igneous
Basalt
Extrusive Igneous Rock
Hardness of 6 on the Mohs scale, dark gray to black in color, aphanitic (fine-grained) crystal structure, dull to sub-metallic luster, 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, aphanitic (fine-grained) crystal structure, dull to sub-metallic luster, specific gravity around 2.8 - 3.0
Formation & geological history
Formed from the rapid cooling of low-viscosity basaltic lava exposed at or very near the Earth's surface, typically originating from volcanic eruptions
Uses & applications
Commonly used in construction as crushed stone for road bases, concrete aggregate, 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 world's ocean basins and also forms major geological features on the Moon and Mars
Field identification & locations
Identified by its dark, fine-grained appearance, often vesicular due to trapped gas bubbles; found worldwide in volcanic provinces and oceanic crust
