Modern Mining May 2015

MINING News

New method for detecting trace gold in drill samples able to detect trace amounts down to 70 parts per billion of gold in water and are currently undertaking tests on real rock samples.

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.” 

Researchers at the Institute for Photonics and Advanced Sensing at the University of Adelaide in Australia 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 meth- ods. 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.” Dr Zuber and Associate Professor Ebendorff-Heidepriem have already been

“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 prelimi- nary, but the first results are promising.” T h e o n l y o t h e r comparably sensitive technique to detect gold in such low con- cen t r a t i ons a t t he moment is the method known as Inductively Coupled Plasma Mass Spectrometry (ICP MS). However, this involves a large off-site machine.

Figure A shows no fluorescence and no gold nanoparticles. Figure B shows a green fluorescence, indicating the presence of gold particles.

May 2015  MODERN MINING  17