Host: Japan Association of Mineralogical Sciences
The crystal structure of sursassite, Mn2+2Al3Si3O11(OH) 3, from four different localities were investigated to find the structural and compositional relationships between sursassite and iso-structural macfallite including the nature of their hydrogen-bonding systems. There are three octahedral sites, M1, M2, and M3. Divalent cations order preferentially on M1 whereas in all samples M2 is occupied by Al only. Although there are three main hydroxyl groups occurring in sursassite, the exact number depends on the concentration of trivalent and divalent cations at the M1 site. If divalent cations occur at M1, a fourth OH group is necessary to maintain charge balance. Due to the influence of divalent cations on M1 in sursassite, the hydrogen-bond systems in sursassite and iso-structural macfallite are different.
