igneous
Basalt
Extrusive Igneous Rock
Hardness of 6 on the Mohs scale, dark gray to black in color, dull to sub-with a fine-grained aphanitic crystal structure, lacks prominent cleavage, specific gravity ranges from 2.8 to 3.0
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Physical properties
Hardness of 6 on the Mohs scale, dark gray to black in color, dull to sub-with a fine-grained aphanitic crystal structure, lacks prominent cleavage, specific gravity ranges from 2.8 to 3.0
Formation & geological history
Formed from the rapid cooling of low-viscosity basaltic lava exposed at or very near the surface of a planet or moon, typically originating from volcanic hotspots, mid-ocean ridges, or rift valleys.
Uses & applications
Commonly used in construction as crushed stone for road bases, concrete aggregate, and railroad ballast, as well as in the production of rock wool insulation and stone countertops.
Geological facts
Basalt is the most common rock type in the Earth's crust underlying the ocean basins, and it is also the primary rock found on the surface of the Moon (forming the lunar maria) and Mars.
Field identification & locations
Identified in the field by its dark, uniform fine-grained appearance, high density, and occasional vesicular textures caused by trapped gas bubbles. Found worldwide in volcanic provinces.
