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, and plagioclase; 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, and plagioclase; Specific gravity: 2.8 - 3.0
Formation & geological history
Formed from the rapid cooling of low-viscosity basaltic lava exposed at or very near the Earth's surface, typically originating from volcanic eruptions.
Uses & applications
Used in construction, aggregate for road building, production of rock wool insulation, and decorative landscaping.
Geological facts
Basalt is the most common rock type in the Earth's crust underlying the world's ocean basins and also makes up extensive volcanic formations on the Moon and Mars.
Field identification & locations
Easily identified by its dark grey to black color, heavy feel relative to size, and fine-grained texture. Frequently found along riverbeds, beaches, and volcanic regions where water action has tumbled it into a smooth pebble.
