Capstone Mining (TSX: CS) has received final approvals from the U.S. Forest Service for a new mine plan for the Pinto Valley copper mine 125 km east of Phoenix, Arizona. The mine life is extended 28 years to 2039, during which time it is expected to produce 2.5 billion lb. of copper.
The mine is located in the Tonto National Forest and gaining approval for the changes took five years.
Capstone completed the $31 million optimization program at Pinto Valley (PV3) earlier this year. Work included replacing ball mill #3, updates to tailings thickeners, and recommissioning of the molybdenum plant.
At the beginning of 2019, a patented catalyst from Jetti Resources was injected into a leach pad. The catalyst alters the smooth surface (passivation layer) of the copper sulphide ore to allow the leach solution to penetrate and extract the metal more efficiently. In the first year of using the catalyst, cathode production per area irrigated doubled.
Not only has catalyst use pushed all-in sustaining costs down to $1.40 to $1.50 per lb., but its use also allows Capstone to re-leach residual waste, turning it into saleable copper.
Pilot plant testing of coarse particle flotation technology began in December 2020 using equipment from Eriez Flotation Division. Testing indicated that a 6% to 8% increase in overall copper recovery is achievable. Other benefits are lower grinding costs, less water and energy consumption, and better tailings impoundment stability.
Year-to-date the Pinto Valley mine, leach operation and mill have produced 96.2 million lb. of copper. This year’s guidance for both the Pinto Valley and Cozamin mine in Mexico is 175 million to 190 million lb. of copper.
(This article first appeared in the Canadian Mining Journal)