igneous
Basalt
Basalt
Hardness: 6 (Mohs scale); Color: Dark gray to black; Luster: Dull to submetallic; Crystal structure: Aphanitic (fine-grained); Specific gravity: 2.8-3.0
- Hardness
- 6 (Mohs scale)
- Color
- Dark gray to black
- Luster
- Dull to submetallic
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Physical properties
Hardness: 6 (Mohs scale); Color: Dark gray to black; Luster: Dull to submetallic; 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. The reported location (Addis Ababa, Ethiopia) is situated on the Ethiopian Plateaus, which are famous for massive Cenozoic flood basalt deposits.
Uses & applications
Extensively used as crushed stone in construction, road base, concrete aggregate, and sometimes as dimension stone or for artistic sculptures.
Geological facts
Basalt is the most common rock on Earth's surface and also makes up a large portion of the crust of Mars and the Moon. The Ethiopian Highlands where this was found contain some of the most extensive basaltic flows in the world.
Field identification & locations
Identify by its heavy weight, dark color, and lack of visible crystals without a lens. Common in volcanic regions like the East African Rift.
