metamorphic
Polished greenstone pebble
Likely serpentinite or chlorite-rich greenschist
AI-generated identification · may be incorrectDark olive-green, fine-grained, smoothly polished, with pale tan veining or weathering rind and a dull-to-waxy luster. Estimated Mohs hardness 3–5; massive structure with no visible cleavage; exact identification requires hardness, streak, and density tests.
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Physical properties
Dark olive-green, fine-grained, smoothly polished, with pale tan veining or weathering rind and a dull-to-waxy luster. Estimated Mohs hardness 3–5; massive structure with no visible cleavage; exact identification requires hardness, streak, and density tests.
Formation & geological history
Likely formed when ultramafic rock underwent low-grade metamorphism and hydration, producing serpentine minerals; alternatively it may be chlorite-rich metamorphic rock. Geological age cannot be determined from the photograph.
Uses & applications
Primarily a decorative, tumbled, or lapidary stone; similar greenstones are used for carvings, ornamental objects, and occasionally jewelry.
Geological facts
The rounded shape indicates abrasion in a river, beach, or glacial environment, followed by polishing. Tan zones may represent iron oxidation or weathered mineral veins.
Field identification & locations
Commonly found as stream or beach cobbles in areas containing altered ultramafic rocks, including California, Oregon, New Zealand, and the Alps. Serpentinite is typically softer and waxier than jade; jadeite or nephrite is harder, denser, and tougher.
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