igneous
Basalt
Extrusive igneous rock
AI-generated identification · may be incorrectHardness 6 on Mohs scale, dark gray to black color, dull luster, fine-grained aphanitic crystal structure, specific gravity around 2.9.
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Physical properties
Hardness 6 on Mohs scale, dark gray to black color, dull luster, fine-grained aphanitic crystal structure, specific gravity around 2.9.
Formation & geological history
Formed from the rapid cooling of low-viscosity, magnesium- and iron-rich lava flows at the Earth's surface.
Uses & applications
Used in construction as crushed stone for road aggregates, railroad ballast, and in the manufacturing of rock wool insulation.
Geological facts
Basalt is the most common rock type in the Earth's crustal portions underlying the ocean basins and forms the famous columns of the Giant's Causeway.
Field identification & locations
Identify by its dense, dark, fine-grained matrix often showing microscopic phenocrysts; commonly found in volcanic regions worldwide.
