igneous
Basalt
Extrusive igneous rock primarily composed of plagioclase and pyroxene
Hardness: 6 on Mohs scale. Color: Dark gray to black. Luster: Dull to sub-vitreous. Crystal structure: Aphanitic (fine-grained) or microcrystalline, sometimes porphyritic.
- Hardness
- 6 on Mohs scale
- Color
- Dark gray to black
- Luster
- Dull to sub-vitreous
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 on Mohs scale. Color: Dark gray to black. Luster: Dull to sub-vitreous. Crystal structure: Aphanitic (fine-grained) or microcrystalline, sometimes porphyritic.
Formation & geological history
Formed from the rapid cooling of low-viscosity lava rich in magnesium and iron exposed at or very near the Earth's surface, often associated with volcanic activity and oceanic crust formation.
Uses & applications
Commonly used in construction as crushed stone for road bases, concrete aggregate, railroad ballast, and in the manufacturing of rock wool insulation.
Geological facts
Basalt is the most common rock type in the Earth's crust, underlying most of the ocean basins and forming major volcanic features such as the Columbia River Basalt Group and the Giant's Causeway in Northern Ireland.
Field identification & locations
Identified by its dark, fine-grained appearance, high density, and occasional presence of vesicles (gas bubbles). Widely distributed globally in volcanic regions.
