igneous
Basalt
Extrusive Igneous Rock
AI-generated identification · may be incorrectHardness of 6 on Mohs scale, dark gray to black color, dull luster, aphanitic crystal structure with microscopic grains, and specific gravity around 2.9.
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Physical properties
Hardness of 6 on Mohs scale, dark gray to black color, dull luster, aphanitic crystal structure with microscopic grains, and specific gravity around 2.9.
Formation & geological history
Formed from the rapid cooling of low-viscosity basaltic lava exposed at or very near the Earth's surface.
Uses & applications
Widely used in construction for road base, aggregate in concrete, asphalt paving, and producing dimension stone.
Geological facts
Basalt is the most common rock type in the Earth's crust underlying the oceans and makes up most of the Hawaiian islands.
Field identification & locations
Identified by its fine-grained dark matrix, often containing small visible phenocrysts of olivine or plagioclase; found globally in volcanic regions.
