igneous
Basalt
Aphanitic Mafic Igneous Rock
Hardness: 6 (Mohs scale), Color: Dark grey to black, Luster: Dull/earthy to sub-metallic, Texture: Aphanitic (fine-grained), Specific Gravity: 2.8–3.0
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Physical properties
Hardness: 6 (Mohs scale), Color: Dark grey to black, Luster: Dull/earthy to sub-metallic, Texture: Aphanitic (fine-grained), 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 at mid-ocean ridges and hotspots.
Uses & applications
Extensively used in construction as aggregate, road base, concrete, and railroad ballast. Also used in stone carvings and high-performance insulation (rock wool).
Geological facts
Basalt is the most common rock type in Earth's crust and makes up most of the ocean floor. It is also common on the Moon, Mars, and Venus.
Field identification & locations
Identify by its dark color, heavy weight (relative to size), and occasionally visible tiny green olivine crystals. Found in volcanic regions like Hawaii or the Pacific Northwest.
