Sillimanite and Foitite Optical Properties

Sillimanite

Foitite

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1 Optical Properties

1.1 Luster

Vitreous, Subadamantine, Silky

Vitreous

1.2 Pleochroism

Colourless to pale brown to yellow

Strong: pale lavender dark blueAnthony et al

1.3 Dispersion

NANA

0.007 1

1.4 Transparency

Transparent, Translucent

TranslucentAnthony et al, Translucent

1.5 Refractive Index

1.653-1.685Not Available

1 3.25

1.6 Optic Character

Not Available

1.7 Crystal System

Orthorhombic

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

1.8 Birefringence

0.020-0.022Not Available

0 0.296

1.9 Clarity

Transparent

TranslucentAnthony et al

Sillimanite and Foitite Optic Character

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

Similar to their colors, Sillimanite and Foitite 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.