igneous
Greenstone / altered basalt fragment
Likely chlorite–epidote–actinolite altered basalt; exact identification requires testing
AI-generated identification · may be incorrectDark green, fine-grained, dull to slightly waxy luster, with no visible crystals or cleavage; estimated Mohs hardness 5–6 and specific gravity about 2.8–3.1. The irregular angular shape suggests a natural broken fragment rather than a polished specimen.
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Physical properties
Dark green, fine-grained, dull to slightly waxy luster, with no visible crystals or cleavage; estimated Mohs hardness 5–6 and specific gravity about 2.8–3.1. The irregular angular shape suggests a natural broken fragment rather than a polished specimen.
Formation & geological history
Probably volcanic basalt altered by low-grade metamorphism or hydrothermal fluids, producing green minerals such as chlorite, epidote, and actinolite. Such alteration commonly formed from the Precambrian through the Cenozoic in volcanic belts and oceanic crust.
Uses & applications
Used locally as aggregate, landscaping stone, or ornamental “greenstone”; attractive pieces may be cut or polished, though this small fragment has little commercial use.
Geological facts
“Greenstone” is a broad field term, not a single mineral or rock. Similar-looking material can include serpentinite, chlorite schist, jade-like rocks, or weathered basalt.
Field identification & locations
Look for a dense, fine-grained dark-green rock with weakly mottled color and no obvious layering; a steel file may scratch it slightly. Common in altered volcanic terrains worldwide, including the Pacific Northwest, Appalachians, New Zealand, and oceanic greenstone belts.
