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Alexandrite
Alexandrite

Sillimanite
Sillimanite



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Alexandrite
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Sillimanite

Alexandrite and Sillimanite Optical Properties

Optical Properties

Luster

Pleochroism

Dispersion

Transparency

Refractive Index

Optic Character

Crystal System

Birefringence

Clarity

 
Vitreous
-
0.02
Transparent, Transparent to nearly opaque
1.739-1.770
Biaxial/+
Orthorhombic
0.007-0.010
Transparent
 
Vitreous, Subadamantine, Silky
Colourless to pale brown to yellow
0.02
Transparent, Translucent
1.653-1.685
-
Orthorhombic
0.020-0.022
Transparent

Alexandrite and Sillimanite Optic Character

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

Alexandrite and Sillimanite Transparency

Similar to their colors, Alexandrite 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, Alexandrite is while Alexandrite is in appearance.