metamorphic
Likely serpentine (serpentinite) pebble
Serpentine-group minerals, chiefly antigorite, lizardite, or chrysotile; commonly with magnetite and minor carbonate
AI-generated identification · may be incorrectTypically olive to yellow-green, waxy to greasy luster, fine-grained and massive; Mohs hardness about 2.5–4, poor cleavage, and specific gravity roughly 2.5–2.6. The wet, smoothly rounded surface and mottled green coloration are consistent with serpentine, though the photograph alone is not diagnostic.
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Physical properties
Typically olive to yellow-green, waxy to greasy luster, fine-grained and massive; Mohs hardness about 2.5–4, poor cleavage, and specific gravity roughly 2.5–2.6. The wet, smoothly rounded surface and mottled green coloration are consistent with serpentine, though the photograph alone is not diagnostic.
Formation & geological history
Forms when ultramafic mantle rocks such as peridotite undergo low-temperature hydration and metamorphism, commonly along faults and subduction zones. Serpentinite occurs from Precambrian to modern geologic settings and is later rounded by stream or beach transport.
Uses & applications
Used as decorative stone, carvings, beads, and occasionally countertops; historically used as a source of asbestos-bearing material, so dusty cutting should be avoided. Common pebbles generally have modest market value.
Geological facts
Serpentine is not one mineral but a mineral group; some varieties may contain fibrous chrysotile asbestos. A polished or wet surface can resemble jade, but serpentine is usually softer and less dense.
Field identification & locations
Common in California, Oregon, Washington, the Appalachians, Italy, New Zealand, and other ophiolite belts. Field tests include a waxy feel, relatively low hardness, green streak or powder, and reaction that is usually weak or absent with dilute acid; definitive identification requires petrography or laboratory testing.
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