Physical properties
Habit: acicular crystals making fibrous aggragates.
Color: brown to dark green.
Diaphaneity: translucent to nearly opaque.
Luster: vitreous to silky.
Fracture: subconchoidal.
Cleavage: perfect [110].
Streak: colorless.
Others: infusible and insoluble in HCl.
Occurrence: contact metamorphic rocks.
