metamorphic
Serpentine-rich ultramafic rock
Serpentinite (predominantly serpentine-group minerals: lizardite, chrysotile, and/or antigorite)
AI-generated identification · may be incorrectTypically Mohs 2.5–4, with mottled green, gray, black, and brown colors; waxy to greasy luster and commonly veined or brecciated texture. It has no consistent crystal habit, and cleavage is generally poor or indistinct; specific gravity is about 2.5–2.6.
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Physical properties
Typically Mohs 2.5–4, with mottled green, gray, black, and brown colors; waxy to greasy luster and commonly veined or brecciated texture. It has no consistent crystal habit, and cleavage is generally poor or indistinct; specific gravity is about 2.5–2.6.
Formation & geological history
Forms when mantle-derived peridotite is hydrated and altered during low-temperature metamorphism, commonly along faults and oceanic crust. Individual specimens may record ancient tectonic events ranging from Precambrian to modern geological settings.
Uses & applications
Used as decorative stone, carvings, lapidary material, and historically as a source of asbestos where chrysotile is abundant; some varieties have been used in building stone. Avoid cutting or abrading unknown material because fibrous asbestos may be present.
Geological facts
The green patches and slick, mottled appearance are characteristic of serpentinization, but the image could also include weathered pyroxene, carbonate, or copper-bearing alteration minerals.
Field identification & locations
Identify it by its low hardness, green-black mottling, waxy surface, and association with ultramafic rocks; a streak, hardness, and specific-gravity test can help. Common occurrences include ophiolites and subduction-zone mélanges worldwide, especially California, Italy, New Zealand, and Canada.
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