Tag Archives: pre-concentration

Pre-concentration: it’s worth asking the question

Comminution of minerals, Environmental, Mineral processing, Mining equipment, Mining services, Sustainable mining, , , , ,

We’ve reviewed a novel, vendor-agnostic pre-concentration screening test in part one and explained a comprehensive five-step pre-concentration evaluation in part two…now for part three in the three-part series with SRK Consulting (Canada) Inc’s Adrian Dance (Principal Metallurgist) and Bob McCarthy (Principal Consultant)

SRK Consulting’s Adrian Dance and Bob McCarthy have devoted years to ensuring the mining industry can make informed decisions about preconcentration within their flowsheets and are now able to screen the opportunities quickly, cost-effectively and without vendor prejudice.

“We have been carrying out the different parts of the five-step evaluation process over the years, refining them independently and sometimes together,” McCarthy tells IM. “It is only now that we can present them all in a holistic way.”

This five-step process – which includes heterogeneity analyses; “size the prize” economics; laboratory test work that involves X-ray Transmission (XRT) based sensor technology; mine planning; and mine economics – has been deliberately designed to allow mining companies to pause at the end of each phase to re-evaluate if there is a strong enough case to continue with a preconcentration investigation.

BobMcCarthy-SRK
Bob McCarthy, Principal Consultant), SRK Consulting (Canada) Inc

The importance of such an approach has grown in recent years as more projects that are “grade-challenged” or metallurgically complex are being considered for exploitation by mining companies as the demand for metal increases worldwide.

Sensing this (pun intended), sorting and sensing manufacturers have been on the mining charm offensive, proclaiming the benefits of their technology – benefits that include cost reductions, improved metallurgical recoveries, rationalised use of energy and water, and more.

These market dynamics have created a void that SRK is looking to fill by providing the tools for both sides to assess the options and carry out informed decision making on which routes to pursue.

“We were concerned that the manufacturers didn’t have the background needed to understand the mining industry’s requirements,” Dance said. “At the same time, mining companies had difficult projects and deposits where they saw pre-concentration potential but didn’t know where to initially go to explore that potential.

“We saw a space for industry representatives like ourselves at SRK to bridge that divide.”

The independent testing that SRK has been able to offer for the last six or so months through its partnership with Base Metallurgical Labs (BML) in British Columbia was the final piece of the puzzle in establishing this nowestablished five-step process.

Able to not only indicate pre-concentration amenability but also provide key inputs into the pre-concentration strategy selection and evaluation, this has been employed for some 36 samples (close to 2,000 particles) being tested using the XRT unit situated in BML’s facility in Western Canada.

Demystifying the tech

While this XRT testing may have only recently become available to SRK and BML customers, the outcomes of SRK’s pre-concentration evaluation have been described to investors and stakeholders trawling through NI 43-101 reports up to the prefeasibility study (PFS) level for some time now. Various parts of the five-step evaluation have come into sections on metallurgical test work, mineral reserves, mining methods, costs and economics.

“Where the results feature is tied to what study stage the company is at and where people feel comfortable with pre-concentration,” McCarthy explains.

Providing comfort to mining companies and their investors is always difficult when examining any new flowsheet addition, hence the reason why many companies are initially pursuing pre-concentration or ore sorting in a ‘recovering ore out of waste’ scenario from material already deemed to be waste and having no economic value.

As a result, SRK has been very deliberate in the protocols it is pursuing.

Dance explains: “Because there is still a perceived ‘magical’ nature to preconcentration in that it can provide reserve upgrades and higher recoveries, we need to do more detailed evaluations at a preliminary economic assessment or PFS level than would be expected for other types of processing technology.”

For instance, the company is currently engaged on a gold operation where it has tested upwards of 22 samples (1,320 particles) for validation. “At this level of study, if you were working on comminution or leaching, the same process validation would be carried out with two or three tests,” Dance said.

McCarthy added: “We firmly believe that this five-step evaluation will allow people to sign off, at least at a PFS level, on whether pre-concentration is a viable route for them to take. Our process will prove this through testing and pulling different economic levers in the economic evaluation to quickly see where the value is, and where it isn’t.

“If pre-concentration is viable, you would then likely see clients moving on to performance testing with some of the sensing/sorting vendors at the feasibility study stage.”

Welcoming the independence

Those who understand the pre-concentration space have welcomed the involvement of SRK through its five-step process and, in particular, have highlighted the industry need for standardised and independent testing.

“They see where we are inserting ourselves into stages of the client and vendor relationship,” Dance said. “In no way are we competing with vendors – we are not suggesting we have the expertise they have. Rather, we are looking at the characteristics and amenability elements for the vendors to then truly apply their expertise, knowledge and sensor selection understanding.”

Adrian Dance, Principal Metallurgist, SRK Consulting (Canada) Inc

At the same time, Dance and McCarthy are looking to arm mining companies with relevant knowledge about pre-concentration principles, where the process could provide a grade uplift and what losses might be associated with the implementation. This is being done through gaining a better understand of their orebody through the testing.

It should result in mining companies providing a more representative sample to the pre-concentration vendors for the performance testing many of them offer. “Mining companies can then understand these pilot test results more broadly and ask more questions, if needed,” Dance said. At the same time, the vendors have a ‘pre-qualification’ check in hand: they would know from the SRK process if there is a strong basis for carrying out the performance test in the first place.

And, of course, SRK can get involved after the five steps are complete, carrying out small-scale work and integrating these results with the larger
scale performance testing that could eventually underpin a flowsheet developed by a third-party engineering company.

“We view pre-concentration as another aspect of geometallurgy that needs to be interrogated just like comminution and flotation,” Dance said.

The future focus

It is potential changes to both of those processes that could have positive implications for pre-concentration in the mining sector.

“We’re now seeing more flowsheets designed with a multi-stage comminution flowsheet that, at every stage, asks: ‘do I need to process the oversize material again?’” Dance said. “There is an opportunity for the right sensors to answer those questions. That is being highlighted in the design of some of this technology; some newer ore sorting units are reminiscent of cone crushers in size and shape, which means they can be inserted into this flowsheet with ease.

And, of course, some pre-concentration-focused companies have gone upstream of the plant to the pit to provide these readings: an area Dance sees as representing the future.

