The mechanism of formation and the structural features of tetragonal Fe-ZrO2-amorphous silica composites and particulated Fe-doped ZrSiO4 solid solutions were studied. A series of specimens with compositions Fex-ZrSiO4, 0 <= x <= 0.10 were prepared by sol-gel techniques and thermally annealed over the range of temperature between 400 degrees C and 1600 degrees C. Results confirmed the formation of tetragonal FeZrO2 solid solution as first crystalline phase on the whole process leading to Fe-doped ZrSiO4 solid solution. The annealing temperature for the preparation of Fe-containing ZrSiO4 solid solutions was dependent on the nominal amount of iron. The Fex-ZrSiO4 solid solutions, with 0.02 < x < 0.08, were almost monophasic at 1100 degrees C. The results of lattice parameter variation, energy-dispersive X-ray (EDX) and diffuse reflectance (DR), showed that in the as-prepared samples, Fe3+ cations entered into the zircon structure being located mainly in tetrahedral sites replacing Si4+. The solubility limit of Fe3+ in ZrSiO4 at 1100 degrees C was in the range 0.07-0.1 mol of iron per mol of zircon (approximately 3-4 wt% as Fe2O3). This study opens new perspectives to the development of more ecological colored zircon-based solid solution materials using mineralizer-free synthetic procedures.