metamorphic
Serpentinite
Serpentinite (Mg, Fe, Ni, Al, Zn, Mn)2-3(Si, Al, Fe)2O5(OH)4
Hardness: 3-6 (Mohs scale), Color: Dull to waxy green, brown-green, or blackish-green, Luster: Waxy, greasy, or silky, Crystal structure: Monoclinic, Cleavage: Poor to perfect depending on mineral variety, Specific gravity: 2.5-3.2, Texture: Smooth, sometimes soapy or slippery to the touch.
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Physical properties
Hardness: 3-6 (Mohs scale), Color: Dull to waxy green, brown-green, or blackish-green, Luster: Waxy, greasy, or silky, Crystal structure: Monoclinic, Cleavage: Poor to perfect depending on mineral variety, Specific gravity: 2.5-3.2, Texture: Smooth, sometimes soapy or slippery to the touch.
Formation & geological history
Formed through serpentinization, a low-temperature metamorphic process where ultramafic rocks from the Earth's mantle are hydrated by water at tectonic plate boundaries. Common in ophiolite complexes where oceanic crust is pushed onto continental crust.
Uses & applications
Used as decorative stone in architecture, carving, and jewelry. Historically used for asbestos production (though this variety is less common today due to health risks) and as a source of magnesium.
Geological facts
Serpentinite is the official state rock of California. It often hosts unique ecosystems because its high magnesium and low calcium content, along with heavy metals, makes the soil toxic to many common plants but home to rare endemic species.
Field identification & locations
Identify in the field by its distinct 'snake-skin' appearance, waxy luster, and soapy feel. Found in mountain ranges near subduction zones, such as the Coast Ranges of California, the Appalachians, and the Alps. Look for the characteristic vibrant green to dark mottled green patterns.
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