igneous
Basalt
Basalt
Hardness: 6 (Mohs scale); Color: Dark grey to black; Luster: Dull to sub-metallic; Crystal structure: Aphanitic (fine-grained); Cleavage: None; Specific gravity: 2.8–3.0
- Hardness
- 6 (Mohs scale)
- Color
- Dark grey to black
- Luster
- Dull to sub-metallic
Identified More igneous →
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Physical properties
Hardness: 6 (Mohs scale); Color: Dark grey to black; Luster: Dull to sub-metallic; Crystal structure: Aphanitic (fine-grained); Cleavage: None; Specific gravity: 2.8–3.0
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava (basaltic lava) exposed at or very near the surface of a terrestrial planet or a moon. Most common rock in the Earth's crust.
Uses & applications
Commonly used in construction as aggregate for concrete and road base, floor tiles, and in monuments.
Geological facts
Basalt also exists on other planetary bodies; much of the Moon's surface 'Maria' are plains of basaltic lava flows. It is the most common volcanic rock on Earth.
Field identification & locations
Identify in the field by its dark color, heavy weight (relative to size), and very fine-grained texture. It often shows vesicular (bubbly) textures if gases were trapped during cooling.
