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Twinning and incommensurate modulation in baumoite, Ba0.5[(UO2)3O8Mo2(OH)3](H2O)~3, the first natural Ba uranyl molybdate

  • Peter Elliott (a1) (a2), Jakub Plášil (a3), Václav Petříček (a4), Jiří Čejka (a5) and Luca Bindi (a6) (a7)...


Baumoite, Ba0.5[(UO2)3O8Mo2(OH)3](H2O)~3, is a new mineral found near Radium Hill, South Australia, where it occurs in a granite matrix associated with baryte, metatorbernite, phurcalite and kaolinite. Baumoite forms thin crusts of yellow to orange–yellow tabular to prismatic crystals. The mineral is translucent with a vitreous lustre and pale yellow streak. Crystals are brittle, the fracture is uneven and show one excellent cleavage. The Mohs hardness is ~2½. The calculated density is 4.61 g/cm3. Optically, baumoite crystals are biaxial (–), with α = 1.716(4), β = 1.761(4), γ = 1.767(4) (white light); and 2Vcalc = 42.2°. Electron microprobe analyses gave the empirical formula Ba0.87Ca0.03Al0.04U2.97Mo2.02P0.03O22H11.99, based on 22 O atoms per formula unit. The eight strongest lines in the powder X-ray diffraction pattern are [dobs Å (I) (hkl)]: 9.175(39)(12 ${\bar 1}$ ), 7.450(100)(020), 3.554(20)(221), 3.365(31)(004, 202), 3.255(31)(123, 30 ${\bar 2}$ ), 3.209(28)(12 ${\bar 4}$ ), 3.067(33)(30 ${\bar 3}$ , 222, 32 ${\bar 2}$ ) and 2.977(20)(142). Single-crystal X-ray studies (R1 = 5.85% for 1892 main reflections) indicate that baumoite is monoclinic, superspace group X2/m(a0g)0s with X = (0,½,0,½), with unit-cell parameters: a = 9.8337(3), b = 15.0436(5), c = 14.2055(6) Å, β = 108.978(3)°, V = 1987.25(13) Å3 and Z = 4. The crystal structure is twinned and incommensurately modulated and is based upon sheets of U6+ and Mo6+ polyhedra of unique topology. Four independent cationic sites partially occupied by Ba atoms are located between the sheets, together with H2O molecules.


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*Author for correspondence: Peter Elliott, Email:


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Associate Editor: Ian T. Graham



