Serpentinite

Hardness: 3-6 (Mohs scale), Color: Green, mottled grey, white streaks, Luster: Waxy to greasy, Crystal Structure: Monoclinic, Cleavage: Poor, Specific Gravity: 2.5-2.6

Formed through serpentinization of ultramafic rocks from the mantle (peridotite) in the presence of water at low temperatures, typically at tectonic plate boundaries or mid-ocean ridges.

Used as decorative architectural stone, source of magnesium, and sometimes carved into small sculptures or jewelry. Historically used for asbestos, though modern uses favor non-fibrous varieties.

Serpentinite is the official state rock of California. It often creates unique soil chemistry that supports rare and endemic plant species. The process of its formation (serpentinization) is believed to provide energy for microbial life in extreme environments.

Identify by its characteristic 'serpent-like' mottled green appearance and waxy feel. It is commonly found in ophiolite complexes, the Coast Ranges of California, the Appalachians, and the Alps. In the field, look for slippery surfaces on outcrops.