Excelsior Mining says it has successfully commenced mining operations at its Gunnison in-situ recovery copper project in southern Arizona, USA.

Following a commissioning program that had been ongoing for several weeks, regulatory approval to commence mining operations through the injection of acid was recently received from the US Environmental Protection Agency.

Delivery of mining fluids to the copper orebody has since commenced with fluids now circulating through a closed-loop system until the concentration of copper held in solution meets sufficient grade to be treated through the Johnson Camp processing facilities. This will lead to extraction of copper and the production of cathode sheets.

Excelsior said first copper cathode sales were expected in the March quarter.

Stephen Twyerould, President & CEO, said: “Following on the heels of the successful completion of the construction phase, mining operations at the Gunnison copper project are now underway. We remain absolutely confident in our capacity to deliver low-cost copper production while maintaining our commitment to safety and the environment.”

Mark J Morabito, Excelsior’s Chairman, said he and the board looked forward to continuing the ramp up of existing operations in 2020 and laying the groundwork for future expansion to Gunnison’s full production capacity of 125 million pounds (56,999 t) of production per year.

Gunnison’s initial capital cost was estimated at $49 million, with the mine expected to produce 2,200 MIb of copper cathode over a 24-year life.