igneous
Basalt
Basalt (Mafic Extrusive Igneous Rock)
Hardness: 6 (Mohs); Color: Dark gray to black; Luster: Dull/Matte; Crystal structure: Aphanitic (fine-grained); Specific gravity: 2.8 - 3.0
- Hardness
- 6 (Mohs)
- Color
- Dark gray to black
- Luster
- Dull/Matte
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Physical properties
Hardness: 6 (Mohs); Color: Dark gray to black; Luster: Dull/Matte; Crystal structure: Aphanitic (fine-grained); Specific gravity: 2.8 - 3.0
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
Widely used in construction for aggregate, road base, railroad ballast, and high-quality concrete. Also used for statues and as a heat-retaining stone in therapies.
Geological facts
Basalt is the most common rock type in the 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 dark color, heavy weight (relative to size), and lack of visible crystals. Commonly found in coastal areas or volcanic fields.
