Sillimanite and Friedelite Optical Properties

Sillimanite

Friedelite

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1 Optical Properties

1.1 Luster

Vitreous, Subadamantine, Silky

Not Available

1.2 Pleochroism

Colourless to pale brown to yellow

NilArthur Thomas

1.3 Dispersion

NANA

0.007 1

1.4 Transparency

Transparent, Translucent

Translucent

1.5 Refractive Index

1.653-1.6851.627-1.663

1 3.25

1.6 Optic Character

Not Available

1.7 Crystal System

Orthorhombic

Monoclinic Prismatic H-M Symbol (2/m) Space Group: C 2/m

1.8 Birefringence

0.020-0.0220.032-0.035

0 0.296

1.9 Clarity

Transparent

Translucent

Sillimanite and Friedelite Optic Character

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

Similar to their colors, Sillimanite and Friedelite 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.