metamorphic

Greenstone / altered basalt (probable)

Chlorite–epidote–actinolite aggregate; commonly metabasalt (greenstone)

AI-generated identification · may be incorrect

Fine-grained, mottled green-brown rock with dull to slightly waxy luster and rusty weathering; hardness about 5–6 Mohs, no obvious cleavage, and moderate density (~2.8–3.2). Exact identification is limited by the photograph.

Identified September 4, 2026More metamorphic →

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Physical properties

Formation & geological history

Formed when basaltic volcanic rock underwent low-grade metamorphism, commonly during ancient ocean-floor alteration or regional mountain building; age depends on its source locality and cannot be determined visually.

Uses & applications

Used locally as crushed aggregate, road stone, or decorative stone; attractive polished pieces may be sold as lapidary material, though this small rough specimen has modest value.

Geological facts

The green color typically comes from chlorite, epidote, actinolite, or serpentinite-related minerals replacing original basalt minerals. “Greenstone” is a descriptive field term rather than one precise mineral or rock species.

Field identification & locations

Look for a dense, fine-grained texture, green coloration, and possible relict basaltic fabric; a streak, hardness test, and thin-section or X-ray analysis would help distinguish it from serpentinite or weathered copper-bearing rock. Common in metamorphic belts and ophiolites.