metamorphic
Likely serpentinite or serpentinized ultramafic rock
Serpentinite; chiefly serpentine-group minerals (Mg₃Si₂O₅(OH)₄), possibly with magnetite and minor olivine/pyroxene
AI-generated identification · may be incorrectDark green-gray, mottled, fine-grained, and weakly waxy to dull in luster; commonly Mohs 2.5–4, with no obvious cleavage and irregular fracture. The rounded surface appears naturally weathered or waterworn, though the image cannot confirm exact mineralogy.
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Physical properties
Dark green-gray, mottled, fine-grained, and weakly waxy to dull in luster; commonly Mohs 2.5–4, with no obvious cleavage and irregular fracture. The rounded surface appears naturally weathered or waterworn, though the image cannot confirm exact mineralogy.
Formation & geological history
Forms when mantle-derived peridotite is hydrated and altered by low-temperature metamorphism, commonly along oceanic crust, faults, and subduction zones. Individual specimens may be geologically ancient, but age depends on the source body.
Uses & applications
Used as decorative stone, carving material, and occasionally aggregate; attractive varieties are collected, but it is not typically a gemstone.
Geological facts
Serpentinite commonly contains magnetite, giving some pieces a magnetic response and dark streaks. It may resemble jade, but is generally softer and less tough.
Field identification & locations
Common in ophiolites and tectonic belts, including California, Italy, New Zealand, and the Appalachian region. Check for a green streak, waxy feel, low hardness, and possible magnetism; definitive identification may require microscopy or chemical testing.
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