metamorphic
Likely greenstone (metamorphosed mafic rock)
Greenschist or altered basalt; exact identification is uncertain from the image
AI-generated identification · may be incorrectSmall, rough, gray-green, fine-grained specimen with a dull to slightly silky luster. Greenstone commonly contains chlorite, actinolite, and epidote; hardness varies roughly 3–6.5 Mohs, with no single diagnostic crystal structure.
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Physical properties
Small, rough, gray-green, fine-grained specimen with a dull to slightly silky luster. Greenstone commonly contains chlorite, actinolite, and epidote; hardness varies roughly 3–6.5 Mohs, with no single diagnostic crystal structure.
Formation & geological history
Typically forms when basalt or other mafic rock is altered by low-grade metamorphism and fluid circulation. Such rocks occur across many geological ages and settings.
Uses & applications
Commonly used as crushed stone or building/decorative stone; attractive pieces may be collected or polished.
Geological facts
The green color in greenstone usually comes from chlorite, epidote, or actinolite formed during alteration.
Field identification & locations
A green color and fine-grained texture can suggest greenstone, but this small image does not reveal diagnostic mineral grains or structure. Greenstone occurs in metamorphic belts worldwide; confirm with close inspection or mineral tests.
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