Thulite and Allanite Optical Properties

Thulite

Allanite

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Optical Properties

Luster

Vitreous

Pleochroism

Present

Dispersion

0.020.02

0.005 1

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Transparency

Opaque, Translucent, Opaque . May be translucent in thin backlit sections.

Refractive Index

1.6951

1 3.25

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Optic Character

Crystal System

Orthorhombic

Birefringence

0.006-0.0180.013-0.036

0 0.296

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Clarity

OpaqueHerve Nicolas Lazzarelli

Thulite and Allanite Optic Character

Thulite and Allanite optical properties play a significant role while distinguishing these gemstones from each other. These properties are influenced by the Thulite 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 Thulite 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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Thulite and Allanite Transparency

Similar to their colors, Thulite 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, Thulite is Opaque, Translucent and Opaque . May be translucent in thin backlit sections. while Thulite is Opaque, Translucent and Opaque . May be translucent in thin backlit sections. in appearance.