PhotonAssay^TM: minerals analysis technology delivers exciting results

Since 1851, Australia has contributed $1t in gold, making it the third largest producer in the world, according to the Minerals Council of Australia. Although we’ve come a long way since the initial gold rush, accurate mineral analysis technology has been largely static, meaning the true value of gold and the essential metals that copresent with it, such as silver and copper, could still be unrealised.

According to Australia’s national science agency, CSIRO, gold processing plants may only recover between 65-85% of the gold present in mined rock. This means hundreds of millions of dollars’ worth of gold and related metals are going to waste.

As the country with the world’s largest gold resources and second largest silver and copper resources, Australia has no lack of opportunity to extract, process, produce and export the valuable metals.

Ensuring operations are profitable is dependent on advanced analytical services. According to CSIRO, analytical services are worth nearly $1b globally. Pair that with the unrealised value of unrecovered gold and related metals and Australia stands to profit significantly.

The Australian Mining Review speaks with Chrysos managing director and chief executive Dirk Treasure about the company’s efforts to unlock the full value of Australia’s ore.

Traditional assaying relies on 1000-year-old fire assay techniques, which are time consuming and resource hungry. With fire assay, samples are heated up to 1200°C. Not only are these energy requirements intensive, but the process also involves hazardous chemicals such as lead and can take six to eight hours to perform, leading to lengthy turnaround times.

But a new technology that is faster, safer and more environmentally friendly exists.

PhotonAssay^TM, originally developed by CSIRO and commercialised by Chrysos Corporation, is disrupting the global gold market with its innovative processes, ushering in a new era in minerals analysis and reporting.

Exciting material

Chrysos’ PhotonAssay^TM technology allows for enhanced, rapid analysis of gold, silver, copper and other elements. The technology uses x-ray excitation, gamma radiation measurement and atom counting to deliver its improved results.

Large samples, typically 400-650g, are sent through the PhotonAssay^TM machines for bulk analysis. These samples are quickly loaded into the machine, as sample preparation requirements are minimal.

The machine then uses a linear accelerator to generate x-rays. When samples are exposed to the x-rays, the nuclei of the atoms in the sample rearrange in an isometric, or excited state. As the nuclei attempt to return to equilibrium, they decay back to their original state, releasing gamma radiation in the process. PhotonAssay^TM then measures the levels of the gamma radiation emitted during the process.

This measurement gives a count of gold atoms present in each sample. Because this is counted at an atomic level, PhotonAssay^TM can achieve improved accuracy and precision when compared to fire assay.

While the process is technically sophisticated, it only takes a few minutes to run samples. PhotonAssay^TM requires as little as two minutes per sample and can run up to 70 samples an hour, delivering truly rapid results.

PhotonAssay^TM is a revolutionary solution allowing for a possible 1-3% improvement in gold recovery through the mining value chain. The technology provides customers with potential productivity gains of more than $1m per year and potentially more than $25m per year for larger miners, according to Chrysos.

Going big

Improved accuracy with PhotonAssay^TM is possible in part due to the use of larger sample sizes. Similarly, while, fire assay destroys samples, PhotonAssay^TM samples can be stored for re-analysis at a later date as required.

Mr Treasure says this means PhotonAssay’s larger samples are more representative and therefore reduce the risk of sampling errors.

“We run half a kilo compared to fire assay that runs much smaller samples,” he said.

“If you were running an oxide material, traditional fire assay uses 50g, so our samples are 10 times bigger.

“If you’re running something like a carbon pulp, we’re typically running around 300g while a normal fire assay would run one gram.

“We are running 300 times the sample size in that regard, and that just gives you a much more representative sample of whatever your bulk sample is.”

This is important because geologists and mining engineers are using the lab results to make decisions about the ore body, mining operations and processing plant operations. The larger, more representative sample in PhotonAssay^TM helps ensure that the data provided to these stakeholders is more accurate and reliable compared to the smaller samples used in traditional fire assay. This allows for better decision-making throughout the mining and processing workflow.

