Mechanical activation by grinding is a complex process involving alteration of structure, chemical composition and properties of solid substances, In this article the characteristic features of mechanically induced changes in minerals with close packed anion sublattice are illustrated on the example of planetary and vibration ground chalcopyrite. Summarizing the results of a longlasting research involving data obtained by Mossbauer spectroscopy, ESR, XPS, XRD and measuring of magnetic susceptibility, the changes in surface composition are characterised and a critical structure favourable loosening for a magnetic order-disorder transformation is specified. The chemical consequences of the structural metastability have been demonstrated by promoting of industrially important processes, namely non-oxidative and oxidative decomposition as well as direct leaching of mechanically activated chalcopyrite.