Igneous
Basalt
Mafic Volcanic Rock (composed of plagioclase, pyroxene, and olivine)
Hardness: 6 on Mohs scale; Color: charcoal gray to black; Luster: dull to earthy; Crystal structure: fine-grained (aphanitic) or porphyritic; Specific gravity: 2.8 - 3.0
- Hardness
- 6 on Mohs scale
- Color
- charcoal gray to black
- Luster
- dull to earthy
Identified More igneous →
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Physical properties
Hardness: 6 on Mohs scale; Color: charcoal gray to black; Luster: dull to earthy; Crystal structure: fine-grained (aphanitic) or porphyritic; Specific gravity: 2.8 - 3.0
Formation & geological history
Formed from the rapid cooling of low-viscosity lava rich in magnesium and iron at or very near the Earth's surface (extrusive igneous process).
Uses & applications
Extensively used in construction for road base, concrete aggregate, railroad ballast, and dimension stone for paving or sculptures.
Geological facts
Basalt is the most common rock type in Earth's crust and makes up most of the ocean floors. It is also common on the Moon, Mars, and Venus.
Field identification & locations
Identify by its dark color, heavy weight (density), and lack of visible large crystals to the naked eye. Found worldwide in volcanic fields and mid-ocean ridges.
