Abstract: Nollmotzite (IMA2017-100), Mg[UV(UVIO2)2F3O4](H2O)4, is a new uranium oxide fluoride mineral found in the Clara mine, Black Forest Mountains, Germany. Electron microprobe analysis provided the empirical formula (Mg1.06Cu0.02)?1.08[UV(UVIO2)2O3.85F3.15][(H2O)3.69(OH)0.31]?4.00 based on three U and 15 O + F atoms per formula unit. Nollmotzite is monoclinic, space group Cm, with a = 7.1015 (12) Å, b = 11.7489?(17) Å, c = 8.1954 (14) Å, ß = 98.087 (14)°, V = 676.98?(19) Å3 and Z = 2. The crystal structure [twinned by reticular merohedry; refined to R = 0.0369 with GoF = 1.09 for 1527 unique observed reflections, I > 3 (I)] is based upon [UV(UVIO2)2F3O4]2- sheets of ?-U3O8 topology and contains an interlayer with MgF2(H2O)4 octahedra. Adjacent sheets are linked through F-Mg-F bonds, as well as via hydrogen bonds. The presence of fluorine and pentavalent uranium in the structure of nollmotzite has potentially important implications for the safe disposal of nuclear waste.
*Abstract online at https://www.ncbi.nlm.nih.gov/pubmed/30141421