igneous
Basalt
Extrusive Igneous Rock
Hardness of 6 on the Mohs scale, typically dark gray to black in color, fine-grained aphanitic texture, dull luster, specific gravity around 2.8 - 3.0
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Physical properties
Hardness of 6 on the Mohs scale, typically dark gray to black in color, fine-grained aphanitic texture, dull luster, specific gravity around 2.8 - 3.0
Formation & geological history
Formed from the rapid cooling of low-viscosity lava rich in magnesium and iron 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 the production of basalt fiber
Geological facts
Basalt is the most common rock type in the Earth's crust underlying the world's oceans and also makes up significant portions of the lunar maria and volcanic regions on Mars
Field identification & locations
Easily identified by its dark color and very fine-grained texture where individual crystals are not visible to the naked eye; commonly found in volcanic provinces worldwide
