metamorphic
Serpentinite (likely)
Serpentinite, dominated by serpentine-group minerals (antigorite, lizardite, chrysotile), commonly with magnetite and relic olivine/pyroxene
AI-generated identification · may be incorrectTypically green to black, mottled, waxy to greasy luster; Mohs hardness 2.5–4, massive texture, poor visible cleavage, and specific gravity about 2.5–2.6. The specimen appears dark green-gray with pale altered patches and metallic-looking flecks, though a photo cannot confirm composition.
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Physical properties
Typically green to black, mottled, waxy to greasy luster; Mohs hardness 2.5–4, massive texture, poor visible cleavage, and specific gravity about 2.5–2.6. The specimen appears dark green-gray with pale altered patches and metallic-looking flecks, though a photo cannot confirm composition.
Formation & geological history
Forms when water alters ultramafic mantle rocks such as peridotite, usually along oceanic crust, subduction zones, and faults. Serpentinization ranges from Precambrian to recent geological ages.
Uses & applications
Used as decorative stone, carving material, aggregate, and historically as a building stone; attractive polished varieties are collected, but asbestos-bearing material should not be cut or powdered.
Geological facts
Often contains magnetite and may be weakly magnetic. Chrysotile-bearing serpentinite can release hazardous fibers when sawn, drilled, or abraded.
Field identification & locations
Check for a green waxy surface, low hardness, and possible magnetism; a streak, hardness test, and laboratory analysis distinguish it from chlorite schist, greenstone, or weathered basalt. Common in California, Italy, New Zealand, Canada, and ophiolite belts worldwide.
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