In the Lower 48, mines were digging up ore that contained 2% copper.
Initially thought to be due to the accumulation of silver, they were first demonstrated to contain copper in 1934.
The key respiratory compounds contain neither iron nor copper; no metal at all, in fact.
Additionally, as the power supplies contained expensive copper this further reduced cost.
Objects from the 10th century have been found containing copper from the mine.
It was the first reported perovskite superconductor that did not contain copper.
Initial surface analysis has shown that the metal contains 11% silver and 0.5% copper.
The dredged sand contained copper that earlier stamping technology had not been able to separate out.
The metal in the bracelet is a gold alloy that contains copper.