igneous
Basalt
Extrusive Igneous Rock
Hardness of 6 on the Mohs scale, dark gray to black in color, dull to sub-withering luster, aphanitic (fine-grained) crystal structure, 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-withering luster, aphanitic (fine-grained) crystal structure, 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, railroad ballast, and 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 it is also abundantly found on the Moon and Mars.
Field identification & locations
Identified by its dark color and fine-grained texture where individual crystals are not visible to the naked eye. Found worldwide in volcanic provinces and oceanic ridges.
