igneous
Basalt
Basalt (Mafic volcanic rock, primarily Plagioclase and Augite)
Hardness: 6 on Mohs scale; Color: Dark grey to black; Luster: Dull/Matte; Crystal structure: Aphanitic (fine-grained); Specific gravity: 2.8 - 3.0. Dense and heavy for its size.
- Hardness
- 6 on Mohs scale
- Color
- Dark grey to black
- Luster
- Dull/Matte
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Physical properties
Hardness: 6 on Mohs scale; Color: Dark grey to black; Luster: Dull/Matte; Crystal structure: Aphanitic (fine-grained); Specific gravity: 2.8 - 3.0. Dense and heavy for its size.
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava 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, railroad ballast, and high-quality concrete. Sometimes used in stone massage therapy for heat retention.
Geological facts
Basalt is the most common rock type in the Earth's crust and makes up nearly most of the ocean floor. It is also found on the Moon and Mars.
Field identification & locations
Identify by its dark color, heavy weight, and fine-grained texture with no visible crystals to the naked eye. Commonly found in volcanic regions or as river stones transported from volcanic highlands.
