Copper - FCU20.75
Semi-Polished Specimen of Michigan Float Copper
Float copper is native copper that was separated from the volcanic rock (basalt) within which it formed (ca. 1.2 billion years ago) and carried by glaciers during the last ice age (ca. 10,000 years ago). The long period of burial since the cessation of glacial movements oxidized the surface copper. The resulting oxidation products are primarily malachite (a green copper carbonate) and cuprite (a red copper oxide).