Metallurgical test work gives Rox Resources confidence in oxidative leaching process for Youanmi gold project

The latest results from metallurgical test work have reaffirmed Rox Resources’ confidence in an oxidative leaching approach for its Youanmi gold project south-east of Mt Magnet. Rox last week said it had achieved gold recovery of 94 per cent and 95.8 per cent in Albion oxidative leaching metallurgical test work on concentrate samples from Youanmi. The company said more Albion test work was under way to further optimise the grind size and oxidation requirement for the definitive feasibility study due in November. Managing director and chief executive Phill Wilding said the company’s goal was to ultrafine-grind the concentrate to 10-12 microns, partially oxidise the sulphides via the Albion process in open-air tanks, and achieve overall gold recoveries of between 90 per cent and 92 per cent. “The results achieved to date represent a significant step towards achieving this goal and delivering maximum value from our Youanmi gold project,” he said. Mr Wilding told the Kalgoorlie Miner at the Diggers & Dealers Mining Forum in Kalgoorlie-Boulder this month that 92 per cent of the Youanmi gold was associated with sulphides — pyrite and arsenopyrite. He said processing the pyrite would involve an ultrafine grind and leaching, while the arsenopyrite required oxidation. “Fortunately for us, the gold is on the outside of the arsenopyrite crystal, so it only needs a partial oxidation,” he said. Mr Wilding said Glencore Technology’s Albion Process — which was used in the metallurgical test work — was simple and proven, and the fine grind would not cost as much as people might think. “If we have a million-tonne plant, we’re then floating our sulphides, and we get about a 9 per cent mass pull from that,” Mr Wilding said. “So it’s only a circa 9-10 per cent of what goes into the mill goes through the fine grind and the oxidation. So its 90-ish thousand tonnes a year, or 270-odd tonnes a day so . . . it’s actually quite small and it’s not that expensive.” Rox’s definitive feasibility study will look to build on the company’s pre-feasibility study released last year. That study estimated Youanmi could produce 786,000 ounces across a 7.7-year mine life, averaging about 100,000oz per annum based on a 750,000 tonnes per annum production rate. Mr Wilding at Diggers & Dealers said the company had done 46,000 metres of drilling and increased the mineral resource estimate by 21 per cent since that study. Youanmi currently had a mineral resource estimate of 12.1 million tonnes at 5.6g per tonne for 2.17 million ounces of gold. “It’s now a larger, more robust MRE which we’ve got,” he said. “Our previous plan was a 750,000-tonne plant delivering about 100,000oz a year for eight years — we’re going to see that grow. It’s going to be bigger, it’s going to do more ounces, and at the end of the day the cash flows — which is already pretty phenomenal — they are going to get another step up again.” The pre-feasibility study estimated Youanmi could generate free cash flow of about $1.3 billion at a gold price of $3700/oz. The gold price on Wednesday was $5220/oz. Younanmi has historically produced 667,000oz at 5.42g/t from open-pit and underground mining. Mr Wilding said underground mining last took place from 1993-97 with an average grade of 10g/t.