The crystal structure of masutomilite , Mn analogue of zinnwaldite

The crystal structure of masutomilite from Tanakamiyama, Ohtsu, Japan, has been refined by the X-ray single crystal method. The chemical formula is (K,.79 Na0-15 Rbo.,4)2.o8 (Li2,'4 Mn~~.. Fe~~18 Fe;~06 Al,.go Tio.o')5.74 (Si6.65 Al",,)8.o0 0'..64 (F'.'6 (OH)'.20)4.36 and the crystal data are as follows: monoclinic, C2, a = 5.262(2), b = 9.102(3), c = 10.094(3)A, i3 = 100.83(2t, Z = 1. The final R-value converged to 0.046 (wR = 0.052), using 519 independent reflections. The octahedral cation ordering, small Al and Fe3+ in the M(2) site, and the remaining large Li and Mn2+ in the M(1) and M(3) sites, results in the non-centro symmetric C2 structure. The mean bond length of M(2)~ o is 1.89A, and those of M(l)~O and M(3)-0 are 2.13 and 2.12A, respectively.