|Michigan Native Copper
Michigan’s Keweenaw Peninsula is the most important locality in the world for pure native copper. Small amounts occur in several areas throughout the world. Mining operations began in 1845 and continued until 1968. During that time over 5 million tons of refined copper were recovered from Michigan’s native copper mines. Near the turn of the century, Michigan led the world in copper production and “Lake Copper” was the purity standard to which other refined copper was compared. The copper occurs in various rock types and ranges in size from microscopic grains to large masses. The largest, discovered in 1857, weighed about 520 tons.