New technology for gold detection at the rig

Researchers at the University of Adelaide have developed a new method for detecting trace amounts of gold in ore samples at the drill rig.

Dr Agneszka Zuber and associate professor Heike Ebendorff-Heidepriem's of the Institute for Photonics and Advanced Sensing used two optical methods to reach detection levels a hundred times lower than the current hand-held devices which use x-ray diffraction (XRD) and x-ray fluorescence  (XRF).

Dr Zuber said the new methods use fluorescence and absorption.

"The most popular methods are XRF and XRD,” she said.

“These methods work but the problem is the level of detection is quite high – around five to ten parts per million. It means that some ore deposits can just be missed.

“Our aim is to detect gold in parts per billion.”

Dr Zuber said the goial was to use optical methods for detection of gold based on specific properties of metals.

“Gold nanoparticles have quite unique properties, not only gold but also silver and other metals, of suface plasmon resonance, a physical property which is only observed for nanoparticles, so we decided to make use of that,” she said.

“The other method we are working on is fluorescence. We found an article which looks at interaction of fluorescence with nanoparticles… we compared how this works for infra-red and also using optical fibres, a speciality of the institute, so we are trying to decrease detection levels that way.

The study will be released as an academic paper in the coming months, and it is anticipated a working prototype will be produced for demonstration by the end of the year.

Tests so far have shown ability to detect trace amounts of gold down to 70 parts per billion in water, tests are ongoing for rock samples from Brukunga, near Adelaide.

The research has been funded by the Deep Exploration Technologies Cooperative Research Centre, which unveiled the coiled tubing drill rig in 2013.

At present the only comparable technology for detecting such low concentrations of gold is Inductively Coupled Plasma Mass Spectrometry, which is a large, off-site machine which requires samples to be specially prepared before testing.

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