metamorphic
Tumbled serpentine (likely)
Serpentinite; chiefly serpentine-group minerals, Mg₃Si₂O₅(OH)₄
AI-generated identification · may be incorrectDark olive-green, mottled, waxy to subvitreous luster with a smooth tumbled surface; Mohs hardness about 2.5–4, generally massive with no visible cleavage. The image is consistent with serpentine, though similar greenstone or nephrite cannot be excluded visually.
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Physical properties
Dark olive-green, mottled, waxy to subvitreous luster with a smooth tumbled surface; Mohs hardness about 2.5–4, generally massive with no visible cleavage. The image is consistent with serpentine, though similar greenstone or nephrite cannot be excluded visually.
Formation & geological history
Forms when ultramafic mantle rocks such as peridotite hydrate during hydrothermal alteration; serpentinite occurs in ophiolites and tectonic fault zones, ranging from ancient Precambrian bodies to modern settings. It is metamorphic rather than an igneous rock.
Uses & applications
Used as ornamental stone, carvings, beads, cabochons, and occasionally architectural facing; historically used for decorative objects. Avoid generating dust, since some serpentinite deposits may contain asbestos-forming minerals.
Geological facts
Its characteristic green color comes from iron-bearing serpentine minerals and associated magnetite or chlorite. Nephrite is harder and tougher, while serpentine is typically softer and more waxy.
Field identification & locations
Identify by mottled green color, waxy feel, low hardness, and density around 2.5–2.6; a steel knife may scratch it. Common sources include California, New Zealand, Italy, Canada, and the Ural Mountains.
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