igneous
Water-worn fine-grained volcanic pebble, likely basalt
Basalt (tentative identification; fine-grained mafic volcanic rock)
AI-generated identification · may be incorrectDark gray-green, smooth and rounded by water; fine-grained with tiny pale mineral grains or spots. Basalt is typically Mohs 5–6, with a dull to weakly vitreous luster and no obvious cleavage; exact composition and density cannot be confirmed from the photo.
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Physical properties
Dark gray-green, smooth and rounded by water; fine-grained with tiny pale mineral grains or spots. Basalt is typically Mohs 5–6, with a dull to weakly vitreous luster and no obvious cleavage; exact composition and density cannot be confirmed from the photo.
Formation & geological history
Likely formed when basaltic lava cooled rapidly at or near Earth’s surface, then became rounded through transport in water. Its geological age cannot be determined from appearance alone.
Uses & applications
Basalt is widely used as crushed aggregate, road stone, and construction material; this small pebble is mainly suitable for collecting or decoration.
Geological facts
Basalt commonly contains plagioclase and pyroxene, sometimes olivine; lighter specks may be mineral grains or weathering features.
Field identification & locations
The uniform fine texture and rounded shape suggest a stream- or beach-worn volcanic pebble. Basalt is common worldwide, but identification is best confirmed by examining a fresh surface and mineral composition.
