igneous
Basalt
Extrusive Igneous Rock
Hardness: 6 on the Mohs scale. Color: Dark gray to black. Luster: Dull to sub-vitreous. Crystal structure: Aphanitic (fine-grained), often containing phenocrysts. Specific gravity: 2.8 - 3.0.
- Hardness
- 6 on the Mohs scale
- Color
- Dark gray to black
- Luster
- Dull to sub-vitreous
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Physical properties
Hardness: 6 on the Mohs scale. Color: Dark gray to black. Luster: Dull to sub-vitreous. Crystal structure: Aphanitic (fine-grained), often containing phenocrysts. Specific gravity: 2.8 - 3.0.
Formation & geological history
Formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the surface of a planet or moon.
Uses & applications
Used in construction as crushed aggregate, building stone, cobblestones, and in the manufacturing of rock wool insulation.
Geological facts
Basalt is the most common rock type in the Earth's crust underlying the ocean basins, and is also found abundantly on the Moon, Mars, and Venus.
Field identification & locations
Identify by its dark, fine-grained, heavy texture. Common worldwide in volcanic regions, oceanic crust, and flood basalt provinces like the Columbia River Plateau.
