igneous
Basalt
Basalt (Extrusive Igneous Rock)
Hardness: 6 (Mohs scale), Color: Dark grey to black, Luster: Dull/Matte, 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/Matte, Structure: Fine-grained (aphanitic), Specific Gravity: 2.8–3.0
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at or very near the Earth's surface. Common in oceanic crust and lava flows.
Uses & applications
Used extensively in construction as crushed stone for road base, railroad ballast, and concrete aggregate. Sometimes used in stone carvings or as floor tiles.
Geological facts
Basalt is the most common volcanic rock on Earth and also makes up most of the surface of the Moon, Mars, and Venus.
Field identification & locations
Identified by its dark color, heavy weight, and fine-grained texture. Often found in volcanic regions, oceanic islands like Hawaii, and massive flood basalt provinces.
