting technologies can be the game-changer in the viability of many projects,” Taylor concluded.

Eurafrican Diamond Corp to mine Marsfontein gravels in South Africa

Diamond mining, Mine operation news, Mineral project development, Mining services, , , , , , , ,

Botswana Diamonds and its associate Vutomi have signed an agreement with Eurafrican Diamond Corp to mine and process the diamond-bearing gravels and residual stockpiles on a portion of the Marsfontein farm, in South Africa.

The agreement gives EDC a contract for the mining and processing of the identified deposits on the Marsfontein Mining Permit, with 25% of the pre-tax revenue from larger or high value ‘Special Stones’ (any stones weighing 10.8 ct or more, or valued at more than $8,000/ct) and 15% from the standard run of mine stones accruing to Vutomi, which is 40% owned by Botswana Diamonds.

Vutomi was recently granted Environmental Authorisation over a substantial portion of the residual diamond-bearing gravels produced from the high grade Marsfontein mine, which is contiguous to Botswana Diamonds’ Thorny River operation. Thorny River has been modelled to contain 1.2-2 Mt of material (to 100 m) with a diamond grade ranging between 46-74 ct/ht and diamond values in the range of $120-$220/ct.

John Teeling, Chairman of Botswana Diamonds, said the partnership with EDC paves the way for commercial production to re-start on Marsfontein and Thorny River.

“EDC has a rich history of successful diamond mining and processing and has excellent technical and financial support,” he said. “Furthermore, EDC and Vutomi projects complement one another, providing a strong project pipeline.”

EDC, established in 1964, has long been a premier diamond miner and processer, and is currently mining and processing the Schuller kimberlite pipe and diamond-bearing gravels around Petra’s Cullinan diamond mine.

The contract mining and processing agreement allows for the continued contractual bulk sampling on the Thorny River project, as well as first refusal rights, between EDC and Vutomi, on all their South African diamond exploration and development projects.

While the Environmental Authorisation was granted for Marsfontein on September 12, Botswana Diamonds said it was expecting the remaining regulatory grants shortly.

TOMRA delivers the goods at Stornoway Diamonds’ Renard mine

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TOMRA’s ore sorting technology has delivered impressive results in its first diamond processing plant application. 

The company worked with Stornoway Diamonds and its Renard diamond mine, in Quebec, Canada.

The Renard mine, in commercial production since 2017, is the first diamond mine in the province and one of six in Canada. It started with an open-pit mine and subsequently opened an underground mine.

The conditions of the mine presented Stornoway Diamonds with particular challenges that required an innovative approach, according to TOMRA.

“Due to the geology of our ore, meaning we produce very high yield, we have lots of material that we need to sort through. At times, we have the possibility of losing some of those very expensive diamonds due to inefficiencies,” explains Marie-Claude Hallé, Marketing Operations Manager for Stornoway Diamonds.

In addition, “our orebody at the Renard mine contains a high level of internal and external dilution called country rock, a significant issue for us, as it can make up to 30 to 40% of the feed to the plant.

“With that comes very, very high energy cost from crushing all this waste material that is not diamond bearing. It causes a tremendous amount of wear and tear on our equipment from screening conveyors, diamond recovery equipment, and on a dollar-per-tonne basis we spend a lot of money processing non-diamond bearing material.”

Stornoway needed to find a way to reduce its costs and optimise its operation, which is where TOMRA came in.

“You have to really envision that TOMRA has actually changed the game in terms rough diamond recovered around the world, and allowed producers to access large exceptional quality goods that perhaps in the past would be crushed to pieces,” Marie-Claude Hallé said.

TOMRA’s solution incorporates ore sorting technology into the mine’s processing plant.

TOMRA analysed the situation and worked closely with Stornoway Diamond’s team to design and install a kimberlite pre-concentration plant.

The specific conditions at the Renard mine meant the traditional Dense Media Separation method could not provide an efficient and cost-effective solution. It led to TOMRA making Renard the first diamond mine to incorporate ore sorting into its processing plant.

TOMRA addressed the mine’s recovery issue with its leading sorting technologies, developing a solution with four key objectives for the ore sorting plant: minimise diamond breakage by removing hard rocks from the crushing plant feed; upgrade the quality of the material to the process plant by increasing the proportion of Kimberlite to waste rock; reduce the energy required for crushing by removing the harder rocks; and improve circuit efficiencies throughout the plant.

TOMRA’s solution features five PRO Near Infrared (NIR) sorters in its ore sorting circuit. This technology is particularly well suited to enable discrimination between the various ore and waste materials that need separation at the Renard mine, based on their different chemical composition, TOMRA said.

TOMRA also included a COM XRT 2400 sorter, which uses X-Ray Transmission technology to separate material according to its specific atomic density, in the plant’s large diamond recovery circuit.