Safe and easy

While accuracy and precision are paramount, PhotonAssay^TM offers other notable improvements outside of raw analytical power. As a result of being fully automated, operations are also simpler and safer.

“People that operate fire assay need to have their blood tested every three to six months for lead contamination, because they use a powdered lead in that process,” Mr Treasure says.

“It’s a pretty gnarly process in general, but it’s very bad from a health and safety point of view.

“It’s not a question of if people are exposed to lead, it’s a question of to what extent are they exposed to lead?

“We have completely removed that as an issue and made the process better for the environment and better for people.”

Traditional fire assay can produce up to 0.31kg of hazardous waste per sample, while PhotonAssay^TM requires no lead and produces no hazardous waste. This mitigates one of the biggest downsides of traditional assaying, being pollution through its production of lead contaminated waste.

In addition to producing zero waste, PhotonAssay^TM requires less energy overall than fire assay. While traditional fire assay requires about 1.3kWh per sample, PhotonAssay^TM only requires about 0.65kWh per sample.

These benefits all contribute to an overall smaller environmental footprint, with PhotonAssay^TM only producing 0.455kg of carbon dioxide per sample, compared to 0.91kg per sample with fire assay.

In addition to being safer for people and the environment, PhotonAssay^TM technology is also extremely simple to operate, requiring only one operator to load samples.

“We have a couple of customers that run fire assay and PhotonAssay simultaneously, and they have told us that PhotonAssay requires one-third of the labour for a similarly sized fire assay,” Mr Treasure says.

“There are a whole lot of benefits to having 33% of the labour demands.

“You have to train less people, you have to pay less people, and you remove opportunities for human error, so your operation cost comes down fairly dramatically.”

Because the process is highly automated, operators don’t need specialised training or certifications. This also means that the ‘skill’ of an operator is not a limiting factor for results.

“If you took a sample and you ran it through the unit in Kalgoorlie and then flew the same sample across to Thunder Bay, Canada, you’d get the same result going through each unit,” Mr Treasure says.

“If you tried to do that with fire assay, you’d get a completely different result.”

Going beyond gold

Chrysos is looking at expanding the applicability of PhotonAssay^TM to other elements, setting its sights on elements that copresent geologically with gold, such as lead and zinc.

“We can go into base metals, rare earths, energy metals, uranium — the technology is applicable to half the periodic table,” Mr Treasure says.

“It’s about finding what we can do really well that the industry does poorly and that’s what we’re developing into.”

Expanding into other elements could be as simple as a software upgrade. The PhotonAssay^TM units are already capable of running from 8.5MeV to 14.5MeV. The higher the energy is, the more elements that are excited during the process. From there, the software just needs small refinements to optimise precision and accuracy, like what has already been achieved with gold.

Looking forward, Chrysos wants to bring PhotonAssay^TM to even more sites within the gold industry.

“We have excellent adoption from some of the biggest miners in the world, but there’s a long way to go just in gold,” Mr Treasure says.

“I see no reason why we won’t be in every single major gold mine around the world in the coming years, and every major laboratory around the world.”

Chrysos’ PhotonAssay^TM technology has already been adopted by the likes of Barrick Gold, Agnico Eagle, Gold Fields, Ravenswood Gold, Novo Resources and more.

Chrysos Corporation

Chrysos combines science and software to create technology solutions for the global mining industry.

With staff across Australia, North America, Africa and Europe, Chrysos’ team of scientists, engineers and industry specialists blend innovation, technical expertise and superior customer service to create cutting-edge assay technologies and services that deliver the crucial operational data customers need to achieve better business outcomes.

The company’s flagship PhotonAssay^TM has rapidly displaced slower, more hazardous and costly processes to become the mining industry’s most innovative and valuable assaying solution.

Chrysos puts science in technology to make technology that matters.

For general enquiries, please email Chrysos at [email protected] or call +61 (0)8 7092 7979.