Celestine

Formula: SrSO4

Reflected/transmitted colour: colourless

Pleochroism: blue crystals weakly pleochroic: indigo, lavender-blue, blue-green, violet, absorption γ > β > α

Optical isotropy/anisotropy: biaxial

Optical sign: +

Refractive indices: α = 1.621-1.622, β = 1.623-1.624, γ = 1.630-1.631

Birefringence δ: ~ 0.009

2Vγ angle: 50°

Dispersion: r < v, moderate

Optical orientation: α = z, β = y, γ = x

Optical axial plane: (010)

 

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