The spinels are any of a class of minerals of general formulation XY2O4 which crystallize in the cubic (isometric) crystal system, with the oxie anions arranged in a cubic close-packed lattice and the cations X and Y occupying some or all of the octahedral and tetrahedral sites in the lattice. X and Y can be divalent, trivalent, or quadrivalent cations, including magnesium, zinc, iron, manganese, aluminium, chromium, titanium, and silicon. Although the anion is normally oxide, structures are also known for the rest of the chalcogenides.