Hallé continued: “The TOMRA solution we have in operation has offered us a very low-cost, efficient reliable means of recovering our coarse diamonds without inefficiency, without causing diamond breakage.

“It’s a very neat way to get those diamonds out of the kimberlite at the very early stage of the process. We reduce our power consumption cost, we reduce our wear and tear on material.

“We are still optimising this unit, and we feel there are even more benefits to come in terms of how it helps enhancing the overall recovery of our diamonds.”

Geoffrey Madderson, Diamond Segment Manager at TOMRA, concludes: “The implementation of this plant proves that TOMRA waste sorting technology can successfully be used to upgrade lower grade run of mine and that sensor-based sorting can be used to further improve value recovery for our clients on lower-grade resources.”

TOMRA said the integration of the ore sorting plant into the main processing plant was completed smoothly, with its full involvement in the ore sorting plant design. TOMRA also had a team onsite for the first three months of operation to ensure a seamless transition, and will continue to provide ongoing support for the entire life of the equipment.

“We chose TOMRA because we find TOMRA’s approach to problem solving to be very innovative,” adds Hallé. “We see them as a solution provider that thinks outside the box, that doesn’t always come with ‘here’s the off-the-shelf solution to your problem’, but in fact engages with us and looks at what are the best possible options.

”In fact, it will develop technology if needed to address those specific problems. We always have outstanding service as well, from TOMRA technicians, from engineers, from every aspect of TOMRA Sorting.”

BlueRock hopes for Kareevlei diamond mining upgrade with Teichmann contract

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BlueRock Diamonds, the owner and operator of the Kareevlei diamond mine, in the Kimberley region of South Africa, has instructed Teichmann South Africa to provide mining services to the company.

BlueRock announced back on May 16 that it was in negotiations with a member of the Teichmann Group to provide the quantity of ore necessary to meet BlueRock’s production plans.

The diamond miner said Teichmann’s extensive experience in mining operations is expected to significantly de-risk the company’s mining activities and allow BlueRock to meet its production targets in a “cost-effective manner”.

The Kareevlei licence area covers 3,000 ha and hosts five known diamondiferous kimberlite pipes. As at November 2018, it was estimated that the remaining inferred resource from the four kimberlitic pipes (KV1, KV2, KV3 and KV5) represents a potential in-ground number of carats of 367,000, BlueRock says.

The contract is for a period of five years commencing with an effective start date of July 1 and includes the extraction of ore and waste, haulage of said material to a stockpile, breaking down ore to the required size when required, and delivering ore to the processing plant.

BlueRock said: “Unlike the agreement with the previous provider of these services which was paid on an hourly basis with a minimum number of hours guaranteed, Teichmann will be paid almost entirely on a cost per tonne basis and, accordingly, the effective cost per tonne is reduced with the planned increased production.”

Based on the lower end of the company’s current production expectations, the estimated cost of Teichmann’s services for the 12 months ending June 30, 2020 will be around ZAR21 million ($1.4 million).

Mike Houston, Executive Chairman, said: “The upgrading of our mining operation is key to the overall success of the business and having an experienced mining contractor is an essential part of this process. I believe that our partnership with the wider Teichmann Group will provide further benefits going forward as we continue to implement our defined growth strategy.”

Namakwa enlists FLSmidth pumps to cut downtime, costs at Kao diamond mine

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The installation of a FLSmidth KREBS millMAX™ pump at Namawka Diamonds’ Kao mine, in Lesotho, is, according to the mining equipment maker, providing the miner with significant cost savings through increased impeller, casing and back liner wear life.

FLSmidth’s engagement at Kao started when the mine required a pump conversion in the field – an undertaking that can be difficult and time consuming, according to the mining OEM. “It is also a high-stakes operation as a cyclone feed is critical to the overall process and ability to generate returns. A wrong decision can mean a lot of lost revenue,” the company said.

It was the potential for cost efficiency that convinced Kao diamond mine to implement the KREBS millMAX Pump. After initial discussions, the first trial pump – a millMAX 8×6 centrifugal seal (C/S) – was installed in a cyclone feed application (DMS 2 pump 1).

Initial results after seven months showed the millMAX was performing extremely well on the wear side, according to FLSmidth.

“So, once you get the green light, you need to confirm the duty details and measure up the existing installation to ensure that when you begin to install the pump there are no surprises,” the company said.

Brad Moralee, Head of Product Unit Pumps, Cyclones and Valves at FLSmidth, said: “It’s high pressure for us: you are typically given a window of opportunity during a shutdown to complete the change, after which the new pump must run as expected when the plant is re-started.

“You need the combination of a great product but, more importantly, great technical understanding of the duty to be able to propose the correct solution. We understand what is at stake from the customer side.”

