igneous
Greenstone pebble, likely altered basalt
Metabasalt/greenstone; commonly chlorite–epidote–actinolite with albite and iron oxides
AI-generated identification · may be incorrectFine-grained, dull to weakly satin luster, rounded and weathered, pale green-gray; hardness approximately 5–6 Mohs, massive with no visible cleavage. The porous-looking surface may reflect weathering rather than vesicles.
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Physical properties
Fine-grained, dull to weakly satin luster, rounded and weathered, pale green-gray; hardness approximately 5–6 Mohs, massive with no visible cleavage. The porous-looking surface may reflect weathering rather than vesicles.
Formation & geological history
Likely basalt altered by low-grade metamorphism or hydrothermal fluids, producing green minerals; such alteration commonly formed during ancient ocean-floor activity, though age cannot be determined from the image. It may also be a weathered green volcanic rock or serpentinite fragment.
Uses & applications
Used locally as landscaping stone, aggregate, or ornamental material; attractive pieces may be tumbled or polished, but this specimen has modest gem value.
Geological facts
“Greenstone” is a field term rather than one exact mineral or rock. Green color commonly comes from chlorite, epidote, actinolite, or serpentine.
Field identification & locations
Check for a fine crystalline texture, green streak or powder, density, and hardness; a steel knife should scratch it only weakly or not at all. Common in altered volcanic terrains and glacial or stream gravels; exact identification requires a fresh surface, streak, magnetism, and ideally thin-section or XRF analysis.
