A sample of andalusite from Tyrol, Austria.
Andalusite is one of many crystalline forms of aluminum silicate, occurring in contact metamorphic rock. It is mined commercially in the United States, Kazakstan, and South Africa to make temperature-resistant and insulating porcelains.
Andalusite is usually pink but white, gray, yellow, green, and violet varieties also occur frequently. It crystallizes in the orthorhombic system. Hardness: 7.5.