Alteration of Glaucophane.

As can be seen on preceding pages, a lot of glaucophane crystals are corroded and altered to another green amphibole. In some parts of the section, only altered material is visible as in the figures shown here. The 2 micrographs were obtained with different orientation of the polarizer. Some crystal area are still pleochroic (blue-green to green), some others are not.
 

Spectrum of a pleochroic green to blue-green region. 

Observe the movement of the charge-transfer absorption band to the lower energies compared to glaucophane.

Spectrum of a non pleochroic green region with rotation of polarizer by 90. Absorption band is now beyond 700 nm.

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