The change produced impressive results in comparison with the previous solution from another supplier, according to FLSmidth, with the millMAX increasing the wear life by nine times, across impeller, casing and back liner. “This has seen Kao make significant cost saving on direct replacement costs, reduced downtime and saved labour expenditure,” the company said.

While Kao mine operators were impressed with the benefits from the switch, a slight gland leakage was causing concern, according to FLSmidth. To resolve this, FLSmidth suggested running a one-month trial with the slurryMAX, which had just recently arrived on the South Africa market.

“The slurryMAX trial was based purely on its sealing capabilities as Kao were confident of the hydraulic performance of the pump and had no concern about wear as they were confident the slurryMAX would show predictable and even wear life across all wet-end parts,” the company said.

Kao’s confidence also came from the fact the slurryMAX design is based on the millMAX range, whose wear ring technology has created an efficient and long-lasting slurry pump.

The main difference between the millMAX and the slurryMAX is that the millMAX is an all-metal pump meaning it does not have an outer casing and an inner wear liner (the casing itself is made from the high chrome wear material), while the slurryMAX is a split casing design that has a replaceable inner liner. The purpose of this design is that multiple material liner options are available to fit in the same outer casing.

“The slurryMAX features an improved, more efficient impeller and an optional water drain plug for easier maintenance, allowing water that might have settled at the bottom of the pump to be drained quickly,” the company said.

Leigh Rieder, FLSmidth Sales Engineer, concluded: “Kao is extremely happy with the hydraulics and lack of excessive wear of our pumps, which has meant that their cost of ownership is low. We have recently received an order from the customer for two more slurryMAX pumps and they have expressed interest in our slurryMAX 6×4 and slurryMAX 10×8 pumps.”

Debswana looks to hit zero harm goal with Sustainability Resource Centre

Diamond mining, Environmental, Mining safety, Sustainable mining, Water management, , , , , , ,

Debswana Diamond Company recently launched a Sustainability Resource Centre (SRC) to, it says, apply a holistic approach to achieving its goal of zero harm across its Orapa, Letlhakane and Damtshaa mines in Botswana.

With its “Put Safety First” strategy, Debswana has been pursuing ways to improve the impact of its awareness raising and training interventions, according to Tefo Molosiwa, Head of Safety & Sustainability at Debswana.

“By using a combination of learning modes – theoretical and practical – the SRC delivers greater learning,” Molosiwa said. “For instance, while employees can learn the theory of how a bund wall must be maintained, there is now also an opportunity to practically clean spillage using the equipment provided.”

Molosiwa highlighted that the SRC facility has been designed to include the “seeing”, “doing” and “discussing” involved with the various aspects of environment, community, occupational health and safety on the mines.

The company said: “This will allow best practice to be effectively displayed and understood by employees, contractors and visitors, including the Fatal Risk Control Standards. E-learning plays an important role in the facility, with 20 workstations available for self-induction.”

Molosiwa added: “Employees gain exposure through being shown both ‘best’ and ‘bad’ practice displays as part of their induction.”

The scope of environmental management aspects of this learning process extends to energy conservation, water saving and waste management, according to Debswana. The facility itself includes solar water heating devices, for instance, with the energy-saving impact of this technology shared with all inductees to motivate adoption.

Water tanks at the SRC harvest rainwater from roof gutters, which is used for cleaning and watering gardens. The dry landscaping itself – featuring a few pockets of greenery – is also an important practical demonstration of how water can be better conserved, the company said.

The SRC also showcases facilities for effective waste management. “Animal-proof waste receptacles in the outside areas are examples of what the mining operations can adopt where appropriate. A bund wall for hydrocarbon management at the SRC demonstrates how the structure is optimally designed, developed and equipped,” Debswana said.

Debswana is one of Botswana’s largest private sector employers – with over 5,200 employees – and is jointly owned by the Botswana government and the De Beers Group of Companies. It is one of the world’s leading diamond producers by value and volume.

North Arrow brings in Imilingo, TOMRA, Microlithics for modular diamond recovery

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North Arrow Minerals says it has engaged Imilingo Mineral Processing of Pretoria, South Africa, TOMRA, and Microlithics Laboratories of Thunder Bay, Ontario, to investigate modular diamond recovery design options incorporating TOMRA’s X-Ray Transmission (XRT) sorting technology at its 100% owned Naujaat diamond project in Nunavut, Canada.

The engagement is with a view to recovering diamonds greater than 3 mm (nominally >0.5 ct) in size from a diamond recovery plant, it said.

North Arrow is currently planning for collection of a 10,000 t bulk sample from the Q1-4 deposit at Naujaat and, as part of this work, has initiated an engineering design and costing study of a small-scale mobile diamond recovery plant. The purpose of the sample will be to evaluate diamond size distribution and value characteristics, with emphasis on a distinct population of high-value, fancy, yellow to orangey-yellow diamonds that have been identified in the deposit, the company said.

