Forsterite

Reflected/Transmitted light color: colorless

Pleochroism: more strongly coloured varieties show weak to moderate pleochroism, titanium-augite moderate to strong, α pale greenish, pale brownish, green, greenish yellow, β pale brown, pale yellow-green, violet, γ pale green, grayish green, violet

Optical isotropy/anisotropy: biaxial

Optical sign: +

Refractive indices: α = 1.635, β = 1.651, γ = 1.670

Birefringence δ: 0.035

2V angle: 82-90°

Dispersion: r > ν