Luster is metallic. Crystals are opaque. Crystals sometines twinned. Also commonly massive, and sometimes botryoidal. Cleavage is rather poor in one direction.
Fracture is conchoidal and brittle.
Streak is dark green. Some striations on most crystal faces. Associated Minerals are quartz , fluorite , barite , dolomite , calcite , pentlandite , pyrite and other sulfides . Notable Occurances include Chile, Peru, Mexico, Europe, South Africa, several USA sites and many others around the world. Best Field Indicators are crystal habit, tarnish, softness and brittleness.