igneous
Basalt
Basalt (Mafic volcanic rock)
Hardness: 5-6 Mohs. Color: Dark gray to black. Luster: Dull to sub-metallic. Crystal structure: Fine-grained/Aphanitic. Specific Gravity: 2.9-3.1.
- Hardness
- 5-6 Mohs
- Color
- Dark gray to black
- Luster
- Dull to sub-metallic
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Physical properties
Hardness: 5-6 Mohs. Color: Dark gray to black. Luster: Dull to sub-metallic. Crystal structure: Fine-grained/Aphanitic. Specific Gravity: 2.9-3.1.
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 common rock on Earth's crust.
Uses & applications
Used in construction, as aggregate in asphalt and concrete, as floor tiles, and in the production of thermal insulation (stone wool).
Geological facts
Basalt is the primary rock of the ocean floor and also makes up the lunar maria on the moon. It can create unique formations like hexagonal columns (Giant's Causeway).
Field identification & locations
Look for a heavy, dark-colored, fine-grained rock often associated with volcanic activity. Common worldwide, especially along mid-ocean ridges and volcanic islands.
