α-Tridymite

Formula: SiO2

Reflected/transmitted colour: colourless

Pleochroism: -

Optical isotropy/anisotropy: biaxial

Optical sign: +

Refractive indices: α = 1.469-1.479, β = 1.470-1.480, γ = 1.473-1.483

Birefringence δ: 0.0025-0.004

2Vγ angle: 40-90°

Dispersion:

Optical orientation: α = y

Optical axial plane: (100)

 

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