Pink tourmaline crystal with
polarizer along optic axis and in a direction perpendicular to it.
Generally for tourmalines the color intensity is higher when the
polarizer is perpendicular to OA. Sometimes the pleochroism could be
very intense. In some cases, the Raman spectrum in the direction
perpendicular to OA is very weak and cannot be recorded. For dark
Dravite crystals only spectra parallel to optic axis have been
reproduced here. |
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Coarse rock with Elbaite (green) and
Quartz as can be seen on the Raman spectra below. Spectra of the
green prismatic Elbaite crystal imaged below are also included. White
material is quartz. |
The Raman spectra of the Elbaite samples presented here are very
similar especially the spectra with laser light polarized along optic
axis even if the color is different. Spectra perpendicular to OA exhibit
some differences mainly in the bands intensities. |
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Green prismatic Elbaite crystal: spectrum above.
Yellow green Liddicoatite: spectrum below. |
Yellow Dravite.
The Raman spectrum of this crystal is partly obscured by fluorescence. |
Some Yellow and black tourmalines Dravite spectra polarized parallel to
optic axis.
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Good resolved spectra of
Liddicoatite. |
Spectra of the OH stretching vibrations of the green-brown Elbaite
section shown above. Figure shows clearly the pleochroism of the OH
band. The triplet of the OH vibrations is also present in the
second harmonic
spectrum recorded before in the NIR wavelength region. The triplet
was obtained only for crystal orientation with optic axis parallel to
polarizer direction. |
Tourmalines OH Band. |
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