igneous
Basalt
Basalt (Extrusive Mafic Igneous)
Hardness: 6 (Mohs scale), Color: Dark grey to black, Luster: Dull/Earthy, Crystal structure: Fine-grained/Aphanitic, Specific Gravity: 2.8 - 3.0
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Physical properties
Hardness: 6 (Mohs scale), Color: Dark grey to black, Luster: Dull/Earthy, Crystal structure: Fine-grained/Aphanitic, Specific Gravity: 2.8 - 3.0
Formation & geological history
Formed from the rapid cooling of low-viscosity magnesium-rich and iron-rich lava at or near the Earth's surface. Can be found in oceanic crust and continental flood lava flows.
Uses & applications
Extensively used in construction for road base, concrete aggregate, railroad ballast, and high-quality floor tiles or statues.
Geological facts
Basalt is the most common rock on Earth's surface; it also makes up most of the surface of the Moon, Mars, and Venus.
Field identification & locations
Identified by its dark color, heavy weight, and lack of visible individual crystals. Commonly found in volcanic regions such as the Pacific Northwest, Hawaii, and Iceland.
