text: The corundum structure has the space group hexagonal crystal family#Crystal classes|. It typically exists in binary compounds of the type AB, where A is metallic and B is nonmetallic, including sesquioxides (AO), sesquisulfides (AS), etc. When A is nonmetallic and B is metallic, the structure becomes the antiphase of corundum, called the anticorundum structure type, with examples including β-CaN and borates. Ternary and multinary compounds can also exists in the corundum structure. The corundum-like structure with the composition ABB'O is called double corundum. A list of examples are tabulated below.