metamorphic
Greenstone (likely chlorite- or epidote-altered basalt)
Metamorphosed mafic volcanic rock; commonly chlorite–epidote–actinolite assemblage
AI-generated identification · may be incorrectDark green, rough and fine-grained with a dull to slightly waxy luster; likely Mohs 5–6, with no obvious cleavage. Exact mineral composition cannot be confirmed from the photograph.
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Physical properties
Dark green, rough and fine-grained with a dull to slightly waxy luster; likely Mohs 5–6, with no obvious cleavage. Exact mineral composition cannot be confirmed from the photograph.
Formation & geological history
Forms when basalt or related mafic rock is altered by low-grade metamorphism and hydrothermal fluids, commonly along ancient oceanic crust or volcanic belts; age depends on locality.
Uses & applications
Primarily a geological or lapidary/collecting specimen; some greenstone is carved or used decoratively, but this small rough piece has no evident industrial use.
Geological facts
“Greenstone” is a field term for green-altered mafic rocks, not one uniquely defined mineral or rock composition.
Field identification & locations
Look for a dense, green, fine-grained rock, often with chlorite or epidote and relic volcanic textures; common in metamorphic belts worldwide. A locality or mineral testing would be needed for a firm identification.
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