metamorphic
Serpentinite
Serpentinite; chiefly serpentine-group minerals (lizardite, antigorite, chrysotile), often with magnetite and minor brucite
AI-generated identification · may be incorrectUsually mottled olive-green to gray-green, waxy to greasy luster, massive texture, and Mohs hardness about 2.5–4. It commonly has a splintery or subtly fibrous texture and no obvious cleavage; the specimen appears weathered and granular.
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Physical properties
Usually mottled olive-green to gray-green, waxy to greasy luster, massive texture, and Mohs hardness about 2.5–4. It commonly has a splintery or subtly fibrous texture and no obvious cleavage; the specimen appears weathered and granular.
Formation & geological history
Forms when ultramafic mantle rocks such as peridotite undergo hydration during low-temperature metamorphism, commonly in oceanic crust and subduction zones. Most examples represent ancient tectonic zones, ranging from Paleozoic to Mesozoic or younger.
Uses & applications
Used as decorative stone, carvings, countertops, and historically as a source of asbestos-bearing material; attractive pieces are collected. Chrysotile-rich material should not be cut or abraded because of inhalation risk.
Geological facts
Often associated with chromite, magnetite, talc, and nickel deposits, and is the state rock of California. Its green color and greasy feel distinguish it from many ordinary igneous rocks.
Field identification & locations
Look for mottled green color, relatively low hardness, waxy feel, and possible magnetism from magnetite; a steel nail may scratch it. Common in ophiolites and major fault or subduction belts worldwide.
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