Arizona-focused copper developer Excelsior Mining (TSX: MIN) has kicked off construction of the Johnson Camp mine site, where it is looking to revive a historic open-pit copper operation with the support of Nuton, a Rio Tinto technology venture.
The construction follows Nuton’s decision earlier this year to proceed with Stage 2 of the companies’ existing option agreement, under which the Rio venture plans to fully deploy its proprietary heap leach technology at Johnson Camp. In return, it will make a $5 million payment to Excelsior for the use of mine infrastructure and fund all of Excelsior’s costs associated with this stage.
The Johnson Camp mine has historically been a heap leach operation since the 1970s. It comprises two open pits, a two-stage crushing-agglomerating circuit, and a fully functioning solvent extraction-electrowinning (SX-EW) plant capable of producing 25 million lb. of copper cathode per year.
Earlier this year, Nuton completed Stage 1 of the work program, consisting of mineralogy, predictive modelling, engineering and other test work. Meanwhile, Excelsior, as project operator, completed diamond drilling, permitting activities, detailed engineering and project execution planning.
The Stage 2 work is anticipated to take five years to complete, and, if successful, would demonstrate key elements of Nuton’s technology at industrial scale. It will proceed based on milestones related to engineering and mobilization, infrastructure and construction, mining, leaching, copper production, and post-leach rinsing.
Mining is expected to commence as soon as year one with first copper produced in the first half of 2025, according to Excelsior.
Achieving all milestones would result in full-scale commercial production of Nuton copper over several years at Johnson Camp. Revenue from operations will first be used to pay back Stage 2 costs to Nuton and will then be credited to Excelsior’s account after fulfillment of Excelsior’s applicable royalty and stream obligations.
In Thursday’s press release, Excelsior said it has completed the bulk of the planning and engineering and has mobilized crews to start construction. Contracts have been awarded for the engineering procurement and the construction of a new leach pad, which has begun.
To facilitate the start of these activities and Stage 2, Nuton recently provided funding of $7.9 million through August 2024. Additional funding and activities will be announced as they progress.
Upon completion of Stage 2, Nuton will have the right to form a joint venture on the Johnson Camp mine, in which Nuton and Excelsior will initially hold 49% and 51% respective interests.
Shares of Excelsior Mining were 7.7% higher at C$0.14 apiece by 1:45 p.m. ET in Toronto, for a market capitalization of C$44.2 million.
