igneous
Basalt
Basalt (Mafic volcanic rock)
Hardness: 6.0 on Mohs scale; Color: Black or dark gray; Luster: Dull to sub-metallic; Structure: Fine-grained/aphanitic; Specific Gravity: 2.8-3.0.
- Hardness
- 6
- Color
- Black or dark gray
- Luster
- Dull to sub-metallic
Identified More igneous →
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Physical properties
Hardness: 6.0 on Mohs scale; Color: Black or dark gray; Luster: Dull to sub-metallic; Structure: Fine-grained/aphanitic; Specific Gravity: 2.8-3.0.
Formation & geological history
Formed from the rapid cooling of low-viscosity magnesium-rich and iron-rich lava (basaltic lava) at or very near the Earth's surface.
Uses & applications
Extensively used in construction for aggregate, road base, concrete, and railroad ballast. Fine-grained specimens are used for stone carving and as thermal insulation (rock wool).
Geological facts
Basalt is the most common rock type in the Earth's crust and makes up the majority of the ocean floor. It is also found in large quantities on the Moon and Mars.
Field identification & locations
Identified by its dark color, high density, and fine-grained texture. Commonly found in volcanic regions, oceanic islands (like Hawaii), and large igneous provinces.
