igneous
Basalt
Extrusive mafic igneous rock
AI-generated identification · may be incorrectHardness 6 on Mohs scale, dark gray to black color, submetallic to dull luster, fine-grained aphanitic texture with microscopic crystals.
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Physical properties
Hardness 6 on Mohs scale, dark gray to black color, submetallic to dull luster, fine-grained aphanitic texture with microscopic crystals.
Formation & geological history
Formed by the rapid cooling of low-viscosity, iron- and magnesium-rich lava flows exposed at or very near the Earth's surface.
Uses & applications
Used extensively in construction as crushed aggregate for roads, railroad ballast, and in the production of rock wool insulation.
Geological facts
Basalt is the most common rock type in the Earth's oceanic crust and also makes up the vast dark maria on Earth's Moon.
Field identification & locations
Identify by its dark, heavy, fine-grained appearance with occasional tiny visible phenocrysts; found worldwide in volcanic provinces.
