Toronto-listed Silver One Resources says non-cyanide leaching of material from one of two large pads at its Candelaria silver-gold venture in Nevada, USA, has shown potential for the proprietary Extrakt Processing Solutions TNS process to favourably impact project economics.
Silver One CEO Gregory Crowe said this week the company aimed to expand testing to cover both leach pads and some fresh mineralisation samples after early results indicated the “innovative technology” performed well in treatment of difficult or refractory mineralised material, such as the partially leached material on the Candelaria heap leach pads.
“The use of these proprietary solutions yields potential for possibly doubling silver recoveries in comparison to traditional cyanide leaching,” Crowe said.
“This may positively impact the overall economics of the project.
“EPS’ leaching agents not only improve silver extraction but are also more environmentally friendly and save water by assisting in the dewatering of tailings, and the extraction process is simpler and potentially less costly.”
In February this year Kentucky-based Extrakt Processing Solutions (EPS) said it had signed a global commercialisation agreement with US engineering major Bechtel aimed at scaling deployments of its TNS solid-liquid separation technology.
TNS had been successfully piloted at an oil-sand tailings dewatering project in Canada and a “major coal operation in the US”. It was also being tested on gold tailings in Canada.
Extrakt CEO William Florman said TNS had undergone “extensive evolution, marked by advancements in metal recovery, equipment, and water management, and has garnered more than 40 global patents”.
“By recovering minerals and materials from previously classified waste, this technology empowers customers to fulfill their sustainability commitments, reducing reliance on virgin resources,” he said.
Bechtel said TNS offered a “simpler, non-toxic, and readily available chemicals solution alternative to conventional offerings [that performed] well in the presence of high clays, making it highly adaptable to various applications in the energy and mining sectors”.
Silver One is looking to revive silver and gold production – via waste recovery and new extraction – in a historically significant Nevada mining district. It acquired 100% of Candelaria from SSR Mining last year and has posted indicated and inferred resources for the two existing leach pads containing an estimated 45 million ounces of silver and c89,000oz of gold.
Silver One said a 228kg mixed sample of leached oxide and partially refractory material averaging an estimated 48.12 grams per tonne silver (considered depleted by Kinross Mining when it wound up production back in 1998) was crushed to minus-2mm, or 2000 microns, before returning an average 49% recovery via the TNS testing. This compared with 21-29% recovery with its previous cyanide leach testing.
Finer crushing to 550 and 110 microns “increases the leach pad recoveries to 59.9% and 64.4%, respectively”, the company said.
Additional testing on material from the leach pads, and fresh ore, is planned for the second half of this year.
Silver One said unlike cyanide leaching, TNS consumed minimal water and produced no toxic effluents. Tailings residues were inert and non-acid generating.
“The traditional silver cyanide leaching typically takes several hours to several days using agitated leaching techniques,” it said.
“However, EPS’ innovative technology uses patented chemistry to extract metals in less time than an agitated leaching system.
“It also separates liquids from solids, enabling dry-stacked tailings.
“Final results from Extrakt are anticipated in the latter part of 2024.
“These results will be used in an anticipated economic study on the Candelaria project.”
By the close of trading in Toronto on Wednesday this week its share price had risen about 65% over five days to C30c, capitalising the company at $74 million.
