Sillimanite and Colemanite Optical Properties

Sillimanite

Colemanite

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1 Optical Properties

1.1 Luster

Vitreous, Subadamantine, Silky

Vitreous

1.2 Pleochroism

Colourless to pale brown to yellow

NilArthur Thomas

1.3 Dispersion

NANA

0.007 1

1.4 Transparency

Transparent, Translucent

Transparent

1.5 Refractive Index

1.653-1.6851.584-1.615

1 3.25

1.6 Optic Character

Not Available

1.7 Crystal System

Orthorhombic

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

1.8 Birefringence

0.020-0.0220.028-0.030

0 0.296

1.9 Clarity

Transparent

Sillimanite and Colemanite Optic Character

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

Similar to their colors, Sillimanite and Colemanite 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.