Anhydrite and Sillimanite Optical Properties

Anhydrite

Sillimanite

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1 Optical Properties

1.1 Luster

Pearly, Greasy

Vitreous, Subadamantine, Silky

1.2 Pleochroism

For violet varieties

Colourless to pale brown to yellow

1.3 Dispersion

0.01NA

0.007 1

1.4 Transparency

Transparent

Transparent, Translucent

1.5 Refractive Index

1.570-1.6141.653-1.685

1 3.25

1.6 Optic Character

Not Available

1.7 Crystal System

Orthorhombic

1.8 Birefringence

0.042-0.0440.020-0.022

0 0.296

1.9 Clarity

Transparent

Anhydrite and Sillimanite Optic Character

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

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Anhydrite and Sillimanite Transparency

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