Excelsior Mining Corp. announced that Nuton LLC (? Nuton?), a Rio Tinto venture has elected to proceed to Stage 2 of the existing Option Agreement (the ?Agreement?) The purpose of the Agreement is for Nuton to evaluate the use of its Nuton??

copper heap leaching technologies at Excelsior's Johnson Camp mine in Cochise County, Arizona. Under the Agreement, Excelsior remains the operator and Nuton funds Excelsior's costs associated with a two-stage work program at Johnson Camp. As Nuton has elected to proceed to Stage 2, it will make a USD 5 million payment to Excelsior for the use of existing infrastructure at the Johnson Camp mine for the Stage 2 work program.

Nuton will also be responsible for funding all of Excelsior's costs associated with Stage 2. The full Stage 2 work program is anticipated to take up to five years, and, if successful, will demonstrate key elements of the Nuton technologies 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 in year one with first Nuton copper produced in 2025.

The completion of 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. Rio Tinto has developed the NutonTM 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 economically using traditional leaching or sulfide processing technologies.

These technologies offer the potential to produce additional copper from new and ongoing operations in a cost-effective manner that has significant environmental benefits when compared with traditional primary sulfide processing technologies. After the completion of Stage 2, Nuton will have the right to form a joint venture on Johnson Camp per mutually agreeable terms whereby Nuton will hold an initial 49% and Excelsior an initial 51% interest. The purpose of the joint venture is to continue the development of the Johnson Camp mine using Nuton technologies.

Should Nuton not exercise its joint venture rights, Nuton and Excelsior will discuss in good faith Excelsior's continued use of the Nuton technologies at the Johnson Camp mine subject to certain licensing terms and conditions. The infrastructure arrangement at Johnson Camp under this Agreement is non-exclusive. During Stage 2, Excelsior may continue to use the Johnson Camp infrastructure for processing Gunnison solutions and other copper sources not related to the Stage 2 work program so long as capacity requirements for the Stage 2 work program are met.