Opal and Alexandrite Optical Properties

Opal

Alexandrite

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Optical Properties

Luster

Vitreous, Pearly

Vitreous

Pleochroism

None

Dispersion

0.010.02

0.005 1

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Transparency

Transparent, Translucent, Transparent to translucent

Transparent, Transparent to nearly opaque

Refractive Index

1.37-1.521.739-1.770

1 3.25

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Optic Character

Biaxial/+

Crystal System

Trigonal

Orthorhombic

Birefringence

-99990.007-0.010

0 0.296

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Clarity

Transparent

Opal and Alexandrite Optic Character

Opal and Alexandrite optical properties play a significant role while distinguishing these gemstones from each other. These properties are influenced by the Opal and Alexandrite 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 Alexandrite 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. Alexandrite has Biaxial/+ character.

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Opal Vs Schorlomite

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Opal and Alexandrite Transparency

Similar to their colors, Opal and Alexandrite 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.