igneous
Basalt Pebble
Extrusive Igneous Rock
Hardness: 6 on the Mohs scale. Color: Dark gray to black. Luster: Dull to sub-vitreous. Crystal structure: Aphanitic (fine-grained), often containing tiny plagioclase feldspar and pyroxene crystals. Specific gravity: 2.8 - 3.0.
- Hardness
- 6 on the Mohs scale
- Color
- Dark gray to black
- Luster
- Dull to sub-vitreous
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Physical properties
Hardness: 6 on the Mohs scale. Color: Dark gray to black. Luster: Dull to sub-vitreous. Crystal structure: Aphanitic (fine-grained), often containing tiny plagioclase feldspar and pyroxene crystals. 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, often shaped into a smooth pebble by water action in rivers or shorelines.
Uses & applications
Used in construction, aggregate, road base, railroad ballast, and decorative landscaping.
Geological facts
Basalt is the most common rock type in the Earth's crust underlying the ocean basins, and it is also found extensively on the Moon and Mars.
Field identification & locations
Easily identified by its dark, fine-grained appearance, heavy feel, and smooth rounded shape typical of water-worn beach or river stones.
