Glaucophane Na2Mg3Al2(OH)2(Si4O11)2

Optical Properties:

Biaxial -; strong pleochroism, blue to violet to colorless to pale brown; amphibole cleavage.

The two photos above are in plane polarized light, illustrating the unique pleochroism of glaucophane.

Occurrence:

Occurs in low grade metamorphic rocks, associated with white mica, albite, quartz, chlorite, epidote, and occasionally lawsonite and jadeite.


The picture on the left, in plane polarized light, is a mixture of lightly colored glaucophane, colorless white mica, and dark, high relief epidote in a low grade schist. On the right is a crossed polarizers view of a glaucophane schist with a large, isotropic garnet in the center, surrounded by highly birefringent glaucophane and white mica.

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