metamorphic
Serpentinite
Serpentinite; chiefly serpentine-group minerals (lizardite, chrysotile, antigorite), with magnetite and relic mafic minerals
AI-generated identification · may be incorrectTypically dark green to black, mottled or veined, with waxy to greasy luster; Mohs hardness about 2.5–4, massive rather than visibly crystalline, and specific gravity roughly 2.5–2.7. The polished/tumbled surface shows pale serpentine veins and darker green patches.
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Physical properties
Typically dark green to black, mottled or veined, with waxy to greasy luster; Mohs hardness about 2.5–4, massive rather than visibly crystalline, and specific gravity roughly 2.5–2.7. The polished/tumbled surface shows pale serpentine veins and darker green patches.
Formation & geological history
Forms when mantle-derived ultramafic rocks such as peridotite undergo low-temperature hydration during metamorphism, commonly in oceanic crust and subduction zones. Individual specimens may span broad Precambrian to modern tectonic settings.
Uses & applications
Used as an ornamental and carving stone, architectural facing, countertops, and decorative tumbled material; historically used for sculpture and some asbestos-bearing products. Value is generally modest unless exceptionally patterned or collectible.
Geological facts
Serpentinite is California’s state rock and commonly records ancient oceanic lithosphere. Some varieties contain chrysotile asbestos, so avoid cutting, drilling, or generating dust without professional testing and controls.
Field identification & locations
Identify it by its green-black color, smooth waxy feel, mottled pattern, and pale veins; it is softer than most igneous rocks and may contain magnetic magnetite. Common localities include California, Italy, New Zealand, Canada, and many former ophiolite belts.
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