Crystal symmetry

Trigonal rhombohedral, 3

Lattice Constant

a_hex = 4.8012(1) Å
c = 16.002 Å
Z = 3

Color

White

Crystal system

Trigonal

Cleavage

Perfect on {1011}, rhombohedral cleavage

Mohs scale hardness

3,5 to 4

Specific gravity

2.84 - 2.86

Optical properties

Uniaxial (-)

Refractive index

n_ಎ = 1.679 - 1.681
n_ԑ = 1.500

Birefringence

δ = 0.179 -0.181