PEA On The Johnson Camp Mine Incorporating Sulfide Leaching Technology

PHOENIX, AZ - Excelsior Mining Corp. reported the results of its Updated Preliminary Economic Assessment (PEA) on the Johnson Camp Mine Heap Leach, located in Cochise County, southeastern Arizona. The PEA considers the results of the drill program completed in 2022 and the implementation of sulfide leaching technology to improve recoveries. As part of the PEA, the combined report will also include a republishing of the Prefeasibility Study Update (PFS) on the North Star Deposit of the Gunnison Copper Project. The Gunnison Project is designed as a copper in-situ recovery (ISR) mine using solvent extraction-electrowinning ("SX-EW") to produce copper cathode and the Johnson Camp mine is a conventional open pit and heap leach operation.

The Johnson Camp Mine (JCM) has historically been an open pit, heap leach operation since Cyprus Minerals opened the property in the 1970's. The operation includes two open pits, a two-stage crushing-agglomerating circuit, a fully functioning SX-EW plant capable of producing 25 million pounds of cathode copper per year, a complete set of PLS and raffinate ponds, and full infrastructure (ancillary facilities, access, power, water, and communications).

Heap leaching of sulfide copper with accelerated pyrite oxidation is proposed in this PEA. The Project plans include mining oxide, sulfide, and transition material from the Burro and Copper Chief pits for 20 years and heap leaching for an additional year to produce copper cathode at a capacity up to 25 million pounds per annum (mppa).

To restart JCM for heap leaching, two developments need to take place simultaneously: pre-stripping and mine development, and the construction of a new heap leach pad, Pad 5. Both are considered to require between six and nine months to complete before irrigation of the new leach pad could commence. Piping of PLS and raffinate lines from Pad 5 to the JCM ponds also fits within this time frame. A PEA has been completed by M3 with respect to this planned re-opening.