igneous
Basalt
Basalt
Hardness: 6.0 on Mohs scale; Color: Black to dark grey; Luster: Dull to sub-vitreous; Crystal structure: Aphanitic (fine-grained); Cleavage: None; Specific gravity: 2.8 - 3.0
- Hardness
- 6
- Color
- Black to dark grey
- Luster
- Dull to sub-vitreous
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Physical properties
Hardness: 6.0 on Mohs scale; Color: Black to dark grey; Luster: Dull to sub-vitreous; 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 exposed at or very near the surface of a terrestrial planet or a moon. Most common rock on Earth's crust.
Uses & applications
Used primarily in construction (crushed stone), road base, concrete aggregate, railroad ballast, and sometimes in decorative landscaping or as garden stones.
Geological facts
Basalt is the most common rock in the Earth's crust and makes up most of the ocean floor; it is also found on the Moon and Mars.
Field identification & locations
Identify by its dark color, fine-grained texture, and high density. Commonly found on beaches, near volcanic regions, and in riverbeds as water-worn pebbles.