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Barik, S.K., Chatterjee, S. and Choudhary, R.P.N. (2014) Molecular and impedance spectrosocpy of Na2Mo2O7 ceramics. Praman – Journal of Physics, 83, 571577.
Bartlett, J.R. and Cooney, R.P. (1989) On the determination of uranium-oxygen bond lengths in dioxouranium(VI) compounds by Raman spectroscopy. Journal of Molecular Structure, 193, 295300.
Callen, R.A. (1990) Curnamona, South Australia, sheet SH/54-14. South Australia Geological Survey 1:250 000 Series Explanatory Notes.
Campana, B. and King, D. (1958) Regional Geology and Mineral Resources of the Olary Province. Geological Survey of South Australia, Bulletin, 34, 133 p.
Čejka, J. (1999) Infrared spectroscopy and thermal analysis of the uranyl minerals. Pp. 521–622 in: Uranium: Mineralogy, Geochemistry and the Environment (Burns, P.C. and Finch, R., editors). Reviews in Mineralogy, 38. Mineralogical Society of America, Chantilly, Virginia, USA.
Dickinson, S.B., Sprigg, R.C., King, D., Wade, M.L., Webb, B.P. and Whittle, A.W.G. (1954) Uranium Deposits in South Australia. Geological Survey of South Australia Bulletin, 30, 151 p.
Elliott, P., Plášil, J., Petríček, V., Čejka, J. and Bindi, L. (2017) Baumoite, IMA 2017-054. CNMNC Newsletter No. 39, October 2017, page 1282; Mineralogical Magazine, 81, 1279–1286.
Fedoseev, A.M., Budantseva, N.A., Shirokova, I.B., Andreev, G.B., Yurik, T.K. and Krupa, J.C. (2001) Synthesis and physicochemical properties of uranyl molybdate complexes of ammonium, potassium, rubidium, and cesium ions. Russian Journal of Inorganic Chemistry, 46, 4043.
Flint, D.J. and Parker, A.J. (1993) Willyama Inliers. Pp. 8293 in: The Geology of South Australia, vol. I, The Precambrian. (Drexel, J.F., Preiss, W.V. and Parker, A.J., editors). South Australia Geological Survey, Bulletin, 54.
Fomichev, V.V., Poloznikova, M.E. and Kondratova, O.I. (1992) Structure features, spectroscopic and energy characteristics of alkali metal molybdates and tungstates. Uspekhi Khimii, 61, 16011622.
Forbes, B.G. (1991) Olary, South Australia, sheet SI 54-2. South Australia Geological Survey I: 250 000 Series Explanatory Notes.
Frost, R.L., Čejka, J. and Dickfos, M.J. (2008) Raman and infrared spectroscopic study of the molybdate-containing uranyl mineral calcurmolite. Journal of Raman Spectroscopy, 39, 779785.
Hardcastle, F.D. and Wachs, I. (1990) Determination of molybden-oxygen bond distance and bond orders by Raman spectroscopy. Journal of Raman Spectroscopy, 21, 683691.
Hunter, B.A. (1998) Rietica – A Visual Rietveld Program. Commission on Powder Diffraction Newsletter, 20, 21.
Jaszczak, J.A., Rumsey, M.S., Bindi, L., Hackney, S.A., Wise, M.A., Stanley, C.J. and Spratt, J. (2016) Merelaniite, Mo4Pb4VSbS15, a new molybdenum-essential member of the cylindrite group, from the Merelani tanzanite deposit, Lelatema Mountains, Manyara Region, Tanzania. Minerals, 6, 115.
Katscher, H., Jehn, H. and Kurtz, W. (editors) (1990) Gmelin Handbook of Inorganic Chemistry, 8th Edition, Mo Supplement Vol. B5, p. 218–220. Springer, Berlin-Heidelberg.
Krivovichev, S.V. (2014) K2Na8(UO2)8Mo4O24[(S,Mo)O4], the first uranium molybdosulfate: synthesis, crystal structure, and comparison to related compounds. Journal of Geosciences, 59, 115121.
Krivovichev, S.V. and Burns, P.C. (2003) Crystal chemistry of uranyl molybdates. X. The crystal structure of Ag10[(UO2)8O8(Mo5O20)]. The Canadian Mineralogist, 41, 14551462.
Le Bail, A., Duroy, H. and Fourquet, J.L. (1988) Ab-initio structure determination of LiSbWO6 by X-ray powder diffraction. Materials Research Bulletin, 23, 447452.
Libowitzky, E. (1999) Correlation of O–H stretching frequencies and O–H···O hydrogen bond lengths in minerals. Monatshefte für Chemie, 130, 10471059.
Lussier, A.J., Lopez, R.A.K. and Burns, P.S. (2016) A revised and expanded structure hierarchy of natural and synthetic hexavalent uranium compounds. The Canadian Mineralogist, 54, 177283.
Mączka, M., Pietraszko, A., Paraguassu, W., Souza Filho, A.G., Freire, P.T.C., Mendes Filho, J. and Hanuza, J. (2009) Strucural and vibrational properties of K3Fe(MoO4)(Mo2O7) – a novel layered molybdate. Journal of Physics: Condensed Matter, 21, 18.
Makovicky, E., Petříček, V., Dušek, M. and Topa, D. (2011) The crystal structure of franckeite, Pb21.7Sn9.3Fe4.0Sb8.1S56.9. American Mineralogist, 96, 16861702.
Mandarino, J.A. (1981) The Gladstone-Dale relationship: Part IV: The compatibility concept and its application. The Canadian Mineralogist, 19, 441450.
Nakamoto, K. (2009) Infrared and Raman Spectra of Inorganic and Coordination Compounds Part A. Theory and Applications in Inorganic Chemistry. Wiley and Sons, Hoboken, USA.
Olds, T.A., Lussier, A.J., Oliver, A.G., Petříček, V., Plášil, J., Kampf, A.R., Burns, P.C., Dembowski, M., Carlson, S.M. and Steele, I.M. (2017) Shinkolobweite, IMA 2016-095. CNMNC Newsletter No. 36, April 2017, page 404; Mineralogical Magazine, 81, 403–409.
Palatinus, L. and Chapuis, G. (2007) Superflip – a computer program for the solution of crystal structures by charge flipping in arbitrary dimensions. Journal of Applied Crystallography, 40, 451456.
Petříček, V., Malý, K., Coppens, P., Bu, X., Císařová, I and Frost-Jensen, A. (1991) The description and analysis of composite crystals. Acta Crystallographica, A47, 210216.
Petříček, V., Dušek, M. and Palatinus, L. (2014) Crystallographic computing system JANA2006: general features. Zeitschrift für Kristallographie, 229, 345352.
Petříček, V., Eigner, V., Dušek, M. and Čejchan, A. (2016) Discontinuous modulation functions and their application for analysis of modulated structures with the computing system JANA2006. Zeitschrift für Kristallographie, 231, 301312.
Plášil, J. (2018) The super-space approach to the structures of selected U6+ minerals and compounds. Aperiodic 2018 (9th Conference on Aperiodic Crystals), Abstract 56.
Plášil, J, Petříček, V., Locock, A.J., Škoda, R. and Burns, P.C. (2017) The (3 + 3) commensurately modulated structure of the uranyl silicate mineral swamboite-(Nd), Nd0.333[(UO2)(SiO3OH)](H2O)2.41. Zeitschrift für Kristallographie, 233, 223232.
Pouchou, J.L. and Pichoir, F. (1985) “PAP” φ(ρZ) procedure for improved quantitative microanalysis. Pp. 104106 in: Microbeam Analysis (Armstrong, J.T., editor). San Francisco Press, California.
Rigaku (2018) CrysAlis CCD and CrysAlis RED. Rigaku-Oxford Diffraction Ltd, Yarnton, Oxfordshire, UK.
Sidorenko, G.A., Chistyakova, N.T., Chukanov, N.V., Naumova, I.S. and Rossulov, V.A. (2005) Carcurmolite: New data on chemical composition and constitution the mineral. New Data on Minerals, 40, 2936.
Stevens, B.P.I, Barnes, R.G. and Forbes, B.G., (1990) Willyama Block – regional geology and minor mineralisation. Pp. 10651072 in: Geology of the Mineral Deposits of Australia and Papua New Guinea (Hughes, F.E., editor). Australasian Institute of Mining and Metallurgy, Monograph Series, 14.
Zhang, J. and Guo, Y. (2012) Preparation and characterization of large-sized ADM monocrystals. Applied Mechanics and Materials, 152–154, 126129.


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