Northmin Corporation (TSXV: NMB) reported silver recoveries of 93% from leach testwork on tailings at its wholly owned Tynagh project in Ireland, alongside 97% zinc, 89% lead and 81% copper.
The work was completed by Loop Hydrometallurgy Operations Pty Ltd. as part of a tailings re-treatment scoping study, using representative material drawn from the West Pond, which hosts an NI 43-101 compliant resource.
Seven leach runs were carried out across sequential standard and enhanced conditions. The standard runs returned 80% to 88% silver, 36% to 89% zinc, 86% to 88% lead and 53% to 79% copper. Enhanced conditions tightened and lifted those ranges to 86% to 93% silver, 87% to 97% zinc, 85% to 89% lead and 74% to 81% copper. Extraction in the second stage proved sufficient, removing the need for a third.
Loop’s Halion Loop process leaches in tanks below 100°C at atmospheric pressure using aqueous salt solutions. Oxidation of sulphide minerals during the leach generates its own acidity, which the company said reduces or eliminates the reagent acid a conventional circuit would require. The system is closed, with no noxious gas emissions or liquid effluents, and arsenic is oxidized and precipitated as scorodite.
West Pond holds 2.69 million tonnes of inferred material grading 49 g/t silver, 3.56% zinc, 2.68% lead, 0.23% copper and 21.6% barium oxide. The Tynagh mine closed in 1982 and the ponds have seen little rehabilitation since.
“The results from this initial study by Loop Hydrometallurgy in Australia are very encouraging and potentially transformative for the surface silver project at Tynagh,” chief executive Julian Vickers said, adding that the other metals contribute additional revenue on top of silver.
Loop will now run economic studies covering revenue, operating costs and capital expenditure across a range of throughput options. Confirmatory testwork, refinement of the product strategy and environmental studies for permitting are set to follow, with the environmental work beginning in parallel.
Northmin Corporation last traded at $0.36 on the TSX Venture.
