Basalt is classified as an extrusive igneous rock. It forms when magma cools and solidifies on the Earth’s surface after a volcanic eruption. Because this process happens relatively quickly, basalt typically has a fine-grained texture, meaning that the individual crystals are not easily visible to the naked eye.
Basalt is primarily composed of minerals such as plagioclase feldspar, pyroxene, and olivine, which contribute to its dark color. It’s one of the most common types of volcanic rock found on Earth and is also a significant component of oceanic crust. The characteristics of basalt make it distinct from intrusive igneous rocks, like granite, which form from magma that cools slowly beneath the surface, resulting in a coarse-grained texture.