Excelsior Mining Corp. announced that it has commenced drilling at Johnson Camp with Nuton LLC, a Rio Tinto venture, to further evaluate the use of its Nuton copper heap leaching technologies at Excelsior's Johnson Camp mine in Cochise County, Arizona. The program consists of drilling 6,000 feet of PQ core for the purposes of further metallurgical evaluation.

Once completed the samples will be processed for mineralogy and tested using the Nuton process. Results are expected late third quarter, 2023. The program is being funded by Nuton and carried out in connection with the previously announced Option Agreement.

Rio Tinto has developed the Nuton Technologies, an extensive portfolio of advanced copper heap leaching technologies targeted at primary sulfide minerals (including lower grade mineral deposits), which could not otherwise be processed using traditional leaching or sulfide processing technologies. These technologies offer the potential to produce additional copper in a cost-effective manner that has significant environmental benefits and reduces waste from new and ongoing operations.