Color is medium to dark brown, reddish bronze or brownish red. Luster is greasy to pearly. Diaphaneity is transparent to translucent in small crystals, masses are opaque. Crystal Habits include well-formed sharp, tabular to bladed crystals to several cm in length. Bladed and acicular microcrystals may also be found.
Fracture is uneven.
Hardness is 3. Streak is brown. Described in 1854.