igneous
Basalt
Extrusive Igneous Rock (Mafic)
Hardness: 6 on Mohs scale, Color: Dark grey to black, Luster: Dull to sub-glossy, Texture: Aphanitic (fine-grained) often with vesicular cavities
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Physical properties
Hardness: 6 on Mohs scale, Color: Dark grey to black, Luster: Dull to sub-glossy, Texture: Aphanitic (fine-grained) often with vesicular cavities
Formation & geological history
Formed from the rapid cooling of low-viscosity lava rich in magnesium and iron exposed at or very near the Earth's surface.
Uses & applications
Used extensively in construction (crushed stone for road bases, concrete aggregate), railroad ballast, and sometimes for decorative stone or tiles.
Geological facts
Basalt is the most common rock type in the Earth's crust underlying the world's ocean basins and forming massive geological features like the Columbia River Basalt Group.
Field identification & locations
Identified by its dark color, fine-grained or vesicular (holey) texture, and high density. Commonly found globally in volcanic regions and oceanic crusts.
