Abstract <p>The paper presents results of an experimental study on the fabrication of ceramics based on MgAl₂O₄ spinel with the addition of cobalt oxide (Co₃O₄) at various concentrations of 0.1, 0.25, 0.75, and 1&#xa0;wt % in a thermal plasma medium. Ceramic samples were synthesized from natural materials with high Al₂O₃ and MgO oxide contents. It has been found that at lower firing temperatures (1400°C), the addition of Co₃O₄ more effectively increases density. At higher firing temperatures (1500–1550°C), density initially decreases and then increases with increasing Co₃O₄ content, a behavior that is associated with phase transitions or changes in the material’s texture. The CIE 1931 chromaticity diagrams characterize the effect of firing temperature and Co₃O₄ concentration on color change of the ceramics. As can be seen, the points on the diagram shift from the blue range with increasing sintering temperature. It is worth noting that the maximum saturated color on the diagram corresponds to the “melting products.” The optimal Co content in MgAl₂O₄ spinel is 0.75 wt %; a heterogeneous nanostructure combining the properties of the matrix spinel and Co-containing phases is formed at this concentration.</p>