igneous
Basalt
Basalt (Mafic volcanic rock)
Hardness: 6 on Mohs scale; Color: Dark grey to black; Luster: Dull to sub-metallic; Crystal structure: Aphanitic (fine-grained) to porphyritic; Specific gravity: 2.8–3.0.
- Hardness
- 6 on Mohs scale
- Color
- Dark grey to black
- Luster
- Dull to sub-metallic
Identified More igneous →
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Physical properties
Hardness: 6 on Mohs scale; Color: Dark grey to black; Luster: Dull to sub-metallic; Crystal structure: Aphanitic (fine-grained) to porphyritic; Specific gravity: 2.8–3.0.
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava (mafic) exposed at or very near the surface of a terrestrial planet or a moon. Most common rock in the Earth's crust.
Uses & applications
Extensively used in construction for aggregate, road base, railroad ballast, and high-quality paving stones. Also used in floor tiles and statues.
Geological facts
Basalt is the most abundant bedrock on Earth, making up most of the ocean floor. It is also common on the Moon (the dark 'Maria' plains) and Mars.
Field identification & locations
Identify by its dark color, heavy weight for its size, and absence of visible large crystals. Common in volcanic regions and ocean basins. Look for vesiculation (gas bubbles) or columnar jointing.
