igneous
Basalt
Mafic Igneous Rock
Hardness: 6-7 (Mohs); Color: dark grey to black; Luster: dull to earthy; Crystal structure: aphanitic (fine-grained); Specific gravity: 2.8-3.0
- Hardness
- 6-7 (Mohs)
- Color
- dark grey to black
- Luster
- dull to earthy
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Physical properties
Hardness: 6-7 (Mohs); Color: dark grey to black; Luster: dull to earthy; Crystal structure: aphanitic (fine-grained); Specific gravity: 2.8-3.0
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at or very near the Earth's surface. Common in oceanic crust and volcanic islands.
Uses & applications
Extensively used in construction as aggregate, road base, railroad ballast, and for floor tiles or statues.
Geological facts
Basalt is the most common rock type in the Earth's crust and makes up most of the ocean floor. It is also found on the Moon and Mars.
Field identification & locations
Look for a heavy, dark-colored, fine-grained rock with occasional small vesicles (gas bubbles) or larger crystals (phenocrysts). Found globally in volcanic regions.
