A fired spinel complex oxide is produced by firing a mixture containing a slag
by-produced in chromium refining, a reducer, and a silica-containing material,
and is essentially composed of: 29 to 40 percent by weight of Fe2O3;
15 to 20 percent by weight of Al2O3; 9 to 14 percent by weight
of MgO; 0 to 4 percent by weight of Na2O; 9 to 17 percent by weight
of Cr2O3; 14 to 20 percent by weight of SiO2;
and 2 percent by weight or less of CaO. The fired spinel complex oxide shows a
Cu—K X-ray diffraction pattern in which the ratio (b/a) of the diffraction
peak intensity of the silica-containing material (b) in the vicinity of 2=26.7
to the {113} plane diffraction peak intensity (a) in the vicinity of 2=36
is 0.1 or less.
