metamorphic
Serpentine (likely serpentinized ultramafic rock)
Serpentinite; chiefly antigorite, lizardite, or chrysotile Mg₃Si₂O₅(OH)₄, often with magnetite and relict olivine/pyroxene
AI-generated identification · may be incorrectTypically mottled gray-green to black, waxy or greasy luster, fine-grained and massive; Mohs hardness 2.5–4, no prominent cleavage, density about 2.5–2.6. The specimen appears green-gray and brecciated, but a photo cannot confirm the identification.
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Physical properties
Typically mottled gray-green to black, waxy or greasy luster, fine-grained and massive; Mohs hardness 2.5–4, no prominent cleavage, density about 2.5–2.6. The specimen appears green-gray and brecciated, but a photo cannot confirm the identification.
Formation & geological history
Forms when mantle-derived peridotite is hydrated and altered by low-temperature metamorphism, commonly along faults and oceanic crust; ages range from Precambrian to modern tectonic settings.
Uses & applications
Used as decorative stone, carvings, countertops, and historically as a source of asbestos-bearing material; attractive pieces are collected as lapidary specimens.
Geological facts
Often has a distinctive mottled or “snakeskin” appearance and may contain magnetite, making some pieces weakly magnetic. Fibrous chrysotile varieties require care because disturbed asbestos fibers are hazardous.
Field identification & locations
Look for green-black mottling, waxy texture, softness, and association with ultramafic rocks; common in California, Italy, New Zealand, Canada, and mountain belts worldwide. Avoid cutting or sanding unknown pieces.
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