MAHLMOODITE, FEZR(PO4)2.4H2O, A NEW IRON ZIRCONIUM-PHOSPHATE MINERAL FROM WILSON-SPRINGS, ARKANSAS

Small (< 0.5 mm) cream white spheres observed in V ore from the Union Carbide mine at Wilson Springs, Garland County, Arkansas, have been id entified as ferrous zirconium phosphate tetrahydrate, FeZr(PO4)2 - 4H2 O. This new mineral, named mahlmoodite, occurs as spherules of radiati ng fibers usually perched on crystals of pyroxene in vugs. The X-ray p owder diffraction data, which are analogous to those of synthetic alph a-MZr(PO4)2.4H2O where M is a divalent cation Mn, Ni, Co, Cu, or Zn, h ave been indexed on a monoclinic lattice in space group P2(1)/c. The r efined unit-cell dimensions are a = 9.12(2) angstrom, b = 5.42(1) angs trom, c = 19.17(2) angstrom, beta = 94.8(1)-degrees; Z = 4. Density (c alc.) is 2.877 g/cm3. The strongest powder lines are (hkl), d, I: (002 ), 9.58, 75; (111BAR), 4.572, 65; (104BAR), 4.382, 80; (104), 4.092, 6 0; (204), 3.160, 1 00; (3 10), 2.640, 70. The soft, lathlike fibers ha ve optically negative refractive indices beta = gamma = 1.650 in the p lane of the laths, and alpha < 1.646.