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Sökning: WFRF:(Bosi Ferdinando)

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  • Biagion, Cristian, et al. (författare)
  • The crystal structure of turneaureite, Ca<sub>5</sub>(AsO<sub>4</sub>)<sub>3</sub>Cl, the arsenate analog of chlorapatite and its relationships with the arsenate apatites johnbaumite and svabite
  • 2017
  • Ingår i: American Mineralogist. - 0003-004X .- 1945-3027. ; 102, s. 1981-1986
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>The crystal structure of turneaureite, ideally Ca<sub>5</sub>(AsO<sub>4</sub>)<sub>3</sub>Cl, was studied using a specimen from the Brattfors mine, Nordmark, Värmland, Sweden, by means of single-crystal X-ray diffraction data. The structure was refinedto R1 = 0.017 on the basis of 716 unique reflectios with F<sub>o</sub> &gt; 4σ(F<sub>o</sub>) in the <em>P</em>6<sub>3</sub>/<em>m</em> space group, with unit-cell parameters <em>a</em> = 9.9218(3), <em>c </em>= 6.8638(2) Å, V = 585.16(4) Å<sup>3</sup>. The chemical composition of the sample, determined by electron-microprobe analysis, is (in wt%; average of 10 spot analyses): SO<sub>3</sub> 0.22, P<sub>2</sub>O<sub>5</sub> 0.20, V<sub>2</sub>O<sub>5</sub> 0.01, As<sub>2</sub>O<sub>5</sub> 51.76, SiO<sub>2</sub> 0.06, CaO 41.39, MnO 1.89, SrO 0.12, BaO 0.52, PbO 0.10, Na2O 0.02, F 0.32, Cl 2.56, H<sub>2</sub>O<sub>calc</sub> 0.58, O(≡F+Cl) –0.71, total 99.04. On the basis of 13 anions per formula unit, the empirical formula corresponds to (Ca<sub>4.82</sub>Mn<sub>0.17</sub>Ba<sub>0.02</sub>Sr<sub>0.01</sub>)∑<sub>5.02</sub> (As<sub>2.94</sub>P<sub>0.02</sub>S<sub>0.02</sub>Si<sub>0.01</sub>)<sub>∑2.99</sub>O<sub>12</sub>[Cl<sub>0.47</sub>(OH)<sub>0.42</sub>F<sub>0.11</sub>]<sub>∑1.00</sub>.Turneaureite is topologically similar to the other members of the apatite supergroup: columns of face-sharing M1 polyhedra running along c are connected through TO<sub>4</sub> tetrahedra with channels hosting M2 cations and X anions. Owing to its particular chemical composition, the studied turneaureite can be considered as a ternary calcium arsenate apatite; consequently it has several partially filledanion sites within the anion columns. Polarized single-crystal FTIR spectra of the studied sample indicate stronger hydrogen bonding and less diverse short-range atom arrangements around (OH) groups in turneaureite as compared to the related minerals johnbaumite and svabite. An accurate knowledge of the atomic arrangement of this apatite-remediation mineral represents an improvement in our understanding of minerals able to sequester and stabilize heavy metals such as arsenic in polluted areas.</p>
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  • Biagioni, Cristian, et al. (författare)
  • The crystal structure of svabite, Ca<sub>5</sub>(AsO<sub>4</sub>)<sub>3</sub>F, an arsenate member of the apatite supergroup
  • 2016
  • Ingår i: American Mineralogist. - 0003-004X .- 1945-3027. ; 101, s. 1750-1755
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>The crystal structure of svabite, ideally Ca<sub>5</sub>(AsO<sub>4</sub>)<sub>3</sub>F, was studied using a specimen from the Jakobsberg mine, Värmland, Sweden, by means of single-crystal X‑ray diffraction data. The structure was refined to <em>R</em><sub>1</sub> = 0.032 on the basis of 928 unique reflections with <em>F</em><sub>o</sub> &gt; 4s(<em>F</em><sub>o</sub>) in the <em>P</em>6<sub>3</sub>/<em>m </em>space group, with unit-cell parameters <em>a </em>= 9.7268(5), <em>c </em>= 6.9820(4) Å, <em>V </em>= 572.07(5) Å3. The chemical