Pinnacle Silver & Gold Corp (TSX-V:PINN, OTCQB:NRGOF) said preliminary metallurgical testing at its high-grade El Potrero gold-silver project in Mexico returned strong results, including gold recoveries of up to 96.79% and an average of 95.09%.
The company said three samples from the mineralized zone within the Pinos Cuates underground mine, one of three historic workings at El Potrero, were tested using grinding, bottle roll cyanide leach and gravity concentration methods.
According to the company, bottle roll cyanide leach tests achieved rapid gold dissolution, with 79–92% recovery after 24 hours, reaching final recoveries of 92.81%, 95.68%, and 96.79% after 72 hours.
Reagent consumption was within expected preliminary ranges, at an average of 0.71 kg/t sodium cyanide (NaCN) and 1.62 kg/t lime (CaO).
The company said the results support continued metallurgical optimization, including testing with material from the other historic mines at El Potrero and evaluating finer grinding and longer leach times.
“We are very pleased with the results from this preliminary round of metallurgical tests, especially for gold recoveries,” said CEO Robert Archer. “These tests were run using simple baseline parameters and without any optimization. The results indicate that we need to conduct mineralogical tests on the mineralization to determine the nature of the gold and silver occurrences.”
Silver recoveries were more variable, ranging between 41.41% and 73.53%, averaging 54.68%, suggesting more complex mineralogy and the potential need for longer leach times or further optimization.
Archer added that while gold likely occurs as free particles or in electrum, silver may be present in more complex forms such as sulphides or sulphosalts. Future testing will aim to fine-tune the metallurgical process to improve silver recoveries and streamline plant design, the CEO added.
The El Potrero project hosts three historic mines within a low-sulphidation epithermal vein system. Pinnacle plans to use future metallurgical results to refine its processing flowsheet ahead of potential plant reconstruction.