metamorphic
Greenstone / serpentinized ultramafic rock (probable)
Serpentinite, chiefly serpentine-group minerals (Mg₃Si₂O₅(OH)₄), with possible magnetite and talc
AI-generated identification · may be incorrectLight green, mottled, fine-grained and rounded/tumbled; typically waxy to dull luster, hardness about 2.5–4, poor cleavage, and specific gravity around 2.5–2.6. The image alone cannot distinguish serpentinite from other greenstones such as altered basalt or chlorite-rich rock.
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Physical properties
Light green, mottled, fine-grained and rounded/tumbled; typically waxy to dull luster, hardness about 2.5–4, poor cleavage, and specific gravity around 2.5–2.6. The image alone cannot distinguish serpentinite from other greenstones such as altered basalt or chlorite-rich rock.
Formation & geological history
Forms when water alters mantle-derived peridotite, commonly along tectonic plate boundaries and faults; alteration is generally Paleozoic to Cenozoic depending on the locality. The specimen appears naturally weathered or polished by handling.
Uses & applications
Used as carving stone, decorative aggregate, countertops, ornaments, and tumbled specimens; historically used for tools and architectural facing. Ordinary pieces have modest collector value.
Geological facts
Serpentinite commonly contains veinlets of white chrysotile or other serpentine minerals and may show dark magnetite specks. Some varieties are associated with asbestos-forming minerals, so avoid cutting or generating dust unless professionally tested.
Field identification & locations
Look for greasy/waxy green surfaces, mottling, softness, and occasional magnetic response; a streak, hardness, acid, and thin-section test would improve identification. Common in California, Italy, New Zealand, Canada, and ophiolite belts worldwide.
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