metamorphic
Serpentinite (probable)
Serpentinite; chiefly serpentine-group minerals, commonly lizardite, chrysotile, or antigorite, with possible magnetite and relict olivine/pyroxene
AI-generated identification · may be incorrectDark green-gray, mottled, fine-grained and weakly waxy to dull luster; typically Mohs 3–5, massive with no obvious cleavage, and relatively dense (about 2.5–2.6). The photograph alone cannot confirm the identification; it could also be a green altered mafic rock.
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Physical properties
Dark green-gray, mottled, fine-grained and weakly waxy to dull luster; typically Mohs 3–5, massive with no obvious cleavage, and relatively dense (about 2.5–2.6). The photograph alone cannot confirm the identification; it could also be a green altered mafic rock.
Formation & geological history
Forms when mantle ultramafic rocks such as peridotite hydrate during hydrothermal alteration, commonly in oceanic crust and subduction zones. Serpentinization occurs at low to moderate temperatures over a wide range of geological ages.
Uses & applications
Used as decorative and architectural stone, carvings, countertops, and historically as a source of asbestos-bearing material; specimens are mainly collected for geology and lapidary work.
Geological facts
Serpentinite often contains magnetite and may be weakly magnetic. Fibrous chrysotile varieties can contain asbestos and should not be cut, drilled, or abraded without proper controls.
Field identification & locations
Look for green mottling, a smooth or waxy feel, low hardness, and possible magnetism; fresh streak and hardness tests help distinguish it from jade or greenstone. Common in ophiolites and subduction-zone belts worldwide, including California, Italy, New Zealand, and the Appalachians.
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