igneous
Basalt
Extrusive Igneous Rock
Hardness: 6 on the Mohs scale, Color: Dark grey to black, Luster: Dull to sub-vitreous, Crystal structure: Aphanitic (fine-grained), specific gravity: 2.8 - 3.0
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Physical properties
Hardness: 6 on the Mohs scale, Color: Dark grey to black, Luster: Dull to sub-vitreous, Crystal structure: Aphanitic (fine-grained), specific gravity: 2.8 - 3.0
Formation & geological history
Formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the surface of a rocky planet or moon.
Uses & applications
Used in construction as crushed stone for road bases, concrete aggregate, 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 found extensively on the Moon and Mars.
Field identification & locations
Identify by its dark, fine-grained, heavy nature, often showing tiny vesicles (gas bubbles) or small mineral phenocrysts.
