Opal and Willemite Optical Properties

Opal

Willemite

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Optical Properties

Luster

Vitreous, Pearly

Vitreous, Resinous

Pleochroism

None

Dispersion

0.010.17

0.005 1

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Transparency

Transparent, Translucent, Transparent to translucent

Transparent, Translucent

Refractive Index

1.37-1.521.687-1.723

1 3.25

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Optic Character

Crystal System

Trigonal

Birefringence

-99990.028-0.030

0 0.296

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Clarity

Transparent

Opal and Willemite Optic Character

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

Similar to their colors, Opal and Willemite 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.