metamorphic
Tumbled greenstone / serpentine pebble
Serpentinite, dominated by serpentine-group minerals (Mg₃Si₂O₅(OH)₄)
AI-generated identification · may be incorrectSmooth, rounded, olive-green stone with a dull to waxy luster; typically Mohs 2.5–4, massive rather than visibly crystalline, with poor cleavage and specific gravity about 2.5–2.6. The image alone cannot distinguish serpentine confidently from greenstone or other altered mafic rock.
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Physical properties
Smooth, rounded, olive-green stone with a dull to waxy luster; typically Mohs 2.5–4, massive rather than visibly crystalline, with poor cleavage and specific gravity about 2.5–2.6. The image alone cannot distinguish serpentine confidently from greenstone or other altered mafic rock.
Formation & geological history
Forms when ultramafic mantle rocks undergo hydration and metamorphism, commonly during oceanic-plate or subduction processes; occurrences range from Precambrian to modern tectonic belts. This specimen appears water-worn or deliberately tumbled.
Uses & applications
Used as decorative stone, carvings, beads, lapidary material, and occasionally architectural stone; softer varieties are unsuitable for heavy construction. Common pieces have modest collector value.
Geological facts
Serpentinite commonly contains magnetite and may show dark veins, mottling, or a greasy feel. Some varieties can contain asbestos-form minerals, so avoid generating dust when cutting or sanding.
Field identification & locations
Common in ophiolites and tectonic zones, including California, New Zealand, Italy, Canada, and the Alps. Field identification requires hardness, streak, density, and ideally microscopy or X-ray analysis; visually, this could also be greenstone or altered basalt.
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