Bellbergite

Formula: (K,Ba,Sr)2Sr2Ca2(Ca,Na)4Al18Si18O72 . 30H2O

Reflected/transmitted colour: colourless

Pleochroism:

Optical isotropy/anisotropy: uniaxial

Optical sign: -

Refractive indices: w = 1.522, e = 1.507

Birefringence δ: 0.015

2V angle:

Dispersion:

Optical orientation:

Optical axial plane:

 

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