“Heterogeneity is better preserved the further upstream of the plant you go, so it is obvious to think that pre-concentration technology – which feeds off this heterogeneity – should be placed here,” he said. “The issue comes with getting a representative sample to test – whether that is a shovel load, or the equivalent of what a 200-t payload truck can carry. Ultimately the mining industry is at a ‘prove it’ stage when it comes to pre-concentration technology. The mining companies want to see results on paper or on a screen before they sign off on this technology and process. At the scale of a truck or shovel, this is very challenging.”

McCarthy added: “The Heterogeneity and Scale analysis we are doing in step one of the evaluation will identify some of these opportunities within the selective mining unit sizing, but it is still early days on factoring that into sorting at a truck or bucket scale.”

This work will require closer examination of the drill core than the typical 1-m assayed intervals, as well as a way to estimate the level of mixing that occurs between vertical blast holes, post-blasting, post-loading and post-conveying.

This comprehensive plan is broadening too, factoring in more than just economics.

For instance, SRK has made a case for carrying out the same sizing and XRT analysis included in the five-step evaluation for mill pebbles – which can represent up to 30% of the entire plant feed in some cases – to assess their true value.

This obviously has a cost benefit, as well as an energy benefit – avoiding recirculation of pebbles avoids excess energy use. This same testing is indicating there could be further energy benefits to be had by using preconcentration, too.

In addition, “We have recently expanded our testing protocol to now measure specific energy requirements of the concentrated material compared with the original feed,” Dance said. “This has shown (at times) a softening effect of pre-concentration that can produce measurable savings in power.”

And the impacts on water and energy use are another avenue that could come into the ‘size the prize’ economics McCarthy uses in step two of the five-step evaluation process. “There is no reason to think this could not be included in the analysis in the future; all we would need are the metrics for the existing proposed operation – the amount of water and energy used for the number of tonnes in the mill feed,” he said. “It will then just be a simple case of amending the two inputs based on the pre-concentration work.”

Against a backdrop of falling grades, increasing metallurgical complexity and perceived future demand for commodities, the pre-concentration question needs to be asked by all companies.

For more information on the XRT pre-concentration screening test SRK and Base Metallurgical Labs can provide, as well as the five-step evaluation process for pre-concentration amenability, click the link here

SRK’s stepwise approach to pre-concentration analysis

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Having outlined a new vendor-agnostic, lab-based “pre concentration screening test” for mining in part one of this three-part series, SRK is back for part two, discussing the wider pre-concentration evaluation process that this testing fits into

“With any pre-concentration analysis, we need to, first, understand the heterogeneity of the deposit; simply put, if you don’t have heterogeneity, you don’t have the ability to separate the good stuff from the bad stuff and carry out pre-concentration,” Bob McCarthy, Principal Consultant, SRK Consulting (Canada) Inc, says.

With this baseline in mind, SRK Consulting has devised a pathway for companies with drill core at their disposal to analyse whether pre-concentration is a viable option for their flowsheet.

Made up of five steps, this staged approach is deliberately designed to allow companies to pause at the end of each phase to re-evaluate if there is a strong enough case to continue investing the time and finances required.

The heterogeneity analysis is first up, which, under SRK’s evaluation, includes two different approaches based off drill hole analysis: Heterogeneity and Scale and Composite-Sample Relationship Analysis.

“Heterogeneity and Scale involves a process of looking up and down the bore hole at different aggregation distances from every sample and interrogating the sample grade – or net smelter return – against the aggregations above and below that individual sample,” he explains. “We then increase the size of the aggregation to see how that relationship changes.”

Such analysis enables SRK experts to derive the heterogeneity measures typically dubbed ‘waste in ore’ (mineralisation below the cutoff grade within an above cutoff grade zone) or ‘ore in waste’ (mineralisation above the cutoff grade within a waste or marginally below cutoff grade zone). Using a cutoff grade derived from industry benchmarking, the consultants assess the aggregation distance, as resolved in the vertical direction, with the “selective mining unit” (SMU), which typically relates to equipment sizing for mining.

“Heterogeneity and Scale involves a process of looking up and down the bore hole at different aggregation distances from every sample and interrogating the sample grade – or net smelter return – against the aggregations above and below that individual sample,” Bob McCarthy says

“The pitfall some companies go down is picking your SMU to match an equipment size and production rate typically aligned to a corporate or strategic objective,” McCarthy says. “This could mean generating a 12-14-year mine life for a gold operation, or some other investor-led metric that doesn’t necessarily respect the deposit’s heterogeneity.”

The second approach – Composite-Sample Relationship Analysis – allows consultants to further quantitatively assess those waste in ore/ore in waste heterogeneity measures.

“Those parameters have multiple uses after being determined,” McCarthy says. “For example, they help guide in the sample selection – you can even visualise them in 3D with something like Leapfrog. You can also see contiguous lengths of above or below cutoff grade material in ore zones or marginal waste zones, representing what an ore sorter may see. These would be targeted for testing.”

Responding to industry calls, SRK now offers a step between this fundamental heterogeneity analysis and the test work it can conduct at Base Metallurgical Labs’ Kamloops facility in British Columbia, with what McCarthy calls “size the prize” economics. It provides insight into possible pre-concentration strategy outcomes and, just as important, justification to continue to the next step of lab test work.

This process – carried out by SRK on several projects in the past – is designed to allow the mining company and consultant to test pre-concentration strategies from an economic perspective, assessing if an operation should be removing waste from ore or looking to recover above cut-off grade material from “marginal waste”.

McCarthy added: “It is about answering these questions: is it best to remove waste from mill feed, and to what maximum grade of feed, or to extract mineralised material from marginal, below cut-off grade material that increases the mineral reserve? And, of course, do the expected results of this process look promising?”

Gold is a good example here as the economic case study for pre-concentration often only stacks up when a “cap” is applied to the grade of ore subjected to pre-concentration. In other words, the highest-grade material should not be targeted. Even high-efficiency pre-concentration methods incur some metal loss, and any amount of “loss” that occurs in a gold project is difficult to make-up within a conventional flowsheet.

Example of drill core intervals showing waste in ore percentages of up to 80%

The third step in this five-step process is the lab test work McCarthy’s colleague, Adrian Dance (Principal Metallurgist at SRK Consulting), previously outlined in detail in the first article in this three-part series.

The “pre-concentration screening test” leveraging X-ray Transmission based sensor technology can not only indicate pre-concentration amenability, but also provide key inputs into the pre-concentration strategy selection and evaluation, Dance says. He says the testing offers an assessment of pre-concentration potential, as well as an estimate of material bypass and metal upgrade from samples as small as half cores.

