Michigan Native Float Copper, Keweenaw Peninsula
14" x 5" x 11" / 18 lbs
Float copper (i.e., copper carried by glaciers) is found throughout the western Upper Peninsula of Michigan and many nearby states. Repeated glaciations thousands of years ago altered the geologic deposits of the native copper when glaciers gouged out the Great Lakes. Copper, along with other rocks, gravel, and sand were constantly tumbled and deposited over large areas of the Upper Midwestern United States. The long period of burial since the cessation of glacial movements (ca. 10,000 years ago) oxidized the surface copper. The resulting oxidation products are primarily malachite (green copper carbonate) and cuprite (red copper oxide).