The Asia Miner

OCT-DEC 2018

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

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the asia miner • volume 15 • issue 4 10 LEADING DEVELOPMENTS The Commonwealth Scienঞfic and Industrial Research Organisaঞon (CSIRO), Australia's naঞonal science agency, has produced the country's first gold using a non-toxic chemical process in an effort to provide an alternaঞve to cyanide and mercury to extract the yellow metal. The first gold is the result of early industry trials of CSIRO's 'going for gold' technology and was produced in partnership with small gold miner Eco Minerals Research at a demonstraঞon plant in the Western Australian goldfields town of Menzies. Cyanide is used in more than 90 per cent of global gold producঞon, but producers are facing increasingly tough regulaঞons that prevent or restrict its use due to environmental and health concerns. Globally, government regulaঞons guiding the use of cyanide in gold processing are becoming increasingly rigorous. Several regional agencies in the United States, South America and Europe have banned the use of cyanide for gold extracঞon as a response to recent spills of toxic cyanide. CSIRO also believes that cost-effecঞve gold recovery alternaঞves are needed to address barriers to entry for small producers and new government regulaঞons. A typical cyanide-based processing plant is esঞmated to cost around AUD$30 million, whereas the new technology has a lower capital investment cosঞng as lile as AUD$2-2.5 million to build. To reduce economic barriers to entry for small producers and help turn stranded gold deposits into producঞon, CSIRO's vision is to deliver the alternaঞve process technology direct to mine sites via a mobile service. CYANIDE AND MERCURY- FREE ALTERNATIVE The technology replaces cyanide with thiosulphate, a non-toxic alternaঞve, and a simple process flowsheet. Thiosulphate dissolves the fine gold – the gold that has not been recovered by gravity – out of ores at similar rates to convenঞonal techniques. It's safe and lowers environmental impacts. Thiosulphate is effecঞve at picking up gold in leach tanks to create a gold thiosulphate complex. The gold can be separated from the thiosulphate using ion exchange resins in what has tradiঞonally been a challenging process. Whilst working on improvements to this separaঞon process, CSIRO discovered that adding sulphite as an addiঞve to the ion exchange resin enabled easier separaঞon. Over ঞme, the method has undergone intensive laboratory tesঞng to understand its leaching performance in associaঞon with reagent recovery and recycle, with results indicaঞng that thiosulphate process is appropriate for the treatment of high- grade gold concentrates, and could also be valuable for use in other applicaঞons such as in-situ leaching in deep mines and CSIRO's cyanide-free gold showcases non-toxic solution Lead scienst Paul Breuer holds up a 1 ounce commemorave gold ingot from the first gold pour using CSIRO's cyanide-free process Improved facility set-up. Image ©2018 CSIRO. All rights reserved Leach soluon processing plant. Image ©2018 CSIRO. All rights reserved

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