Reflected/Transmitted light color: colorless

Pleochroism: colorless or pale yellow

Optical isotropy/anisotropy: Biaxial

Optical sign: -

Refractive indices: a=1.553-1.563, b=1.559-1.569, g=1.56-1.57, 0.0070

Birefringence δ: 0.0070