The thermal analysis of Fe-8(OOH)(16)Cl-1.3 (Akagancite-M) nanospindles prepared by the hydrolysis of FcCl(3) solutions are determined by thermogravimetric analyses and differential scanning calorimetry (TG/DSC), in conjunction with field-emission scanning electron microscopy (FE-SEM), and X-ray diffraction (XRD). Different products are formed after Fe-8(OOH)(16)Cl-1.3 nanospindles are calcined at different temperatures for 30 min in N-2 atmosphere: Fe-1.833(OH)(0.5)O-2.5 and magnetite obtained at 250 degrees C: pure magnetite (Fe3O4) obtained at 630 degrees C; and magnetite containing some iron nitrides (Fe2N and Fe4N) obtained at 800 degrees C. The calcination of Fe-8(OOH)(16)Cl-1.3 provides a new method to prepare pure magnetite. (C) 2007 Elsevier Ltd. All fights reserved.