igneous
Basalt
Basalt (Mafic Extrusive)
Hardness: 6 (Mohs); Color: Dark gray to black; Luster: Dull to earthy; Crystal Structure: Aphanitic (fine-grained); Specific Gravity: 2.8-3.0
- Hardness
- 6 (Mohs)
- Color
- Dark gray to black
- Luster
- Dull to earthy
Identified More igneous →
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Physical properties
Hardness: 6 (Mohs); Color: Dark gray to black; Luster: Dull to earthy; Crystal Structure: Aphanitic (fine-grained); 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.
Uses & applications
Commonly used as crushed stone for construction projects, road base, concrete aggregate, railroad ballast, and sometimes in decorative landscaping.
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 found on the Moon and Mars.
Field identification & locations
Identify by its weight (dense), dark color, and fine-grained texture. Found worldwide in volcanic regions and oceanic crustal areas.
