igneous
Likely basalt or other fine-grained volcanic rock
Indeterminate dark mafic volcanic rock; commonly basalt, composed mainly of plagioclase and pyroxene, often with olivine
AI-generated identification · may be incorrectGray, rounded, fine-grained specimen with a dull to slightly glassy surface; visible image is insufficient to confirm minerals or texture. Typical basalt hardness is about 6 on Mohs scale, with no prominent cleavage and specific gravity around 2.8–3.0.
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Physical properties
Gray, rounded, fine-grained specimen with a dull to slightly glassy surface; visible image is insufficient to confirm minerals or texture. Typical basalt hardness is about 6 on Mohs scale, with no prominent cleavage and specific gravity around 2.8–3.0.
Formation & geological history
If basalt, it formed when mafic lava cooled rapidly at or near Earth’s surface; its age and precise origin cannot be determined from the photograph.
Uses & applications
Basalt is used as crushed aggregate, road stone, construction material, and occasionally for decorative objects or specimen collections.
Geological facts
Basalt is among Earth’s most abundant volcanic rocks and also forms much of the ocean floor.
Field identification & locations
The rounded shape may reflect water-wearing or handling. A fresh broken surface showing fine grains and no fizz with dilute acid would support basalt identification; the pictured specimen alone is not definitive.
