The crystal structure of jungite from the Hagendorf Süd pegmatite, Bavaria, has been determined using synchrotron diffraction data collected at the Australian Synchrotron microfocus beamline MX2.

The mineral has orthorhombic symmetry, space group Aba2, with cell parameters a = 11.995(2), b = 24.692(5) and c = 9.920(2) Å. The structure was refined to wRobs = 0.063 for 3558 reflections with I > 3σ(I). It is built from double heteropolyhedral layers parallel to (010) with [Ca(H2O)6]2+ hydrated cations and H-bonded H2O in the interlayer region. The heteropolyhedral layers comprise seven-member rings of corner-connected ZnO4 and PO4 tetrahedra and Fe3+2O10 dimers of edge-shared octahedra. From the refined structural model the formula is established as [Ca(H2O)6]2Zn4Fe3+8(PO4)8(OH)12(H2O)4·4H2O. The jungite specimen also contains crystals that indexed with triclinic cell parameters, a ≈ 11.95, b = 10.05, c = 9.9 Å, α ≈ 86.7, β =89.9 and γ = 83.4°. They gave poor diffraction due to multiple components with different orientations, but it was possible to extract intensity data for a single component and solve the structure. The model contains identical double heteropolyhedral layers parallel to (010) as in the orthorhombic mineral, but differs in that the Ca atoms are coordinated predominantly to layer anions. The formula obtained from the structural model is [Ca2(H2O)5]Zn4Fe3+8(PO4)8(OH)12(H2O)4·2H2O, corresponding to a dehydrated form of jungite, with a contraction in the layer spacing from 12.35 to 10.0 Å.