Formula: (Na, Ca)Mn2+(Fe3+, Mn2+, Fe2+, Mg)2(PO4)3
Reflected/transmitted colour: yellow to yellow-green
Pleochroism: α pale olive-green, straw-yellow to greenish yellow, γ pale olive-greenish to brownish yellow
Optical isotropy/anisotropy: biaxial
Optical sign: +
Refractive indices: α = 1.782, β = 1.802, γ = 1.835
Birefringence δ: 0.053
2V angle: measured: 50° to 90°, calculated: 78°
Dispersion: r > v, strong, crossed
Optical orientation:
Optical axial plane:
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