igneous
Basalt Pebble
Basalt (SiO2 range 45-52%)
Hardness: 6 on Mohs scale; Color: Dark grey to black with slight brownish weathering; Luster: Dull to sub-vitreous; Texture: Fine-grained (aphanitic), stream-rounded pebble.
- Hardness
- 6 on Mohs scale
- Color
- Dark grey to black with slight brownish weathering
- Luster
- Dull to sub-vitreous
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Physical properties
Hardness: 6 on Mohs scale; Color: Dark grey to black with slight brownish weathering; Luster: Dull to sub-vitreous; Texture: Fine-grained (aphanitic), stream-rounded pebble.
Formation & geological history
Formed by the rapid cooling of low-viscosity magnesium-rich and iron-rich lava at or near the surface of Earth. Frequently rounded into pebbles via water erosion in riverbeds or beaches.
Uses & applications
Commonly used as crushed stone in construction, road base, asphalt concrete, and ballast. Also popular for decorative landscaping and aquariums.
Geological facts
Basalt is the most common rock type in the Earth's crust, making up most of the oceanic crust as well as vast volcanic plateaus.
Field identification & locations
Identified by its dark color, heavy feel relative to size, fine-grained texture, and smooth, rounded water-worn exterior when found as a river stone.
