metamorphic
Serpentinite
Serpentinite (composed primarily of mineral group (Mg, Fe, Ni, Al, Zn, Mn)2-3(Si, Al, Fe)2O5(OH)4)
Hardness: 3-6 (Mohs scale), Color: Mottled green, black, and yellow-green, Luster: Greasy to waxy, Crystal Structure: Monoclinic (often massive or fibrous), Specific Gravity: 2.5-2.6
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Physical properties
Hardness: 3-6 (Mohs scale), Color: Mottled green, black, and yellow-green, Luster: Greasy to waxy, Crystal Structure: Monoclinic (often massive or fibrous), Specific Gravity: 2.5-2.6
Formation & geological history
Formed through the hydrothermal metamorphism of ultramafic rocks (like peridotite) from the Earth's mantle, a process called serpentinization. This typically occurs at tectonic plate boundaries/subduction zones.
Uses & applications
Used as decorative architectural stone, for stone carvings, as a source of magnesium, and historically as a source of asbestos. Tumbled pieces are popular for mineral collecting and metaphysical use.
Geological facts
Serpentinite is the official state rock of California. It often creates unique soil chemistry that supports rare and endemic plant species that cannot grow elsewhere.
Field identification & locations
Identify in the field by its distinctive 'snakeskin' appearance, greasy feel, and green-mottled color. Commonly found in ophiolite complexes, the Coast Ranges of California, and parts of the Appalachian Mountains.
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