Formula: ZnS
Reflected/transmitted colour: yellow to brown or colourless, polished section gray in air, in oil very dark gray, sometimes with a brownish tint, internal reflections always visible, especially in oil and in badly polished sections, for Fe-rich species reddish or reddish brown, Fe-poor more yellowish brown or yellowish white
Pleochroism: -
Optical isotropy/anisotropy: isotropic, polished section usually isotropic, but if anisotropic then light gray to dark gray, mostly disturbed by the internal reflections, may be due to tectonic deformation or to chemical admixtures, a high iron content causes distinct anisotropy
Optical sign:
Refractive indices: n = 2.37
Birefringence δ:
2V angle:
Dispersion:
Optical orientation:
Optical axial plane:
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