igneous
Basalt
Mafic extrusive igneous rock
AI-generated identification · may be incorrectHardness of 6 on the Mohs scale, dark gray to black color, dull to sub-aphanitic luster, fine-grained microcrystalline structure, and high specific gravity around 2.9 to 3.0.
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Physical properties
Hardness of 6 on the Mohs scale, dark gray to black color, dull to sub-aphanitic luster, fine-grained microcrystalline structure, and high specific gravity around 2.9 to 3.0.
Formation & geological history
Formed from the rapid cooling of low-viscosity, magnesium- and iron-rich lava flows at the Earth's surface, commonly associated with volcanic hotspots and oceanic divergent boundaries.
Uses & applications
Widely used in construction as crushed aggregate for roads, railroad ballast, building foundations, and in the production of stone wool insulation.
Geological facts
Basalt is the most common rock type in the Earth's crust underlying the world's ocean basins and forms famous geological formations like the Giant's Causeway in Northern Ireland.
Field identification & locations
Easily identified by its dark, heavy, fine-grained appearance, often found in volcanic regions, and primarily of industrial rather than high-end collector value.
