igneous
Basalt
Extrusive mafic igneous rock
Hardness: 6 on Mohs scale; Color: dark grey to black or greenish-grey; Luster: dull to sub-metallic; Crystal structure: aphanitic (fine-grained) to porphyritic; Specific gravity: 2.8-3.0.
- Hardness
- 6 on Mohs scale
- Color
- dark grey to black or greenish-grey
- Luster
- dull to sub-metallic
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Physical properties
Hardness: 6 on Mohs scale; Color: dark grey to black or greenish-grey; Luster: dull to sub-metallic; Crystal structure: aphanitic (fine-grained) to porphyritic; 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. Most common rock type in the Earth's crust.
Uses & applications
Used extensively in construction (crushed stone for road base and concrete aggregate), high-quality floor tiles, monument stone, and as a raw material for stone wool insulation.
Geological facts
Basalt is the most common rock on Earth's surface and covers most of the ocean floor. It is also common on the Moon, Mars, and Venus.
Field identification & locations
Identify in the field by its dark color, fine grain, and high density. Commonly found at volcanic sites, tectonic divergent boundaries, and oceanic seafloors.
