Abstract
Bustamite is triclinic, space group Fl, with cell dimensions a = 15.412 A., b=7.157A., c=13.824A., a=89°29', fJ=94°51', y=102°56'. The unit cell ideally contains 12(CaMnSiz06). Three-dimensional intensity data were gathered with the single-crystal Geiger-counter diffractometer. Application of the minimum function to P(xz), and comparison of the unit cells of bustamite and wollastonite yielded a trial structure which was refined with least-squares. Planes of approximately close-packed oxygen atoms are oriented parallel to (101). Planes containing Ca and Mn atoms in octahedral coordination alternate with planes of Si atoms in tetrahedral coordination between oxygen planes. Ca and Mn are ordered. Si tetrahedra are linked to form chains parallel to b with a repeat unit of three tetrahedra.
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