metamorphic

Greenstone pebble

Greenschist-facies mafic rock, commonly derived from basalt; likely rich in chlorite, actinolite, and epidote

AI-generated identification · may be incorrect

Rounded, dark green to bluish-green stone with pale mineral veins and a fine-grained, mottled texture. Likely hardness 5–6.5 Mohs; mineral grains are too small to identify crystal structure or cleavage from the photo.

Identified October 4, 2026More metamorphic →

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Physical properties

Formation & geological history

Typically forms when basalt or other mafic rock is altered by low- to medium-grade metamorphism and hydrothermal fluids. Such rocks occur in ancient metamorphic belts; the specimen’s age and exact formation setting cannot be determined from the image.

Uses & applications

Used as an ornamental or landscaping stone and collected as a polished pebble; greenstone has also been carved into tools and ornaments.

Geological facts

“Greenstone” is a broad field term for green-colored, altered mafic rocks, not one precise mineral species.

Field identification & locations

The green color and pale vein network suggest an altered mafic rock, but a fresh break, hardness tests, and mineral analysis would be needed for confident identification. Greenstone occurs in metamorphic terranes worldwide.