Copper is a native element and often occurs in fine-grained volcanic rocks such as basalt. It is red and orange in color until exposed to oxygen which can cause it to turn green and black over time. It was one of the first metals to be used by humans and was the first to be smelted from ores. This specimen was found in a conglomerate, a sedimentary rock made of rounded fragments cemented together by calcium carbonate, iron oxide, silica, or hardened clay. This specimen was found in the Keweenaw Peninsula of Northern Michigan and was donated by Walter McBride.