A spinel is an important class of oxides consisting of two types of metal ions with the oxide ions arranged in ccp layers. The normal spinel has one-eighth of the tetrahedral holes occupied by one type of metal ion and one-half of the octahedral holes occupied by another type of metal ion. Such a spinel is formed by ${\mathrm{Mg}}^{2+},{\mathrm{Al}}^{3+}\text{ and }{\mathrm{O}}^{2-}$. The neutrality of the crystal is being maintained. Antispinels will differ in arrangements among cations, but anions will be still fcc . 

The formula of the spinel is:  

$\text{ Type of hole occupied by }{\mathrm{Al}}^{3+}\text{ ions in inverse spinel will be }$

Type of hole occupied by Mg²⁺ ions is:

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