RIO Rio Tinto Limited

By Robb M. Stewart

Excelsior Mining has agreed to further test Rio Tinto-developed technology to extract copper at its no longer producing Johnson Camp mine in Arizona.

The mineral exploration and production company said Monday it entered an option agreement with Rio Tinto venture Nuton to use the copper heap leaching technologies.

Excelsior will remain the operator and Nuton will fund Excelsior's costs associated with a two-stage work program at Johnson Camp, providing a $3 million prepayment for first-stage costs and $2 million for an exclusive option to form a joint venture with Excelsior over the Johnson Camp mine after the completion of stage two. If Nuton proceeds to stage two, it will make a $5 million payment to Excelsior for the use of existing infrastructure at the mine.

Nuton's technologies offer the potential to realize the value of sulfide resources at Johnson Camp in a way that is economical and beneficial to the environment, Excelsior said.

Rio Tinto developed the technologies targeted at primary sulfide minerals, including lower-grade mineral deposits, that couldn't otherwise be processed using traditional leaching or sulfide processing technologies.

Excelsior said mining is expected to commence in year one of the agreement, and the full stage two work program is anticipated to take up to five years. The completion of all milestones under the agreement would result in full-scale commercial production over several years at Johnson Camp using Nuton technologies, with revenue from operations first used to pay back stage two costs to Nuton and credited to Excelsior's account, the company said.

Write to Robb M. Stewart at robb.stewart@wsj.com

(END) Dow Jones Newswires

July 31, 2023 08:24 ET (12:24 GMT)

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