Eight-Membered Cyclosilicate Rings in Muirite

Science  03 Sep 1971:
Vol. 173, Issue 4000, pp. 916-918
DOI: 10.1126/science.173.4000.916


The determination of the crystal structure of muirite, Ba10(Ca,Mn,Ti)4Si8O24(Cl,OH,O)12 · 4H2O, revealed the presence of discrete cyclic silicate anions, (Si8O24)16-, formed by the condensation of eight silicate tetrahedra. This first reported occurrence of eight-membered rings is of particular interest, because rings with eight tetrahedra are reported to be energetically less stable than rings with six tetrahedra, which have been found in many minerals.