Opal and Spinel Optical Properties

Opal

Spinel

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Optical Properties

Luster

Vitreous, Pearly

Vitreous

Pleochroism

None

Absent

Dispersion

0.010.02

0.005 1

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Transparency

Transparent, Translucent, Transparent to translucent

Refractive Index

1.37-1.521.73

1 3.25

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Optic Character

Crystal System

Trigonal

Isometric

Birefringence

-9999-9999

0 0.296

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Clarity

Transparent

TransparentUlrich Henn and Claudio C. Milisenda

Opal and Spinel Optic Character

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

Similar to their colors, Opal and Spinel 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.