metamorphic
Serpentinite
Serpentinite; chiefly serpentine-group minerals (antigorite, lizardite, chrysotile), with magnetite and minor chromite/talc
AI-generated identification · may be incorrectTypically dark green-gray, mottled, and waxy to dull with a massive or scaly texture; Mohs hardness about 2.5–4, no consistent cleavage, and specific gravity roughly 2.5–2.7. The specimen’s green-gray color and uneven metamorphic texture are consistent with serpentinite, though image-only identification is provisional.
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Physical properties
Typically dark green-gray, mottled, and waxy to dull with a massive or scaly texture; Mohs hardness about 2.5–4, no consistent cleavage, and specific gravity roughly 2.5–2.7. The specimen’s green-gray color and uneven metamorphic texture are consistent with serpentinite, though image-only identification is provisional.
Formation & geological history
Forms when ultramafic mantle rocks such as peridotite are hydrated during hydrothermal alteration, commonly along oceanic crust and subduction zones. It can range from Paleozoic to modern tectonic settings, depending on the exposure.
Uses & applications
Used as decorative stone, carvings, countertops, and historically as a source rock for asbestos; many specimens are collected for their color and tectonic significance.
Geological facts
Serpentinite often contains magnetite and may be weakly magnetic. Chrysotile-bearing material can release hazardous fibers when cut or abraded, so avoid dust and do not saw unknown specimens dry.
Field identification & locations
Look for green mottling, a relatively soft surface, waxy luster, and possible magnetism; common occurrences include California, Oregon, Italy, New Zealand, and ophiolite belts worldwide. A streak, hardness, magnetism, and thin-section or chemical test would help distinguish it from chlorite schist or altered basalt.
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