Graywacke Sandstone Just Off The Golden Gate Bridge. Royalty-Free Stock Photography

Graywacke sandstone is a type of sandstone because it is comprised of tiny, sand sized particles that are very rapidly deposited near the surface of the ocean. It starts out deep in the ocean where there is a lot of movements by the earth itself, be it volcanos or landslides. Because of how they form, there might be fossils within the stone to tell its age, You can see from these three pieces the violent activity still going on in this region, with earthquakes, as these three pieces were apparently one piece originally.