Sillimanite and Zoisite Optical Properties

Sillimanite

Zoisite

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Optical Properties

Luster

Vitreous, Subadamantine, Silky

Vitreous

Pleochroism

Colourless to pale brown to yellow

X = pale pink to red-violet; Y = nearly colorless to bright pink or deep blue; Z = pale yellow to yellow-green

Dispersion

0.020.02

0.005 1

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Transparency

Transparent, Translucent

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

Refractive Index

1.653-1.6851.685-1.707

1 3.25

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Optic Character

Crystal System

Orthorhombic

Birefringence

0.020-0.0220.006-0.018

0 0.296

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Clarity

Transparent

Sillimanite and Zoisite Optic Character

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

Similar to their colors, Sillimanite and Zoisite 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, Sillimanite is Transparent and Translucent while Sillimanite is Transparent and Translucent in appearance.