igneous
Basalt
Basalt (Mafic Extrusive Igneous Rock)
Hardness: 6 on the Mohs scale; Color: Dark grey, brownish-black, to black; Luster: Dull to earthy; Texture: Aphanitic (fine-grained), dense; Specific Gravity: 2.8 - 3.0
- Hardness
- 6 on the Mohs scale
- Color
- Dark grey, brownish-black, to black
- Luster
- Dull to earthy
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Physical properties
Hardness: 6 on the Mohs scale; Color: Dark grey, brownish-black, to black; Luster: Dull to earthy; Texture: Aphanitic (fine-grained), dense; 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. Commonly found in volcanic regions, oceanic crust, and continental flood basalt provinces.
Uses & applications
Used extensively in construction as crushed stone, aggregate for concrete and asphalt, railroad ballast, and dimension stone.
Geological facts
Basalt is the most common rock type in the Earth's crust, making up most of the ocean floors. It is also abundant on the Moon and Mars.
Field identification & locations
Identify by its dark color, heavy weight for its size, fine grain, and dull, non-glassy appearance. Found worldwide in volcanic areas.
