A study has been made of the magnetic properties of the system of quenched magnesium ferrites (MgxIIFe1−xIII) · (Mg1−xIIFe1+xIII)O4, wherex, the fraction of magnesium ions in tetrahedral sites, varies from 0.14 to 0.26. Included among the properties examined are: saturation moment, Curie point, initial permeability, and coercive force. A limited study of the kinetics of the cation redistribution has also been made. Samples quenched from 1100°C and then tempered at 600°C require somewhat less than 16 hours to attain an equilibrium cation distribution at the latter temperature. The approach to equilibrium is consistent with a model in which the rate of approach is proportional toexp(−&thgr;0′+&thgr;1′x)/Twhere &thgr;0′ and &thgr;1′ are activation constants.