Reference Type | Journal (article/letter/editorial) |
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Title | Franconite, NaNb2O5(OH)·3H2O: structure determination and the role of H bonding, with comments on the crystal chemistry of franconite-related minerals |
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Journal | Mineralogical Magazine |
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Authors | Haring, M. M. M. | Author |
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McDonald, A. M. | Author |
Year | 2014 (June) | Volume | 78 |
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Page(s) | 591-607 | Issue | 3 |
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Publisher | Mineralogical Society |
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DOI | doi:10.1180/minmag.2014.078.3.09Search in ResearchGate |
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Mindat Ref. ID | 244522 | Long-form Identifier | mindat:1:5:244522:3 |
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GUID | 7c5c5cc3-d568-4cb6-9229-664845b39e18 |
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Full Reference | Haring, M. M. M., McDonald, A. M. (2014) Franconite, NaNb2O5(OH)·3H2O: structure determination and the role of H bonding, with comments on the crystal chemistry of franconite-related minerals. Mineralogical Magazine, 78 (3) 591-607 doi:10.1180/minmag.2014.078.3.09 |
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Plain Text | Haring, M. M. M., McDonald, A. M. (2014) Franconite, NaNb2O5(OH)·3H2O: structure determination and the role of H bonding, with comments on the crystal chemistry of franconite-related minerals. Mineralogical Magazine, 78 (3) 591-607 doi:10.1180/minmag.2014.078.3.09 |
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Abstract/Notes | AbstractThe crystal structure of franconite, NaNb2O5(OH)·3H2O, has been characterized by single-crystal X-ray diffraction using material from Mont Saint-Hilaire, Québec, Canada. Results givea= 10.119(2),b= 6.436(1),c= 12.682(2) Å and β = 99.91(3)° and confirm the correct space group asP21/c. The crystal structure, refined toR= 4.63% andwR2=11.95%, contains oneNasite, two distorted octahedralNbsites and nineOsites. It consists of clusters of four edge-sharing Nb(O,OH)6octahedra, linked through shared corners to adjacent clusters, forming layers of Nb(O,OH)6octahedra. These alternate along [100] with layers composed of NaO(H2O)4polyhedra, the two being linked together by well defined H bonding. The predominance of H bonding, essential to the mineral, results in a perfect {100} cleavage. Chemical analyses (n= 7) of four crystals give the empirical formula (Na0.73Ca0.13☐0.14)∑=1.00(Nb1.96Ti0.02Si0.02Al0.01)∑=2.01O5(OH)·3H2O (based on nine oxygens) or ideally NaNb2O5(OH)·3H2O. Franconite is crystallo-chemically related to SOMS [Sandia Octahedral Molecular Sieves; Na2Nb2−xMxO6−x(OH)x·H2O with M = Ti, Zr, Hf], a group of synthetic compounds with strong ion-exchange capabilities. Both hochelagaite (CaNb4O11·nH2O) and ternovite (MgNb4O11·nH2O) have X-ray powder diffraction patterns and cation ratios similar to those of franconite indicating that these minerals probably have similar structures. |
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