igneous
Basalt
Basalt (Mafic Extrusive)
Hardness: 6.0 on Mohs scale; Color: Dark grey to black; Luster: Dull to sub-metallic; Structure: Fine-grained/aphanitic; Specific Gravity: 2.8–3.0
- Hardness
- 6
- Color
- Dark grey to black
- Luster
- Dull to sub-metallic
Identified More igneous →
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Physical properties
Hardness: 6.0 on Mohs scale; Color: Dark grey to black; Luster: Dull to sub-metallic; Structure: Fine-grained/aphanitic; 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 surface of a terrestrial planet or a moon. Most common rock in Earth's crust.
Uses & applications
Used in construction as crushed stone for road base, railroad ballast, and concrete aggregate. Also used in high-temperature insulation (stone wool).
Geological facts
Basalt is the most common rock type on the seafloor and covers most of the ocean basins. It is also found on the Moon and Mars.
Field identification & locations
Identify by its dark color, heavy weight (density), and fine-grained texture. It often shows vesiculation (small holes) if gas was trapped during cooling.
