igneous
Basalt
Extrusive Igneous Rock
Hardness: 6 on the Mohs scale, Color: Dark grey to black, Luster: Dull to sub-vitreous, Crystal structure: Aphanitic (fine-grained), often containing tiny plagioclase feldspar and pyroxene phenocrysts, Specific gravity: 2.8 - 3.0
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Physical properties
Hardness: 6 on the Mohs scale, Color: Dark grey to black, Luster: Dull to sub-vitreous, Crystal structure: Aphanitic (fine-grained), often containing tiny plagioclase feldspar and pyroxene phenocrysts, Specific gravity: 2.8 - 3.0
Formation & geological history
Formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the surface of a planet or moon, primarily through volcanic eruptions.
Uses & applications
Used extensively 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 ocean basins, and it is also the most abundant volcanic rock on the terrestrial planets, including the Moon and Mars.
Field identification & locations
Identify in the field by its dark, fine-grained, heavy appearance; commonly found in volcanic regions, oceanic islands, and continental flood basalt provinces.
