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), often vesicular with small gas cavities, Specific Gravity: 2.8 - 3.0
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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), often vesicular with small gas cavities, 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 Earth's surface, often from volcanic eruptions.
Uses & applications
Used in construction as crushed aggregate for roads, railroad ballast, and in the production of rock wool insulation.
Geological facts
Basalt is the most common rock type in the Earth's crust underlying the ocean basins, and it is also found extensively on the Moon and Mars.
Field identification & locations
Identify by its dark, fine-grained appearance and sometimes vesicular (bubbly) texture. Common worldwide in volcanic provinces and oceanic crust.
