metamorphic
Greenstone pebble (likely metamorphosed basalt)
Greenstone, commonly chlorite- and actinolite-bearing metabasalt
AI-generated identification · may be incorrectSmall, rounded, dark olive-green specimen with a fine-grained, matte surface. Likely Mohs hardness 5–6; mineral proportions and crystal structure cannot be confirmed from the photograph.
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Physical properties
Small, rounded, dark olive-green specimen with a fine-grained, matte surface. Likely Mohs hardness 5–6; mineral proportions and crystal structure cannot be confirmed from the photograph.
Formation & geological history
Typically forms when basalt is altered by low-grade metamorphism and hydrothermal fluids; such rocks occur in geological belts of varied ages. The pebble’s exact source and age cannot be determined visually.
Uses & applications
Usually collected as a natural pebble; greenstone has also been used historically for tools, ornaments, and carved objects.
Geological facts
“Greenstone” is a broad field term for green-colored altered volcanic rock, not a single precisely defined mineral species.
Field identification & locations
Its green color and fine grain are consistent with greenstone, but visual inspection alone cannot distinguish it reliably from other green rocks. Common in metamorphic terrains and stream or beach gravels; a hardness test or thin-section analysis would help identify it.
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