Sillimanite and Inderite Optical Properties

Sillimanite

Inderite

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1 Optical Properties

1.1 Luster

Vitreous, Subadamantine, Silky

Vitreous, Pearly, Greasy

1.2 Pleochroism

Colourless to pale brown to yellow

Not Available

1.3 Dispersion

NANA

0.007 1

1.4 Transparency

Transparent, Translucent

Gemmological Tables (2004)

1.5 Refractive Index

1.653-1.6851.488-1.505

1 3.25

1.6 Optic Character

Not Available

Biaxial/+

1.7 Crystal System

Orthorhombic

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

1.8 Birefringence

0.020-0.0220.017

0 0.296

1.9 Clarity

Transparent

TransparentUlrich Henn and Claudio C. Milisenda

Sillimanite and Inderite Optic Character

Sillimanite and Inderite optical properties play a significant role while distinguishing these gemstones from each other. These properties are influenced by the Sillimanite and Inderite 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 Inderite 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. Inderite has Biaxial/+ character.

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Sillimanite and Inderite Transparency

Similar to their colors, Sillimanite and Inderite 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.