The effect of temperature on the crystallization of alpha-Fe2O3 particles from dense beta-FeOOH suspensions was monitored by Fe-57 Mossbauer spectroscopy, X-ray powder diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscopy and energy dispersive spectroscopy. Dense suspensions of very long laterally arranged beta-FeOOH fibrils were obtained at 90 degrees C. Crystallization at 120 degrees C between 18 and 72h yielded monodisperse alpha-Fe2O3 particles of a shape close to that of double spheres with ring. The double spheres with ring showed two narrow particle size distributions. In these particles a substructure was detected, i.e., the spheres consisted of the linear chains of interconnected alpha-Fe2O3 subparticles. With further rise in the crystallization temperature the increase in alpha-Fe2O3 particles and porosity became pronounced. Obviously, the aggregation mechanism played an important role in the formation of alpha-Fe2O3 particles. (C) 2009 Elsevier B.V. All rights reserved.