metamorphic
Greenstone pebble (likely altered basalt)
Chlorite–actinolite–epidote altered basalt; precise identification requires testing
AI-generated identification · may be incorrectFine-grained, rounded, gray-green rock with dull to slightly waxy luster and pale veins or patches. Typical hardness is about 5–6 Mohs; no visible cleavage and relatively high density (~2.8–3.1).
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Physical properties
Fine-grained, rounded, gray-green rock with dull to slightly waxy luster and pale veins or patches. Typical hardness is about 5–6 Mohs; no visible cleavage and relatively high density (~2.8–3.1).
Formation & geological history
Probably basalt altered by low-grade metamorphism or hydrothermal fluids, producing chlorite, epidote, and/or actinolite; commonly Paleozoic or younger in exposed volcanic terrains, though age cannot be determined from the photo.
Uses & applications
Used mainly as a landscaping, lapidary, or collector stone; greenstone and related altered basalt may also be crushed for aggregate or building stone.
Geological facts
The term “greenstone” is descriptive rather than a single mineral or rock species. Its green color commonly reflects chlorite, epidote, actinolite, or serpentine.
Field identification & locations
Identify it by its dense fine-grained texture, muted green-gray color, and lack of glassy surfaces; a streak, hardness, magnetism, and acid test can refine identification. Common in volcanic belts and glacial or beach gravels.
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