Used in conjunction with crushing and screening, this testing rapidly – and cost effectively – assesses the potential for pre-concentration, which can then be applied to scoping or pre-feasibility studies, according to SRK and Base Metallurgical Labs.

Which is where steps four and five of the SRK evaluation – mine planning and mine economics – come in.

“With the heterogeneity measures assigning the distribution of waste in ore, ore in ore, and ore in marginal material in mining block models, the test results reflecting these conditions can be populated into those same models for mine planning,” McCarthy explains.

Typical mine planning steps of pit/stope optimisation, mine design and scheduling can proceed on the assumption of one or more pre concentration strategies, with different versions of mine schedules, reflecting different pre concentration strategies, evaluated.

This type of analysis typically works for a project in pre-feasibility study stage, where engineers can go into the existing block model, bringing the results from the heterogeneity and lab tests into the mine optimisation, design and scheduling process that takes place.

“The challenge is that the scheduling needs to assume a certain strategy – maybe you have determined what that strategy is close enough with the ‘size the prize’, but there are always a few elements you may want to tweak,” McCarthy says. “This could be the mass pull, or waste rejection targets, for instance.”

As a result, sensitivity analyses – mostly numerical tweaks – are embedded in the process.

When not dealing with a pre-feasibility-level project, the SRK team typically rely on an existing schedule that has been run during a scoping study or preliminary economic assessment. This model is modified and tested with different schedule scenarios and pre-concentration strategies based on the heterogeneity measures (step 1) integrated with the lab test results (step 3).

Out of the mine planning step comes a schedule that would go onto the next step: mine economics modelling.

“The model is configured to take in the heterogeneity measures, recovery curves, etc to change the amount of metal reporting to revenue and so forth,” McCarthy says. “Once I get schedules – based on the upgraded block models or it may be a pre-existing schedule – I would then put them into an economic model that has all the levers to pull for different pre-concentration strategies.”

Such a stepwise approach is indicative of where the mining industry is at the moment with vendor-agnostic pre-concentration analysis, enabling companies to get comfortable with the data and assessments as their understanding of their deposit’s heterogeneity grows.

There are potential refinements and fine-tuning opportunities too.

For example, if SRK was gifted with drill core or assay data that was more granular than the 1-2 m intervals typically taken at the exploration stage, it could indicate with greater certainty how particle sorting – typically analysing grades at intervals around a few centimetres – could benefit the deposit in question.

Also, if mine modelling software had matured to the point where block models could be tailored specifically to these waste-in-ore and ore-in-waste characteristics, SRK could segregate the areas in question, instead of applying the type of dilution factors they currently have in place to account for the grade-based realities. This would more clearly communicate the deposit’s heterogeneity to all stakeholders.

Yet, McCarthy and Dance know this will come in time, and are happy to work within the current confines to continue the industry’s education process and identify where the pre-concentration opportunities are

Further discussion on this and what SRK’s pre concentration analysis evaluation – with that embedded pre-concentration screening test – means within the broader mining industry context will follow in the final article in this three-part series later this year

STEINERT sensor-based sorting solutions helping Ferbasa adopt ESG practices in Brazil

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The use of sensor-based sorting (SBS) technology is allowing Companhia de Ferro Ligas da Bahia (Ferbasa) to avoid unnecessary processing by separating a fraction of the high-grade material from the metallurgical process feed in advance, a recent case study from STEINERT has revealed.

Ferbasa is in Ipueira, a municipality in the state of Bahia in the northeast of Brazil. It operates one of the largest chromite mines in Brazil and is considered a pioneer in the use of SBS technology, STEINERT says. The company processes chromite obtained from an underground mine, with the extracted material pre-concentrated using sorting technology that employs sensors, and is later used in the production of specialised steel alloys.

With a processing capacity of 12 Mt/y, the company has been using sensor-based sorting for 10 years, in a completely dry process that separates waste from high-grade chromite.

Eriberto Nascimento Leite, Mining Director at Ferbasa, says the ability to avoid unnecessary processing by separating a fraction of the high-grade material from the metallurgical process feed in advance through the use of SBS removes the requirement for any additional processing. In that way, particles which are not economically viable are eliminated from the process beforehand with only valuable material undergoing the follow-on concentration steps.

At Ferbasa, the use of SBS technology has enabled an increase in production, in addition to reducing costs in the subsequent processes, such as comminution and the use of inputs, such as reagents.

“Today, at Ferbasa, sensor-based sorting technology helps us adopt ESG practices, reducing waste, maximising production efficiency and contributing to the conservation of natural resources,” Nascimento says.

Nowadays, it is not only the mined ore that is processed, but also the stockpiles, which contain considerable amounts of chromium. The treatment of these stockpiles is only possible thanks to process automation and its high-capacity levels, which reach up to 180 t/h. Stockpile treatment has the potential to increase productivity in the mine. In terms of resource use, there is potential to reduce the consumption of water, energy and chemical reagents primarily because SBS is a dry separation process, unlike other pre-concentration processes such as dense media separation.

Ferbasa has always used a pre-concentration process with the aim of separating lump ore, which has a high chromite content, from the low-grade ore that goes to the concentration plant. However, this used to be a manual separation process. Bartolomeu Fonseca, the former Processing Manager at Ferbasa, discovered an article about sensor-based sorting technology from STEINERT. In 2012, he prepared material to be sent for tests at STEINERT’s Test and Development centre in Germany, and these were deemed successful.

A STEINERT KSS XT L in the chromite preconcentration setup

Ten years ago, when the first equipment was being installed, Ferbasa’s employees were sceptical about its capacity to support the adverse conditions in the mine. This is why STEINERT Latinoamericana, a subsidiary of STEINERT GmbH in Germany, offered a “try and buy agreement”. Over the years, the equipment’s high level of durability has been verified, resulting in the first unit still being in operation today, with a total of 34,000 hours of runtime.

“Looking back, it was not easy to apply the technology, but I decided to move forward because I believed that the technology could be effective,” Fonseca says. “Now, already retired, I am very proud of the legacy that I have left to the company. I had the full support from the mining director at that time, Wanderley Lins, but it was my responsibility to make it work.”

In 2014, during the commissioning of the first sorting system, a STEINERT XSS-T, STEINERT Latinoamericana started a partnership with Ferbasa.

Alonside this, STEINERT currently has a team of 30 collaborators who serve several mining clients in Latin America, in addition to having a test centre near the office in Brazil, enabling tests to be carried out with more convenience and efficiency for local clients.

