metamorphic
Tumbled greenstone (likely serpentine or chlorite-rich metamorphic rock)
Serpentinite, approximately Mg₃Si₂O₅(OH)₄, or chlorite-rich greenstone
AI-generated identification · may be incorrectDark green to black, fine-grained, mottled, and dull to waxy; likely Mohs hardness 3–5, with no visible cleavage and a compact crystalline texture. The rounded shape and smooth surface indicate tumbling or water wear.
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Physical properties
Dark green to black, fine-grained, mottled, and dull to waxy; likely Mohs hardness 3–5, with no visible cleavage and a compact crystalline texture. The rounded shape and smooth surface indicate tumbling or water wear.
Formation & geological history
Serpentinite forms when ultramafic rocks such as peridotite are altered by hydrothermal fluids, commonly along tectonic plate boundaries; chlorite-rich greenstones form during low-grade metamorphism. Exact age and identity require testing.
Uses & applications
Used for carvings, beads, landscaping, and decorative stone; attractive pieces may be sold as ornamental or lapidary material rather than high-value gemstones.
Geological facts
The specimen resembles common serpentine/greenstone but cannot be identified conclusively from a photograph. Serpentine may contain magnetite and can show a characteristic waxy polish.
Field identification & locations
Look for a green-black color, fine mottling, waxy luster, low hardness, and possible white veining; a streak, hardness, density, magnetism, and acid test can distinguish it from jade or basalt. Common sources include California, Italy, New Zealand, Canada, and serpentinite belts worldwide.
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