Phoenix, Arizona--(Newsfile Corp. - July 31, 2023) - Excelsior Mining Corp. (TSX: MIN) (FSE: 3XS) (OTCQB: EXMGF) ("Excelsior" or the "Company") is pleased to announce that it has entered into an Option Agreement (the "Agreement") 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. Under the Agreement, Excelsior remains the operator and Nuton funds Excelsior's costs associated with a two-stage work program at Johnson Camp. Nuton will provide a US$3 million pre-payment to Excelsior for Stage 1 costs and a payment of US$2 million for an exclusive option to form a joint venture with Excelsior over the Johnson Camp Mine after the completion of Stage 2.

"We are very pleased to be moving Johnson Camp forward with Nuton. With their support and technologies, we have the potential to realize the value of the sulfide resources at Johnson Camp in a way that is both economical and beneficial to the environment. Johnson Camp has the potential to progress towards cash-flow whilst we continue to develop our other assets, including progressing Gunnison towards well-stimulation trials later this year," comments Stephen Twyerould, President and CEO of Excelsior Mining. "The strength of this agreement is that it allows both Gunnison and Johnson Camp to advance in parallel."

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 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.

Under the terms of the Agreement, the Stage 1 work program involves Excelsior completing diamond drilling, permitting activities, detailed engineering, and project execution planning. Nuton will complete mineralogy, predictive modelling, engineering and other test work. Based on the results of the Stage 1 work program, Nuton has the option to proceed to Stage 2. The Stage 1 work program is expected to commence in August and take 6 to 9 months to complete.

If Nuton proceeds to Stage 2, it will make a US$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 but 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. The completion of all milestones would result in full scale commercial production over several years at Johnson Camp utilizing NutonTM Technologies. 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 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%. The purpose of the joint venture is to continue the development of the Johnson Camp Mine using NutonTM Technologies. Should Nuton not exercise their 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 are non-exclusive. During Stages 1 and 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.

ABOUT NUTON

Nuton is an innovative new venture that aims to help grow Rio Tinto's copper business. At the core of Nuton is a portfolio of proprietary copper leach related technologies and capability - a product of almost 30 years of research and development. The Nuton technologies offer the potential to economically unlock known low-grade copper sulfide resources, copper bearing waste and tailings, and achieve higher copper recoveries on oxide and transitional material, allowing for a significantly increased copper production outcome. One of the key differentiators of Nuton is the potential to deliver leading environmental performance, including more efficient water usage, lower carbon emissions, and the ability to reclaim mine sites by reprocessing mine waste.

ABOUT EXCELSIOR MINING

Excelsior "The Copper Solution Company" is a mineral exploration and production company that owns and operates the Gunnison Copper Project in Cochise County, Arizona. The project is a low cost, environmentally friendly in-situ recovery copper extraction project that is permitted to 125 million pounds per year of copper cathode production. Excelsior also owns the past producing Johnson Camp Mine and a portfolio of exploration projects, including the Peabody Sill and the Strong and Harris deposits.

For more information on Excelsior, please visit our website at www.excelsiormining.com.

For further information regarding this press release, please contact:

Excelsior Mining Corp.
Concord Place, Suite 300, 2999 North 44th Street, Phoenix, AZ, 85018.

Shawn Westcott
T: 604.365.6681
E: info@excelsiormining.com
www.excelsiormining.com