composition of the sample, determined by electron-microprobe analysis, is (in wt%, average of 10 spot analyses): SO<sub>3</sub> 0.49, P<sub>2</sub>O<sub>5</sub> 0.21, V<sub>2</sub>O<sub>5</sub> 0.04, As<sub>2</sub>O<sub>5</sub> 51.21, SiO<sub>2</sub> 0.19, CaO 39.31, MnO 0.48, SrO 0.03, PbO 5.19, Na<sub>2</sub>O 0.13, F 2.12, Cl 0.08, H<sub>2</sub>O<sub>calc</sub> 0.33, O (≡ F+Cl) –0.91, total 98.90. On the basis of 13 anions per formula unit, the empirical formula corresponds to (Ca<sub>4.66</sub>Pb<sub>0.16</sub>Mn<sub>0.04</sub>Na<sub>0.03</sub>)<sub>Σ4.89</sub>(As<sub>2.96</sub>S<sub>0.04</sub>Si<sub>0.02</sub>P<sub>0.02</sub>)<sub>Σ3.04</sub>O<sub>12</sub>[F<sub>0.74</sub>(OH)<sub>0.24</sub>Cl<sub>0.01</sub>]. Svabite is topologically similar to the other members of the apatite supergroup: columns of face-sharing <em>M</em>1 polyhedra running along <strong>c </strong>are connected through <em>T</em>O<sub>4</sub> tetrahedra with channels hosting <em>M</em>2 cations and <em>X </em>anions. The crystal structure of synthetic Ca<sub>5</sub>(AsO<sub>4</sub>)<sub>3</sub>F was previously reported as triclinic. On the contrary, the present refinement of the crystal structure of svabite shows no deviations from the hexagonal symmetry. An accurate knowledge of the atomic arrangement of this apatite-remediation mineral represents an improvement in our understanding of minerals able to sequester and stabilize heavy metals such as arsenic in polluted areas.</p>
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  • Bosi, Ferdinando, et al. (författare)
  • Crystal-chemical aspects of the roméite group, A<sub>2</sub>Sb<sub>2</sub>O<sub>6</sub>Y, of the pyrochlore supergroup
  • 2017
  • Ingår i: Mineralogical magazine. - 0026-461X .- 1471-8022. ; 81:6, s. 1287-1302
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>Four specimens of the roméite-group minerals oxyplumboroméite and fluorcalcioroméite from the Långban Mn-Fe deposit in Central Sweden were structurally and chemically characterized by single-crystal X-ray diffraction, electron microprobe analysis and infrared spectroscopy. The data obtained and those on additional roméite samples from literature show that the main structural variations within the roméite group are related to variations in the content of Pb<sup>2+</sup>, which is incorporated into the roméite structure via the substitution Pb<sup>2+</sup> → A<sup>2+</sup> where A<sup>2+</sup> = Ca, Mn and Sr. Additionally, the cation occupancy at the six-fold coordinated B site, which is associated with the heterovalent substitution <sup>B</sup>Fe<sup>3+</sup> + <sup>Y</sup>□ →<sup> B</sup>Sb<sup>5+</sup> + <sup>Y</sup>O<sup>2–</sup>, can strongly affect structural parameters.</p><p>Chemical formulae of the roméite minerals group are discussed. According to crystal-chemical information, the species associated with the name ‘kenoplumboroméite’, hydroxycalcioroméite and fluorcalcioroméite most closely approximate end-member compositions Pb<sub>2</sub>(SbFe<sup>3+</sup>)O<sub>6</sub>□, Ca<sub>2</sub>(Sb<sup>5+</sup>Ti)O<sub>6</sub>(OH) and (CaNa)Sb<sub>2</sub>O<sub>6</sub>F, respectively. However, in accord with pyrochlore nomenclature rules, their names correspond to multiple end-members and are best described by the general formulae: (Pb,#)<sub>2</sub>(Sb,#)<sub>2</sub>O<sub>6</sub>□, (Ca,#)<sub>2</sub>(Sb,#)<sub>2</sub>O<sub>6</sub>(OH) and (Ca,#)Sb<sub>2</sub>(O,#)<sub>6</sub>F, where ‘#’ indicates an unspecified charge-balancing chemical substituent, including vacancies.</p>
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