metamorphic

Serpentine-rich altered ultramafic rock

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

AI-generated identification · may be incorrect

Typically green, gray, cream, or mottled; waxy to dull luster, massive texture, and Mohs hardness about 2.5–4. The specimen appears rounded and weathered, with pale green patches and darker veins, though the image is not detailed enough for certainty.

Identified September 21, 2026More metamorphic →

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Physical properties

Formation & geological history

Forms when mantle peridotite is hydrated and altered during metamorphism, commonly along faults and plate boundaries. Serpentinization can occur from the Precambrian to the present; age depends on the source terrane.

Uses & applications

Used as decorative stone, carvings, countertops, and occasionally crushed aggregate; attractive varieties are collected, but it is generally not a jewelry-grade gemstone.

Geological facts

Serpentinite may contain magnetite and can be weakly magnetic. Some occurrences are associated with asbestos-forming minerals, so avoid cutting or generating dust unless its composition is tested.

Field identification & locations

Identify by its low hardness, greasy/waxy feel, green-black mottling, and possible white streak; a steel nail may scratch it. Common in ophiolites and tectonic belts, including California, Italy, New Zealand, and the Alps.