igneous
Basalt River Pebble
Aphanitic Mafic Volcanic Rock (Basalt)
Hardness: 6 (Mohs scale); Color: Dark grey to black with faint iron staining; Luster: Dull to sub-metallic; Structure: Fine-grained/aphanitic; Specific Gravity: 2.8-3.0
- Hardness
- 6 (Mohs scale)
- Color
- Dark grey to black with faint iron staining
- Luster
- Dull to sub-metallic
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Physical properties
Hardness: 6 (Mohs scale); Color: Dark grey to black with faint iron staining; Luster: Dull to sub-metallic; Structure: Fine-grained/aphanitic; Specific Gravity: 2.8-3.0
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at or near the Earth's surface. This specimen has been rounded and smoothed by fluvial erosion in a river or coastal environment.
Uses & applications
Commonly used as aggregate for construction, road base, and landscape decoration. Polished versions are used for massage stones or aquarium decor.
Geological facts
Basalt is the most common rock in Earth's crust and makes up most of the ocean floor. It is also found extensively on the Moon and Mars.
Field identification & locations
Identify by its weight (denser than most light rocks), dark color, and fine-grained texture. Commonly found in volcanic regions and riverbeds.
