igneous
Weathered greenish mafic rock fragment
Likely altered basalt or basaltic-andesite; exact identification is uncertain from the photograph
AI-generated identification · may be incorrectFine- to medium-grained, pale green/yellow-gray, dull to slightly granular luster, with probable alteration minerals such as chlorite, epidote, and calcite. Basaltic rocks typically have Mohs hardness 5–6, specific gravity about 2.8–3.1, and no prominent cleavage.
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Physical properties
Fine- to medium-grained, pale green/yellow-gray, dull to slightly granular luster, with probable alteration minerals such as chlorite, epidote, and calcite. Basaltic rocks typically have Mohs hardness 5–6, specific gravity about 2.8–3.1, and no prominent cleavage.
Formation & geological history
Likely volcanic lava that cooled rapidly at or near Earth’s surface, later altered by groundwater or hydrothermal fluids; commonly Cenozoic or older depending on locality. The dark surrounding material may be the host lava or weathered volcanic surface.
Uses & applications
Used as crushed aggregate, road material, and occasionally dimension stone; ordinary fragments have negligible commercial value.
Geological facts
Green coloration commonly indicates chloritization or epidote alteration rather than a distinct green gemstone. A fresh broken surface and a hand lens would help distinguish basalt, andesite, serpentinite, or altered volcanic tuff.
Field identification & locations
Look for dense fine grain, dark fresh interior, weak magnetism, and lack of visible quartz; common in volcanic belts worldwide. Collector value is typically low unless the specimen displays unusual alteration or associated minerals.
