Rio Tinto’s Nuton makes first copper cathode at Gunnison mine

Rio Tinto (NYSE, LSE, ASX: RIO) venture partner Nuton has produced the first copper using new technology at Gunnison Copper’s (TSX: GCU; US-OTC: GCUMF) Johnson Camp Mine (JCM) in Arizona.

The Nuton-made copper cathode, produced last month with a unique sulphide bioleaching technology, is part of a four-year demonstration period at JCM using its heap leach pad for the production of about 30,000 tonnes of refined copper, Gunnison said Thursday. JCM is about 105 km east of Tucson.

“This is a breakthrough achievement for our Nuton technology, which is proving that cleaner, faster, and more efficient copper production is possible at an industrial scale,” Rio Tinto Copper CEO Katie Jackson said in a release. “In an industry where projects typically take about 18 years to move from concept to production, Nuton has now proven its ability to do this in just 18 months.”

Trio of milestones

The milestone comes three months after Gunnison produced its first copper cathode at JCM, making the mine the United States’ newest red metal producer. The first Nuton-produced cathode is the result of more than 30 years of research and development, Gunnison said. Nuton began its collaboration with Gunnison’s predecessor Excelsior Mining at the site in 2023.

Gunnison shares gained 2.7% to C38¢ apiece on Thursday morning in Toronto for a market capitalization of C$146.4 million. The stock has traded in a 12-month range of C17¢ to C55¢.

Microbes aid processing

The technology uses natural microorganisms grown in Nuton’s proprietary bioreactors to extract copper from sulphide ores, which tend to be difficult to process. The microbes speed up the oxidation of minerals in the heap leach pad, generating heat and allowing the red metal to dissolve into a leach solution. It’s then processed into 99.99% pure cathode.

Nuton achieves recovery rates of up to 85% and cuts out milling, tailings, smelting and refining, thus shortening supply chains and delivering copper cathode right at the mine, Gunnison said.

The technology could reduce water usage by up to 80% and carbon emissions by as much as 60% compared to traditional copper concentration. It can also extend mine life by extracting metals from waste material.

‘Low-carbon copper’

The achievement at JCM in such a short time frame shows the possibilities of innovation, strong operational performance and a shared vision coming together, Gunnison CEO Stephen Twyerould said.

“With Nuton copper now entering the U.S. supply chain, this milestone underscores the critical role we can play in strengthening domestic access to cleaner, low-carbon copper,” he said.

The next stage at JCM is to focus on validating Nuton’s long-term technical performance, Gunnison said. That would comprise multi-year testing, independent third-party verification and an internal review by Rio Tinto to ensure recovery consistency and environmental performance.

Nuton has invested $100 million (C$140 million) in technology deployment and construction at JCM, while Gunnison holds ownership and operational control. The two-stage partnership is to last for four or five years during which copper output would pay down Nuton’s investment.   

In the second stage, and after full-scale commercial production using Nuton technology is underway, the companies would form a joint venture, with Gunnison holding 51% and Nuton 49%.

15 to 20-year life

The JCM open pit and heap leach mine has an annual capacity of 25 million lb. of copper over a 15 to 20-year life, according to a 2023 preliminary economic assessment prepared for Excelsior.

It hosts about 108 million measured and indicated tons grading 0.31% copper and 51 million inferred tons at 0.32% copper.

In a base case, JCM has a post-tax internal rate of return of 30% with a payback period of about four years, and a net present value of $180 million, at a 7.5% discount rate. Initial capital costs are pegged at $58.9 million.