The individual steps of the preparation of M-type Ba-hexaferrite particles by the glass crystallization method were studied by means of Moessbauer spectroscopy. As starting materials, three different compositions of the system Fe2O3-BaO-B2O3were used. The amorphous base materials were prepared by the twin roller quenching method. In these materials Fe3+ions occupy both the tetrahedral and the octahedral sites in the glassy network. At high annealing temperatures not only the crystalline Ba-hexaferrite phase, but also an amount of approximately 16% of glassy phase can be found. The Fe3+content at octahedral sites in the glassy phase rises from about 25% at an annealing temperature of 300°C to about 70 to 90% in annealing above 780°C.