metamorphic
Serpentine (likely serpentinite)
Serpentine-group minerals, chiefly antigorite/lizardite, commonly with magnetite and chlorite
AI-generated identification · may be incorrectTypically green to yellow-green with mottled or web-like dark patches, waxy to greasy luster, and a massive texture; Mohs hardness about 2.5–4, with poor or absent cleavage. The pictured piece appears smoothly tumbled and polished.
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Physical properties
Typically green to yellow-green with mottled or web-like dark patches, waxy to greasy luster, and a massive texture; Mohs hardness about 2.5–4, with poor or absent cleavage. The pictured piece appears smoothly tumbled and polished.
Formation & geological history
Forms when ultramafic mantle rocks such as peridotite are hydrated during low-temperature metamorphism; associated alteration can range from Paleozoic to modern tectonic settings. Common in ophiolites and subduction-zone mélange.
Uses & applications
Used as ornamental stone, carvings, tumbled specimens, and historically as a decorative building stone; some varieties are collectible. Avoid cutting or generating dust because certain serpentinites may contain asbestos-form minerals.
Geological facts
Serpentinite is California’s state rock and commonly contains magnetite, which can make pieces weakly magnetic. Its green color results from serpentine minerals and related alteration products.
Field identification & locations
Identify by its soft, waxy feel, green mottling, low density, and ability to scratch relatively easily with a steel blade; a definitive identification may require microscopy or X-ray analysis. Common localities include California, New Zealand, Italy, Canada, and the Appalachians.
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