The iron sulfate Na3Fe(SO4)3 studied here has been obtained as a high-temperature (HT) product (-400 °C) from the thermal decomposition of sideronatrite from Sierra Gorda (Chile) having composition Na2Fe(SO4)2(OH)⋅3H2O. The structure determination was carried out using synchrotron X‑ray powder diffraction. Structural data refined by the Rietveld method, up to Rp = 11.95%, are: space group R3̅, lattice parameters a = b = 13.6231(1) Å and c = 9.0698(1) Å, V = 1457.76(2) Å3, and Z = 6. The structure of Na3Fe(SO4)3 can be described in terms of FeO6 octahedra connected to sulfate tetrahedra by corner-sharing to form infinite chains [Fe(SO4)3]∞, running along c. These chains are joined together by Na atoms to build up a three-dimensional network of strong (Fe-O-S) and weak (Na-O) bonds. The topological relationships of Na3Fe(SO4)3 to the structure of some analog minerals are also discussed.
© 2015 by Walter de Gruyter Berlin/Boston