Schist

Schist

This piece of shist displays gneissic banding (foliation). The dark minerals are fine crystals biotite and and horneblende recrystallized under great heat and pressure into thin parallel bands. The thin white layers are feldspar and quartz. This stream-cobble sample is from the Palomar Mountain area of San Diego County, and probably was derived from a roof-pendant block derived from the Triassic-age Julian Schist.
https://gotbooks.miracosta.edu/rocks/metamorphic/35.html 2/2/2021