Copper

About it

Copper-red masses, wires, and branching crystals that tarnish brown or green and bend instead of breaking. The Keweenaw Peninsula of Michigan is the classic source; also Arizona and Namibia.

Type

Mineral

Group

Native element, gold group

Formula

Cu

Hardness (Mohs)

2.5–3

Specific gravity

8.94–8.95

Streak

copper red, shiny

Lustre

metallic

Crystal system

Isometric (cubic)

Colours

copper red, tarnishing brown, black, or green

Transparency

opaque

Cleavage and fracture

none; hackly fracture, malleable

Typical values: real specimens vary. For more, see mindat.org.