Diopside specimens from Castellaccio are difficult to find today. They show aggregates of radiated prismatic diopside crystals with a lavender hue due to manganese content. It is the best known species found in rodingite (a metasomatic rock) from this Italian quarry. Various analyzes have shown the presence of Co (0.5% by weight in CoO) and Mn (1.5% by weight in MnO). Associated minerals include perovskite, grossular, andradite, magnetite, titanite, apatite, pyrrhotite, and calcite (Bedognè et al., 2006). With an interesting label, from the Naïf mineral dealer (Bormio), but I have not found more information about.

Bedognè, F., Montrasio, A., Sciesa, E. (2006): I minerali della medio-alta Valtellina delle Orobie e della Val Poschiavo. Aggiornamenti sulle altre località della provincia di Sondrio. Tipografia Bettini, Sondrio, 255 pp.