igneous
Basalt
Mafic extrusive igneous rock
Hardness: 6 on Mohs scale. Color: Dark gray to black. Luster: Aphanitic (fine-grained), dull to sub-vitreous. Crystal structure: Microcrystalline, often containing olivine, pyroxene, and plagioclase feldspar. Specific gravity: 2.8 - 3.0.
- Hardness
- 6 on Mohs scale
- Color
- Dark gray to black
- Luster
- Aphanitic (fine-grained), dull to sub-vitreous
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Physical properties
Hardness: 6 on Mohs scale. Color: Dark gray to black. Luster: Aphanitic (fine-grained), dull to sub-vitreous. Crystal structure: Microcrystalline, often containing olivine, pyroxene, and plagioclase feldspar. Specific gravity: 2.8 - 3.0.
Formation & geological history
Formed from the rapid cooling of low-viscosity lava rich in magnesium and iron exposed at or very near the surface of a planet or moon.
Uses & applications
Commonly used in construction as crushed stone for road bases, concrete aggregate, and railroad ballast, as well as in manufacturing stone wool insulation.
Geological facts
Basalt is the most common rock type in the Earth's crust underlying the ocean basins and also makes up extensive volcanic formations on the Moon and Mars.
Field identification & locations
Identify in the field by its dark, dense, fine-grained appearance, often found in volcanic regions, layered flows, or as weathered field stones.
