Sillimanite and Dravite Optical Properties

Sillimanite

Dravite

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1 Optical Properties

1.1 Luster

Vitreous, Subadamantine, Silky

Vitreous

1.2 Pleochroism

Colourless to pale brown to yellow

Very strong: pale yellow colorless

1.3 Dispersion

NA0.02

0.007 1

1.4 Transparency

Transparent, Translucent

Transparent

1.5 Refractive Index

1.653-1.6851.614-1.666

1 3.25

1.6 Optic Character

Not Available

1.7 Crystal System

Orthorhombic

Trigonal Ditrigonal Pyramidal H-M Symbol (3m) Space Group: R 3m

1.8 Birefringence

0.020-0.0220.014-0.032

0 0.296

1.9 Clarity

Transparent

Sillimanite and Dravite Optic Character

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

Similar to their colors, Sillimanite and Dravite 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.