TOMRA

Vista Gold Corporation owns the Mt. Todd project in Australia, which was acquired in 2006 and is one of the country’s biggest undeveloped gold resource. The project, briefly operated in the 1990s, is known for having hard ore (Figure 1). This, and the fact that the project was operated previously, presented particular challenges for Vista Gold.

“We had a desire to find a way to only be spending money to process the rock that had gold in it,” explains Fred Earnest, President and CEO of Vista Gold. “We started looking for ways that we could get rid of the non-mineralised host rock prior to the grinding circuit. The company looked at different technologies to address the issues at the Mt. Todd project and contacted TOMRA Sorting Mining to find out about its sensor-based sorting technology.”

TOMRA Sorting Mining, Langenfeld/Germany, invited the Vista Gold team to visit their testing facility in Germany with a sample from the project to see first-hand what could be achieved. The test was an eye opener for Earnest.

Following extensive testing, Vista Gold has integrated TOMRA’s two-stage sorting solution in its flow sheet at Mt. Todd. The system sorts 20 t/h, using X-Ray Transmission (XRT) technology to remove particles containing sulphide minerals and subsequently lasers to remove particles containing quartz and calcite.

The benefits of TOMRA’s solution to the Mt. Todd project are two-fold. On the one hand, operating costs have been reduced: “We’re getting rid of material and we’re not spending money grinding rock that has no value,” explains Earnest. On the other hand, gold recovery has improved: “We’ve been able to make design changes in the plant. Because we’re processing less material, we’re now able to do a finer size. With finer grind our gold recovery has gone up. This has resulted in improvements of grade by 10 %. Our feed grade to the mill has gone up from 0.84 g/t to now 0.91 g/t.”

What’s more, the savings in operating costs have paid for the improvements to the plant: “We’ve been able to achieve all of this on a capital-neutral basis. We’ve been able to incorporate the equipment for the sorting to add fine grinding equipment, all with the money that we’ve saved from the ball mills. And so, ore sorting has opened up a whole new window of opportunity for us with the Mt. Todd project. We’re very excited about what this technology means to the mining industry and specifically to our projects in the future. And we look forward to seeing this technology grow and become even more efficient and of greater value to us,” concludes Earnest.

TOMRA worked closely with Vista Gold’s team to identify the best solution for the Mt. Todd project – from testing rock from the mine at its facility in Germany, to analysing the situation at the project and advising on how its sensor-based sorting technology could fit in their operation to deliver the best results.

Further information:
TOMRA Sorting Mining
www.tomra.com/mining

Stornoway Diamonds is a leading Canadian diamond exploration and producing company. It owns and operates the Renard Mine (Figure 1), in commercial production operation since 2017. It is the first diamond mine in Québec and one of six in Canada. Renard Mine 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: “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 ore body 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 come very high energy costs 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 Diamonds needed to find a way to reduce its costs and optimise its operation, and they are fully satisfied with the solution provided by TOMRA Sorting Mining, Langenfeld/Germany: “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,” states Hallé.

TOMRA analyzed 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 that the traditional Dense Media Separation method could not provide an efficient and cost-effective solution. It required innovative approach, which TOMRA delivered, making Renard the first diamond mine to incorporate ore sorting into its processing plant.

TOMRA addressed the mine’s recovery issue with its industry-leading sorting technologies, developing a solution with four key objectives for the ore sorting plant: minimize 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 also included in a COM XRT 2400 sorter, which uses X-Ray Transmission (XRT) technology to separate material according to its specific atomic density, in the plant’s large diamond recovery circuit.

“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,” comments Hallé. “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 ROM and that Sensor-based Sorting can be used to further improve value recovery for our clients on lower-grade resources.”

The integration of the ore sorting plant into the main processing plant was completed smoothly, with TOMRA’s 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.

Further information:
TOMRA Sorting Mining
www.tomra.com/mining

Lucara Diamond Corporation owns the Karowe diamond mine in Botswana, which has been in production since 2012. The mine is recognised as one the foremost producers of very large, high-quality Type IIA diamonds in excess of 10.8 carats. Historic recoveries include the 1,109 carat Lesedi La Rona – the second-largest gem quality diamond ever found – and the 813 carat Constellation diamond. Lucara’s success at the Karowe mine continues, most recently with rare gem quality blue and pink diamonds recovered in September 2019.

TOMRA’s technology and know-how unlocks the massive potential of the Karowe mine

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: “what we realised in looking at the diamonds that resulted from that work is that many of them were actually broken,” explains Eira Thomas, CEO of Lucara. “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 mineralized ore in a more efficient way and in a way that actually maximizes the value of those diamonds and minimizes the damage of those goods.”

