What is intrusive crystallisation?

Intrusive crystallization refers to the process by which minerals crystallize from molten rock (magma) as it cools and solidifies beneath the Earth's surface. This occurs slowly, allowing larger crystals to form, resulting in coarse-grained igneous rocks, such as granite. The process is contrasted with extrusive crystallization, where magma erupts at the surface and cools rapidly, leading to finer-grained rocks like basalt. Intrusive crystallization plays a crucial role in the formation of various geological features and mineral deposits.