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), 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), 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.
Uses & applications
Used in construction, road 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 also forms major geological features like the Giant's Causeway in Northern Ireland.
Field identification & locations
Identify by its dark, fine-grained appearance, often containing small vesicles or crystals of olivine and plagioclase. Found worldwide in volcanic provinces.
