Formula: (Fe,Ni)9S8
Reflected/transmitted colour: opaque, polished section strongly varying, even in well polished sections. Usually pinkish or reddish gray. No bronze or brown colours as for valleriite.
Pleochroism:
Optical isotropy/anisotropy: polished section very strong anisotropic. Completely crossed nicols: grayish white to dark gray or black. Not completely crossed nicols: bluish white to sienna brown. Anisotropy decreases markedly after a few weeks, polishing restores the original effects.
Optical sign:
Refractive indices:
Birefringence δ/bireflectance: polished section moderate to strong, pinkish gray to gray
2V angle:
Dispersion:
Optical orientation:
Optical axial plane:
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