Crystals are opaque. Crystal Habits include pseudohexagonal tabular to prismatic crystals often with a shallow pyramidal truncation with a flat point. Also found massive and compact. Twinning is common and sometimes results in a six pointed star shaped cyclic twin called a trilling or in elbow shaped twins. Cleavage is imperfect in two directions, prismatically.
Fracture is conchoidal.
Streak is shiny black to lead gray. Crystals are usually deeply grooved with lateral striations and a tarnish will tend to dull the luster of crystals over time. Associated Minerals are quartz , enargite , malachite , azurite , copper , cuprite , tetrahedrite , bornite , tennantite , chalcopyrite , covellite , pyrite and other sulfides . Best Field Indicators are crystal habit, streak, striations, color and associations.