Formula: Cu2S

Colour: Blue black, gray, black, black gray, or steel gray

Lustre: Metallic, Sub-Metallic

Hardness: 2½ – 3

Specific Gravity: 5.5 – 5.8

Crystal System: Monoclinic

Member of: Chalcocite-Digenite Group. A secondary mineral in or near the oxidized zone of copper sulfide deposits. Easily confused with djurleite.

Name: Named chalcosine in 1832 by François Sulpice Beudant from Greek, “chalkos”, copper. This mineral was known by a wide variety of names previously. In 1868, James D. Dana and George J. Brush renamed this material “chalcocite”.

Dimorph of: Wuyanzhiite