Opal and Benitoite Optical Properties

Opal

Benitoite

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Optical Properties

Luster

Vitreous, Pearly

Vitreous

Pleochroism

None

O = colorless; E = purple

Dispersion

0.010.04

0.005 1

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Transparency

Transparent, Translucent, Transparent to translucent

Transparent

Refractive Index

1.37-1.521.757-1.804

1 3.25

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Optic Character

Crystal System

Trigonal

Hexagonal

Birefringence

-99990.047

0 0.296

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Clarity

Transparent

Opal and Benitoite Optic Character

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

Similar to their colors, Opal and Benitoite 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, Opal is Transparent, Translucent and Transparent to translucent while Opal is Transparent, Translucent and Transparent to translucent in appearance.