Burckhardtite

Formula: Pb2(Fe,Mn)Te(AlSi3)O12(OH)2 . H2O

Reflected/transmitted colour: pale magenta to carmine

Pleochroism: α = pale magenta, β = γ = carmine

Optical isotropy/anisotropy: biaxial

Optical sign: -

Refractive indices: α = 1.82, β = 1.85, γ = 1.85

Bireflectance/Birefringence δ: 0.03

2V angle: small

Dispersion:

Optical orientation:

Optical axial plane:

 

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