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, and 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, 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 as crushed aggregate for roads, railroad ballast, and in the production of stone wool insulation.
Geological facts
Basalt is the most common rock type in the Earth's crustal portions underlying the ocean basins and forms massive volcanic formations like the Giant's Causeway.
Field identification & locations
Identify in the field by its dark, dense, fine-grained matrix, often found in volcanic regions and ancient lava flows.
