Bertrandite and Sillimanite Optical Properties

Bertrandite

Sillimanite

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1 Optical Properties

1.1 Luster

Vitreous

Vitreous, Subadamantine, Silky

1.2 Pleochroism

none.

Colourless to pale brown to yellow

1.3 Dispersion

NANA

0.007 1

1.4 Transparency

TransparentAnthony et al, Handbook of mineralogy (2001)

Transparent, Translucent

1.5 Refractive Index

1.583-1.6141.653-1.685

1 3.25

1.6 Optic Character

Not Available

1.7 Crystal System

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

Orthorhombic

1.8 Birefringence

Not Available0.020-0.022

0 0.296

1.9 Clarity

TransparentAnthony et al

Transparent

Bertrandite and Sillimanite Optic Character

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

Similar to their colors, Bertrandite 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, Bertrandite is Handbook of mineralogy (2001) and TransparentAnthony et al while Bertrandite is Handbook of mineralogy (2001) and TransparentAnthony et al in appearance.