Andalusite is a common metamorphic mineral which forms under low pressure and low to high temperatures. The mineral skyanite and sillimanite are polymorphs of andalusite, each occurring under different temperature-pressure regimes and are therefore rarely found together in the same rock. Because of this the three minerals are a useful tool to help identify the pressure-temperature paths of the host rock in which they are found. An example rock includes hornfels.
It was first described and named after the type locality in the Ronda Massif, Málaga, Andalusia, Spain in 1789.