Ferbasa started operating its first equipment in 2014. By 2019, it already had six units installed for the processing of run of mine and low-grade stockpiles.

The production benefits from flexibility of the sorting systems, which generate waste material, pre-enriched material and high-grade material. The processing capacities are up to 120 t/h for particles of 1- 3 in (25-76 mm), reaching up to 180 t/h for particles from 2-5 in. In terms of the sizes processed, the combination of sensors facilitates the separation of particles up to 5 in; a feature that, STEINERT says, reinforces the robustness and efficiency of the equipment for the detection and ejection of extremely coarse particles. In total, recoveries reach values of up to 90%, with upgrades of up to 1.5-3 times the feed levels.

Currently, Ferbasa applies SBS technology to process 100% of their run of mine, using two units from STEINERT, the STEINERT XSS T and STEINERT KSS | XT L, in a two-step process. In the first step, waste material is rejected, and, in the second, pre-enriched and high-grade materials are generated. The high grade-material meets the content specifications to be sent to the metallurgic plant, while the pre-enriched material is sent to another plant to follow other concentration procedures. Furthermore, the technology is applied in the processing of low-grade stockpiles, using two STEINERT KSS | XT L units – which combines the X-ray transmission sensor with three other additional sensor options (Induction, 3D laser, and Colour) – in two steps to separate waste, pre-enriched material and high-grade material. As a result, the low-grade stockpiles are processed in an economically viable way and with high sustainability gains.

SRK Consulting, Base Metallurgical Labs tackling pre-concentration amenability

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In this first of a three-part series of articles on pre-concentration in the mining space, SRK’s Adrian Dance outlines a new vendor-agnostic, lab-based testing process that could have huge ramifications for a sector in need of guidance and strategy.

Stay tuned for part two in the series, which will see SRK’s Bob McCarthy explain how results of such testing can be used by the mining community.

The need to expand the values or lives of assets while reducing both energy and water use is leading to a flood of new enquiries landing on the doorsteps of the pre-concentration and ore sorting company fraternity.

Anybody that takes a passing interest in the junior mining sector has seen the TOMRAs and Steinerts referenced in numerous TSX-V, ASX and AIM releases, with early-stage test work often detailing results from particle sorting trials.

On the bulk sorting side of the business, more sensor-based solutions are emerging to cope with the need to build or expand copper assets in the most sustainable ways possible. Some progressive companies are including such innovations in initial flowsheet plans.

The bottleneck in the current environment is testing, according to Adrian Dance, Principal Metallurgist at SRK Consulting, with many of the vendors simply overrun with requests to test material or provide modular pilot plants that can be re-located after samples are processed.

At the same time as demand is outpacing supply, there is an argument that a standardised, vendor-agnostic test should be devised to screen for ore sorting or pre-concentration amenability before any vendors are even engaged.

SRK is one company arguing for this.

“At the moment, the manufacturers are driving the action, dictating what the sample has to look like for something that resembles a pilot plant trial,” Dance told IM. “Like any pilot plant run, these trials often give you an excellent result on that specific sample, but the question is: is that sample truly representative of the orebody? Or, is it representative of what a sorter would actually see in operation?”

An increase in available data and transfer of said data across the mine site is going some way to disproving the idea of mass homogeneity at many bulk mining operations – at copper porphyries, for example.

Dance believes this same thought process should be applied to pre-concentration.

This is where SRK Vancouver and Base Metallurgical Labs, both in British Columbia Canada, are looking to provide a “pre-concentration screening test” using X-ray Transmission (XRT) based sensor technology that can not only indicate pre-concentration amenability, but also provides key inputs into the pre-concentration strategy selection and evaluation.

The two companies are offering an assessment of pre-concentration potential, as well as an estimate of material bypass and metal upgrade from samples as small as half cores.

The XRT sensor lab unit

Used in conjunction with crushing and screening, this testing rapidly – and cost effectively – assesses the potential for pre-concentration, which can then be applied to scoping or prefeasibility studies, according to the companies.

“The testing has two parts to it,” Dance explains. “It was originally designed to see what the grade distribution of fines is after crushing and to see how that grade distribution varies depending on the amount of crushing energy applied to the material.

“The second part is looking to see if the material is amenable to pre-concentration when it is coarse and dry – ie conveyable.”

According to the companies, the XRT-based test can provide this within 24 hours of a sample arriving at the lab.

All of this helps characterise deposits (or low-grade stockpiles) using small samples, cutting down sample mass requirements, and potentially running multiple scenarios to obtain what Dance refers to as the “optimal sort”.

The two companies are not looking to replicate what may be done at one of the sorting vendors’ testing facilities. Instead, they are looking at whether the material wants to respond to this type of particle sorting exercise in the first place and at what size fractions pre-concentration would make sense.

Should the indications prove positive, the information on what appears to be the optimal sort can be passed onto the vendors for more accurate follow-on testing of a bulk sample.

“In this way, we are qualifying the opportunity ahead of the vendors getting samples,” Dance said. “The vendors also have knowledge about how a sample has responded to amenability testing in the first place and what other tests were conducted concurrently.

“We will be providing complementary testing that will, ultimately, benefit the project in question.”

Dance says the aim is to create an industry standard test for pre-concentration that can be replicated by commercial laboratories all over the globe and is carried out routinely with hardness and crushing and grinding testing.

“One of the samples we have already tested was being assessed for rock hardness and we were able to offer them pre-concentration amenability results at the same time,” he said. “We’re not trying to provide the ultimate or ‘perfect’ test; it just needs to be a standard test that can be benchmarked and easily replicated across the industry.

“The value is in the data shared. People want to know how their sample compares with other operations, but this will only come with a large volume of testing.”

XRT scan results of particles
XRT scan results of particles

While XRT is first up, Dance says the company could soon add an X-ray Fluorescence option to the unit.

And, further out, he is confident this type of testing will open the door to more sensors coming into the mining sector outside of the ones already on offer.

“When we show the electronics industry that we have a viable market by dictating the terms of how we want to sort material through knowledge of such testing, the sensors will come,” he said.

“I’m not saying everyone should implement pre-concentration; far from it, as I expect a minority of the tests will show strong amenability. What I am saying is that everyone should test for it.

“By providing a no licence fee test that has no bias towards any vendor, we are allowing mining companies to scope that out.”

