igneous
Basalt
Extrusive igneous rock
Hardness: 6 on Mohs scale; Color: Dark gray to black; Luster: Dull to sub-vitreous; Texture: Aphanitic (fine-grained), often vesicular.
- Hardness
- 6 on Mohs scale
- Color
- Dark gray to black
- Luster
- Dull to sub-vitreous
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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), often vesicular.
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.
Uses & applications
Used in construction (crushed stone for road base, concrete aggregate), railroad ballast, and manufacturing of stone wool insulation.
Geological facts
Basalt is the most common rock type in the Earth's crust underlying the world's oceans, and it also forms extensive volcanic provinces on the Moon and Mars.
Field identification & locations
Identify by its dark, fine-grained appearance, often heavy weight, and common occurrence as dark volcanic pebbles or lava flows.
