metamorphic

Greenstone / altered basalt (likely serpentinite or chlorite-rich rock)

Chlorite–actinolite schist or weakly metamorphosed basalt; exact identification requires testing

AI-generated identification · may be incorrect

Fine-grained, rounded, blue-green to gray-green, dull to faintly silky luster; likely Mohs 5–6, massive with no visible cleavage, and moderate-to-high specific gravity. The smooth surface appears naturally weathered or tumbled.

Identified August 13, 2026More metamorphic →

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Physical properties

Formation & geological history

Probably altered mafic volcanic rock metamorphosed by hydrothermal fluids or low-grade regional metamorphism; commonly Paleozoic or younger, though age cannot be determined visually. Serpentinite forms when mantle peridotite hydrates, while chlorite-actinolite greenstone forms from basalt alteration.

Uses & applications

Used locally as landscaping stone, aggregate, carving material, and decorative lapidary stone; generally limited jewelry value unless it has attractive patterning or polish.

Geological facts

Its green color commonly comes from chlorite, actinolite, epidote, or serpentine rather than a single mineral. A magnetism, streak, hardness, and acid test would help distinguish basaltic greenstone from serpentinite.

Field identification & locations

Common in ophiolite belts, volcanic terrains, and metamorphic zones worldwide; notable sources include California, Vermont, the Appalachians, New Zealand, and parts of Australia. Estimated value: $2–$15 as a common hand specimen, or $20–$75 if polished and attractively patterned.