The venture is also part of Dance’s own ambitions to educate the mining sector on its waste-generating ways, he says.

“In the grinding space there is so much material that is recycled throughout the plant inefficiently,” he said. “We must question why we are putting things back in the mill to ultimately take it to tailings.

“There is simply no way we can carry on pursuing the economies of scale argument to reduce our energy consumption and water use. We need to embrace new technology in the right way – not running towards it but walking with purpose and data-backed decisions.”

Metso Outotec and Malvern Panalytical to collaborate on bulk ore sorting projects

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Metso Outotec and Malvern Panalytical have signed a collaboration agreement to, the OEM says, provide sensor-based bulk ore sorting solutions to the mining industry.

The combination of the companies’ expertise in crushing and bulk material handling solutions, and ore analysers enables the parties to offer an industry-leading portfolio of solutions for bulk ore sorting, Metso Outotec said.

“With this offering, mining customers can substantially improve the head grade by pre-concentrating the ore at the crushing stage and, thereby, reduce their energy consumption and related environmental footprint in the comminution stage,” Metso Outotec said.

The agreemeent will see Metso Outotec’s crushing and bulk material handing solutions integrated with Malvern Panalytical’s cross-belt analysers. The latest generation of cross-belt analysers, CNA³, has been designed for tough environments such as underground mines, and features the Sodern neutron solution, which is powered by Pulsed Fast Thermal Neutron Activation (PFTNA) technology. The technology has been used by Anglo American, among others.

Rashmi Kasat, Vice President, Digital technologies at Metso Outotec, said: “Sustainability is a top priority for our entire industry. Collaboration with partners like Malvern Panalytical will allow us to meet the industry’s increasing sustainability and resource efficiency needs in an enhanced way in the early comminution stage. Sensor-based bulk ore sorting and data-driven analysis upgrades low grade or waste stockpiles making them economical and far less energy-intensive to treat.”

Jarmo Lohilahti, Sales Manager at Malvern Panalytical, said: “Malvern Panalytical’s cross-belt analysers provide high-frequency online data for cost-efficient bulk material analysis of major commodities. This collaboration enables customers to benefit from the in-depth know-how from both companies.”

Renato Verdejo, Business Development Lead for Bulk Ore Sorting at Metso Outotec, concluded: “Bulk ore sorting allows waste rock elimination early in the process and, when combined with Metso Outotec’s complementary crushing and bulk material handing solutions portfolio, it provides more sustainable flowsheets for our customers. Enhanced bulk ore sorting will contribute to Metso Outotec’s Planet Positive portfolio.”

On the particle sorting side of the business, Metso Outotec and TOMRA have a non-exclusive cooperation in place to supply particle ore sorting solutions for the mining and metallurgical industries.

Hudbay’s Constancia continuous improvement quest leads to MineSense XRF trial

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Hudbay Minerals has one of the lowest cost per tonne copper sulphide operations in Peru on its hands at Constancia, but it is intent on continuously improving the mine’s margins and environmental performance through a commitment to continuous improvement. This has recently led it to exploring the potential of sensor-based ore sorting.

Hudbay’s operations at Constancia include the Constancia and Pampacancha pits, an 86,000 t/d ore processing plant, a waste rock facility, a tailings management facility and other ancillary facilities that support the operations.

The company increased reserves at the mine, located in the Cusco department, by 33 Mt at a grade of 0.48% Cu and 0.115 g/t Au last year – an increase of approximately 11% in contained copper and 12% in contained gold over the prior year’s reserves.

With the incorporation of Pampacancha and Constancia North, annual production at Constancia is expected to average approximately 102,000 t of copper and 58,000 oz of gold from 2021 to 2028, an increase of 40% and 367%, respectively, from 2020 levels, which were partially impacted by an eight-week temporary mine interruption related to a government-declared state of emergency.

Constancia now has a 16-year mine life (to 2037) ahead of it, but the company thinks there is a lot more value it can leverage from this long-life asset and it has been looking at incorporating the latest technology to prove this.

In recent years it has, for instance, worked with Metso Outotec to improve rougher flotation performance at Constancia using Center Launders in four e300 TankCells and installed a private LTE network to digitise and modernise its open-pit operations.

Peter Amelunxen, Vice President of Technical Services at Hudbay, said the Constancia ore sorting project – which has seen Hudbay partner with MineSense on a plan to trial the Vancouver-based cleantech company’s ShovelSense X-ray Fluorescence (XRF)-based sorting technology – was one of many initiatives underway to further improve the operating efficiency at Constancia.

“The ore sorting program is separate from the recovery uplift program at Constancia,” Amelunxen said, referring to a “potentially high-return, low capital opportunity” that could boost milled copper recovery by 2-3%.

He added: “The ore sorting program is expected to yield positive results at the mining phase of the operation and is expected to increase the mill head grade and reduce metal loss to the waste rock storage facility.”

Back in April 2021 during a virtual site visit, Hudbay revealed it was trialling bulk sorting at Constancia as one of its “optimisation opportunities”, with Amelunxen updating IM in mid-January on progress.

Hudbay has previously evaluated particle sorting at its Snow Lake operations in Manitoba – with the benefits outlined in a desktop study “muted” given “bottlenecks and constraints”, Amelunxen said – but, at Constancia, it considered XRF sorting from the onset for copper-grade only pre-concentration, due to its perception that this application came with the lowest potential risk and highest probability of success.

The company has a three-phase evaluation process running to prove this, with phase one involving a “bulk sorting amenability study”, phase two moving up to laboratory-scale testing and phase three seeing trials in the field.

The “bulk sorting amenability study” looked at downhole grade heterogeneity to estimate curves of sortability versus unit volume, Amelunxen detailed. Laboratory testing of drill core samples to evaluate the sensor effectiveness was then carried out before an economic analysis and long-range-plan modelling was conducted.

With the concept and application of bulk sorting having cleared all these stage gates, Hudbay, in November, started pilot testing of XRF sensors on a loader. This involved fitting a ShovelSense unit onto the 19 cu.m bucket of a Cat 994H wheel loader, with around 20 small stockpiles of “known grades” loaded onto the bucket and dispatched into a feeder and sampling system (pictured below, credit: Engels Trejo, Manager Technical Services, Hudbay Peru). With this process completed, the company is now awaiting the results.

At a similar time, the company moved onto demonstration trials of a “production” ShovelSense sensor unit on the 27 cu.m bucket of a Hitachi ECX5600-6 shovel operating in one of the pits. It has collected the raw spectral data coming off this unit since the end of November, with plans to keep receiving and analysing sensor data through to next month.

