metamorphic
Likely greenstone (metamorphosed mafic rock)
Greenstone; commonly metamorphosed basalt or dolerite, with chlorite, actinolite, epidote, and albite
AI-generated identification · may be incorrectCoarse, mottled gray-green rock with a granular, sparkly surface. Likely Mohs hardness about 5–6; exact mineral makeup and properties cannot be confirmed from the photo.
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Physical properties
Coarse, mottled gray-green rock with a granular, sparkly surface. Likely Mohs hardness about 5–6; exact mineral makeup and properties cannot be confirmed from the photo.
Formation & geological history
Typically forms when basaltic lava or shallow intrusive rock is altered by low-grade metamorphism and hydrothermal fluids. Such rocks occur in ancient metamorphic belts, ranging from Precambrian to younger ages.
Uses & applications
Used locally as crushed aggregate, landscaping stone, and building stone; attractive pieces may be collected or polished.
Geological facts
“Greenstone” is a field term for several green-hued, altered mafic rocks rather than one precise mineral or rock composition.
Field identification & locations
The green color and mafic, granular appearance support this identification, but a fresh surface and mineral tests would be needed to distinguish it from other green rocks. Common in metamorphic belts worldwide.
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