Serpentinite

Physical Properties

Hardness: 3-6 (Mohs scale), Color: Greenish-gray to dark green with reddish-brown oxidation crust, Luster: Waxy to greasy or dull, Crystal structure: Monoclinic (microcrystalline), Cleavage: Poor, Specific Gravity: 2.2-2.9

Formation & Geological History

Formed by the low-temperature hydrothermal alteration (serpentinization) of ultramafic rocks from the Earth's mantle, such as peridotite, usually at tectonic plate boundaries/subduction zones.

Uses & Applications

Used as decorative stone, for industrial heat protection (asbestos source historically), and in some types of specialized concrete for nuclear shielding. Occasionally used for carvings.

Geological Facts

It is the official state rock of California. The green color comes from the presence of serpentine group minerals including lizardite and chrysotile.

Field Identification & Locations

Look for a characteristic 'waxy' or 'soapy' feel and a distinct green color often accompanied by reddish-brown iron-oxide weathering. Common in ophiolite complexes and fault zones.

Identified on: 5/16/2026

Mode: Standard