The initial reagents taken in different proportions FeO/ZnO = (1-x)/x (0 < x ≤ 0.6 with a step of 0.1) were thoroughly ground in an agate mortar under acetone. The reaction mixtures were then pressed into tablets using a hand press and placed in gold capsules. Samples of single-phase solid solutions rs-Fe 1-x Zn x O (0 < x ≤ 0.5) in the form of disks with diameter ~5 mm and thickness ~1 mm were synthesized at 7.7 GPa and temperature ~1500 K according to the procedure described previously . It should be noted that the reaction mixture with x = 0.6 composition after high-pressurehigh-temperature treatment also yields a single-phase solid solution with rock salt structure, but after quenching the sample was not a solid disk but crumbled to powder during recovery from a high-pressure cell. Some samples of cubic FeO-ZnO solid solutions were synthesized under similar pressuretemperature conditions but using different starting reagents. The series of solid solutions (Nos. 7-9) were synthesized using "FeO" (Ruschim, reagent grade) containing an impurity of mixed-valent iron(II,III) oxide. Sample No. 10 of nominal composition Fe 0.5 Zn 0.5 O was synthesized from the stoichiometric mixture 3 w-ZnO + α-Fe (Alfa Aesar, 99.9%, 325 mesh) + α-Fe 2 O 3 (ultrapure).