Crystal-chemistry of sulfates from the Apuan Alps (Tuscany, Italy). VI. Tl-bearing alum-(K) and voltaite from the Fornovolasco mining complex
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in: American mineralogist, The, Jahrgang 105, Nr. 7, 28.07.2020, S. 1088-1098.
Publikationen: Beitrag in Fachzeitschrift › Artikel › Forschung › (peer-reviewed)
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T1 - Crystal-chemistry of sulfates from the Apuan Alps (Tuscany, Italy). VI. Tl-bearing alum-(K) and voltaite from the Fornovolasco mining complex
AU - Biagioni, Cristian
AU - Mauro, Daniela
AU - Pasero, Marco
AU - Bonaccorsi, Elena
AU - Lepore, Giovanni Orazio
AU - Zaccarini, Federica
AU - Skogby, Henrik
N1 - Publisher Copyright: © 2020 Walter de Gruyter GmbH, Berlin/Boston 2020
PY - 2020/7/28
Y1 - 2020/7/28
N2 - Thallium-bearing samples of alum-(K) and voltaite from the Fornovolasco mining complex (Apuan Alps, Tuscany, Italy) have been characterized through X‑ray diffraction, chemical analyses, micro-Raman, infrared (FTIR), Mössbauer, and X-ray absorption spectroscopy (XAS). Alum-(K) occurs as anhedral colorless grains or rarely as octahedral crystals, up to 5 mm. Electron-microprobe analysis points to the chemical formula (K0.74Tl0.10)ς0.84(Al0.84Fe0.14)ς0.98S2.03O8·12H2O. The occurrence of minor NH4+ $\text{NH}_{4}^{+}$ was detected through FTIR spectroscopy. Its unit-cell parameter is a = 12.2030(2) Å, V = 1817.19(9) Å3, space group Pa3¯. $Pa\bar{3}.$Its crystal structure has been refined down to R1 = 0.0351 for 648 reflections with F o > 4σ(Fo) and 61 refined parameters. The crystal structure refinement agrees with the partial substitution of K by 12 mol% Tl. This substitution is confirmed by XAS data, showing the presence of Tl+ having a first coordination shell mainly formed by 6 O atoms at 2.84(2) Å. Voltaite occurs as dark green cubic crystals, up to 1 mm in size. Voltaite is chemically zoned, with distinct domains having chemical formula (K1.94Tl0.28)σ2.22(Fe2+3.57Mg0.94Mn0.55)σ5.06Fe3+3.06Al0.98S11.92O4818H2O and (K2.04Tl0.32)σ2.36(Fe2+3.83Mg0.91Mn0.29)σ5.03Fe3+3.05Al0.97S11.92O48 18H2O, respectively. Infrared spectroscopy confirmed the occurrence of minor NH4+ also in voltaite. Its unit-cell parameter is a = 27.2635 Å, V = 20265(4) Å3, space group Fd3c. The crystal structure was refined down to R1 = 0.0434 for 817 reflections with Fo > 4σ(Fo) and 87 refined parameters. The partial replacement of K by Tl is confirmed by the structural refinement. XAS spectroscopy showed that Tl+ is bonded to six O atoms, at 2.89(2) Å. The multi-technique characterization of thallium-bearing alum-(K) and voltaite improves our understanding of the role of K-bearing sulfates in immobilizing Tl in acid mine drainage systems, temporarily avoiding its dispersion in the environment.
AB - Thallium-bearing samples of alum-(K) and voltaite from the Fornovolasco mining complex (Apuan Alps, Tuscany, Italy) have been characterized through X‑ray diffraction, chemical analyses, micro-Raman, infrared (FTIR), Mössbauer, and X-ray absorption spectroscopy (XAS). Alum-(K) occurs as anhedral colorless grains or rarely as octahedral crystals, up to 5 mm. Electron-microprobe analysis points to the chemical formula (K0.74Tl0.10)ς0.84(Al0.84Fe0.14)ς0.98S2.03O8·12H2O. The occurrence of minor NH4+ $\text{NH}_{4}^{+}$ was detected through FTIR spectroscopy. Its unit-cell parameter is a = 12.2030(2) Å, V = 1817.19(9) Å3, space group Pa3¯. $Pa\bar{3}.$Its crystal structure has been refined down to R1 = 0.0351 for 648 reflections with F o > 4σ(Fo) and 61 refined parameters. The crystal structure refinement agrees with the partial substitution of K by 12 mol% Tl. This substitution is confirmed by XAS data, showing the presence of Tl+ having a first coordination shell mainly formed by 6 O atoms at 2.84(2) Å. Voltaite occurs as dark green cubic crystals, up to 1 mm in size. Voltaite is chemically zoned, with distinct domains having chemical formula (K1.94Tl0.28)σ2.22(Fe2+3.57Mg0.94Mn0.55)σ5.06Fe3+3.06Al0.98S11.92O4818H2O and (K2.04Tl0.32)σ2.36(Fe2+3.83Mg0.91Mn0.29)σ5.03Fe3+3.05Al0.97S11.92O48 18H2O, respectively. Infrared spectroscopy confirmed the occurrence of minor NH4+ also in voltaite. Its unit-cell parameter is a = 27.2635 Å, V = 20265(4) Å3, space group Fd3c. The crystal structure was refined down to R1 = 0.0434 for 817 reflections with Fo > 4σ(Fo) and 87 refined parameters. The partial replacement of K by Tl is confirmed by the structural refinement. XAS spectroscopy showed that Tl+ is bonded to six O atoms, at 2.89(2) Å. The multi-technique characterization of thallium-bearing alum-(K) and voltaite improves our understanding of the role of K-bearing sulfates in immobilizing Tl in acid mine drainage systems, temporarily avoiding its dispersion in the environment.
KW - Alum-(K)
KW - Apuan alps
KW - Crystal structure
KW - Fornovolasco
KW - Italy
KW - thallium
KW - Tuscany
KW - Voltaite
KW - Xas
UR - http://www.scopus.com/inward/record.url?scp=85089885300&partnerID=8YFLogxK
U2 - 10.2138/am-2020-7320
DO - 10.2138/am-2020-7320
M3 - Article
VL - 105
SP - 1088
EP - 1098
JO - American mineralogist, The
JF - American mineralogist, The
SN - 0003-004X
IS - 7
ER -
