igneous
Basalt
Extrusive igneous rock
AI-generated identification · may be incorrectHardness 6 on Mohs scale; dark gray to black color; dull or aphanitic luster; fine-grained crystal structure; specific gravity 2.8-3.0.
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Physical properties
Hardness 6 on Mohs scale; dark gray to black color; dull or aphanitic luster; fine-grained crystal structure; 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 surface of a planet or moon.
Uses & applications
Used extensively 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 world's ocean basins and forms massive geological features like the Giant's Causeway.
Field identification & locations
Identify by its dark, fine-grained groundmass, sometimes containing small visible olivine or pyroxene phenocrysts; found globally in volcanic provinces.
