When the solubility products or other thermodynamic data are not known, the optimum experimental procedures for preparing complex mixed oxides/hydroxides can be approximately predicted by extrapolation of the solubility behaviours of individual metal ions in aqueous solutions. This simple approach determined a probable co-precipitation domain ranging from pH = 0.7 to pH = 4 for Fe III -V V -H 2 O system. To control the kinetic aspect of condensation mechanisms in order to obtain crystallized compounds, three different experimental protocols were developed leading to successful syntheses of FeVO 4 • 1.1 H 2 O, Fe 4 V 6 O 21 •3 H 2 O and FeV 3 O 9 •2.6 H 2 O. These vanadates were characterized by X-ray diffraction (XRD), thermal analysis, scanning or transmission electron microscopy (SEM/TEM), and Brunauer-Emmett-Teller (BET) surface area measurements. The results notably revealed that FeVO 4 •1.1 H 2 O and FeV 3 O 9 •2.6 H 2 O have close structural similarities with two minerals fervanite and kazakhstanite, respectively.