“We should have the finalised XRF calibration in February, at which time we’ll process the raw data collected during the three-month trial period and compare it with the short-term mine plan (ie grades of ore shipped),” Amelunxen said. “So, by the end of February or early March, we’ll be able to validate or finetune the economic model.”

Should the results look favourable, Amelunxen is confident that leasing additional sensors and installing them on the other two Hitachi ECX5600-6 shovels will not take long.

Credit: Engels Trejo, Manager Technical Services, Hudbay Peru

“Plans may change somewhat as the program unfolds,” he said. “For example, we may have success sorting ore, but feel additional calibration is required for waste sorting at Pampacancha, in which case we may install production sensors on Constancia ores while doing another trial program at Pampacancha.

“It all depends on the precision of the XRF calibration.”

Higher head grades and potentially higher copper recoveries may be the headline benefits of using ore sorting technology, but Hudbay is equally focused on obtaining several key environmental benefits, including reduced consumption of energy and water.

On the latter, Amelunxen said: “This is expected due to the processing of less ‘waste’ by removing uneconomic material earlier in the process and reducing the hauling and processing costs of the uneconomic material.”

Looking even further forward – past a potential commercial implementation of XRF-based ore sorting at Constancia – the company plans to evaluate the application of other sensors, too.

“For our future development copper project in Arizona, we plan to look at other sensors as well,” Amelunxen said, referencing the company’s Rosemont asset.

This ore sorting project is not the only project the processing team at Constancia are examining, as Amelunxen already hinted at.

As part of the recovery uplift project, it is installing equipment that will allow the operation to increase the overall mass recovery of the roughers, which is currently constrained by the downstream pumps and cleaning circuit.

“This will allow us to achieve an expected 2-3% increase in copper recoveries without impacting concentrate grade,” Amelunxen said.

It has various initiatives underway under the “Moly plant improvement projects” banner, too. This includes flowsheet optimisation, pH control in the cleaners and pH reduction in the bulk cleaners.

“This project has been in the works since late 2019, and the new mechanical agitator installation in the cleaning cells was completed during the August 2021 schedule mill maintenance shutdown and the new nitrogen plant was commissioned in the second half of the year,” Amelunxen explained. “The next steps are pH control in the cleaners (with CO2), water balance optimisation and potentially installing a Jameson flotation cell as a pre-rougher (the cell is already on site and not in use, it will be repurposed pending results of the pH trials).”

A flotation reagent optimisation study is also on the cards, aimed at reducing zinc and lead contamination in the copper concentrate.

“A depressant addition system is on the way to site and should be installed in February, with plant trials commencing in March,” Amelunxen said, explaining that this followed laboratory test work completed in 2021.

CRC ORE, CSIRO look at broadening pre-concentration tech applications

Bulk handling, Comminution of minerals, Mineral processing, Mining finance, Mining services, Mining software, Power supply for mines, Sustainable mining, Water management, , , , , , , , , ,

CRC ORE and Australia’s national science agency, CSIRO, have formed a Future Research Program to, they say, take CRC ORE’s most promising fields of research into new areas to broaden the impact on the Australian mining industry and economy.

This work will boost the sustainability of the mining industry by helping reduce energy and water consumption, generation of tailings and residues, the physical footprint of operations, as well as optimise the extraction of valuable minerals from resources, the companies said.

The Future Research Program, launched in September 2021, will ensure the work of CRC ORE and its research continues to benefit the Australian mining industry.

The program will expand upon CRC ORE’s foundation research into the development of ore pre-concentration technologies that can be deployed within the mine and ahead of the mineral processing plant. The new research scope will investigate ways to apply these principles further down the mining value chain, targeting smaller particle sizes and a wider range of ore types.

Focus areas will include:

  • Incorporating the principles of Selective Breakage into the design and operation of comminution circuits;
  • Optimising ore feed to coarse and fine particle separators to enhance their performance;
  • Step change reductions in energy and water intensity; and
  • Developing new options for sustainable management of waste material

CRC ORE’s former General Manager of Research and Innovation, Paul Revell, who is now overseeing the program at CSIRO, said, if successful, the research will increase the number of potential locations where pre-concentration can be deployed, providing a larger overall impact for the minerals industry.

“Our aim is to extend the resource base that pre-concentration can be applied to,” Revell said. “The pre-concentration technology developed through CRC ORE is currently best suited to structurally controlled, vein-hosted ores, however these only represent about one third of the resource base on average.

“A key ambition of the new program is, therefore, to initiate research into technologies that can pre-concentrate disseminated ores. This group of ore types can be difficult to pre-concentrate with contemporary mineral processing technology, however they host a significant proportion of valuable base and precious metals.”

Revell said some 3% of global direct energy consumption is used in the mining industry just in crushing rock, so if pre-concentration technology could be applied more broadly across the resource base, it would have a wider global environmental and economic impact.

“The opportunity is to develop more energy efficient crushing and grinding processes that are integrated with a pre-concentration capability, to remove as much barren material from the ore as possible prior to subjecting the remaining ore to energy and water intensive fine grinding and concentration processes,” he said. “We’re focusing on the largest energy consuming portion of the mining value chain.”

Revell said it was important to note that the program is initially small scale and aims to undertake preliminary research into these areas that others could then build upon.

The program will be run for an initial three years with the possibility for extension through continuing industry sponsorship and collaboration.

“We will explore opportunities to engage with the mining industry to build a self-sustaining and on-going applied research portfolio in this field to advance promising developments to commercialisation,” Revell said.

“We are fortunate to have CSIRO as a research partner who are supportive, share this vision, and have a depth of research capability and excellent facilities.”

The program will also support CRC ORE’s mission to help build a highly skilled workforce for the nation amid an ongoing skills shortage in the resources sector. It will initially support a number of Research Higher Degree scholarships, which will be fully funded and placed across several selected Australian universities.

“One of CRC ORE’s key objectives has always been to build research capacity across Australia, which it did very successfully during its government-funded term,” Revell said. “By taking this new seed research and offering higher degree students a Masters degree or a PhD, it will build capacity for the minerals industry as well as getting the work done. It’s a great outcome.”

CSIRO Mineral Resources’ A/Director, Dr Rob Hough, said CSIRO is looking forward to commencing activities within the Future Research Program, initiated in partnership with CRC ORE.

