igneous
Basalt
Basalt
Hardness: 6 (Mohs scale); Color: Dark grey to black, often weathering to brown; Luster: Dull/earthy; Crystal structure: Aphanitic (fine-grained); Specific gravity: 2.8 - 3.0
- Hardness
- 6 (Mohs scale)
- Color
- Dark grey to black, often weathering to brown
- Luster
- Dull/earthy
Identified More igneous →
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Physical properties
Hardness: 6 (Mohs scale); Color: Dark grey to black, often weathering to brown; Luster: Dull/earthy; 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 exposed at or very near the surface of a terrestrial planet or moon. Most oceanic crust is composed of basalt.
Uses & applications
Extensively used in construction for aggregate, road base, railroad ballast, and high-quality concrete. Also used for pavers and as a component in stonewash applications for textiles.
Geological facts
Basalt is the most common volcanic rock on Earth and also makes up much of the surface of the Moon, Venus, and Mars.
Field identification & locations
Identify by its dark color, heavy weight (relative to size), and fine-grained texture with no visible crystals to the naked eye. Often found in volcanic regions or riverbeds near volcanic flows.
