igneous
Basalt
Basalt (Aphanitic Mafic Igneous Rock)
Hardness (Mohs scale): 6; Color: Dark grey to black; Luster: Dull to sub-metallic; Crystal structure: Fine-grained, often aphanitic; Specific gravity: 2.8 - 3.0
- Color
- Dark grey to black
- Luster
- Dull to sub-metallic
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Physical properties
Hardness (Mohs scale): 6; Color: Dark grey to black; Luster: Dull to sub-metallic; Crystal structure: Fine-grained, often aphanitic; 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 a moon. Most common rock of the Earth's crust.
Uses & applications
Extensively used in construction for aggregate, road base, railroad ballast, and concrete production. Can be used in stone wool insulation and occasionally used in jewelry as beads or pendants.
Geological facts
Basalt is the most common rock in the Earth's crust and makes up the majority of the ocean floor. It is also found on Mars and the Moon.
Field identification & locations
Identify in the field by its dark color, fine-grained texture, and high density. Commonly found at volcanic sites, mid-ocean ridges, and in areas with extensive lava flows like the Deccan Traps or the Columbia River Plateau.
