Foitite and Sillimanite Optical Properties

Foitite

Sillimanite

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1 Optical Properties

1.1 Luster

Vitreous

Vitreous, Subadamantine, Silky

1.2 Pleochroism

Strong: pale lavender dark blueAnthony et al

Colourless to pale brown to yellow

1.3 Dispersion

NANA

0.007 1

1.4 Transparency

TranslucentAnthony et al, Translucent

Transparent, Translucent

1.5 Refractive Index

Not Available1.653-1.685

1 3.25

1.6 Optic Character

Not Available

1.7 Crystal System

Trigonal Ditrigonal Pyramidal H-M Symbol (3m) Space Group: R 3m

Orthorhombic

1.8 Birefringence

Not Available0.020-0.022

0 0.296

1.9 Clarity

TranslucentAnthony et al

Transparent

Foitite and Sillimanite Optic Character

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

Similar to their colors, Foitite 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, Foitite is Translucent and TranslucentAnthony et al while Foitite is Translucent and TranslucentAnthony et al in appearance.