A material that enchants us as ruby or sapphire and is applied in watches or lasers. A material that gives us a better life in the form of implants. A material that provides irreplaceable technical services with its hardness and heat resistance. A fascinating material. Its name is aluminium oxide. In this book you will find a lot of exciting and often astonishing information about this extraordinary material. First, the necessary facts about the substance aluminium oxide are given. Then the world of the gemstones ruby and sapphire is described. And finally, the world of alumina as well as technical ceramics is illuminated.