Hochleitnerite, [K(H2O)]Mn-2(Ti2Fe)(PO4)(4)O-2(H2O)(10)center dot 4H(2)O, a new paulkerrite-group mineral, from the Hagendorf-Sud pegmatite, Oberpfalz, Bavaria, Germany

Hochleitnerite, [K(H2O)]Mn-2(Ti2Fe)(PO4)(4)O-2(H2O)(10)center dot 4H(2)O, is a new paulkerrite-group mineral from the Hagendorf-Sud pegmatite, Oberpfalz, Bavaria, Germany. It was found in specimens of altered zwieselite, in association with fluorapatite, rockbridgeite, columbite and sub-micrometre rods of uranophane. Hochleitnerite occurs as isolated and intergrown pale-yellow, diamond-shaped tablets with thicknesses reaching 50 mu m and lengths of 120 mu m. The crystals are flattened on {010}, slightly elongated on [001], and bounded by the {111} and {010} forms. The calculated density is 2.40 g cm(-3). Optically, hochleitnerite crystals are biaxial (+), with alpha = 1.615(2), beta = 1.621(2) and gamma = 1.645(2) (measured in white light). The calculated 2V is 53.8 degrees. The empirical formula is [K(H2O)](Mn1.512+Fe0.492+)(Sigma 2.00)(Ti1.624+Fe0.193+Al0.15)(Sigma 2.96)(PO4)(4.00)[O1.50F0.23(OH)(0.27)](Sigma 2.00)(H2O)(10)center dot 4H(2)O. Hochleitnerite has space group Pbca and unit-cell parameters alpha = 10.5513(3) angstrom, b = 20.6855(17) angstrom, c = 12.4575(4) angstrom, V = 2718.96(15) angstrom(3) and Z = 4. The crystal structure was refined using single-crystal data to wR(obs) = 0.082 for 2242 reflections with I > 3 sigma(I). The crystal structure contains corner-connected linear trimers of Ti-centred octahedra that share corners with PO4 tetrahedra to form 10-member rings parallel to (010). K+ cations and water molecules are located within the rings. Additional corner sharing of the PO4 tetrahedra with MnO2(H2O)(4) octahedra occurs along [010] to complete the 3D framework structure.