loodusliku mineraaliga spinell (MgAl2O3) sarnase struktuuriga keraamiline materjal üldistatud koostisega AB2O4, kus A -kahevalentne element Mn, Ni, Co, Zn, Cu, Mg, Fe, Ca, Ba, Sr ja B - kolmevalentne element Al, Fe, Cr, the mineral MgAl2O4, but also a group of minerals of the formula AB2O4, in which A is a divalent metal or mixture of divelent metals, such as Mg, ferrous Fe, Zn, Mn, Co, Ca, Cu, Ba, Ni, and Sr, and B is a trivalent metal, such as Al, ferric Fe and Cr