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Formula: (K,Na)2(UO2)2Si5O13.4H2O

Reflected/transmitted colour:

Pleochroism: Colourless (x), pale yellow green (y), yellow green (z)

Optical isotropy/anisotropy: Biaxial

Optical sign: -

Refractive indices: α = 1.596, β = 1.603, γ = 1.606

Bireflectance/Birefringence δ: 0.010

2V angle: 66° (calculated), 60° (measured)

Dispersion: Strong, r > v

Optical orientation:

Optical axial plane:

 

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