metamorphic

Serpentinite

Serpentinite; chiefly serpentine-group minerals (antigorite, lizardite, chrysotile), with magnetite and minor chromite/talc

AI-generated identification · may be incorrect

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.

Identified August 20, 2026More metamorphic →

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Physical properties

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.