igneous
Basalt
Extrusive Igneous Rock
Hardness: 6 on the Mohs scale. Color: Dark gray to black. Luster: Dull to sub-vitreous. Crystal structure: Aphanitic (fine-grained), often containing microscopic crystals or volcanic glass. Specific gravity: 2.8 - 3.0.
- Hardness
- 6 on the Mohs scale
- Color
- Dark gray to black
- Luster
- Dull to sub-vitreous
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Physical properties
Hardness: 6 on the Mohs scale. Color: Dark gray to black. Luster: Dull to sub-vitreous. Crystal structure: Aphanitic (fine-grained), often containing microscopic crystals or volcanic glass. Specific gravity: 2.8 - 3.0.
Formation & geological history
Formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the surface of a planet or moon. Geological age can range from recent volcanic eruptions to billions of years old.
Uses & applications
Used extensively in construction (crushed stone for road base, concrete aggregate), railroad ballast, and in manufacturing stone wool insulation.
Geological facts
Basalt is the most common rock type in the Earth's crust underlying the ocean basins, and it is also the most common volcanic rock on terrestrial planets like Earth, Mars, and Venus.
Field identification & locations
Identify in the field by its dark color, heavy feel relative to its size, and fine-grained texture. Commonly found in volcanic regions, oceanic islands, and continental flood basalt provinces worldwide.