“The R&D focus areas align well with our existing initiatives and plans, which have significant potential to positively impact the Australian minerals industry,” Dr Hough said.

Metso Outotec on ore sorting’s potential ‘revolutionary change’

Automation, Comminution of minerals, HOF, Metallurgy, Mineral processing, Mining equipment, Mining services, Mining software, Sustainable mining, , , , , , , , , , , , , , , , ,

Metso Outotec stands out among the mining original equipment manufacturers for having publicly acknowledged ore sorting is on its radar.

The Outotec business had a relationship with TOMRA Sorting Solutions dating back to 2014 when the two companies signed an agreement that would see the particle sorting company supply Outotec-branded sorting solutions to the mining and metallurgical industry. Metso, meanwhile, has previously disclosed it was developing “breakthrough proprietary technology to address the demand of high throughput accurate sorting”.

Close to eight months after the two companies merged to become Metso Outotec, IM put some questions to Erwin Huber, Vice President, Crushing and Conveying Systems; David Di Sandro, Business Development Manager – Optimisation and Test Labs; and Rashmi Kasat, VP, Digital Technologies, Minerals, to find out the current state of play with ore sorting at the mineral processing major.

IM: Back in November at your Capital Markets Day, there was mention of ‘AI-powered Ore Sorting Solutions’ during a presentation. Can you expand on what this offering might include? What stage is it at in terms of commercialisation?

DDS: Ore sorting is one of the most exciting recent developments in our industry. With improvements in sensor capabilities and adoption of artificial intelligence (AI), this may well become the revolutionary change this industry needs to sustain itself in the face of diminishing grades and orebody quality.

EH: With our ore sorting solution development, we are targeting the ability to deliver complete offerings of hardware and sensor-fusion platforms as it relates to both bulk and particle ore sorting. These platforms would utilise AI to optimise the feed material for the downstream process. Metso Outotec is uniquely positioned to understand and optimise that plant feed stream with deep knowledge and almost complete technology coverage in both the concentrator and tailings processing areas.

We plan to bring new solutions to the market in the short term and continuously launch new technologies to increase capabilities and capacities when the developments are mature enough.

IM: Will these solutions leverage existing tools within the Metso Outotec product offering? Will they make use of existing agreements with other companies (for instance, the agreement with TOMRA that Outotec previously had in place)?

EH: Metso Outotec carries out its own development of these solutions, and some partnerships are part of it once sensoring and analysing different minerals and elements are not possible with a single or only a few technologies. Mining and concentration are becoming more and more a digital world where breakthrough innovation is finding its space towards efficiency and sustainable possibilities. Smart systems will enable improved equipment uptime, efficiency and remote diagnosis of process and maintenance, and will be the bonding element between our traditional offering portfolio and new technologies.

IM: Previously Metso has talked about the development of a bulk sorting solution: do these ‘AI-powered Ore Sorting Solutions’ fit into that category, or are they more particle sorting solutions?

EH: Bulk ore sorting enables material selection at high throughput flows and particle technology is limited by capacity while bringing the benefit of high accuracy on selectivity.

RK: Bulk sorting is in its early stages in industry and no single sensor can determine minerals content across all ore types and mine sites. This is where AI algorithms play a significant role in ‘self-learning’ ore characteristics, mine site by mine site. It also provides great opportunities to do sensor fusion and more accurately determine the minerals content based on outputs from various sensors and sensor types. AI augments our expert’s tacit knowledge and provides a more reliable way over time to analyse big data generated from online mineral analysis.

IM: Where in the flowsheet do you envisage these solutions going?

EH: The earlier we can remove the gangue from the flow stream, the better our energy efficiency will be by reducing the volume of waste material that is processed by downstream equipment. Deposits in advanced development allow for in-pit backfill bulk ore sorters that may be deployed behind mobile in-pit crushers, or before the coarse ore stockpile where backfilling is not an option. There are several pre-concentration technologies that can be applied at each stage of mineral processing and the ideal operation should combine those tools to remove the liberated gangue at multiple stages of the processing plant in order to achieve the most sustainable process (ie bulk/particle ore sorting, selective breakage, coarse flotation).

IM: Will the benefits of your solution be felt beyond the crushing and grinding stage? Do you intend to use the data generated from the ore sorting solutions to benefit the whole downstream flowsheet?

DDS: One of the benefits of ore sorting is more efficient removal of waste from the process feed. Under certain circumstances, this also means removal of deleterious material which otherwise would adversely affect downstream process performance such as flotation recoveries. In these cases, the downstream benefits are intrinsic. The key would be understanding the geometallurgical mapping of all rock types and their mineralogy, so a philosophy of ‘include or reject’ can be applied on a metallurgical response basis. This mapping can be improved with SmartTag™ and GeoMetso™ technologies from Metso Outotec.

EH: The ability to sort, the geometallurgical mapping and metallurgical response obviously feed back into the block model and allow for more options in the mine plan and life of mine resource recovery, for example with the deployment of low-grade stockpiles. This further enhances the sustainability of the mining operation.

IM: Is the market ready for and receptive to such a powerful ore sorting solution?

DDS: As we all know, for good reason, our industry is full of early adopters rather than innovators. Most operations will need to see the technology succeed elsewhere before increasing their uptake of the technology. The initial implementation will likely occur in partnership with customers whose operations need this technology to be economically viable.

EH: The key is to understand the ore variability through the deposit and through the life of mine. Adopting ore sorting as an integrated processing step does not differ that much from testing and sizing flotation circuits, where small changes in ore properties can affect the overall recovery. It is important to understand these changes and how to react to them during operations.

The confidence level in sensor-based ore sorting testing will grow over time. We already see real-life examples where customers report on ore reserves based on lower cutoff grades due to ore sorting.

IM: Anything else to add?

EH: Despite the fact that the concept of ore sorting, and the sensors required to detect the valuable ore from the waste, have existed for several years, if not decades, the implementation of these systems in full-scale operations have been relatively restricted to particular cases with the right kind of orebody to make the process viable. Implementing ore sorting more broadly remains the challenge and requires the dual application of the right sensors working effectively with the right mechanical handling systems to detect and remove the waste stream efficiently and accurately. The skills required to solve these challenges are not just for the traditional mining and mineral processing engineers, but need to include a cross-disciplinary team addressing the issues from all angles.

