igneous
Basalt
Basalt
Hardness: 6; Color: Dark grey to black; Luster: Dull; Crystal structure: Aphanitic (fine-grained); Specific gravity: 2.8 - 3.0
- Hardness
- 6
- Color
- Dark grey to black
- Luster
- Dull
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Physical properties
Hardness: 6; Color: Dark grey to black; Luster: Dull; 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 exposed at or very near the surface of a terrestrial planet or a moon.
Uses & applications
Used in construction as aggregate, for paving, and as railroad ballast. Some varieties are used in sculpture and high-end countertops.
Geological facts
Basalt is the most common rock type in 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 dark color, heavy weight (relative to size), and very fine-grained texture. It often shows vesiculation (small holes) or a smooth, weather-worn appearance.
