There are claims that it was actually originally mines there thousands of years ago.
Yup.
Much copper was mined there before the Europeans arrived in 1492. Many archaeologists say that the American Indians don't have it. Others say, ancients from Europe, maybe even Egypt mined it many years ago for making bronze during the early Bronze Age.
Missing: 500,000 Tons Of Copper
For some 1800 years, beginning abruptly about 3000 BC, some industrious peoples mined ore equivalent to 500,000 tons of copper from Michigan's Isle Royale and Keweenaw Peninsula. Who were these mysterious miners, and what happened to all all that copper? It certainly hasn't been found in the relics of North American Indians. And where was the ore smelted? About all the unidentified miners left behind are some of the crude tools they used to pound out chunks of ore from their pit mines (5000 pit mines on Isle Royale alone). Outside of some cairns and slabrock ruins, there is little to help pin down these miners. Mainstream archeologists attribute all these immense labors to a North American "Copper Culture" -- certainly not to copper-hungry visitors from foreign shores. Admittedly, many copper artifacts have been dug up from North American mounds, but only a tiny fraction of the metal the Michigan mines must have yielded."