This Q&A interview was carried out as part of the IM March 2021 annual ore sorting feature, to be published early next month

ValeOre Metals considering Platsol, Falcon separator, Steinert ore sorting for Pedra Branca

Base metals, Metallurgy, Mineral processing, Mineral project development, Mining services, Precious metals, , , , , , , , , , , , , , , , , , ,

ValeOre Metals Corp’s Pedra Branca platinum group element (PGE) project, in north-eastern Brazil, looks increasingly like leveraging the Platsol™ high temperature pressure leaching process judging by the latest test work.

Metallurgical results from sample material collected from outcrops at the Trapia and Curiu deposits areas at Pedra Branca for two preliminary Platsol tests conducted at SGS Lakefield, Ontario, have shown recoveries of 93.4-93.6% for palladium and 95.3-95.7% for platinum were achieved.

The company now plans two additional Platsol tests, to be performed by SGS, to determine the effects of adding elemental sulphur to the autoclave to optimise conditions required for PGE and gold recoveries, it said.

Platsol is a high temperature (>200°C) pressure leaching process designed to recover PGEs, gold and base metals. It has been shown to be particularly effective with PGE ore feeds characterised by high concentrations of chromium and low concentrations of sulphide, much like Pedra Branca, according to ValeOre Metals. The PGEs and gold are solubilised as chloro-complexes by the addition of chloride salt to the autoclave, while base metal sulphides are oxidised to form soluble metal sulphate complexes. The precious metals can be recovered directly from the autoclave discharge slurry by carbon absorption, or by precipitation with sulphide ions.

Platsol consists of standard, proven traditional technologies that are in use in mines around the world, according to the company.

The Platsol tests are part of a comprehensive mineralogical evaluation ongoing at SGS to characterise the speciation of palladium and platinum in Pedra Branca mineralisation to guide future process optimisation initiatives.

As part of this, the company is continuing with Falcon Ultrafine gravity separation test work as a potential pre-concentration circuit to upgrade feed material and improve mass pull.

The company has also initiated hot cyanide leach test work to assess the recovery rates of palladium, platinum and gold in a cyanide leaching process, and will shortly commence shipment of 100 representative chip samples from historic drilling at the Esbarro deposit to Steinert’s facility in Minas Gerais, to evaluate the potential of sensor-based ore sorting test work.

ValOre’s Chairman and CEO, Jim Paterson, said: “The pace of success at Pedra Branca has increased dramatically in the last three months, including today’s release of PGE metallurgical recovery rates of in excess of 93% for palladium and 95% for platinum using the Platsol process.

“Together with an aggressive property-wide exploration program, we are now focused on rapidly optimising the conditions, procedures and processes to further maximise the upside potential of the Pedra Branca project.”

Kalgoorlie-Boulder Mining Innovation Hub uncovers a fraction of processing value

Base metals, Comminution of minerals, Energy minerals, Environmental, Metallurgy, Mineral processing, Mining equipment, Mining services, Precious metals, Sustainable mining, , , , , , , , , , , , , ,

Extensive testing conducted by a Kalgoorlie, Western Australia-based research hub has found Western Australian Goldfields mine sites can add value to their operations by focusing on small size fractions.

In recent decades, the primary driver to maximise profitability of mining operations has been to mine and process as much material as possible to exploit economies of scale. This has led to bigger equipment, higher throughput and greater production, but not necessarily efficient use of resources.

With the concerns of declining grades, more complex orebodies, greater haulage distances, higher energy costs and water usage, any approach that can alleviate the impact of these issues is highly desirable.

The Kalgoorlie-Boulder Mining Innovation Hub recently explored use of a pre-concentration technique known as “Grade by Size Deportment”.

“This technique exploits the propensity for some ores to exhibit preferential breakage leading to concentration of minerals in specific size fractions,” it explained.

Several sites within the Goldfields region of WA showed significant potential for separation by size to provide value to their operations, according to the hub. This is particularly the case where either marginal grades are present or growing distances from face to surface, or, from mine to mill, are subject to increasing transport costs, it said.

Research and test work by the hub show that natural grade by size deportment during coarse rock breakage and screening is a key lever for generating high-value coarse separation, it said. This, in turn, can drive better productivity and returns for mine operators.

The Kal Hub, established in 2018 by the Cooperative Research Centre for Optimising Resource Extraction (CRC ORE), enables focused collaboration between researchers; mining equipment, technology and services suppliers; and mining companies to unlock value for Australian mining through technology development.

CRC ORE Chief Operating Officer, Dr Luke Keeney, said: “In a short amount of time, the hub has been able to bring together some of the most innovative people in industry and research, enabling collaborative innovation to occur.

“This collaboration is good for the Goldfields, and for the wider mining industry, as it demonstrates the benefits mine sites can experience by deploying various aspects of Grade Engineering®, including grade-by-size deportment.”

Grade Engineering is a system-based methodology developed by CRC ORE designed to reject low value material early in the extraction value chain and pre-concentrate processing plant feed. A key lever for successful Grade Engineering is grade-by-size deportment, the hub said.

The Kal Hub Technical Advisor, Dr Laurence Dyer, said the objective of the Grade-by-Size Deportment project was to undertake initial representative sample testing to determine natural deportment Response Rankings at a range of deposits in the Kalgoorlie-Boulder region.

“This project provided an introduction for industry participants to Grade Engineering and an indication of potential opportunities that grade-by-size deportment may present,” Dr Dyer said.

“A number of companies came on board and we were able to obtain diamond drill core and reverse circulation (RC) drilling samples from a variety of sites in the Goldfields to crush, screen and assay to develop a snapshot of responses to this approach.”

Samples were crushed where necessary and screened into up to six size fractions, with a finer set of screens used for the RC samples to accommodate the difference in particle size distribution.

As expected, gold sites displayed significant variation in response, while all nickel sites tested showed significant upgrade in the finer fractions of both nickel and cobalt, the hub said.

“RC samples were a compelling sample option due to their prevalence and self-preparation for screening, however there remains a question as to the legitimacy of the results they generate,” it added.

Dr Dyer said: “Gold samples produced varied data with the majority of sites producing low to moderate upgrades on average.

“The RC samples generated greater variation and often decreased in grade at the finest size fractions, likely due to particles being below liberation size, creating issues with the response ranking fit.”

The Kal Hub research also showed nickel produced far more consistent behaviour with all sites producing moderate to high responses for both nickel and cobalt. While for some samples the nickel and cobalt response rankings matched well, in others, the nickel upgraded significantly better, it said.