| Reference Type | Journal (article/letter/editorial) |
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| Title | The crystal structure of the new mineral dyrnaesite-(La),Na8CeIVREE2(PO4)6 |
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| Journal | Mineralogical Magazine |
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| Authors | Balić-Žunić, Tonči | Author |
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| Year | 2017 (February) | Volume | 81 |
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| Issue | 1 |
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| Publisher | Mineralogical Society |
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| DOI | doi:10.1180/minmag.2016.080.096Search in ResearchGate |
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| Classification | Not set | LoC | Not set |
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| Mindat Ref. ID | 244869 | Long-form Identifier | mindat:1:5:244869:9 |
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| GUID | 0 |
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| Full Reference | Balić-Žunić, Tonči (2017) The crystal structure of the new mineral dyrnaesite-(La),Na8CeIVREE2(PO4)6. Mineralogical Magazine, 81 (1) 199-208 doi:10.1180/minmag.2016.080.096 |
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| Plain Text | Balić-Žunić, Tonči (2017) The crystal structure of the new mineral dyrnaesite-(La),Na8CeIVREE2(PO4)6. Mineralogical Magazine, 81 (1) 199-208 doi:10.1180/minmag.2016.080.096 |
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| Abstract/Notes | Dyrnaesite-(La), Na7.89(Ce0.94Ca0.06)∑1.00(La1.14Ce0.40Pr0.10Nd0.24Ca0.12)∑2.00(PO4)6 is orthorhombic, Pnma, a = 18.4662(7), b= 16.0106(5), c = 7.0274(2) Å, V = 2077.7(1) Å3, Z = 4. The crystal structure is related to the group of Na3REE(XO4)2 compounds (with X = P, V, As), based on the aphthitalite/glaserite structural type. Dyrnaesite is distinct in having ordered Na vacancies, and a rare-earth element (REE) site occupied preferentially by Ce4+. This also distinguishes it from closely related vitusite-(Ce) [Na3REE(PO4)2]. The relation of their unit cells is: ad= bv, bd = 3av, cd = 1/2 cv. The distinct Ce4+ site in dyrnaesite-(La) has smaller coordination with shorter bond lengths than the other REE site in the same structure or the REE sites in vitusite-(Ce). It is adjacent to the predominately vacant Na site, which in its turn has the largest coordination of all Na sites in the structure. REE sites, or Na sites in a [010] row (similar to [100] in vitusite(Ce)) assume two types of coordinations with and without mirror symmetry and two different configurations of surrounding PO4 tetrahedra. This summarizes the topological difference to vitusite-(Ce) where the corresponding coordinations are similar in the same row and intermediate in character to the two types in dyrnaesite-(La). |
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