Michigan Copper in the Mediterranean (Isle Royale and Keweenaw Peninsula, c. 2400BC-1200BC)
Jay Stuart Wakefield
Recent scientific literature has come to the conclusion that the major source of the copper that swept through the European Bronze Age after 2500BC is unknown. However, these studies claim that the 10 tons of copper oxhide ingots recovered from the late Bronze Age (1300BC) Uluburun shipwreck off the coast of Turkey was "extraordinarily pure" (more than 99,5% pure), and that it was not the product of smelting from ore. The oxhides are all brittle "blister copper", with voids, slag bits, and oxides, created when the oxhides were made in multiple pourings outdoors over wood fires. Only Michigan Copper is of this purity, and it is known to have been mined in enormous quantities during the Bronze Age.