You are looking down onto the folded surface of a phlogopite sheet. Phlogopite is a member of the mica family. Micas are like stacks of paper in that they have a crystal structure formed by sheets of atoms. The bonds between the sheets are very weak; therefore, the sheets can easily slide past one another during deformation. Think of the phlogopite as a crumpled throw rug lying on a smooth floor. Most crumpled rugs have nice rounded folds, but the folds in this phlogopite are sharp, zigzag kinks.

Crossed polarizers