Acta Cryst. (2003). E59, i125-i128 [ doi:10.1107/S1600536803017537 ]
Abstract: Mg-rich wolfeite [diiron(II) hydroxide phosphate], (FeII,Mg)2(PO4)(OH), from the Big Fish River area, Yukon Territory, Canada, is isotypic with its MnII-dominant analogue triploidite. The framework structure contains edge- and corner-sharing, distorted MO4(OH) and MO4(OH)2 (M = FeII or FeII,Mg) polyhedra linked by fairly regular PO4 tetrahedra. All atoms are on general positions. Four of the eight independent Fe sites contain between 9 and 25% Mg substituting for Fe. Two of these four sites show distorted trigonal-bipyramidal coordination, whereas the remaining two sites show distorted octahedral coordination. The average (FeII,Mg)-O bond length decreases with increasing Mg content. Average P-O distances range between 1.538 and 1.543 Å. The hydrogen bonds are all strongly bent and weak, with O
O distances > 2.73 Å, an observation confirmed by single-crystal Raman spectroscopic data which show five bands due to O-H stretching vibrations between 3478 and 3557 cm-1.
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