igneous
Basalt
Basalt
Hardness: 5-6 (Mohs scale); Color: Dark gray to black; Luster: Dull/earthy; Crystal structure: Aphanitic (fine-grained); Specific gravity: 2.8-3.0
- Hardness
- 5-6 (Mohs scale)
- Color
- Dark gray to black
- Luster
- Dull/earthy
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Physical properties
Hardness: 5-6 (Mohs scale); Color: Dark gray to black; Luster: Dull/earthy; Crystal structure: Aphanitic (fine-grained); Specific gravity: 2.8-3.0
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava exposed at or very near the surface of a terrestrial planet or a moon.
Uses & applications
Crushed stone for road base, concrete aggregate, railroad ballast, and sometimes for floor tiles or monument carving.
Geological facts
Basalt is the most common volcanic rock on Earth, covering much of the ocean floors. It is also found on the Moon, Mars, and Venus.
Field identification & locations
Identify by its dark color, heavy weight compared to similar looking rocks, and fine-grained texture. Found globally in volcanic regions like Hawaii, Iceland, and the Pacific Northwest.
