igneous
Basalt
Extrusive Igneous Rock
Hardness: 6 on Mohs scale. Color: Dark grey to black. Luster: Dull to sub-vitreous. Crystal structure: Aphanitic (fine-grained), often containing phenocrysts. Specific gravity: 2.8 - 3.0.
- Hardness
- 6 on Mohs scale
- Color
- Dark grey to black
- Luster
- Dull to sub-vitreous
Identified More igneous →
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Physical properties
Hardness: 6 on Mohs scale. Color: Dark grey 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 stone in road base, concrete aggregate), railroad ballast, and in the production of stone wool insulation.
Geological facts
Basalt is the most common rock type in the Earth's crust underlying the world's oceans. It is also found extensively on the Moon (forming the lunar maria) and Mars.
Field identification & locations
Identified by its dark color, fine-grained texture, and high density. Commonly found in volcanic regions, oceanic islands, and continental flood basalt provinces.
