igneous
Basalt
Extrusive Igneous Rock
Hardness: 6 on Mohs scale; Color: Dark gray to black; Luster: Dull to sub-vitreous; Crystal structure: Aphanitic (fine-grained), sometimes porphyritic; Specific gravity: 2.8 - 3.0
- Hardness
- 6 on Mohs scale
- Color
- Dark gray to black
- Luster
- Dull to sub-vitreous
Identified More igneous →
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Physical properties
Hardness: 6 on Mohs scale; Color: Dark gray to black; Luster: Dull to sub-vitreous; Crystal structure: Aphanitic (fine-grained), sometimes porphyritic; 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 widespread across Earth's oceanic crust.
Uses & applications
Used extensively in construction as crushed aggregate for roads, building foundations, 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 ocean basins, and it is also abundantly found on the Moon (forming the lunar maria) and Mars.
Field identification & locations
Identify in the field by its dark color, fine-grained or vesicular texture, and heavy weight relative to its size. Commonly found in volcanic regions, ancient lava flows, and ophiolite complexes.
