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 plagioclase feldspar and pyroxene; 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 plagioclase feldspar and pyroxene; 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 surface of a planet or moon.
Uses & applications
Used in construction, as aggregate in road building, railroad ballast, and sometimes in stonework and landscaping.
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 globally in volcanic regions, oceanic islands, and ancient lava flows. Easily identified by its dark, fine-grained, heavy appearance.
