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Deliensite, ideally Fe(UO2)(2)(SO4)2(OH)(2).3H(2)O, is a new mineral species from the Mas d'Alary uranium deposit, in Lodeve, Herault, France. It occurs as submillimetric tabular crystals arranged in spherical aggregates, and is associated with uraninite, gypsum and pyrite. The crystals are pale yellow to grayish white in color with a vitreous luster, and nonfluorescent. D-meas 3.268 and D-calc 3.31 (empirical formula), 3.26 g/cm(3) (idealized formula); H-Mobs = 2 Optically biaxial negative, 2V = 73(2)degrees, alpha 1.432(calc.), beta 1.470(2) and gamma 1.492(3) with optical orientation Y and Z in plane (100), and Z parallel to elongation. The dispersion r > v is weak, and the crystals are nonpleochroic. Deliensite is orthorhombic, space group Pnnm or Pnn2, with unit-cell parameters refined from powder data: a 15.908(5), b 16.274(3), c 6.903(1) Angstrom, V 1787(1) Angstrom(3), a:b:c: 0.9775:1:0.4242, Z = 4. The crystals show a tabular habit, tenacity is weak, and the {100} cleavage is perfect. The strongest ten reflections of the X-ray powder-diffraction pattern [d in (Angstrom)(I)(hkl)] are: 7.95(81)(200), 5.90(100)(111), 4.26(31)(031), 4.20(37)(301), 3.94(71)(140), 3.45(67)(002), 3.165(50)(202), 2.893(41)(151), 2.596(70)(142) and 2.118(27)(033). Electron-microprobe and thermogravimetric analyses gave: FeO 7.42, UO3 67.63, SO3 17.37, H2O 8.63, total 101.05 wt.%. The empirical formula (based on O = 13) is Fe-0.909(UO2)(2.081)(SO4)(1.919)(OH)(2.082).3.179 H2O. Deliensite originates from the alteration of uraninite and primary sulfides, with a contribution from the host rocks. The mineral name honors Belgian mineralogist Michel Deliens. Holotype material is deposited in the mineralogical collection of the Royal Belgian Institute of Natural Sciences, Brussels, Belgium. |
