Nestled among the Oquirrh Mountains in Utah is the deepest open-pit copper mine on Earth. The Bingham Canyon mine, once owned by the Guggenheims and now run by Rio Tinto, has been in operation since 1903. Even now about 275,000 tonnes of the red metal are dug from it every year, nearly a quarter of America’s annual production. Its rocks are sent down a five-mile conveyor belt to be crushed. The mineral is then separated out, smelted into liquid and refined into 99.99% pure copper plates. The vertically integrated mine is the last of its kind in America, which until the 1960s was the world’s biggest producer of copper.