Euclase and Sillimanite Optical Properties

Euclase

Sillimanite

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Optical Properties

Luster

Vitreous

Vitreous, Subadamantine, Silky

Pleochroism

Weak: colorless-(greenish) yellow

Colourless to pale brown to yellow

Dispersion

0.020.02

0.005 1

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Transparency

Transparent, Translucent

Refractive Index

1.650-1.6771.653-1.685

1 3.25

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Optic Character

Crystal System

Monoclinic Prismatic H-M Symbol (2/m) Space Group: P 21/a

Orthorhombic

Birefringence

0.019-0.0250.020-0.022

0 0.296

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Clarity

TransparentUlrich Henn and Claudio C. Milisenda

Transparent

Euclase and Sillimanite Optic Character

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

Similar to their colors, Euclase and Sillimanite 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, Euclase is while Euclase is in appearance.