Formula: Ca4(Al, Fe, Mg)10Si12 O36 (OH)12 (CO3). 12H2O
Reflected/transmitted colour: beige-blue
Pleochroism: intense, α = bright blue, b = γ = pale beige
Optical isotropy/anisotropy: biaxial
Optical sign: -
Refractive indices: a = 1.510, b = 1.560, g = 1.580
Birefringence δ: 0.07
2V angle: 63°
Dispersion:
Optical orientation:
Optical axial plane:
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