The bright fringe, called symplectite, is composed of epidote, quartz, and calcite. It formed around the edges of the irregular patch of garnet. The garnet crystallized at high temperature in this metamorphic rock. Then, in response to cooling and the addition of water and carbon dioxide to the rock, the garnet decomposed to form the symplectite. Further cooling stopped the reaction before all the garnet was consumed. Twinned feldspar and quartz make up the remainder of the scene.

Crossed polarizers