Detecting gold with x-ray vision

We developed a way to use powerful x-rays to rapidly and accurately detect gold in ore samples. This could save Australia's minerals industry hundreds of millions of dollars each year.

The Challenge

Golden waste

Australia is the world's second largest gold producer, producing over $14 billion worth of gold in 2014–15. However, gold processing plants may only recover between 65 and 85 per cent of gold present in mined rock. Given a typical plant produces around $1 billion of gold each year, this means hundreds of millions of dollars worth of gold is going to waste. Even a modest five per cent improvement in recovery would be worth around half a billion dollars annually to the industry.

Our Response

Gamma activation analysis: x-rays for ore samples

We worked with Canadian company Mevex to develop a technique that offers a much faster, more accurate way to detect gold than traditional chemical analysis methods.

Internal structure of gold under a microscope

Called gamma activation analysis, the technique works by scanning mineral samples – typically weighing around half a kilogram – using high-energy x-rays similar to those used to treat patients in hospitals. The x-rays activate any gold in the sample, and the activation is then picked up using a sensitive detector.

This method is two-to-three times more accurate than the standard industry 'fire assay' technique, which requires samples to be sent off to a central lab, where they are heated up to 1200°C. Fire assay results can take several days.

The Results

Speedy, accurate analysis saving time and money

Using gamma activation analysis mining companies can measure what's coming in and out of their processing plants with greater accuracy, allowing them to monitor process performance and recover small traces of gold – worth millions of dollars – that would otherwise be discarded.

Gamma activation analysis is also easily automated, allowing for analysis of ore samples in a matter of minutes. This means companies can respond much more quickly to the data they're collecting than they have been able to in the past. A compact facility could be trucked out to remote sites for rapid, on-the-spot analysis.

Unlike fire assay, gamma activation analysis doesn't require the use of heavy metals such as lead, so it is more sustainable than the current assay method.

It is also very adaptable. 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.

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