igneous
Basalt Pebble
Extrusive Igneous Rock
Hardness: 6 on Mohs scale; Color: Dark grey to black; Luster: Dull to sub-vitreous; Crystal structure: Aphanitic (fine-grained), often containing microscopic olivine, pyroxene, or plagioclase; Cleavage: None; Specific Gravity: 2.8 - 3.0
- Hardness
- 6 on Mohs scale
- Color
- Dark grey to black
- Luster
- Dull to sub-vitreous
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Physical properties
Hardness: 6 on Mohs scale; Color: Dark grey to black; Luster: Dull to sub-vitreous; Crystal structure: Aphanitic (fine-grained), often containing microscopic olivine, pyroxene, or plagioclase; Cleavage: None; Specific Gravity: 2.8 - 3.0
Formation & geological history
Formed from the rapid cooling of low-viscosity lava rich in iron and magnesium exposed at or very near the Earth's surface.
Uses & applications
Used in construction, road aggregate, railroad ballast, and sometimes in landscaping or decorative stones.
Geological facts
Basalt is the most common rock type in the Earth's crust underlying the ocean basins and is also found abundantly on the Moon and Mars.
Field identification & locations
Found widely in beach and river environments where water action has smoothed and rounded the rock into a pebble.
