igneous
Basalt
Extrusive mafic igneous rock
Hardness: 6.0; Color: Dark grey to black; Luster: Dull/earthy; Structure: Fine-grained/aphanitic; Specific gravity: 2.8 - 3.0
- Hardness
- 6
- Color
- Dark grey to black
- Luster
- Dull/earthy
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Physical properties
Hardness: 6.0; Color: Dark grey to black; Luster: Dull/earthy; 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 exposed at or very near the surface of a terrestrial planet or moon. Most basalt on Earth is formed at mid-ocean ridges.
Uses & applications
Used primarily in construction (crushed stone for road base, concrete aggregate, railroad ballast), and as a raw material for stone wool insulation.
Geological facts
Basalt is the most common rock on Earth's surface, making up most of the ocean floor and much of the surfaces of the Moon, Mars, and Venus.
Field identification & locations
Identify by its dark color, fine-grained texture (crystals are too small to see with the naked eye), and high density. Commonly found in volcanic fields and oceanic crust areas.
