Native copper occurs rarely as isometric cubic and octahedral crystals, but more typically as irregular masses and fracture fillings.

It has a reddish, orangish, and/or brownish color on fresh surfaces, but typically is weathered and coated with a green tarnish of copper(II) carbonate (also known as patina or verdigris).

Isle Royale in western Lake Superior was also a site of many tons of native copper.

Some of it was extracted by native peoples, but only one of several commercial attempts at mining turned a profit there.

[6] An archived record of native copper originally found up river from Lake Superior, on the west branch of the Ontonagon River, via being dragged by a glacier is seen in the Ontonagon Boulder now in the possession of the Department of Mineral Sciences, National Museum of Natural History, Smithsonian Institution.