igneous
Basalt (Vesicular/Waterworn)
Basalt (Mafic Extrusive Igneous Rock)
Hardness: 5-6 Mohs. Color: Dark gray to black. Luster: Dull to sub-metallic. Structure: Very fine-grained (aphanitic), sometimes vesicular. Specific Gravity: 2.8–3.0.
- Hardness
- 5-6 Mohs
- Color
- Dark gray to black
- Luster
- Dull to sub-metallic
Identified More igneous →
Explore Basalt (Vesicular/Waterworn) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 5-6 Mohs. Color: Dark gray to black. Luster: Dull to sub-metallic. Structure: Very fine-grained (aphanitic), sometimes vesicular. Specific Gravity: 2.8–3.0.
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at the earth's surface. Given the location in the Ethiopian Highlands (9.1°N, 41.6°E), this is likely part of the extensive Ethiopian flood basalt province formed during the Cenozoic era.
Uses & applications
Commonly used as crushed stone for road base, concrete aggregate, and railroad ballast. Highly durable for construction.
Geological facts
Basalt is the most common rock type in the Earth's crust and makes up most of the ocean floor. The region near Dire Dawa and the Awash valley is dominated by volcanic activity associated with the East African Rift.
Field identification & locations
Identify by its dark color, heavy weight for its size, and lack of visible crystals. It is ubiquitous in the Ethiopian Highlands and surrounding rift zones.
