Sillimanite and Dallasite Optical Properties

Sillimanite

Dallasite

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1 Optical Properties

1.1 Luster

Vitreous, Subadamantine, Silky

Not Available

1.2 Pleochroism

Colourless to pale brown to yellow

Not Available

1.3 Dispersion

NANA

0.007 1

1.4 Transparency

Transparent, Translucent

Not Available

1.5 Refractive Index

1.653-1.6851.540

1 3.25

1.6 Optic Character

Not Available

1.7 Crystal System

Orthorhombic

Not Available

1.8 Birefringence

0.020-0.0220.008-0.010

0 0.296

1.9 Clarity

Transparent

Not Available

Sillimanite and Dallasite Optic Character

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

Similar to their colors, Sillimanite and Dallasite 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.