Crystal chemistry of stilbites: structure refinements of one normal and four chemically anomalous samples

Structural refinements were performed on 4 stilbites with anomalous chem. compns. as regards the monovalent/divalent cation ratio, and a normal stilbite. The 4 anomalous samples showed, moreover, a monoclinic angle lower than that expected from an empirical correlation between monovalent cation content and β angle. In all samples the 2 cationic sites characteristic of stilbite, were found; in only 1 sample was a new cationic site localized. One site is fully occupied by Ca alone, or, with some Na, whereas the other sites are fully or partially occupied by monovalent cations only. In the 5 stilbites, different nos. of water mol. sites were localized. The frameworks, however, seem to be unaffected by the no. and compn. of extra framework sites. The small β angle of the anomalous samples was only partially explained by structural data.