Colemanite and Sillimanite Optical Properties

Colemanite

Sillimanite

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1 Optical Properties

1.1 Luster

Vitreous

Vitreous, Subadamantine, Silky

1.2 Pleochroism

NilArthur Thomas

Colourless to pale brown to yellow

1.3 Dispersion

NANA

0.007 1

1.4 Transparency

Transparent

Transparent, Translucent

1.5 Refractive Index

1.584-1.6151.653-1.685

1 3.25

1.6 Optic Character

Not Available

1.7 Crystal System

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

Orthorhombic

1.8 Birefringence

0.028-0.0300.020-0.022

0 0.296

1.9 Clarity

Transparent

Colemanite and Sillimanite Optic Character

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

Compare Colorless Gems

Colemanite Vs Datolite

Colemanite Vs Cubic Zirconia

Colemanite Vs Diaspore

Colemanite and Sillimanite Transparency

Similar to their colors, Colemanite 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, Colemanite is Transparent while Colemanite is Transparent in appearance.