Two commercially-available technologies, each with their own advantages, offer a new level of data on gold concentrations and can be used to optimise processes for greater value recovery. LOUIS WHITE reports
New Aussie-developed technologies for gold analysis
Gold is one of our most precious commodities, worth $1,281 per ounce at the time of writing. Its value on the stockmarket is as fascinating as its history and it continues to be one of the most popular investment options for many people today.
Everyone wants to extract more value out of their own investment and gold is no exception to that rule of thumb. Recognising the potential to capture more value in the processing step, CSIRO has developed new analysis technologies for gold and other precious metals.
These technologies will help the gold industry to recover more value from ore and waste streams at the processing stage.
“Over the last few years we have developed two technologies for use in gold mining and processing,” CSIRO group leader, Michael Millen, says.
Chrysos' PhotonAssay for rapid gold analysis
“One is based on gamma activation analysis (GAA) and the other uses x-ray fluorescence (XRF).
“The GAA technique, marketed as PhotonAssay, was launched in late 2016 via a new company, Chrysos.”
Ausdrill will be the first company to install PhotonAssay in 2018.
As an advanced laboratory method to replace conventional fire-assay technology, PhotonAssay uses high powered x-rays to bombard ore samples and activate atoms of gold and other metals. A sensitive detector then picks up the unique gamma-ray signatures from these elements to determine their concentrations in just a few minutes.
By reducing the turnaround time for analysis from days down to minutes, PhotonAssay provides mining companies with the opportunity to monitor their operations in real time, and to respond to problems more rapidly than ever before. As a result, miners can more readily optimise their processes and make better-informed decisions.
With unique sensitivity for gold, PhotonAssay is suitable for use across the mining value chain, including exploration, resource definition, mine planning and process monitoring. With sample sizes at least 10 to 20 times those used for fire-assay, analysis of heterogeneous ores much simpler using this technology.
OnLine Gold Analyser technology available from Gekko Systems
The second CSIRO-developed analyser, which is based on XRF, is capable of detecting ultra-low levels of gold and other elements on a continuous process stream or ‘on-line’, hence its name the OnLine Gold Analyser (OLGA).
“OLGA is now available to the market through leading Australian mining equipment, technology and services company, Gekko Systems,” Mr Millen says.
“This analyser is a true on-line analyser providing data in real time.”
Conventional XRF is widely used in the base metals industry for monitoring and control of concentration plants, however these systems generally have detection limits in the tens to hundreds of parts-per-million (ppm) range, precluding their use in precious metal concentrators.
OLGA is specifically designed to enable direct measurement of gold in tailings, feed and concentrate slurry streams at ppm and sub-ppm levels.
It incorporates new developments in x-ray detectors and x-ray tubes combined with CSIRO’s patented x-ray optics technology and spectral analysis techniques to detect previously unachievable trace concentrations for elements.
“A rapid on-line measure of gold at a few ppm to sub-ppm has never been available to the industry before this technology,” Mr Millen says.
“This adds value as the data can be used to optimise process control and prevent gold going to waste streams.”
This critical new tool will enable plant metallurgists and operators to monitor and adjust their operations in real time in order to increase recovery and minimise gold losses from process excursions.
“We have been a world leader in the development of analysis systems for the mining, minerals processing and other industries for over 30 years,” Mr Millen says.
“These analysers have been under development for several years by a team of physicists, and mechanical, electronic and software engineers.”
CSIRO plans to extend the XRF technology for other precious metals that conventional analysis techniques cannot measure at trace levels.