Villiaumite

Formula: NaF

Reflected/transmitted colour:

Pleochroism: Strong, yellow (E), pink to deep carmine (O)

Optical isotropy/anisotropy: Isotropic, weak anomalous anisotropism, then uniaxial (-_

Optical sign:

Refractive indices: n = 1.327-1.328

Bireflectance/Birefringence δ:

2V angle:

Dispersion:

Optical orientation:

Optical axial plane:

 

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