By Ryan Dezember | Photography by Mark Lipczynski for WSJ
DRAGOON, Ariz. -- In the boulder-strewn desert east of Tucson, miners are using sulfuric acid and bacteria to bring online the first new U.S. copper production in more than a decade.
The metal is coming from Gunnison Copper's Johnson Camp mine, where excavation stopped in 2010 when the previous owners reached ores that weren't rich enough to profitably process. It is being restarted in partnership with Rio Tinto's Nuton venture, which uses microbes to strip copper from ores that are otherwise uneconomical to mine.
Advances in mining technology, insatiable demand for the metal that is essential to everything electric, and President Trump's push to boost U.S. raw-material output have made it worthwhile to revisit old mines and marginal deposits around copper-rich Arizona.
Johnson Camp is one of several copper projects racing to production in the state. Most plan to use heap-leaching technologies to produce ready-to-use slabs of copper, called cathodes, without expensive and energy-gobbling concentrators, smelters and refineries.
The U.S. has plenty of copper in the ground, but smelting capacity is a pinch point. A big chunk of U.S. mine output is shipped abroad and sent back in processed forms that manufacturers can use.
"About 50% of our total consumption is being imported because we're not making enough," said Craig Hallworth, Gunnison's finance chief. "This could go a long way to fixing that."
Gunnison started selling cathodes made using conventional heap-leaching methods of Johnson Camp's oxide ores in September. The first batch of copper extracted from its sulfide ores using the Nuton technology is expected in the coming days. Ramped up, Johnson Camp should annually produce 25 million pounds of cathode.
The timing is auspicious. Copper prices have notched record highs this year and are expected to keep climbing.
Miners anticipate soaring copper demand to produce electric vehicles, renewable energy and data centers -- not to mention all the wiring and plumbing needed to keep pace with population growth and rising living standards in the developing world.
Industry executives are bracing for copper consumption over the next 25 years that could exceed all of the copper that humanity has used until now.
The U.S. Geological Survey added copper to its list of critical minerals deemed vital to national security and the economy. The White House is weighing tariffs beyond the 50% levy that Trump slapped on semifinished products like wire and pipe. An import tax on less-processed copper would put a premium on U.S.-made cathodes.
"If the U.S. is serious about energy independence, Arizona's low-grade and legacy materials is where we need to start," said Liz Dennett, chief executive of Endolith, which is testing its AI-optimized methods of using microbes to boost copper recovery in the state.
Efforts to economically produce abundant but low-grade copper deposits aren't unlike wildcatters' quest a quarter-century ago to unleash the flood of oil and natural gas that was known to be locked in shale formations but beyond the reach of profitable drilling. The frackers figured it out and remade the U.S. into the world's leading fuel producer. For miners, Arizona is their Texas.
Few states dominate the domestic production of a natural resource like Arizona does copper. Last year, it accounted for about 70% of U.S. output.
Native Americans mined for thousands of years before prospectors arrived in the 19th century ahead of surging demand for the original electrical build-out. When Arizona became a state, in 1912, mining was its most common job and a copper star was sewn at the center of its flag.
The new projects tend to be in Arizona's historic mining districts, such as the Copper Corridor southeast of Phoenix, where Taseko Mines is expecting first production early next year at its Florence project.
Rather than excavating ore and adding acid to heaps of it to extract the copper, Taseko is taking a page from uranium miners and pumping acid down into wells to separate the copper below the surface. When fully operational, Taseko expects Florence to annually produce 85 million pounds of cathode.
An oil driller tapped into the wet, crumbly ore at Florence in the 1970s. The idea to use what are called in-situ recovery methods dates back about 30 years, said Taseko chief executive Stuart McDonald.
"It's taken a lot of perseverance for the permitting," he said. "And also the test work."
It isn't unusual for decades to pass between discovery and production. A prime example is Rio and BHP Group's Resolution Copper venture. Resolution filed more than a decade ago for federal permits to tunnel into one of the world's largest undeveloped copper deposits in the mountains east of Phoenix but has been mired in legal challenges.
Rio executives had that in mind when they looked for a shovel-ready spot to launch Nuton following decades in the lab and a 70,000-ton test batch at the Anglo-Australian firm's massive copper mine near Salt Lake City.
They aim to show Nuton's bioleaching technology works at scale and can be deployed throughout the Americas to uncork the low-grade sulfide ores left in old mines.
"Of all the copper that exists in the ground globally, 70% of those resources are comprised of primary sulfides, this mineralogy that we're looking to unlock," said Nuton chief executive Adam Burley. "That size of prize is enormous."
The Nuton name plays on Isaac Newton, the alchemist, as well as the hunt for "a new ton" of copper, which had become elusive via deal or discovery, Burley said.
"We needed a different model because the one that we'd been trying for years wasn't delivering the results we wanted," said Clayton Walker, who is responsible for the growth and development of Rio's copper business in the Americas.
A skeleton crew had kept Johnson Camp in compliance with its permits, so it could restart quickly. It had the right type of rock, a heap leach pad and solvent-extraction electrowinning plant, where the copper dripping in solution from the ore is plated on cathodes. Nuton and Gunnison reached an agreement in 2023.
Nuton has funded the mine's restart, including building a new heap leach pad that is the size of about 140 football fields and wired with thousands of censors. The sulfide ores that stopped the previous miners are piled there after they have been crushed then coated with bacteria and acid, which separates the copper from the rest of the rock.
Nuton has partnerships at 10 other mines in the Americas. Among them is Arizona Sonoran Copper's Cactus project, located in an industrial corridor between Phoenix and Tucson.
Low copper prices and declining ore grades closed the mine in 1984, leaving a pit roughly 1,000 feet deep and 3,000 feet around. Arizona Sonoran plans to start producing cathodes from richer ore beneath an adjacent tract and eventually reopen the old mine.
It expects average production of about 100,000 tons of cathode annually over 22 years.
Nuton is testing microbes on the old mine's ore. The more it can boost copper recovery and the mine's value, the larger a stake in the project the Rio subsidiary can earn. Construction is scheduled to start in 2027 with the first cathodes made in 2029.
"In our business that's like tomorrow," said Arizona Sonoran executive Bernie Loyer.
Write to Ryan Dezember at ryan.dezember@wsj.com
(END) Dow Jones Newswires
December 02, 2025 12:00 ET (17:00 GMT)
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