metamorphic
Weathered greenstone (metabasalt)
Chlorite–actinolite metabasalt; composition varies, commonly plagioclase with chlorite, actinolite, epidote, and amphibole
AI-generated identification · may be incorrectDull, mottled olive-green to brown, fine-grained and rounded by weathering; likely Mohs 5–6, with no obvious cleavage or visible crystals. Exact mineralogy cannot be confirmed from the photo alone.
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Physical properties
Dull, mottled olive-green to brown, fine-grained and rounded by weathering; likely Mohs 5–6, with no obvious cleavage or visible crystals. Exact mineralogy cannot be confirmed from the photo alone.
Formation & geological history
Typically forms when basalt is altered by low-grade metamorphism and hydrothermal fluids, often in ancient oceanic crust or greenstone belts; age depends on its source locality.
Uses & applications
Used locally as aggregate or landscaping stone; attractive pieces may be collected, but it is not usually a jewelry material.
Geological facts
The green color commonly comes from chlorite, epidote, or actinolite replacing minerals in the original basalt.
Field identification & locations
Look for a dense, fine-grained rock with green tones and possible remnants of basaltic texture; greenstone occurs in metamorphic belts worldwide. A photograph cannot establish its precise identification or locality.
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