New highly sensitive method for detecting gold at drill sites
RESEARCHERS at the University of Adelaide's Institute for Photonics and Advanced Sensing have developed a portable method for detecting trace amounts of gold in ore samples – on-site at the drilling rig.
Using advanced photonics, Dr Agneszka Zuber and Associate Professor Heike Ebendorff-Heidepriem's method can find gold nanoparticules at detection limits a hundred times lower than current methods such as X-ray Diffraction (XRD) and X-ray Fluorescence (XRF).
"We are working on two optical methods. One of them uses fluorescence and the other is absorption," says Dr Zuber.
"The most popular methods are XRF and XRD. 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."
The project could save explorers from missed opportunities when drilling for gold. It's a timely project, as gold isn't limited to use in jewellery – it's an increasingly important and in-demand component in electronics and medical devices.
Dr Zuber and Associate Professor Ebendorff-Heidepriem have already been able to detect trace amounts down to 70 parts per billion of gold in water, and are currently undertaking tests on real rock samples.
"The project we are working on is sponsored by the Deep Exploration Technologies Cooperative Research Centre (DET CRC). They have a drilling site in Brukunga, close to Adelaide, and we have used drill samples from there. They are preliminary, but the first results are promising."
The only comparably sensitive method of detecting gold in such low concentrations at the moment is with Inductively Coupled Plasma Mass Spectrometry (ICP MS). That is a large off-site machine.
Samples have to be sent to the lab and prepared through special methods such as fire assay and acid digestion before testing. Results can take weeks to arrive.
"It's about time and place," Dr Zuber says, "the point is to analyse it quickly and at the place of drilling. We can achieve similarly sensitive results with a very small setup with a very easy to use method."