Schist

Schist is a metamorphic rock form characterized by strong foliation so that it is readily split into thin flakes or slabs.

This example of schist is from Warm Springs, Georgia where a stressed formation produces it along with quartzite and gneiss, two other metamorphic rocks. The formation produces a large warm spring.

The lowest group in the Grand Canyon is referred to as Vishnu Schist The projected age for these rocks is about 1750-1840 Myr.