Afghanite

Formula: (Na, Ca, K)8(Si, Al)12O24(SO4, Cl, CO3)3.H2O

Reflected/transmitted colour: colourless

Pleochroism:

Optical isotropy/anisotropy: uniaxial

Optical sign: +

Refractive indices: w = 1.523, e = 1.529

Birefringence δ: 0.006

2V angle:

Dispersion:

Optical orientation:

Optical axial plane:

 

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