The Sandstones tend to be in more massive layers because of the relative abundance of sand. These rocks form closer to the edge of the ocean. Further out in the ocean mudstones form from finer sediments which do not drop to the bottom as quickly as the the heavier sands. These rocks tend to have thinner layers. Cherts form deep in the ocean from the siliconaceous skeletons of millions of microscopic plankton which die and drop to the ocean floor.
Cherts come in a variety of colors such as red and green.
Chert is a hard, glassy rock that was used by indians to make arrowheads and other sharp tools when they were not able to trade for higher-quality Obsidian. There are a number of limestone caves in the area, the best known being the Del Loma Caverns. This cave was discovered by gold miners in the 1850s. There were rumors that it extended all the way to Denny. This site created and maintained with assistance by Auriver Consultants.