igneous
Basalt
Extrusive Igneous Rock
Hardness: 6 on Mohs scale; Color: Dark gray to black; Luster: Dull to sub-vitreous; Texture: Aphanitic (fine-grained), sometimes vesicular; 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; Texture: Aphanitic (fine-grained), sometimes vesicular; Specific Gravity: 2.8 - 3.0
Formation & geological history
Formed from the rapid cooling of low-viscosity basaltic lava exposed at or very near the surface of a planet or moon. Typically associated with volcanic eruptions, mid-ocean ridges, and hotspot islands.
Uses & applications
Used in construction as crushed stone for road base, concrete aggregate, and railroad ballast, as well as in manufacturing stone wool insulation.
Geological facts
Basalt is the most common rock type in the Earth's crust, making up most of the oceanic crust and forming massive geological features like the Columbia River Basalt Group and the Giant's Causeway in Northern Ireland.
Field identification & locations
Found abundantly worldwide in volcanic regions, oceanic islands, and continental flood basalt provinces. Identify by its dark color, heavy weight, and fine-grained texture where individual crystals are generally not visible to the naked eye.
