Crystal symmetry

Orthorhombic (2/m 2/m 2/m) - dipyramidal

Unit cell

a =  3.88 Å
b = 12,54 Å
c =  3.07 Å
Z =  4

Color

Ruby-red

Crystal habit

Flattened scales aggregated

Crystal sytem

orthorhombic

Cleavage

{010} Perfect

Mohs scale hardness

5

Diaphaneity

Transparent

Specific gravity

4

Optical properties

Biaxial (-)

Refractive index

n_α =1.940
n_β = 2.200
n_γ = 2.510

Birefrigence

δ = 0,570

Pleochroism

Strong; 
X = colorless to yellow
Y= orange, yellow, dark red-orange
Z = orange, yellow, darker red-orange

2V angle

Measured: 83°