Abstract
Jahnsite, CaMn2+Mg2(H2O)8Fe3+2(OH)2[PO4]4,a 14.94(2)Å,b7.14(1)Å,c9.93(1) Å,β110.16(8)°,P2/a,Z=2, is one of the 7 Åoctahedral comer-linked chain structures allied to laueite, pseudolaueite, childrenite,etc. R(hkl)–0.09 for 2292 independent non-zero reflections.
The structure is based on a backbone of corner-linked … Fe3+-OH-Fe3+…octahedra with a novel arrangement of [PO4] tetrahedra about these chains. The structure possesses denses labs of [CaMn2+ Fe3+=(OH)2[PO]4]44− oriented parallel to {001} which are bridged by PO4 corner-sharing to Mg (O,H2O)8octahedra.
Polyhedral interatomic averages are viFe(l)-O 1.973Å,viFe(2)-0 1.973,viCa-0 2.418,viMn2+-O 2.190, viMg(l)-O 2.088, viMg(2)-O 2.089,ivP(l)-O 1.543, and viP(2)-O 1.533.
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