igneous
Basalt
Basalt (Extrusive volcanic rock)
Hardness: 6.0 on Mohs scale; Color: dark grey to black; Luster: dull to sub-metallic; Crystal structure: fine-grained (aphanitic); Specific Gravity: 2.8 - 3.0.
- Hardness
- 6
- Color
- dark grey to black
- Luster
- dull to sub-metallic
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Physical properties
Hardness: 6.0 on Mohs scale; Color: dark grey to black; Luster: dull to sub-metallic; Crystal structure: fine-grained (aphanitic); Specific Gravity: 2.8 - 3.0.
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava exposed at or very near the surface of a terrestrial planet or a moon. Most basalt flows are from the Cenozoic era.
Uses & applications
Extensively used in construction, especially as aggregate for roads and concrete, railroad ballast, and for manufacturing stone wool insulation.
Geological facts
Basalt is the most common rock on Earth's surface, making up most of the ocean floor. It is also found on the Moon, Mars, and Venus.
Field identification & locations
Identify by its heavy weight, dark color, and fine-grained texture with occasional small holes (vesicles). Found in volcanic regions like Hawaii, Iceland, and the Columbia River Plateau.
