igneous
Basalt
Extrusive Igneous Rock
Hardness of 6 on Mohs scale, dark gray to black in color, dull to sub-aphanitic luster, fine-grained aphanitic or porphyritic texture, specific gravity around 2.8-3.0.
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Physical properties
Hardness of 6 on Mohs scale, dark gray to black in color, dull to sub-aphanitic luster, fine-grained aphanitic or porphyritic texture, 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
Used in construction as crushed stone for road bases, concrete aggregate, and railroad ballast, as well as in the production of basalt fiber.
Geological facts
Basalt is the most common rock type in the Earth's crust underlying the world's ocean basins and forms massive features like the Columbia River Plateau and the Giant's Causeway.
Field identification & locations
Found abundantly worldwide in volcanic regions, oceanic crust, and basaltic traps. Easily identified by its dark color, heavy feel, and very fine-grained texture.
