Abstract
The crystal structure of four samples from natural wolframite solid solutions, (Fe,Mn)WO4, was obtained with synchrotron high-resolution powder X-ray diffraction (HRPXRD) data, Rietveld refinements, space group P2/c, and Z = 2. Wolframite solid solutions extend from ferberite (FeWO4) to hübnerite (MnWO4). The W and (Mn,Fe) cations are in six-fold coordination. This study shows that the unit-cell parameters, a, b, c, and β angle, vary linearly with the unit-cell volume, V, across the wolframite series. The average <Mn,Fe–O> distance increases linearly because of larger Mn2+ (0.83 Å) replacing smaller Fe2+ (0.78 Å) cations, whereas the average <W–O> distance increases slightly because of the higher effective charge of the smaller Fe2+ cation. The distortions of the two types of polyhedra across the series are discussed.
Highlights
Wolframite solid solutions extend from ferberite (FeWO4) to hübnerite (MnWO4)
The wolframite structure is based on W and (Fe,Mn) distorted octahedra forming infinite zig zag chains along the c-axis (Figure 1c)
This study examines the structural variations across wolframite solid solutions based on the crystal structure of four natural samples that were obtained using synchrotron highresolution powder X-ray diffraction (HRPXRD) data and Rietveld structure refinements
Summary
Wolframite solid solutions extend from ferberite (FeWO4) to hübnerite (MnWO4). According to IMA CNMNC, wolframite with Fe > Mn is called ferberite and those with Mn > Fe is called hübnerite. The monoclinic wolframite-group minerals (space group P2/c) contain small divalent cations, such as Fe2+, Mn2+, Mg2+, Ni2+, and Co2+ in six-coordination with O atoms from six different octahedral WO6 groups (Figure 1).
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