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), sometimes vesicular. Specific gravity: 2.8 - 3.0
- Hardness
- 6 on the Mohs scale
- Color
- Dark gray to black
- Luster
- Dull to sub-vitreous
Identified More igneous →
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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), sometimes vesicular. Specific gravity: 2.8 - 3.0
Formation & geological history
Formed from the rapid cooling of low-viscosity lava rich in magnesium and iron exposed at or very near the surface of a planet or moon. Geologically young to ancient.
Uses & applications
Used in construction, road aggregate, railroad ballast, production of stone wool insulation, and manufacturing basalt fiber.
Geological facts
Basalt is the most common rock type in the Earth's crust underlying the ocean basins, and it is also commonly found on the Moon and Mars.
Field identification & locations
Identify by its dark, fine-grained groundmass, sometimes containing small phenocrysts of olivine or plagioclase, and vesicular cavities. Found globally in volcanic provinces and oceanic ridges.
