The principal goal of the Rome group is studying crystalline materials, especially minerals: MS information (Fe oxidation state, Fe3+/Fetot ratios, Fe ions ordination number, Fe atoms aggregation state) is used together with stmchlral and chemical data collected on the same single-phase material to retrieve the topochemical model and to explain the physical properties. Outstanding materials shldied so far are: nahlral and synthetic spinels, natural borosilicates (tourmaline and axinite), natural amphiboles (especially fibres), natural and synthetic zeolites, but also obsidian, pumice, day and other heterogeneous materials.