The Asia Miner

JUL-SEP 2017

The ASIA Miner - Reporting Important Issues to Mining Companies in the Asia Pacific Region

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8 | ASIA Miner | Volume 14 • Issue 3 | 2017 X-RAY technology is set to increase the efficiency of assessing ore grades and reduce mining's environmental footprint. South Austra- lian company Chrysos has developed a gold analysis process that is up to three times more accurate than conventional methods. PhotonAssay uses high-powered x-ray machines to activate the gold in a given sample and measure the signal it gives off to quickly and accurately quantify how much gold is present. The process also helps reduce the environmental impact of mineral processing as it eliminates the need for toxic chemicals and lead. Chrysos is setting up its first production unit in Western Australia, working in partnership with Ausdrill and MinAnalytical. The company aims to have a smaller on-site model available next year to better support in-field exploration and exports. Chrysos CTO James Tickner said the A$6 million project to take the technology to market would address mineral processing inef- ficiencies. "Technology is advancing and many industries are get- ting information in real-time. Down the track we see the technology being deployed to mining sites so that we can provide substantial gains for the industry. "The current challenge is that methods for analysing gold ore are not fast enough and require too much work. Our process is not new but we have developed it further to be more accurate and it also has potential to assess other metals." During the procedure, a sample is put into a plastic screw top jar weighing about 500gm. The jar is placed on a conveyor belt inside Chrysos' analysis machine where x-rays determine how much gold is in the sample. Chrysos partnered with CSIRO to trial its technology in Canada and results showed PhotonAssay was able to estimate the mea- surements of samples down to 30 parts per billion. The precision level depends on the amount of gold in each sam- ple but for high-grade samples, accuracy was within about 1%. Ausdrill COO Andrew Broad said the destructive nature of con- temporary procedures such as fire assays and the speed of Pho- tonAssay led the company to partner with Chrysos. "There are two major issues with fire assays – they are laborious and it is difficult to get skilled labour. They take anywhere between 24-48 hours to get results, reduced to just minutes using PhotonAssay. Fire assay is also destructive but with PhotonAssay you can run further tests on a sample at a later date." ENCOURAGING results from a cattle grazing trial run by the New South Wales Department of Primary Industries (DPI) continue to showcase Rio Tinto's rehabilitation efforts at its Hunter Valley mines. The four-year project is investigating the effects of grazing on reha- bilitated mine land and whether it can sustainably support produc- tive grazing livestock. At a final weighing on June 1 it was confirmed that steers reared on land rehabilitated by Rio Tinto were 100kg heavier on average than cattle grazed on unmined farm land. Both groups started on a level playing ground in terms of lineage and weight. In the trial's second stage, stocking rates on the reha- bilitated land were increased above the unmined land to take ad- vantage of excess feed that DPI researchers had observed during grazing in the first stage. The steers were run on rehabilitated paddocks at the Hunter Valley Operations mine site near Singleton and an adjoining control prop- erty as part of the Upper Hunter Mining Dialogue Grazing Study. Rio Tinto manager environment and community Andrew Speechly said, "The weighing confirmed that cattle on rehabilitated paddocks are outperforming those on unmined paddocks and this time de- spite 50% higher stocking rates on rehabilitated paddocks. "The results have been consistently promising and are an indi- cator that Rio Tinto's rehabilitation work has paid off. From the data we are collecting it is clear that when done well rehabilitated mine land provides a commercially sustainable option for grazing. "We continue to draw on the agriculture sector's expertise to improve our rehabilitation performance." The project is managed by the NSW DPI in collaboration with Upper Hunter Mining Dialogue's joint working group on Land Management, comprising representatives from local grazing and community groups, government and mining companies. DPI technical specialist pasture production Neil Griffiths said, "Greater available pasture biomass on the rehabilitated pasture can largely explain the weight gain advantage. 'The final results for the second group showed the steers on the rehabilitated site had an average weight of 480kg/head and 4.3mm fat, while on the analogue site steers weighed 381kg/ head and 2.4mm fat. "This was consistent with the first group, where steers grazing the rehabilitated mine land were on average 153kg/head heavier, and worth $450 more than their mates grazing the nearby native pasture, which was similar to original pasture on the mine site." Rio's rehabilitation shines in cattle study The PhotonAssay process where different metals are counted atom-by-atom after unique signatures are produced when a sample is hit with an x-ray beam. New gold standard in mineral analysis

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