Physical properties
Habit: twinning, prismatic, tabular, striated (001).
Color: green, white, brown, or yellow.
Streak: white.
Luster: vitreous (i.e., glassy).
Diaphaneity: transparent to translucent.
Cleavage: (110) distinct, (010) imperfect.
Twinning: {031}.
Fracture: brittle.
Occurrence: granitic pegmatite dikes.
