Franklinite and Sillimanite Optical Properties

Franklinite

Sillimanite

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1 Optical Properties

1.1 Luster

Not Available

Vitreous, Subadamantine, Silky

1.2 Pleochroism

Not Available

Colourless to pale brown to yellow

1.3 Dispersion

NANA

0.007 1

1.4 Transparency

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

Isometric Hexoctahedral H-M Symbol (4/m 3 2/m) Space Group: F d3m

Orthorhombic

1.8 Birefringence

Not Available0.020-0.022

0 0.296

1.9 Clarity

Translucent

Transparent

Franklinite and Sillimanite Optic Character

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

Similar to their colors, Franklinite 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, Franklinite is Translucent while Franklinite is Translucent in appearance.