Magnesia-calcium zirconate (MCZ) composite brickswere recently used in the transition zones of cement kilnsbecause they are environment-friendly and hard-wearing towards cement clinker phases at high temperatures. Modifiers such as hercynite spinel (FA: FeO·Al2O3) can be added in small amounts to enhance elasticity, coatability, and load bearing of the brick structure. In the current study, different amounts (2, 4 and 6 wt. %) of hercynite spinelwere added to the MCZ composite clinkermade from Egyptian magnesite and zirconia (9,8 wt. %)then densification parameters, cold compressive strength (CCS), attacking by cement clinker components (CCC), and other technical characteristics of the formedbricks were explored. The maximum strength was gotten by 2,00 wt. % FA spinel addition,where excessive micro-cracks and glassy phase were the limiting factors for further added spinel. The penetration depth of the cement clinker components into MCZ‒FA bricks was downsized as FA spinel was added and further reduction occurred as FA increased. Furthermore, the coating character and the thermal shock cycles of the bricks were greatly improved as FA spinelraised to 6,00 wt. %. Those bricks with different FA spinel ratios can be put forward for lining different zones in the rotary cement kiln where different affinities for coating formations occur. Ill. 8. Ref. 31. Tab. 3.