igneous
Basalt
Mafic extrusive igneous rock
AI-generated identification · may be incorrectHardness of 6 on the Mohs scale, dark black or gray color, dull to sub-aphanitic luster, and a fine-grained aphanitic crystal structure.
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Physical properties
Hardness of 6 on the Mohs scale, dark black or gray color, dull to sub-aphanitic luster, and a fine-grained aphanitic crystal structure.
Formation & geological history
Formed by the rapid cooling of low-viscosity, magnesium- and iron-rich 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 crust, primarily making up oceanic crust as well as major extraterrestrial volcanic provinces on the Moon and Mars.
Field identification & locations
Identify in the field by its dark, heavy, fine-grained appearance, often found in volcanic regions, oceanic islands, and ancient lava flows.
