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 incorrectFine-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.
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Physical properties
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.
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.
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