Copper From Keweenaw Peninsula Copper District, Houghton County, Michigan (307.4 grams)
Michigan's Keweenaw Peninsula is the most important locality in the world for pure native copper. Mining began in 1845 and continued until 1982 and over 7 million tones of refined copper were recovered from Michigan's copper mines. In the early 1900's, it led the world in copper production and "lake Copper" was the purity standard to which other refined copper was compared.
307.4 grams, 4 x 2.75 x .5 inches