Sillimanite and Cobaltite Optical Properties

Sillimanite

Cobaltite

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1 Optical Properties

1.1 Luster

Vitreous, Subadamantine, Silky

Not Available

1.2 Pleochroism

Colourless to pale brown to yellow

Very weak

1.3 Dispersion

NANA

0.007 1

1.4 Transparency

Transparent, Translucent

Gems

1.5 Refractive Index

1.653-1.685Not Available

1 3.25

1.6 Optic Character

Not Available

1.7 Crystal System

Orthorhombic

Orthorhombic Pyramidal H-M Symbol (mm2) Space Group: P ca21

1.8 Birefringence

0.020-0.022Not Available

0 0.296

1.9 Clarity

Transparent

Gems

Sillimanite and Cobaltite Optic Character

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

Similar to their colors, Sillimanite and Cobaltite 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.