Metachert

Metachert

This is a sample of green metachert that displays crenulation. The original sedimentary chert layers have been tightly folded. The metachert is from the Jurassic-age Franciscan Formation. This sample came from a gravel bar along Tres Pinos Creek in San Benito County, CA.
https://gotbooks.miracosta.edu/rocks/metamorphic/32.html 2/2/2021