Color is brownish gray to dark brown. Luster is metallic. Transparency crystals are opaque. Crystal Habits include acicular, fibrous or radiating crystals. Cleavage is perfect in the lengthwise direction.
Fracture is uneven.
Streak is a dark brown. Crystals are not flexible. Associated Minerals include quartz , stibnite and other sulfides . Best Field Indicators are crystal habit, streak, softness and inflexibility of crystals.