igneous
Basalt
Basalt (Mafic volcanic rock)
Hardness: 6 on Mohs scale; Color: Dark grey to black; Luster: Dull to sub-metallic; Crystal structure: Aphanitic (fine-grained) to porphyritic; Specific gravity: 2.8-3.0.
- Hardness
- 6 on Mohs scale
- Color
- Dark grey to black
- Luster
- Dull to sub-metallic
Identified More igneous →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6 on Mohs scale; Color: Dark grey to black; Luster: Dull to sub-metallic; Crystal structure: Aphanitic (fine-grained) to porphyritic; 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. It is the most common rock type in Earth's crust.
Uses & applications
Extensively used in construction for road base, concrete aggregate, railroad ballast, and high-quality floor tiles or monuments.
Geological facts
Basalt is equivalent to gabbro in mineral composition, but basalt is fine-grained while gabbro is coarse-grained. It is also found on the Moon and Mars.
Field identification & locations
Identify by its heavy weight (high density), dark color, and fine-grained texture. It often shows columnar jointing in large outcrops. Common worldwide in volcanic regions.
