| Reference Type | Journal (article/letter/editorial) |
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| Title | Contribution to the crystal chemistry of lead-antimony sulfosalts: systematic Pb-versus-Sb crossed substitution in the plagionite homologous series, Pb2N−1(Pb1−xSbx)2(Sb1−xPbx)2Sb6S13+2N |
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| Journal | European Journal of Mineralogy |
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| Authors | Moëlo, Yves | Author |
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| Biagioni, Cristian | Author |
| Year | 2020 (November 14) | Volume | 32 |
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| Issue | 6 |
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| Publisher | Copernicus GmbH |
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| URL | |
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| Download URL | https://ejm.copernicus.org/articles/32/623/2020/ejm-32-623-2020.pdf+ |
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| DOI | doi:10.5194/ejm-32-623-2020Search in ResearchGate |
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| Classification | Not set | LoC | Not set |
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| Mindat Ref. ID | 16773145 | Long-form Identifier | mindat:1:5:16773145:2 |
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| GUID | 0 |
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| Full Reference | Moëlo, Yves, Biagioni, Cristian (2020) Contribution to the crystal chemistry of lead-antimony sulfosalts: systematic Pb-versus-Sb crossed substitution in the plagionite homologous series, Pb2N−1(Pb1−xSbx)2(Sb1−xPbx)2Sb6S13+2N. European Journal of Mineralogy, 32 (6) 623-635 doi:10.5194/ejm-32-623-2020 |
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| Plain Text | Moëlo, Yves, Biagioni, Cristian (2020) Contribution to the crystal chemistry of lead-antimony sulfosalts: systematic Pb-versus-Sb crossed substitution in the plagionite homologous series, Pb2N−1(Pb1−xSbx)2(Sb1−xPbx)2Sb6S13+2N. European Journal of Mineralogy, 32 (6) 623-635 doi:10.5194/ejm-32-623-2020 |
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| In | (2020) European Journal of Mineralogy Vol. 32 (6) Schweizerbart |
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| Abstract/Notes | The plagionite homologous series contains four well-defined members with the general formula Pb1+2NSb8S13+2N: fülöppite (N=1), plagionite (N=2), heteromorphite (N=3), and semseyite (N=4). The crystal structure of several natural and synthetic samples of fülöppite, plagionite, and semseyite have been refined through single-crystal X-ray diffraction, confirming the systematic Pb-versus-Sb crossed substitution observed previously in semseyite and fülöppite. This crossed substitution takes place mainly in two adjacent cation sites in the middle of the constitutive SnS-type layer. The substitution coefficient x appears variable, even for a given species, with the highest values observed in synthetic fülöppite samples. The developed structural formula of the plagionite homologues can be given as Pb2N−1(Pb1−xSbx)2(Sb1−xPbx)2Sb6S13+2N. In the studied samples, x varies between ∼ 0.10 and 0.40. In the ribbons within the SnS-type layer, (Pb∕Sb) mixing can be considered the result of the combination, in a variable ratio, of two cation sequences, i.e. (Sb–Sb–Sb)–Pb–Sb–(…), major in plagionite and semseyite, and (Sb–Sb–Sb)–Sb–Pb–(…), major in fülöppite and, probably, in heteromorphite. The published crystal structure of synthetic “Pb-free fülöppite” is revised according to this approach. It would correspond to a Na derivative, with a proposed structural formula of (Na0.5Sb0.5)(Na0.2Sb0.8)2(Na0.3Sb0.7)2Sb6S15, ideally Na1.5Sb9.5S15. In fülöppite, increasing x induces a flattening of the unit cell along c, with a slight volume decrease. Such a general Pb-versus-Sb crossed substitution would attenuate steric distortions in the middle of the SnS-type layer of the plagionite homologous series. Crystallization kinetics seem the main physical factor that controls such an isochemical substitution. |
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