Inorganic oxysalts represent one of the most important and widespread groups of inorganic compounds. They constitute more than half of the mineral species known today, they form in the environment around us, their structure and properties determine a wide range of natural and technological processes. This book deals with the crystallography of inorganic oxysalts, i.e. with a description of the organization of atoms in their crystal structures. The world of inorganic oxysalts is so diverse that a systematic and adequate description of this diversity seems to be almost impossible. The imagination and knowledge of structural crystallographers are very often restricted to their own objects of study. They work out the structure solution (sometimes easy, sometimes diffi cult), produce crystallographic information fi les (CIF) and leave the structure aside.