The test programme performed by professional chemist Richard Hammen is one of several he has conducted successfully in chemical separations and applied to mineral processing to improve metal recovery rates. Bayhorse is currently determining effectiveness of the technology at commercial production.
The hydrometallurgical leaching test on 25kg of mineralised material from the Bayhorse silver mine that graded at 25.6oz per ton returned essentially total silver recovery by Hammen. That silver can now be formed to bars using ion exchange purification and reduction.
"The combined use of both electrophilic and nucleophilic classes of chemicals that has been developed for leaching the silver-bearing material at the Bayhorse silver mine lifts the yield of silver that can be extracted from the 60% range to the 99+% level," the company explained. "If the process is effective at commercial levels of production, it may affect the potential economics of the company's silver mine."
Hammen added that quality of reagents used will be refined in further testing that will include a one-ton sample of Bayhorse's ore-sorted mineralised material. That will be followed by silver purification via ion exchange or solid phase extraction. Previous hydrometallurgy done on Bayhorse mineralisation with other chemical leaching methods extracted just 55% to 65% of the silver, and flotation tests achieved a maximum recovery of only 89-90%.
"At this stage we are focused on reducing our mining and processing costs, including minimising the normal downstream losses that occur from shipping, smelting and refining," Bayhorse CEO Graeme O'Neill said.
"Addressing these issues now, rather than down the road, will improve our ability to operate in a lean metals pricing environment."
As the company prepares to scale the testing, one ton of crushed development material will be shipped to Hammen for a 30-day test period. It is now crushing and bagging the bags for shipping.