Formula: V3O4(OH)4
Reflected/transmitted colour: opaque, transparent in very thin splinters, reddish brown to reddish yellow, polished section gray, variable along elongation of the crystals
Pleochroism:
Optical isotropy/anisotropy: biaxial, polished section very strong anisotropic,
Optical sign: could not be determined, probably due to lamellar submicroscopic twinning
Refractive indices: n = ~1.90
Birefringence δ/bireflectance: polished section bireflectance present
2V angle:
Dispersion:
Optical orientation:
Optical axial plane:
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