A new x-ray technique developed by the CSIRO could save the Australian gold mining industry hundreds of millions of dollars each year, by detecting gold that would otherwise go unseen.
The technique uses powerful x-rays to rapidly and accurately detect small amounts of gold in ore samples and is much more effective than traditional chemical analysis methods.
The CSIRO, together with Canadian electron accelerator and manufacturer Mevex, undertook a pilot study on the use of gamma-activation analysis (GAA).
The technique involves scanning mineral samples – typically weighing about 500 grams – using high-energy x-rays similar to those used in medical imaging.
The x-rays activate any gold in the sample, and the activation is then picked up using a sensitive detector.
Project leader Dr James Tickner said the study had shown that the technique was up to three times more accurate than the current industry standard – a ‘fire assay’ technique that required the sample to be heated up to 1200 degrees Celsius.
“The big challenge for this project was to push the sensitivity of GAA to detect gold at much lower levels – well below a threshold of one gram per tonne,” Dr Tickner said.
“Fire assay usually involves sending samples off to a central lab and waiting several days for the results. Using GAA we can do the analysis in a matter of minutes, allowing companies to respond much more quickly to the data they’re collecting.
“A compact GAA facility could even be trucked out to remote sites for rapid, on-the-spot analysis.”
According to the CSIRO, Australia produced more than $10 billion worth of gold in 2012.
“One of the surprising things is that gold processing plants often only recover between 65 and 85 per cent of the gold,” Dr Tickner said.
“If a big plant produces a billion dollars of gold every year, that means potentially hundreds of millions of dollars of gold are going to waste and could perhaps be recovered.”
Even if the GAA technique only led to a 5 per cent improvement in gold recovery, this could still equate to $500 million of recovered gold per year for the industry.
The GAA technique is easily automated, provides fast analysis and is more sustainable than current techniques, as it doesn’t require the use of heavy metals such as lead. It is also an adaptable technique that could soon be used for other commodities.
“While most of the work we’ve done has been based on the gold industry, the technique can be modified for other valuable commodities such as silver, lead, zinc, tin, copper and the platinum group metals,” Dr Tickner said.
He said the CSIRO would look to partner with local and international companies to start up a full-scale GAA facility in Australia within the next two years.
