Formula: (Fe,Cu)4S4(Mg,Al)3(OH)6
Reflected/transmitted colour: opaque, polished section varies strongly in colour, even in well-polished sections, usually brown or bronze-coloured
Pleochroism:
Optical isotropy/anisotropy: polished section extreme anisotropic, white to gray-bronze
Optical sign:
Refractive indices:
Birefringence δ/bireflectance: polished section very strong, not as strong as for graphite or mackinawite, w light gray-brown or creamy bronze, ε bluish gray to dark gray
2V angle:
Dispersion:
Optical orientation:
Optical axial plane:
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