Sillimanite and Bertrandite Optical Properties

Sillimanite

Bertrandite

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1 Optical Properties

1.1 Luster

Vitreous, Subadamantine, Silky

Vitreous

1.2 Pleochroism

Colourless to pale brown to yellow

none.

1.3 Dispersion

NANA

0.007 1

1.4 Transparency

Transparent, Translucent

TransparentAnthony et al, Handbook of mineralogy (2001)

1.5 Refractive Index

1.653-1.6851.583-1.614

1 3.25

1.6 Optic Character

Not Available

1.7 Crystal System

Orthorhombic

Orthorhombic Pyramidal H-M Symbol (mm2) Space Group: Ccm21

1.8 Birefringence

0.020-0.022Not Available

0 0.296

1.9 Clarity

Transparent

TransparentAnthony et al

Sillimanite and Bertrandite Optic Character

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

Similar to their colors, Sillimanite and Bertrandite 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.