Sillimanite and Atacamite Optical Properties

Sillimanite

Atacamite

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1 Optical Properties

1.1 Luster

Vitreous, Subadamantine, Silky

Adamantine, Vitreous

1.2 Pleochroism

Colourless to pale brown to yellow

X = pale green; Y = yellow-green; Z = grass-green

1.3 Dispersion

NANA

0.007 1

1.4 Transparency

Transparent, Translucent

Not Available

1.5 Refractive Index

1.653-1.6851.831

1 3.25

1.6 Optic Character

Not Available

1.7 Crystal System

Orthorhombic

1.8 Birefringence

0.020-0.0220.049

0 0.296

1.9 Clarity

Transparent

Not Available

Sillimanite and Atacamite Optic Character

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

Similar to their colors, Sillimanite and Atacamite 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, Sillimanite is Translucent and Transparent while Sillimanite is Translucent and Transparent in appearance.