metamorphic

Serpentinite

Serpentinite (Mg, Fe, Ni, Al, Zn, Mn)2-3(Si, Al, Fe)2O5(OH)4

AI-generated identification · may be incorrect

Hardness: 3-6 (variable), Color: Waxy shades of green with dark speckles (magnetite/chromite), Luster: Greasy or waxy, Crystal structure: Monoclinic, Cleavage: Poor, Specific Gravity: 2.2-2.9

Identified June 19, 2026More metamorphic →

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Physical properties

Hardness: 3-6 (variable), Color: Waxy shades of green with dark speckles (magnetite/chromite), Luster: Greasy or waxy, Crystal structure: Monoclinic, Cleavage: Poor, Specific Gravity: 2.2-2.9

Formation & geological history

Formed through serpentinization, the low-temperature metamorphic alteration of ultramafic rocks (peridotite) from the Earth's mantle by hydrothermal fluids at tectonic plate boundaries.

Uses & applications

Used for architectural cladding, decorative stone (California State Rock), as a source of magnesium, and limited use in carvings/jewelry.

Geological facts

Serpentinite is the state rock of California. It often creates unique, nutrient-poor soils that support rare endemic plant species that can tolerate high heavy metal concentrations.

Field identification & locations

Identify by its 'slickensides' (polished surfaces) and distinctive greasy feel. Commonly found in ophiolite complexes, the Coast Ranges, and the Appalachian Mountains. Use a magnet to check for dark magnetite grains.