Copper, symbol Cu, occurs both as the native metal and as mineral ores.

Crystal system: Cubic (crystals are mostly cubic, dodecahedral or tetrahedral)
Hardness: 2.5 to 3
Density: 8.95 gms/cm³
Colour: Light rose when fresh, darkening on exposure to reddish-brown.

Copper is associated with porous zones of mafic (magnesium and iron rich) extrusive rocks.

Copper has been mined since the Bronze Age. It is found almost world-wide. The richest deposits are in the USA and in particular in the Keeweenaw Peninsula, north Michigan where native copper nodules weighing several tons have been found. Some were so large that they had to be cut up under ground before they could be removed.

This specimen shown left, which is about 65mm long, came from the Keeweenaw Peninsula.