metamorphic
Greenstone (likely chlorite-rich greenschist)
Greenschist facies metamorphic rock, typically composed of chlorite, actinolite, and albite; exact identification requires testing
AI-generated identification · may be incorrectGreen-gray, dull to slightly sparkly, with a fine-to-medium crystalline texture and weak foliation. Hardness varies roughly 3–6 Mohs depending on mineral proportions; individual grains may show cleavage.
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Physical properties
Green-gray, dull to slightly sparkly, with a fine-to-medium crystalline texture and weak foliation. Hardness varies roughly 3–6 Mohs depending on mineral proportions; individual grains may show cleavage.
Formation & geological history
Forms when basaltic or other mafic rocks undergo low-grade regional metamorphism, commonly in ancient oceanic crust and mountain belts. The specimen’s age and precise origin cannot be determined from the image.
Uses & applications
Greenstone is used as a decorative or carving stone and, historically, for tools and construction aggregate; attractive pieces are collected.
Geological facts
“Greenstone” is a broad field term for green-hued rocks, not one fixed mineral composition. The pictured specimen’s color and texture are consistent with chlorite-bearing metamorphic rock.
Field identification & locations
Look for a green, compact rock with fine foliation or tiny shiny mineral grains; distinguish it from serpentine or jade with hardness, streak, and density tests. Occurs in metamorphic belts worldwide.
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