igneous
Basalt
Basalt (Mafic volcanic rock)
Hardness: 6-7 on Mohs scale; Color: dark grey to black; Luster: dull to sub-metallic; Crystal structure: fine-grained (aphanitic); Specific gravity: 2.8-3.0
- Hardness
- 6-7 on Mohs scale
- Color
- dark grey to black
- Luster
- dull to sub-metallic
Identified More igneous →
Explore Basalt in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6-7 on Mohs scale; Color: dark grey to black; Luster: dull to sub-metallic; Crystal structure: fine-grained (aphanitic); 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. Forms in oceanic crust and volcanic regions.
Uses & applications
Extensively used in construction, especially as crushed stone for road base, railroad ballast, and concrete aggregate. Sometimes used in monuments or as high-quality pavement.
Geological facts
Basalt is the most common rock type in Earth's crust, covering most of the ocean floors. It is also found on the Moon, Mars, and Venus.
Field identification & locations
Identify by its dark color, heavy weight (density), and fine-grained texture with no visible individual crystals. Commonly found in coastal areas, volcanic islands, and around tectonic plate boundaries.
