A pseudomorph is a mineral that has replaced another mineral atom by atom, but it leaves the original mineral's crystal shape intact. Chalcocite has been known to form pseudomorphs of the minerals bornite , covellite , chalcopyrite , pyrite , enargite , millerite , galena and sphalerite . Pseudo means false and morph means shape or form, thus pseudomorph means false shape since the mineral is chalcocite but the shape is that of a covellite crystal, for example. Color is dark gray to black. Luster is metallic.
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.