igneous
Basalt
Basalt (containing plagioclase feldspar, pyroxene, and olivine)
Hardness: 6-7 on Mohs scale; Color: dark grey to black; Luster: dull to sub-metallic; Crystal structure: fine-grained (aphanitic); Specific gravity: 2.8-3.0.
- Hardness
- 6-7 on Mohs scale
- Color
- dark grey to black
- Luster
- dull to sub-metallic
Identified More igneous →
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Physical properties
Hardness: 6-7 on Mohs scale; 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 Earth's surface. Common in oceanic crust and volcanic hotspots.
Uses & applications
Extensively used in construction for aggregate, road base, concrete, and railroad ballast. Can be used for stone carvings and floor tiles.
Geological facts
Basalt is the most common rock type in the Earth's crust and also makes up most of the surface of the Moon and Mars.
Field identification & locations
Identify by its dark color, heavy weight (relative to size), and very fine grains. Commonly found in volcanic regions, oceanic islands, and mid-ocean ridges.
