igneous
Basalt
Basalt (Mafic Extrusive)
Hardness: 6 (Mohs scale), Color: Dark gray to black, Luster: Dull or earthy, Crystal Structure: Aphanitic (fine-grained), Cleavage: None, Specific Gravity: 2.8–3.0
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Physical properties
Hardness: 6 (Mohs scale), Color: Dark gray to black, Luster: Dull or earthy, Crystal Structure: Aphanitic (fine-grained), Cleavage: None, Specific Gravity: 2.8–3.0
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at the surface of a terrestrial planet or a moon. It is the most common rock in Earth's crust, primarily making up the ocean floors.
Uses & applications
Widely used in construction for road base, concrete aggregate, railroad ballast, and dimension stone for pavers or countertops.
Geological facts
Basalt is the most abundant rock in the solar system, covering most of the lunar maria on the Moon and much of the surface of Mars and Venus.
Field identification & locations
Identify by its heavy weight (high density), dark color, and lack of visible crystals. It is commonly found near volcanic sites and ocean ridges.
