igneous
Basalt Pebble (Beach Pebble)
Mafic Volcanic Rock (Basalt)
Hardness: 6 on Mohs scale. Color: Dark brown to dark gray or black when wet. Luster: Dull to sub-vitreous. Grain Size: Aphanitic (fine-grained), heavily rounded and smoothed by wave action.
- Hardness
- 6 on Mohs scale
- Color
- Dark brown to dark gray or black when wet
- Luster
- Dull to sub-vitreous
Identified More igneous →
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Physical properties
Hardness: 6 on Mohs scale. Color: Dark brown to dark gray or black when wet. Luster: Dull to sub-vitreous. Grain Size: Aphanitic (fine-grained), heavily rounded and smoothed by wave action.
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at or very near the Earth's surface. Later eroded and smoothed into a rounded pebble by wave action along a coastline.
Uses & applications
Commonly collected as beach souvenirs, used in decorative landscaping, aquarium decor, and lapidary arts.
Geological facts
Wave action acts as a natural rock tumbler, rounding sharp basalt fragments over decades to centuries into perfectly smooth beach stones.
Field identification & locations
Look for dark, dense, fine-grained pebbles along ocean beaches near coastal volcanic outcrops or ocean basalt formations. Very heavy for its size.
