native copper

Copper, as native copper, is one of the few metallic elements to occur in uncombined form as a natural mineral, although most commonly occurs in oxidized states and mixed with other elements. Native copper was an important ore of copper in historic times and was used by pre-historic peoples.Native copper occurs as rarely isometric cubic and octahedral crystals, but more typically as irregular masses and fracture fillings. It is a copper-red color on fresh surfaces, but typically is weathered and coated with a green tarnish of copper(II) carbonate. Its specific gravity is 8.9 and the hardness is 2.5.
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