igneous
Basalt
Basalt
Hardness: 6.0; Color: Dark grey to black, greenish-black; Luster: Dull to vitreous; Crystal structure: Aphanitic (fine-grained); Specific gravity: 2.8-3.0
- Hardness
- 6
- Color
- Dark grey to black, greenish-black
- Luster
- Dull to vitreous
Identified More igneous →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6.0; Color: Dark grey to black, greenish-black; Luster: Dull to vitreous; 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 surface of a terrestrial planet or a moon. Common in oceanic crust and volcanic regions.
Uses & applications
Used extensively in construction for asphalt pavement, concrete aggregate, and railroad ballast. Also used as floor tiles and garden sculpture material.
Geological facts
Basalt is the most common volcanic rock on Earth and also makes up much of the surface of the Moon and Mars. It is the primary component of the oceanic crust.
Field identification & locations
Identified by its dark color, heavy weight (relative to size), and fine-grained texture. It often shows vesicles (gas bubbles) or small phenocrysts of olivine or plagioclase. Found in volcanic plains and ocean floor exposures.
