igneous
Basalt
Basalt
Hardness: 6 (Mohs scale); Color: Dark grey to black, weathering to brown or green; Luster: Dull to sub-metallic; Crystal structure: Aphanitic (fine-grained); Specific gravity: 2.8 - 3.0
- Hardness
- 6 (Mohs scale)
- Color
- Dark grey to black, weathering to brown or green
- Luster
- Dull to sub-metallic
Identified More igneous →
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Physical properties
Hardness: 6 (Mohs scale); Color: Dark grey to black, weathering to brown or green; Luster: Dull to sub-metallic; Crystal structure: Aphanitic (fine-grained); Specific gravity: 2.8 - 3.0
Formation & geological history
Forms 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. Often found in oceanic crust and volcanic regions.
Uses & applications
Extensively used in construction for road base, concrete aggregate, and railroad ballast. Also used as dimension stone and in the manufacture of stone wool insulation.
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, Mars, and Venus.
Field identification & locations
Identify by its dark color, heavy weight (relative to size), and fine-grained texture. It often shows a pitted or vesicular texture if gas bubbles were present during cooling. Common in volcanic islands and mountain ranges.
