igneous
Basalt
Basalt (Aphanitic Mafic Igneous Rock)
Hardness: 6 (Mohs scale); Color: dark grey to black; Luster: dull to earthy; Crystal structure: fine-grained (aphanitic), sometimes vesicular; Specific gravity: 2.8–3.0
- Hardness
- 6 (Mohs scale)
- Color
- dark grey to black
- Luster
- dull to earthy
Identified More igneous →
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Physical properties
Hardness: 6 (Mohs scale); Color: dark grey to black; Luster: dull to earthy; Crystal structure: fine-grained (aphanitic), sometimes vesicular; 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
Extensively used in construction for aggregate, road base, railroad ballast, and high-quality concrete. Can also be used as a dimension stone for flooring or monuments.
Geological facts
Basalt is the most common rock type in the Earth's crust, covering most of the ocean floor. It is also found on the Moon, Mars, and Venus.
Field identification & locations
Look for a heavy, dark-colored, fine-grained rock. It often breaks into angular pieces. Widely found in volcanic regions such as the Pacific Northwest, Hawaii, and Iceland.
