metamorphic

Polished greenstone pebble

Greenstone (chlorite–epidote–actinolite-rich metamorphosed mafic rock)

AI-generated identification · may be incorrect

Olive-green, fine-grained, mottled and polished with a subdued sheen. Hardness commonly about 5–6 Mohs; mineral mix and exact composition cannot be confirmed from the photo.

Identified October 14, 2026More metamorphic →

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Physical properties

Olive-green, fine-grained, mottled and polished with a subdued sheen. Hardness commonly about 5–6 Mohs; mineral mix and exact composition cannot be confirmed from the photo.

Formation & geological history

Typically formed when basalt or related mafic rock was altered by low-grade metamorphism and hydrothermal fluids. Such rocks occur in ancient and modern volcanic belts; the specimen’s age and locality are unknown.

Uses & applications

Used as a decorative or lapidary stone and sometimes for carvings or jewelry; greenstone also has historical use as a tool material.

Geological facts

“Greenstone” is a field term for several green, altered volcanic rocks, not one single mineral or precisely defined rock type.

Field identification & locations

Look for a dense, fine-grained olive-green rock, often with chlorite or epidote and no obvious large crystals. Common in metamorphic belts worldwide; the photo does not establish a specific source.