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Crystal structure of the (REE)-uranyl carbonate mineral kamotoite-(Y)

Published online by Cambridge University Press:  02 January 2018

Jakub Plášil*
Affiliation:
Institute of Physics ASCR, v.v.i., Na Slovance 2, CZ-182 21 Prague 8, Czech Republic
Václav Petříček
Affiliation:
Institute of Physics ASCR, v.v.i., Na Slovance 2, CZ-182 21 Prague 8, Czech Republic
*

Abstract

Kamotoite-(Y) is a rare supergene product of uraninite hydration–oxidation weathering and its structure is unknown. Based on single-crystal X-ray diffraction data collected with high-redundancy using a microfocus source, kamotoite-(Y) is monoclinic, has space group P21/n,with a = 12.3525(5), b = 12.9432(5), c = 19.4409(7) Å, β = 99.857(3)°, V = 3069.8(2) Å3 and Z = 4. Crystals are pervasively twinned (two-fold rotation around [0.75 0 0.75]), giving a strongly pseudo-orthorhombic diffractionpattern. The pseudoorthorhombic pattern can be described with an orthorhombic super-cell (transformation matrix 0,1,0/1,0,1/3,0,1), approximately four times larger in volume then a true monoclinic unit cell. This unit-cell is the same as the cell given elsewhere for the structure of bijvoetite-(Y),another (REE)-containing uranyl carbonate. The successful structure solution and refinement (R = 0.044 for 6294 unique observed reflections), carried out using our choice of unit cell, as well as the superstructure refinement and comparison of the original structure data forbijvoetite-(Y) reveal that these two crystal structures are identical. The crystal structure of kamotoite-(Y) consists of electroneutral sheets of the bijvoetite-(Y) uranylanion topology and an interlayer with H2O molecules not-coordinated directly to any metal cation. Despite determinationof the kamotoite-(Y) structure and demonstration that bijvoetite-(Y) has the same structure, the identity of these two minerals cannot be proved without additional study of the holotype material.

Type
Research Article
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2017

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References

Brown, I.D. (1981) The bond-valence method: an empirical approach to chemical structure and bonding. Pp. 130 in: Structure and Bonding in Crystals (M. O'Keeffe and A. Navrotsky, editors). Vol. 2, Academic Press, New York.Google Scholar
Brown, I.D. (2002) The Chemical Bond in Inorganic Chemistry. The Bond Valence Model. Oxford University Press, Oxford, UK.Google Scholar
Burns, P.C. (2005) U6+ minerals and inorganic compounds: insights into an expanded structural hierarchy of crystal structures. The Canadian Mineralogist, 43, 18391894.CrossRefGoogle Scholar
Burns, P.C. and Finch, R.J. (1999) Wyartite: crystallo-graphic evidence for the first pentavalent-uranium mineral. American Mineralogist, 84, 14561460.CrossRefGoogle Scholar
Burns, P.C., Ewing, R.C. and Hawthorne, F.C. (1997) The crystal chemistry of hexavalent uranium: polyhedron geometries, bond-valence parameters, and polymerization of polyhedra. The Canadian Mineralogist, 35, 15511570.Google Scholar
Deliens, M. and Piret, P. (1982) Bijvoetite et lepersonnite, carbonates hydrates d'uranyle et de terres rares de Shinkolobwe, Zaïre. The Canadian Mineralogist, 20, 231238.Google Scholar
Deliens, M. and Piret, P. (1986) La kamotoïte-(Y), un nouveau carbonate d'uranyle et de terres rares de Kamoto, Shaba, Zaïre. Bulletin de la Société française de Minéralogie et de Cristallographie, 109, 643647.Google Scholar
Deliens, M. and Piret, P. (1989) La shabaite-(Nd), Ca (TR)2(UO2)(CO3)4(OH)2.6H2O, nouvelle espece minerale de Kamoto, Shaba, Zaire. European Journal of Mineralogy, 1, 8588.CrossRefGoogle Scholar
Deliens, M. and Piret, P. (1990) L'astrocyanite-(Ce), Cu2 (TR)2(UO2)(CO3)4(OH)2.1.5H2O, nouvelle espece minerale de Kamoto, Shaba, Zaïre. European Journal of Mineralogy, 2, 407411.CrossRefGoogle Scholar
Finch, R.J., Cooper, M.A., Hawthorne, F.C. andEwing, R. C. (1999) Refinement of the crystal structure of rutherfordine. The Canadian Mineralogist, 37, 929938.Google Scholar
Ginderow, D. and Cesbron, F. (1985) Structure de la roubaultite, Cv-fTJO-CO-O-OH--O. Acta Crystallographica, C41, 654657.Google Scholar
Hawthorne, F.C. and Schindler, M. (2008) Understanding the weakly bonded constituents in oxysalt minerals. Zeitschrift für Kristallographie, 223, 4168.Google Scholar
Hughes, K.A. and Burns, P.C. (2003) A new uranyl carbonate sheet in the crystal structure of fontanite, Ca [(UO2)3(CO3)2O2](H2O)6 . American Mineralogist, 88, 962966.CrossRefGoogle Scholar
Langmuir, D. (1978) Uranium minerals-solution equilibria. Geochimica et Cosmochimica Acta, 42, 547569.CrossRefGoogle Scholar
Li, Y., Burns, P.C. and Gault, R.A. (2000) A new rare-earth-element uranyl carbonate sheet in the structure of bijvoetite. The Canadian Mineralogist, 38, 153162.CrossRefGoogle Scholar
Oxford Diffraction (2006) CrysAlis RED andABSPACK in CrysAlis RED. Oxford Diffraction Ltd, Abingdon, UK.Google Scholar
Petricek, V., Dušek, M. and Palatinus, L. (2014) Crystallographic Computing System Jana 2006: general features. Zeitschrift für Kristallographie, 229, 345352.Google Scholar
Plášil, J. (2014) Oxidation—hydration weathering of uraninite: the current state-of-knowledge. Journal of Geosciences, 59, 99114.CrossRefGoogle Scholar
Schindler, M. and Hawthorne, F.C. (2008) The stereo-chemistry and chemical composition of interstitial complexes in uranyl-oxysalt minerals. The Canadian Mineralogist, 46, 467501.CrossRefGoogle Scholar
Sheldrick, G.M. (2015) SHELXT-Integrated space-group and crystal-structure determination. Acta Crystallographica, A71, 38.Google Scholar
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