metamorphic
Likely weathered greenstone
Metabasalt (greenstone), composed chiefly of chlorite, actinolite, epidote, and albite
AI-generated identification · may be incorrectDark olive-gray, fine-grained, dull to weakly waxy luster, with possible epidote/chlorite specks; hardness about 5–6, non-cleavable to weakly foliated, and typically dense (specific gravity ~2.8–3.2). Identification is tentative because the photograph lacks scale, texture, and diagnostic testing.
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Physical properties
Dark olive-gray, fine-grained, dull to weakly waxy luster, with possible epidote/chlorite specks; hardness about 5–6, non-cleavable to weakly foliated, and typically dense (specific gravity ~2.8–3.2). Identification is tentative because the photograph lacks scale, texture, and diagnostic testing.
Formation & geological history
Formed when basaltic lava was metamorphosed under low-grade, water-rich conditions, commonly during ancient ocean-floor alteration; ages vary widely from Precambrian to modern tectonic belts.
Uses & applications
Used locally as crushed aggregate, landscaping stone, and occasionally as a carving or ornamental material; generally has little gem value.
Geological facts
The green color commonly comes from chlorite, actinolite, and epidote replacing original basalt minerals. A greenstone may represent metamorphosed oceanic crust.
Field identification & locations
Look for a fine-grained green-gray body, high density, and possible faint foliation; a streak, hardness, magnetism, and acid test would improve identification. Common in metamorphic belts and altered volcanic terrains worldwide.
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