Different Zn and Mn-Zn ferrites have been obtained by High Energy Ball Milling (HEBM) from elemental oxides. By varying the rotation speed of vials and main disk, several modes of milling can be obtained. In this paper, the materials prepared by two modes of milling, called shock (S) and high shock (HS), are studied by XRD and Mossbauer spectroscopy. Several mechanisms for spinel phase formation have been proposed. In particular, a reduction of Fe(III) occurs for the S mode, which leads to the formation of a wustite-type phase which disappears after a long milling time. (C) 2004 Kluwer Academic Publishers.