Onyx and Andalusite Optical Properties

Onyx

Andalusite

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1 Optical Properties

1.1 Luster

Vitreous

Vitreous, Greasy

1.2 Pleochroism

Not Available

strongly trichroic

1.3 Dispersion

NA0.02

0.007 1

1.4 Transparency

Translucent, Opaque, Translucent to opaque

Transparent, Translucent

1.5 Refractive Index

1.530-1.5431.627-1.650

1 3.25

1.6 Optic Character

Not Available

1.7 Crystal System

Trigonal

Orthorhombic

1.8 Birefringence

Not Available0.009-0.010

0 0.296

1.9 Clarity

OpaqueHerve Nicolas Lazzarelli

Transparent

Onyx and Andalusite Optic Character

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

Similar to their colors, Onyx and Andalusite 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.