Formula: Na(Ca,Na)(Mg,Fe)4Fe(SI7AlO22)(OH,F)2
Reflected/transmitted colour: yellow, reddish brown, bluish green
Pleochroism: α yellow, yellow-red, pale brown, β greenish brown, brownish red, deep brown, γ reddish yellow, deep purple-red-brown, greenish brown (α pale yellow, β bluish green, γ dark green to black for Fe-rich varieties), absorption γ < β > α for magnesiokatophorite
Optical isotropy/anisotropy: biaxial
Optical sign: -
Refractive indices: α 1.639-1.681, β = 1.658-1.688, γ = 1.600-1.690
Birefringence δ: 0.007-0.021
2Vα angle: 0-70°
Dispersion: r < v, strong
Optical orientation: α Λ z = 36-70°, β = y, γ Λ x = 50-85° (orientation correct?)
Optical axial plane: ┴ (010)
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