Ken Armstrong, President and CEO of North Arrow, said: “We are pleased to be working with Imilingo, TOMRA and Microlithics to study diamond recovery plant design options for use in our continued evaluation of the Q1-4 diamond deposit.

“Over the last number of years, TOMRA’s XRT sorting technology has changed the diamond mining landscape by providing an XRT sorting solution that improves diamond recoveries while reducing breakage and water use compared to more traditional diamond recovery circuits. We believe XRT sorting technology can also be used for the evaluation of diamond deposits and is an ideal recovery solution for the Q1-4 diamond population.

“Locating a small-scale diamond recovery plant at or near the project site will also reduce costs, improve logistics and increase local employment and business opportunities for the residents of Naujaat,” he said.

Imilingo’s iPlant packages combine XRT solutions from the likes of TOMRA to sort and deliver feed material in a clean and well classified state, Managing Director, Jaco Prinsloo, told IM recently. Microlithics Laboratories, meanwhile, provides a number of diamond-specific services to clients in North America.

The focus on recovery of diamonds greater than 3 mm is an important component of the study, the company said, with a significant amount of the cost associated with processing past Q1-4 kimberlite samples related to ensuring and documenting the recovery of smaller diamonds (down to 1 mm in size).

Armstrong added: “While information on the 1 mm to 3 mm diamonds is important, most often the value of these diamonds does not impact the potential viability of the deposit being tested. This is certainly the case for Q1-4 where the value and size distribution of the fancy coloured diamond population will be critical in determining the economic potential of the deposit.

“We are therefore looking to design a small-scale mobile plant that can produce a hand-sortable concentrate for the recovery of +3 mm diamonds while saving significant costs and time delays associated with shipping bulk samples south for processing.”

Locating a diamond recovery plant at Naujaat as part of the Q1-4 bulk sampling program is possible due to the deposit’s proximity to marine transportation infrastructure and the improved accessibility that will be provided by a proposed new community access trail, the company said.

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

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

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.”

Integrated Pump Rental’s SlurrySucker saves the day at Botswana diamond mine

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Dredging technology provider, Integrated Pump Rental, says its innovative SlurrySucker has resolved a process water challenge for a diamond mine in Botswana.

Managing Director, Lee Vine, said attempts by the mine to desilt the main process tank using different methods of dredging had proved inadequate and the challenge of this reservoir continuously filling with slurry remained a concern, especially with regards to storage capacity. In addition, the silt build-up was causing damage to the process pumps resulting in unscheduled downtime and unnecessary maintenance expenditure.

Initially, Integrated Pump Rental proposed a SlurrySucker rental unit as this was deemed the quickest solution and there were also some reservations on the part of the mine due to failures with other equipment. The rental unit was installed on the main process tank for a trial period of two weeks.

The SlurrySucker dredging unit was required to pump 250 cu.m of mixed material out of the 40-m diameter by 8-m deep process water tank. This translates into 60 t/h of dry material.

“The performance of the SlurrySucker in that initial two-week period was so good the mine made the decision to purchase its own unit. Our equipment quickly proved itself capable of dealing with the silt issue, and keeping the level of the main process water tank within acceptable parameters,” Vine said.

Vine said that the SlurrySucker, equipped with the Grindex Bravo 700 submersible pump, suited the mine so well because of the mobility it offers.

“The unit can be moved from one tank to another, facilitating desilting of all process water and other water storage tanks and dams, ensuring these remain fully operational and silt free,” he said.

ALROSA weighs up restoration and closure options at Mir underground diamond mine

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Following the analysis of several options for deposit opening and deep level development, ALROSA has laid out plans regarding restoration or full closure of the currently suspended Mir underground mine in the Far East of Russia.

ALROSA said the concept requires deep level exploration down to -1,300 m to confirm the mine’s reserves. These activities are scheduled to be completed by early 2022. Budgeted at around RUB2 billion ($31 million), this work is included in the group’s RUB28.7 billion capital expenditure programme for 2019.

Last year, the company suspended the construction of deep mine levels below the level -800 m where it was necessary to carry out works to prevent gas-dynamic phenomena recorded there, ALROSA said.

Based on the results of the exploration works, pilot holes will be drilled to start preparation of deposit opening design documents (within one to two years). This work is to be completed before 2024.

“Simultaneously, the company will carry out conceptual design activities to ensure water disposal at the mine and choose the best mining technology as well as ventilation and gas safety options,” ALROSA said.

If it is decided that the restoration of the Mir underground mine is feasible, the construction is estimated to take six to eight years.

“In summary, Mir mine restoration can start no earlier than 2024 and only if the studies yield positive results, and if it is confirmed that construction and mining can be done with the highest level of occupational safety,” ALROSA said.

“ALROSA’s decision about further development of this mine will be based solely on safety considerations and economic viability.”