igneous
Water-worn green pebble
Likely altered basalt or greenstone; precise identification requires testing
AI-generated identification · may be incorrectFine-grained, rounded, olive-green, and dull to slightly waxy; likely Mohs 5.5–7, with no visible cleavage or crystals. The smooth shape and wet surface reflect stream or beach abrasion.
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Physical properties
Fine-grained, rounded, olive-green, and dull to slightly waxy; likely Mohs 5.5–7, with no visible cleavage or crystals. The smooth shape and wet surface reflect stream or beach abrasion.
Formation & geological history
Probably a basaltic volcanic rock altered by low-grade metamorphism or hydrothermal fluids, producing chlorite/epidote-rich greenstone; age and locality cannot be determined from the image.
Uses & applications
Typically a decorative or lapidary pebble; suitable for tumbling, crafts, landscaping, and specimen collecting, but not usually gem-grade.
Geological facts
Greenstone is a field term for green, altered mafic rock and may include chlorite, epidote, actinolite, and albite. Similar-looking pebbles can also be serpentinite or green jasper.
Field identification & locations
Common in river gravels, beaches, and areas underlain by basalt or metamorphosed oceanic crust. Check streak, hardness, density, magnetism, and acid reaction; a fresh unpolished surface and locality information are especially useful.
