igneous
Basalt
Extrusive Igneous Rock
AI-generated identification · may be incorrectBasalt has a Mohs hardness of 6, a dark black to gray color, and a dull to sub-metallic luster with an aphanitic, fine-grained crystal structure.
Identified More igneous →
Explore Basalt in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Basalt has a Mohs hardness of 6, a dark black to gray color, and a dull to sub-metallic luster with an aphanitic, fine-grained crystal structure.
Formation & geological history
It forms from the rapid cooling of low-viscosity, magnesium- and iron-rich lava flows at the Earth's surface.
Uses & applications
Commonly used in construction as crushed aggregate for roads, railroad ballast, and in the production of stone wool insulation.
Geological facts
Basalt is the most common rock type in the Earth's crust, making up most of the oceanic crust and forming massive features like the Columbia River Basalts.
Field identification & locations
Identify it in the field by its dark, fine-grained matrix and heavy feel, often found in volcanic regions and ancient lava plateaus.
