This copper specimen is from the Keweenaw Copper Mining District in Keweenaw County, Michigan, USA. Keweenaw County contains hundreds of once operational mines and unnamed copper deposits with a long history that predates colonial times. It produced millions of tons of copper and has over 150 associated mineral species. The district produced some of the finest copper specimens known. They are highly priced by collectors for their excellent and varied crystal characteristics. This piece has a slightly curved fan-like shape consisting of hundreds of branching spinel twinned formations. Each branch supports dozens of crystals that vary in morphology and definition. Parts of the piece contain secondary deposits of oxides such as tenorite. Photo 7 is the reverse side .This piece measures 4 11/16 x 2 7/8 x approximately 3/8 average thickness or 120 x 73 x 9 mm.