igneous
Basalt
Basalt
Hardness: 6.0; Color: Dark grey to black; Luster: Dull to sub-metallic; Crystal structure: Aphanitic (fine-grained); 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; Color: Dark grey to black; Luster: Dull to sub-metallic; 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 exposed at or very near the surface of a terrestrial planet or a moon.
Uses & applications
Extensively used in construction, especially as crushed stone for road base, railroad ballast, and concrete aggregate. Specifically used in basalt fiber for reinforcement.
Geological facts
Basalt is the most common rock type in Earth's crust and makes up most of the ocean floor. It is also common on the Moon and Mars.
Field identification & locations
Identify by its dark color, heavy weight (density), and lack of visible large crystals. Common in volcanic regions and oceanic islands like Hawaii or Iceland.
