Color:White, Yellow, Red, Orange, Blue, Green, Brown, Grey

Streak: White

Luster: Vitreous, Pearly

Habit: crystals thick tabular, massive, compact or granular

Hardness: 3

Specific gravity: 2.7

Cleavage: Perfect on {1011}

Tenacity: Brittle

Twinning: At least four twin laws have been described, the most common being when the twin plane and the composition plane are {0112}. Also common with twinning on {0001} with {0001} as the compositional surface, producing re-entrant angles. Uncommon with {1011} or {0221} as twin planes, producing somewhat heart-shaped crystals ("butterfly" twins)

Crystal system: Trigonal

Crystal class: 3m (3 2/m)

Unit Cell: a1=a2=a3= 4.9896(2) Å, c = 17.061(11) Å