igneous
Basalt
Basalt (Extrusive Mafic Igneous)
Hardness: 6 (Mohs); Color: dark grey to black; Luster: dull to sub-metallic; Crystal structure: fine-grained (aphanitic); Specific gravity: 2.8 - 3.0.
- Hardness
- 6 (Mohs)
- Color
- dark grey to black
- Luster
- dull to sub-metallic
Identified More igneous →
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Physical properties
Hardness: 6 (Mohs); Color: dark grey to black; Luster: dull to sub-metallic; Crystal 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.
Uses & applications
Extensively used in construction for aggregate, road base, railroad ballast, and high-quality concrete. Also used for making floor tiles and countertops.
Geological facts
Basalt is the most common rock type in the Earth's crust, covering most of the ocean floor and also found on the Moon and Mars.
Field identification & locations
Identified by its heavy weight, dark color, and lack of visible individual crystals to the naked eye. Commonly found in volcanic regions.
