igneous
Basalt Pebble
Basalt
Hardness: 6-7 on the Mohs scale; Color: Dark grey to blackish-green; Luster: Dull to sub-vitreous; Crystal structure: Aphanitic (fine-grained); Cleavage: None; Specific Gravity: 2.8-3.0
- Hardness
- 6-7 on the Mohs scale
- Color
- Dark grey to blackish-green
- Luster
- Dull to sub-vitreous
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Physical properties
Hardness: 6-7 on the Mohs scale; Color: Dark grey to blackish-green; Luster: Dull to sub-vitreous; Crystal structure: Aphanitic (fine-grained); Cleavage: None; Specific Gravity: 2.8-3.0
Formation & geological history
Formed from the rapid cooling of low-viscosity magnesium-rich and iron-rich lava exposed at or very near the surface of a terrestrial planet or moon. Subsequently rounded and smoothed by water or wind erosion.
Uses & applications
Crushed basalt is used in construction as aggregate, in asphalt, railroad ballast, and ground cover. Stream-rounded pebbles are often used in landscaping and aquariums.
Geological facts
Basalt is the most common rock type in the Earth's crust, forming most of the oceanic crust. It is also found extensively on the Moon, Mars, and Venus.
Field identification & locations
Identified by its dark color, heavy weight relative to size, fine-grained smooth texture, and well-rounded pebble shape from stream transport. Commonly found along riverbeds, beaches, and volcanic terrains.
