Associated with subduction zones, serpentinite is a metamorphic rock that is formed from the action of high pressure and heat upon hornblende schists or igneous rocks composed chiefly of mafic minerals, such as peridotite, gabbro, or basalt. The substance is most often found in areas where mountain ranges have formed due to the sealing off of an ocean basin. For instance, the Coast Ranges in California, where serpentinite is the official state rock, primarily consist of slices of the ocean’s crust that have been faulted and folded along the coastline. Relatively weak, mountains containing high levels of serpentinite may suffer from recurrent landslides and a brisk erosion process.