Andalusite is an aluminosilicate mineral with a chemical composition of Al2SiO5. It forms at low to medium metamorphic temperatures and pressures where argillaceous rocks (such as shale) are exposed to regional and contact metamorphism.
Andalusite is a rock-forming mineral most commonly found in schist, gneiss, and hornfels. Minor amounts are also found in granite and granitic pegmatite.
The most important use of andalusite is in making heat-resistant bricks and ceramic objects used in the steel-making and metal processing industries. It is also used to make chemicals, glass and a variety of ceramic products. Exceptional crystals of andalusite are valued by mineral collectors. Specimens with spectacular color and clarity are cut into gemstones.
