Enargite - Cu₃AsS₄

Habit: Crystals are usually grayish black to iron-black small, tabular or prismatic, typically striated parallel to c; also massive and granular. Metallic to dull Luster, opaque.

Environment: Formed at moderate temperatures in veins and replacement deposits associated with chalcopyrite, covellite, galena, pyrite and sphalerite.

Etymology: From the Greek enarge meaning 'distinct', referring to its perfect Cleavage