igneous
Basalt
Basalt (Extrusive Mafic Igneous)
Hardness: 6 (Mohs); Color: Dark gray to black; Luster: Dull/earthy; Crystal structure: Aphanitic (fine-grained); Specific gravity: 2.8–3.0.
- Hardness
- 6 (Mohs)
- Color
- Dark gray to black
- Luster
- Dull/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 (Mohs); Color: Dark gray to black; Luster: Dull/earthy; 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. Common in oceanic crust and volcanic regions.
Uses & applications
Extensively used in construction as aggregate (crushed stone), road base, railroad ballast, and sometimes for floor tiles or stone carvings.
Geological facts
Basalt is the most common rock type in the Earth's crust and also makes up most of the surface of the Moon and Mars.
Field identification & locations
Identified by its heavy weight (high density), dark color, and lack of visible crystals to the naked eye. Found worldwide in volcanic fields and coastlines.
