metamorphic

Likely serpentinite

Serpentinite, chiefly serpentine-group minerals (Mg₃Si₂O₅(OH)₄), with possible magnetite, talc, and carbonate

AI-generated identification · may be incorrect

Typically dark green to gray, mottled, waxy to dull luster, fine-grained and massive; Mohs hardness about 2.5–4, with no obvious cleavage. The specimen’s green-gray, subtly mottled appearance is consistent with serpentinite, though image-only identification is provisional.

Identified September 13, 2026More metamorphic →

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Physical properties

Formation & geological history

Forms when ultramafic mantle rocks such as peridotite are hydrated during tectonic alteration, commonly in oceanic crust and subduction zones. It can form from Paleozoic to modern tectonic events, depending on the locality.

Uses & applications

Used as decorative facing stone, carvings, countertops, and lapidary material; historically used as a heat-resistant stone. Ordinary rough pieces generally have modest collector value.

Geological facts

Serpentinite may contain fibrous chrysotile, a naturally occurring asbestos mineral, so avoid cutting, drilling, or generating dust until tested. It is California’s official state rock.

Field identification & locations

Look for a green-black mottled color, waxy feel, low hardness, and possible magnetism from magnetite; a steel nail may scratch it. Common occurrences include California, Italy, New Zealand, Canada, and many ophiolite belts.