basalt

This term describes a specific volcanic rock characterized by its dense, dark appearance and fine-grained texture. It is most commonly associated with oceanic crust and massive lava flows, often forming distinctive hexagonal columns through a process of slow cooling and contraction.

As a mass noun referring to a geological material, it is typically treated as uncountable. When referring to specific samples or types of the rock in a scientific context, it may occasionally be used as a countable noun, though this is less common in general usage.