Color is Black to grey or brown. Luster is submetallic to resinous. Transparency crystals are translucent to opaque. The crystals are elongated along the c axis and are generally flattened in the a axis direction. Also as columnar aggregates and lamellar masses.
Cleavage is perfect in one direction parallel to the a and c axes.
Fracture is uneven. Hardness is 4 - 4.5. Streak is brown to black. Associated Minerals are quartz , hematite , tourmalines , cassiterite , micas and pyrite . Best Field Indicators are crystal habit, color, density, luster and cleavage.