metamorphic
Tumbled greenstone, likely serpentine or altered basalt
Probable serpentinite (Mg-rich phyllosilicates, chiefly antigorite/lizardite) or chlorite-rich basalt
AI-generated identification · may be incorrectDark green-gray, rounded and polished, with fine-grained texture and subdued waxy to dull luster. Likely Mohs 3–6 depending on composition; no visible cleavage or crystals, and specific gravity commonly about 2.6–3.0.
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Physical properties
Dark green-gray, rounded and polished, with fine-grained texture and subdued waxy to dull luster. Likely Mohs 3–6 depending on composition; no visible cleavage or crystals, and specific gravity commonly about 2.6–3.0.
Formation & geological history
If serpentinite, it formed when oceanic ultramafic rock hydrated during metamorphism, commonly in ophiolite belts; if basaltic greenstone, it reflects low-grade metamorphism. Exact age and identity cannot be determined from the photograph.
Uses & applications
Used as a decorative tumbled stone, ornamental carving material, and occasionally in landscaping; typically not a gemstone of high commercial value.
Geological facts
The term “greenstone” is a trade and field name rather than a single mineral. Serpentine may feel slightly soapy and can scratch relatively easily, while basaltic greenstone is harder and denser.
Field identification & locations
Common in metamorphic terrains and glacial gravels. Test with a steel knife or glass cautiously: easy scratching suggests serpentine; stronger resistance suggests basalt/greenstone. A streak, hardness, and specific-gravity test would improve identification.
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