metamorphic
Weathered greenstone (probable)
Greenstone; likely altered mafic rock composed chiefly of chlorite, epidote, and albite
AI-generated identification · may be incorrectDull, earthy green-brown surface with a fine-grained, massive appearance; individual crystals are not visible. Typical greenstone minerals have Mohs hardness around 5–7; exact hardness, density, and composition cannot be established from the image.
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Physical properties
Dull, earthy green-brown surface with a fine-grained, massive appearance; individual crystals are not visible. Typical greenstone minerals have Mohs hardness around 5–7; exact hardness, density, and composition cannot be established from the image.
Formation & geological history
Commonly forms when basalt or other mafic volcanic rock is altered by low-grade metamorphism and hydrothermal fluids. The specimen’s age and precise formation setting cannot be determined visually.
Uses & applications
Greenstone is sometimes used as crushed aggregate, building stone, or decorative material; this rough specimen has no obvious gem-grade features.
Geological facts
Green color commonly comes from chlorite and epidote replacing original volcanic minerals.
Field identification & locations
Its muted green color and massive texture suggest greenstone, but confirmation requires tests such as hardness, streak, and examination of a fresh surface. Greenstone occurs in metamorphic belts worldwide.
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