Sillimanite and Cordierite Optical Properties

Sillimanite

Cordierite

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1 Optical Properties

1.1 Luster

Vitreous, Subadamantine, Silky

Greasy, Vitreous

1.2 Pleochroism

Colourless to pale brown to yellow

X = pale yellow

1.3 Dispersion

NANA

0.007 1

1.4 Transparency

Transparent, Translucent

Not Available

1.5 Refractive Index

1.653-1.685Not Available

1 3.25

1.6 Optic Character

Not Available

1.7 Crystal System

Orthorhombic

1.8 Birefringence

0.020-0.022Not Available

0 0.296

1.9 Clarity

Transparent

Not Available

Sillimanite and Cordierite Optic Character

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

Similar to their colors, Sillimanite and Cordierite 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.