Onyx and Topaz Optical Properties

Onyx

Topaz

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Optical Properties

Luster

Vitreous

Pleochroism

Weak

Dispersion

0.010.01

0.005 1

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Transparency

Translucent, Opaque, Translucent to opaque

Transparent

Refractive Index

1.530-1.5431.606-1.644

1 3.25

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Optic Character

Crystal System

Trigonal

Orthorhombic

Birefringence

-99990.008-0.011

0 0.296

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Clarity

OpaqueHerve Nicolas Lazzarelli

TransparentUlrich Henn and Claudio C. Milisenda

Onyx and Topaz Optic Character

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

Similar to their colors, Onyx and Topaz 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, Onyx is Translucent, Opaque and Translucent to opaque while Onyx is Translucent, Opaque and Translucent to opaque in appearance.