Police investigations assist geochronology

06 July 2012

Geochronologist, Andrew Cross, uses a Scanning Electron Microscope to identify tiny monazite crystals. Copyright Geoscience Australia 2012

Geochronologist, Andrew Cross,
uses a Scanning Electron Microscope
to identify tiny monazite crystals.
© Geoscience Australia

Scientific methods applied by scientific officers in the Australian Federal Police (AFP) to locate traces of gunshot residue have resulted in an innovation to assist Australia’s mining exploration industry.

Geochronologists from Geoscience Australia have adapted the AFP forensic techniques to identify crystals of monazite measuring only 10 micrometres, or 0.01 of a millimetre, in diameter. Monazite can be closely associated with deposits of gold and rare earth elements.

Geochronologist, Dr Keith Sircombe, said that by using a Scanning Electron Microscope minerals such as monazite are initially located by their brightness relative to most other minerals and their identification is then confirmed or rejected by X-ray analysis.


"The AFP uses a software application to scan what is effectively dust from a crime scene to look for evidence such as metal particles from a bullet. We have made a unique adaption of this technique to scan a geological sample specifically for monazite – a process which otherwise would require many hours of painstaking manual searching," Dr Sircombe said.

"Application of this automatic location and identification technique can reduce the time taken to identify monazite targets by around 90 per cent, freeing up the scientist to work on other tasks," he said.

"The technique can be applied to other minerals and will accurately identify material from complex and rare samples which can be extracted and analysed using the Sensitive High Resolution Ion MicroProbe (SHRIMP) to provide explorers with valuable pre-competitive geological age and isotopic data to reduce exploration risk," Dr Sircombe said.

Monazite is an important rare earth element bearing mineral with a widespread but small volume in many different rock types, including mineralised systems. Because of its excellent properties as a geochronometer, monazite is an important mineral to establish the geological history of specific rocks and regions and plays a significant role in identifying areas of potential mineralisation.

Topic contact: media@ga.gov.au Last updated: October 4, 2013