igneous
Basalt
Extrusive igneous rock
Hardness: 6 on Mohs scale, Color: Dark grey to black, Luster: Dull to sub-glossy, Crystal structure: Aphanitic (fine-grained) with visible vesicles or mineral phenocrysts, Cleavage: None, Specific gravity: 2.8 to 3.0
Identified More igneous →
Explore Basalt in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6 on Mohs scale, Color: Dark grey to black, Luster: Dull to sub-glossy, Crystal structure: Aphanitic (fine-grained) with visible vesicles or mineral phenocrysts, Cleavage: None, Specific gravity: 2.8 to 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, primarily through volcanic eruptions.
Uses & applications
Used in construction, road aggregate, railroad ballast, stone wool insulation, and occasionally as dimension stone or in sculptures.
Geological facts
Basalt is the most common rock type in the Earth's crust underlying the ocean basins, and is also found abundantly on the Moon, Mars, and Venus.
Field identification & locations
Easily identified by its dark, fine-grained matrix, often containing visible gas cavities (vesicles) or small crystals of plagioclase and pyroxene. Found worldwide in volcanic provinces and oceanic crust.
