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How to unlock unviable gold deposits

As global gold prices continue to climb, miners are investing in exploration activities when they may be better off finding new ways to unlock previously unviable or ‘stranded’ deposits.

Stranded deposits – that is, gold deposits that are too small, too far from a mill with an inappropriate open pit stripping ratio to be economically mined or processing with cyanide is not possible – dominate many countries and jurisdictions where easy-to-find deposits have already been exploited.

Most larger miners determine these deposits not feasible to mine, while smaller miners can’t afford the infrastructure or lack the expertise to bring them to realisation.

Environmental regulations can also hold back gold processing where cyanide or mercury extraction methods, most widely and traditionally used, are rigorous and ban the use of these toxic chemicals.

Clean Mining is unlocking the potential of these stranded deposits by offering a safe, sustainable and economic way to extract gold from ore.

Clean Mining Managing Director, Jeff McCulloch, said the company’s cyanide-free processing solution suited a range of ores, including double refractory ores, and not only addressed environmental regulations but was flexible, scalable and therefore cost efficient.

The leaching plant that forms part of the Clean Mining solution is smaller in scale than an entry level CiP/CiL plant that uses cyanide, which means it has a lower capital cost. The plant can also be made in modular components and it is mobile, enabling it to be reused and relocated to mine sites, rather than trucking and relocating ore.

Suddenly, the feasibility of unlocking previously unviable gold deposits opens up, especially for small high-grade deposits.

“Clean Mining’s technology uses an inorganic compound, thiosulphate, as the leaching reagent to extract gold from ore without the use of cyanide,” Mr McCulloch said

“The compound is not only organic; it requires less water than traditional processing and can be reused.

“Miners with high-grade, smaller deposits can get their gold quickly and move to the next site using the same plant and process. Miners do not need to raise or borrow vast amounts of money to develop a single large-scale project.

“This segment of the industry has stagnated, particularly in Australia, so Clean Mining is aiming to be able to open up new opportunities in this area.”

The cyanide-free processing technology was developed over 10 years and tested at scale in 2018 with Clean Mining’s parent company – Eco Minerals Research Limited – which showed it could achieve similar gold recovery rates to cyanide-based ore extraction methods.

Initial test demonstration plant in Australia

Image: Initial test demonstration plant in Australia.

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