metamorphic

Weathered greenstone

Metamorphosed mafic rock, commonly chlorite–actinolite schist or altered basalt

AI-generated identification · may be incorrect

Typically dark green to gray-green, dull to weakly silky, fine- to medium-grained, and irregularly fractured; hardness about 5–6 Mohs. The reddish patches may be iron-oxide weathering, while pale green areas commonly contain chlorite, epidote, or actinolite.

Identified August 20, 2026More metamorphic →

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Physical properties

Formation & geological history

Formed when basalt or gabbro underwent low- to moderate-grade metamorphism and hydrothermal alteration, commonly during ancient oceanic or mountain-building events. Exact age cannot be determined from the photograph.

Uses & applications

Used locally as crushed aggregate, landscaping stone, and occasionally as a decorative lapidary material; this weathered specimen has little jewelry value.

Geological facts

Its green color usually reflects alteration of iron- and magnesium-rich minerals rather than a single mineral. The cavities and rough surface likely result from weathering, dissolved veins, or formerly gas-filled spaces.

Field identification & locations

Look for a green, dense rock with black amphibole or chlorite, epidote-like grains, and no obvious sedimentary layering; a streak, hardness, and acid test can help distinguish it from serpentine or green jasper. Common in metamorphic belts and altered volcanic terrains worldwide.