SAMPLING , ANALYSIS AND LAB ASSAY
Developed by CSIRO researchers and now owned by Chrysos Corporation , PhotonAssay delivers faster , more accurate gold analysis , being a quantitative , chemistry-free replacement for fire assay on site and in the laboratory .
The technology uses high-power X-rays to activate and measure gold atoms in mineral samples and , when compared with conventional technologies , allows true bulk measurements of large samples of up to 500 g independent of their physical or chemical form , according to Chrysos .
The industry momentum around PhotonAssay ’ s use has been building .
Chrysos was formed in 2016 to commercialise the technology and , in June 2021 , the company announced it had assayed over 1 million customer samples with the number of samples analysed more than tripling in the first half of 2021 .
In mid-December , Dirk Treasure , CEO of Chrysos , told IM that count was now “ accelerating ” toward the 2-million milestone .
The longer-term trends shaping the mining industry – namely environmental , social and governance ( ESG ) requirements – bode well for PhotonAssay technology finding an even wider audience .
“ Chrysos , its customers and suppliers all believe that we exist in a stakeholder ecosystem which benefits from continual improvement in ESG governance outcomes ,” Treasure said . “ Certainly , there is growing interest from customers and the wider industry in PhotonAssay ’ s unique ability to deliver faster , more accurate analysis whilst also treading more lightly on the planet .
“ Chrysos is proud that every sample analysed with PhotonAssay results in reduced CO 2 emissions and less hazardous waste , and we expect to have many more customer conversations focused on these environmental benefits over the next few years .”
With ambitions to deploy 80 PhotonAssay units through to 2026 – with each unit capable of processing up to 480,000 samples per annum – Chrysos expects to help customers reduce CO2 emissions by an estimated 18,000 t and decrease hazardous waste by some 12,000 t every year .
Along with improvements in gold sensitivity over the last year , Chrysos has made significant progress assaying and analysing silver , copper and wet samples , according to Treasure .
“ Our multi-elemental approach certainly played a role in Barrick Gold ’ s decision to utilise PhotonAssay at the Bulyanhulu gold-silver-copper mine in Tanzania ,” he said . “ This on-site installation is part of our wider agreement with MSALABS , which sees multiple PhotonAssay units deployed across the globe over the next couple of years .”
MSALABS and Intertek are not the only labs with PhotonAssay units at their disposal . Only recently the company signed an agreement with SGS to deploy a unit at its Australian Minerals Regional Hub in Perth , Western Australia , and , with the closing of Perenti ’ s MinAnalytical Laboratory Services Australia transaction , ALS will also have several units to leverage on behalf of its customers .
Award-winning assaying
PhotonAssay is not the only fire assay alternative for miners looking to verify the metal content of their ores .
Gamma-activation analysis ( GAA ) is , Baltic Scientific Instruments ( Latvia ) says , a method uniquely suited to the analysis of ore samples for gold , other precious metals and complementary elements .
The method is based on the irradiation of ore samples with high energy gamma quanta generated by a linear accelerator and detection of the induced activity of the excited gold nuclei by a gamma spectrometer . The high penetrating power of gamma radiation facilitates the analysis of large samples ( up to 300 ml , with sample sizes no bigger than 3 mm ), eliminating the need to crush and grind the sample , while offering the following advantages over conventional methods : n A significant increase in the accuracy of the analysis representation ; n Reduced analysis time due to the short halflife of excited gold nuclei . This means irradiation of a sample , detection of the induced activity and calculation of the gold content can be carried out in 20-30 seconds ; n Sufficient analysis sensitivity , accuracy , selectivity , representativeness and productivity required for modern gold mines . For gold ore content up to 1 ppm , measurement error of 8 % or below , while ore content with up to 10 ppm comes with a
measurement error of 4 % or below ; n Consistent analysis results regardless of chemical composition of the sample ; n No negative impact on the environment : the induced activity of the sample decreases to background levels several minutes after analysis is concluded ; n Non-destructive processing of ore samples , allowing repeated analysis of ore sample ; n The method allows multi-element analysis over the course of a single cycle and measurements ; n Ability to automate the GAA analysis ; and n Can be incorporated into a quality control / assurance process for gold mining and extraction of particular minerals and elements . The advantages listed above were first realised in three industrial GAA laboratories , commissioned in Muruntau , Uzbekistan , in 1977 , in Magadan , Russia , in 1979 , and in Batagay , Russia , in 1986 . The early installations led to GAA being awarded the USSR State Award in 1982 for the advancement of the gamma activation method in gold mining control processes .
Currently , only one of these laboratories is still operating – at the Muruntau mine in Uzbekistan . After modernisation of the main systems at this installation , the minimum detectable activity ( MDA ) gold detection limit in ore in this laboratory is 0.04 parts per million ( ppm ) with a measurement error of no more than 10 % for gold concentrations of 1.08 ppm or above .
At the same time , the laboratory has demonstrated great productivity , according to Baltic Scientific Instruments , achieving at least 120 measurements per hour . In 2020 , about 1.7 million samples were measured on two measurement lines with two linear accelerators at the lab .
Baltic Scientific Instruments and CORAD Ltd are in the process of commissioning a new industrial GAA “ Au-Isomer ” facility for the Pavlik Gold Mining Company operation , owned by JSC Pavlik , in Russia . This entire facility is designed
Baltic Scientific Instruments and CORAD Ltd are in the process of commissioning a new Au-Isomer GAA facility for the Pavlik Gold Mining Company operation ( left ), while Baltic Scientific has , for many years , supplied the CON-X XRF conveyor analyser ( right ) to the market to identify and measure the concentration of the elements and minerals in ores and materials on a conveyor belt
80 International Mining | FEBRUARY 2022