igneous
Basalt
Basalt (Mafic volcanic rock)
Hardness: 6.0; Color: dark grey to black; Luster: dull to earthy; Texture: aphanitic; Specific Gravity: 2.8-3.0
- Hardness
- 6
- Color
- dark grey to black
- Luster
- dull to earthy
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: 6.0; Color: dark grey to black; Luster: dull to earthy; Texture: aphanitic; 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 surface of a terrestrial planet or a moon. Common in oceanic crust and volcanic islands.
Uses & applications
Used extensively in construction as road base, railroad ballast, and aggregate in concrete. Some types are used as dimension stone or for floor tiles.
Geological facts
Basalt is the most common volcanic rock on Earth and also makes up most of the surface of the Moon and Mars. It covers about 70 percent of Earth's surface.
Field identification & locations
Identified by its heavy weight, dark color, and fine-grained texture. Found near volcanic hotspots, mid-ocean ridges, and continental rift zones.
