Onyx and Alexandrite Optical Properties

Onyx

Alexandrite

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1 Optical Properties

1.1 Luster

Vitreous

1.2 Pleochroism

Not Available

1.3 Dispersion

NANA

0.007 1

1.4 Transparency

Translucent, Opaque, Translucent to opaque

Transparent, Transparent to nearly opaque

1.5 Refractive Index

1.530-1.5431.739-1.770

1 3.25

1.6 Optic Character

Not Available

Biaxial/+

1.7 Crystal System

Trigonal

Orthorhombic

1.8 Birefringence

Not Available0.007-0.010

0 0.296

1.9 Clarity

OpaqueHerve Nicolas Lazzarelli

Transparent

Onyx and Alexandrite Optic Character

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

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