Iolite and Allanite Optical Properties

Iolite

Allanite

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Optical Properties

Luster

Vitreous

Pleochroism

Dispersion

0.020.02

0.005 1

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Transparency

Transparent, Translucent, Transparent to translucent

Refractive Index

1.52-1.561

1 3.25

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Optic Character

Crystal System

Orthorhombic

Birefringence

-99990.013-0.036

0 0.296

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Clarity

Transparent to translucent

Iolite and Allanite Optic Character

Iolite and Allanite optical properties play a significant role while distinguishing these gemstones from each other. These properties are influenced by the Iolite and Allanite Physical Properties like crystallographic symmetry, pleochroism,etc. in the crystal. Some of the optical properties are refractive index, luster, optic character, pleochroism etc. Prominent among these is Iolite and Allanite optic character. You might have noticed your gemologist rotating the gemstone while testing it. Rotating a gemstone along its optic axis helps in determining its optic character.

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Iolite and Allanite Transparency

Similar to their colors, Iolite and Allanite transparency can also be used as criteria for their primary identification. Although transparency cannot be the only criteria for gemstone identification, it can efficiently used in gemstone grading. Talking about their transparency, Iolite is Transparent, Translucent and Transparent to translucent while Iolite is Transparent, Translucent and Transparent to translucent in appearance.