The Gunnison project is a low cost, in-situ recovery copper extraction project that is permitted to 125 million pounds (56.7t) per year of copper cathode production.

Following a comprehensive commissioning programme that has been ongoing for several weeks, regulatory approval to commence mining operations through the injection of acid was received from the US Environmental Protection Agency in December.

Delivery of mining fluids to the copper orebody has commenced; fluids will now circulate 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 to then extract copper and produce copper cathode sheets. First copper cathode sales are expected in the March 2020 quarter.

Stephen Twyerould, president and CEO of Excelsior Mining, 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, chairman of Excelsior Mining, added: "On behalf of the board, I would like to congratulate the entire Excelsior team for achieving the commencement of production. Your hard work and your dedication have made possible this significant milestone, and we look 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 of production per annum."