Capstone Mining Corp.’s Pinto Valley mine enhanced its dump leach performance after partnering with Jetti Resources to apply catalytic technology at the Arizona mine’s existing dump leach operation.
Capstone reported that during the first year of its partnership with Jetti, cathode production per area irrigated has doubled, and a plan to increase activity is being implemented with the goal of generating strong cash flow from Pinto Valley’s underutilized 25-million-lb-per-year (lb/y) solvent extraction and electrowinning (SX-EW) plant, which is currently operating at 20% of capacity. The plan is to increase cathode production to 300 million lb to 350 million lb from residual and high-grade waste over the next two decades.
Capstone President and CEO Darren Pylot said, “The mining industry has long been pursuing a viable technology to leach low-grade chalcopyrite ores. The results after year one of our partnership with Jetti Resources are exciting because it means we can generate high margin from material that would have been waste. This project represents an opportunity to position Pinto Valley more competitively, which will create and sustain jobs, and economic benefits in a socially and environmentally responsible manner.”
The engagement of Jetti and use of its proprietary technology was an extension of Pinto Valley’s existing PV3 Optimization Study, which is focused on several low-capex, high-impact projects aimed at having a material increase to the net present value of the operation. The PV3 Optimization Study’s report is scheduled for release in Q4 2020.
Jetti has developed and commercially deployed a catalytic technology that it claims allows for the efficient and effective heap and stockpile leach extraction of copper trapped in challenging ore types such as low-grade primary sulphides, including chalcopyrite. Jetti said its catalysts enable the disruption of the sulfur metal bond of the mineral, allowing copper extraction to take place unimpeded.
Pinto Valley started producing copper cathode in 1981 from material below the cut-off grade of its mill that had been stockpiled since the early 1970s. This provided a 12%-15% boost to total copper production as cathode accounted for an average of 16 million lb/y through to the early 2000s. Since then, the production of cathode has decreased consistently to under 4 million lb/y due to the impact of reduced leach kinetics as chalcopyrite is subjected to a passivation layer inhibiting further breakdown.
As a result of the positive commercial demonstration phase, Pinto Valley intends to significantly expand leaching activity, targeting approximately 280-300 million metric tons (mt) of historic leach stockpile and 175-185 million mt of high-grade waste already scheduled for removal over the remaining 19 years of mine life. Potential to increase the mill cut-off grade to bolster copper concentrate production, thereby increasing the tonnage of high-grade waste available for leaching, will be studied during H2 2020. An updated NI 43-101 Technical Report is expected in 2021.
A total of 11 million-12 million mt of high-grade waste has been placed since early 2019 and by the end of 2022, approximately 48 million mt to 52 million mt are expected to be under irrigation.