Formula: (Fe,Mg)(Cr,Al,Fe)2O4
Reflected/transmitted colour: variable, darker varieties almost opaque, polished section shows differences in colour shades and reflectance with varying substitutions, dark gray to brownish gray. Red-brown internal reflections very common in Mg and Al rich species, Chromite with high Fe-content has no internal reflections.
Pleochroism: -
Optical isotropy/anisotropy: isotropic, polished section isotropic, many specimens show weak to distinct anisotropy, especially zoned crystals, may also be caused by deformation
Optical sign:
Refractive indices: n = 2.16
Birefringence δ:
2V angle:
Dispersion: moderate
Optical orientation:
Optical axial plane:
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