Reaching the site of the biggest undeveloped US copper deposit requires a 15-minute drop by steel cage into the sweltering bowels of the Arizona desert. There, more than a mile beneath the surface, the temperature can reach 175F (79C), so massive cooling units run constantly, churning out mist that condenses and drips from the ceiling, calcifying the pipes lining the tunnel walls.
It’s called Resolution Copper, and it holds enough of the critical metal to supply a quarter of US demand for years. Yet two decades and over $2 billion later, not a single ounce of copper has been mined. ...