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Sillimanite and Alunite Optical Properties


Alunite and Sillimanite Optical Properties


Optical Properties

Luster
Vitreous, Subadamantine, Silky   
Vitreous, Pearly   

Pleochroism
Colourless to pale brown to yellow   
Not Available   

Dispersion
Not Available   
Not Available   

Transparency
Transparent, Translucent   
Not Available   

Refractive Index
1.653-1.685   
1.572   

Optic Character
Not Available   
Not Available   

Crystal System
Orthorhombic   
Trigonal   

Birefringence
0.020-0.022   
0.020   

Clarity
Transparent   
Not Available   

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Sillimanite and Alunite Optic Character

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

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

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