The crystal structure of blatterite, Sb (super 5+) (sub 3) (Mn (super 3+) ) (sub 9) (Mn (super 2+) ,Mg) (sub 35) (BO (sub 3) ) (super 16) O (super 32) , and structural hierarchy in Mn (super 3+) -bearing zigzag borates

The crystal structure of blatterite (a 37.654, b 12.615, c 6.2472 Aa, V 2968 Aa (super 3) , space group Pnnm, Z = 2, D (sub calc) 4.25 g/cm (super 3) ) has been solved and refined to R 4.3%. The structure and the result of EPMA on the same crystal has led to a major revision of the chemical formula. There are 31 crystallographically distinct cations: two Sb sites occupied by Sb (super 5+) , five Mn sites occupied by octahedrally coordinated Mn (super 3+) , nine M sites occupied by octahedrally coordinated (Mn (super 2+) ,Mg), eight B sites occupied by triangularly coordinated B, and seven X sites occupied by Mn (super 2+) ,[]); five of the X sites are octahedrally coordinated and two are tetrahedrally coordinated. Blatterite is a member of the 3 Aa 'wallpaper-borate' structures in which [MO (sub 4) ] chains of edge-sharing octahedra extend along c and are cross-linked by (BO (sub 3) ) groups. There is a group of Mn (super 3+) -bearing structures (fredrikssonite, orthopinakiolite, takeuchiite, blatterite, pinakiolite) here designated as the zigzag borates; the crystal chemistry of this group is discussed and revised chemical formulae are given for all members of the group.