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May 2015
MODERN MINING
17
MINING News
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
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.
“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.
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.”
Figure A shows no fluorescence and no gold nanoparticles. Figure B shows a
green fluorescence, indicating the presence of gold particles.