igneous
Basalt
Basalt
Hardness: 6 on Mohs scale; Color: Dark grey to black; Luster: Dull to submetallic; Crystal structure: Aphanitic (fine-grained); Specific gravity: 2.8–3.0; Cleavage: None (conchoidal fracture).
- Hardness
- 6 on Mohs scale
- Color
- Dark grey to black
- Luster
- Dull to submetallic
Identified More igneous →
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Physical properties
Hardness: 6 on Mohs scale; Color: Dark grey to black; Luster: Dull to submetallic; Crystal structure: Aphanitic (fine-grained); Specific gravity: 2.8–3.0; Cleavage: None (conchoidal fracture).
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 type in the Earth's crust.
Uses & applications
Extensively used in construction for aggregate, road base, railroad ballast, and high-quality concrete. Also used for paving stones and some sculpture.
Geological facts
Basalt is the primary component of oceanic crust and also covers large areas on the Moon (the dark lunar maria) and Mars.
Field identification & locations
Identify in the field by its dark color, heavy weight (relative to size), and fine-grained texture. Found worldwide, especially in volcanic regions like Hawaii, Iceland, and the Pacific Northwest.
