metamorphic
Serpentinite
Serpentinite; chiefly serpentine-group minerals (lizardite, chrysotile, antigorite), commonly with magnetite and minor talc
AI-generated identification · may be incorrectTypically dark green to black, mottled or veined, with waxy to greasy luster and fine-grained texture; Mohs hardness 2.5–4, relatively dense, and lacking visible cleavage. The specimen appears polished or naturally smoothed, so texture is partly obscured.
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Physical properties
Typically dark green to black, mottled or veined, with waxy to greasy luster and fine-grained texture; Mohs hardness 2.5–4, relatively dense, and lacking visible cleavage. The specimen appears polished or naturally smoothed, so texture is partly obscured.
Formation & geological history
Forms when ultramafic mantle rocks, especially peridotite, undergo hydration and metamorphism, commonly along oceanic crust and subduction zones. Its age varies widely with the host tectonic belt.
Uses & applications
Used as decorative and architectural stone, carving material, and occasionally as a source of magnesium or asbestos-bearing material; attractive pieces are collected. Chrysotile-bearing varieties require caution because asbestos fibers can be hazardous when airborne.
Geological facts
Its characteristic green color results from serpentine minerals and iron-rich alteration. It may feel unusually smooth or soapy and can show black magnetite specks or veins.
Field identification & locations
Common in California, Italy, New Zealand, Canada, and many ophiolite belts. Confirm with a soapy feel, low hardness, green mottling, and possible magnetism; avoid sawing or abrading unknown specimens.
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