Kyanite Al2SiO5

Optical Properties:

Biaxial -; very high 2V; colorless to pale blue in plane polarized light; tabular crystals; 2 cleavages; high relief; maximum first order red interference colors; inclined extinction that can almost be parallel.

The photos above and below show kyanite in crossed polarized view on the left, and in plane polarized light on the right. Kyanite is surrounded by biotite and muscovite in the top photos, and by quartz in the lower photos. The cleavage, relief, and bladed form of kyanite are clearly visible.