metamorphic
Serpentinite (probable)
Serpentinite, dominated by serpentine-group minerals (Mg₃Si₂O₅(OH)₄), with dark magnetite or chromite and pale carbonate/talc possible
AI-generated identification · may be incorrectHardness typically 2.5–4 Mohs; mottled dark green, black, and pale green; waxy to dull luster; very fine-grained, massive texture with no visible crystal faces. The rounded shape suggests natural weathering or tumbling.
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Physical properties
Hardness typically 2.5–4 Mohs; mottled dark green, black, and pale green; waxy to dull luster; very fine-grained, massive texture with no visible crystal faces. The rounded shape suggests natural weathering or tumbling.
Formation & geological history
Forms when ultramafic mantle rocks such as peridotite are hydrated during low-temperature metamorphism, commonly in oceanic crust and subduction zones. Ages range from modern alteration to ancient ophiolite belts.
Uses & applications
Used as decorative stone, carving material, aggregate, and historically as a source of asbestos-bearing serpentine; attractive pieces are collected, but asbestos risk requires avoiding dust and cutting.
Geological facts
The distinctive green color results from serpentine minerals; dark veins or patches may contain magnetite or chromite. This small specimen cannot be identified definitively without hardness, streak, or mineralogical testing.
Field identification & locations
Common in ophiolite terrains, including California, Italy, New Zealand, and Greece. Field clues are green color, waxy feel, low hardness, and often a smooth, greasy-looking weathered surface.
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