igneous
Basalt
Basalt (Vitreous to Aphanitic Mafic Igneous Rock)
Hardness: 6 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 on Mohs scale
- Color
- Dark grey to black
- Luster
- Dull to sub-metallic
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Physical properties
Hardness: 6 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 at or near the Earth's surface. Common in oceanic crust and volcanic islands.
Uses & applications
Extensively used in construction for aggregate, road base, concrete, and railroad ballast. Also used in high-temp insulation (rock wool).
Geological facts
Basalt is the most common rock in Earth's crust and covers most of the ocean floor. It is also found on the Moon, Mars, and Venus.
Field identification & locations
Identify by its heavy weight (high density), dark color, and lack of visible crystals to the naked eye. Found at volcanic sites and ocean ridges.
