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 distinct cleavage, and has a specific gravity around 2.8-3.0.
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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 distinct cleavage, and has a specific gravity around 2.8-3.0.
Formation & geological history
Formed from the rapid cooling of low-viscosity lava rich in iron and magnesium exposed at or very near the surface of a planet or moon.
Uses & applications
Commonly used in construction as crushed aggregate for road bases, concrete production, asphalt pavements, and railroad ballast, as well as in manufacturing stone wool insulation.
Geological facts
Basalt is the most common rock type in the Earth's crust underlying the ocean basins, and it is also found abundantly on the Moon, Mars, and Venus.
Field identification & locations
Identified easily by its dark, dense, fine-grained appearance, often found in volcanic regions, oceanic islands, and continental flood basalt provinces worldwide.
