igneous
Basalt
Basalt
Hardness: 6.0; Color: Dark grey to black; Luster: Dull to vitreous; Crystal structure: Aphanitic (fine-grained); Cleavage: None; Specific gravity: 2.8 - 3.0
- Hardness
- 6
- Color
- Dark grey to black
- Luster
- Dull to vitreous
Identified More igneous →
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Physical properties
Hardness: 6.0; Color: Dark grey to black; Luster: Dull to vitreous; 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 exposed at or very near the Earth's surface. Common in oceanic crust and volcanic islands.
Uses & applications
Used primarily in construction for road base, concrete aggregate, asphalt pavement aggregate, railroad ballast, and high-quality stone tiles.
Geological facts
Basalt is the most common rock type in the 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 in the field by its dark color, heavy weight (relative to its size), and lack of visible crystals. Commonly found in volcanic regions, near oceanic ridges, and river beds near volcanic plains.
