The pretty kind of corona

The pretty kind of corona

by Kristina G Dunkel

Coronas can be beautiful, as in this piece of abstract art created by a meta-gabbro from the Kragerø area in Norway. Olivine (centre) and plagioclase (outside) reacted to a corona of amphibole and orthopyroxene. The reaction did not go to completion, and the transition from gabbro to granulite was frozen in time.

Cross-polarized light photomicrograph with lambda-plate inserted.
The width of the image is approximately 2 mm.