The AK6 Kimberlite found in the Karowe presents a difficult challenge, as John Armstrong, Vice President, Technical Services for Lucara explains: “it has a very high Dense Media Separation 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 ore body 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 2 weeks of making this investment, which was somewhere around 30 to 35 Million dollars, that we recovered those two exceptionally large diamonds, so in this case it was under 2 weeks we’d already had two times our return on that investment,” says Eira Thomas.

(Find the customer testimonial video here )

TOMRA’s true collaborative, partnership approach stands out and delivers

The Lucara project clearly shows that TOMRA stands out not only for its industry-leading technology but, very importantly, for its extensive know-how and approach to working with customers, which it views as a true business partnership.

Eira Thomas explains the reasons for their choice of working with TOMRA: “We felt, certainly, that the technology that TOMRA offered was the best. But, more importantly, I think it was really around the approach, the attitude of collaboration and willingness to actually work with Lucara as we undertook to solve this problem, and that to us was a very appealing element because 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.”

John Armstrong agrees: “As part of the process that made working with TOMRA unique and special was their willingness to view the relationship between Lucara and TOMRA as a partnership, and we were both investing in this, and we were both going to learn a lot from it, and we relied on each other to ensure that we were going to be successful.”

TOMRA: a game changer for the future of diamond mining

“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,” comments Eira Thomas.

John Armstrong agrees: ‘With the early record-breaking diamond recoveries, “we were able to demonstrate to the world that we can recover large high-quality gem stones using the TOMRA technology and using the systems and processes that we have in place at the Karowe mine. And we look forward to challenging the convention further with other innovations that we will employ with TOMRA going forward.’

Further information:
TOMRA Sorting Mining
www.tomra.com/mining

TOMRA’s advanced sensor-based sorting technologies offer mining operations the dual benefits of energy efficiency and the ability to recover valuable ore even from sub-economic deposits or dumps. This has become increasingly relevant as the mining industry – a very large consumer of energy – is shifting towards a Green Mining approach to reduce its environmental footprint in the face of climate change, while running profitable operations.

Tord Svensson, TOMRA’s Head of Sorting Mining, explains: “For a mining company to become more sustainable and profitable, it requires a shift in focus that places more value on potentially limited commodities like water and ore. To achieve an environmentally-focused and efficiency-oriented production process – which is integral to Green Mining – it is necessary to implement solutions right from the beginning of the process. This is where ore sorting equipment comes in: using these technologies in the early stages of mining reduces waste material and shrinks the carbon footprint, while increasing profitability.”

TOMRA is a leading pioneer of sensor-based sorting technologies, which are able to give a significant contribution to a more environmentally sustainable approach in mining. It offers smart technologies for sorting and separating a variety of valuable substances (Figure 1). Its solutions range from industrial mineral processes to sorting gemstones, ferrous and non-ferrous metals, coal and other fuels and slag metal. The sensor-based sorting technology by TOMRA not only significantly reduces the amount of energy and water required compared to more traditional methods such as grinding and DMS (Dense Media Separation), but also maximizes the efficiency and quality recovery of valuable ores.

X-Ray Transmission (XRT), one of TOMRA’s leading solutions, separates dry material of various ore and minerals based on their atomic density, irrespective of surface properties and thickness. This means that it is not necessary to crush or grind every rock into smaller particles, which results in massive savings of energy, water, and their related costs. Considering that grinding is the most energy-intensive part of the production cycle, as an estimated 50-75% of the energy used in mining is for the liberation and comminution of ore and minerals¹, this technology can have a significant impact on the sustainability and profitability of a mining operation.

Pre-concentration techniques like sensor-based sorting have been proven to reduce energy consumption by about half, resulting in a considerable reduction of the CO₂ footprint and providing a highly cost-effective solution.

TOMRA has created a Green Counter that displays on its website the total amount of CO₂ reduced through the utilization of TOMRA’s sorting machines in real time. It uses the smart technology within the equipment, which records the amount of rock sorted and eliminated, as well as throughput and total hours of operation. With this data, TOMRA and mining companies are able to calculate the energy in kWh saved by not treating the waste which has been removed by the sorters. The amount of energy saved is converted into CO₂ equivalents, which in turn are converted into CO₂ metric tons. Through the use of TOMRA sorting machines, client companies have saved 123,696 metric tons of CO₂ in 2018 alone.

TOMRA’s sorting solutions have proven to be more than just technological innovation – they are also considered the benchmark for industry standards in both efficiency and sustainability. TOMRA remains committed to evolving its technology with a clear focus towards preserving our shared natural resources.

¹Source: “The Mining Industry and the Circular Economy” Mines – NREL Joint Workshop September 13, 2018

Further information:
TOMRA Sorting Mining
www.tomra.com/mining