| Reference Type | Journal (article/letter/editorial) |
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| Title | Redefinition of thalénite-(Y) and discreditation of fluorthalénite-(Y): A re-investigation of type material from the Österby pegmatite, Dalarna, Sweden, and from additional localities |
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| Journal | Mineralogical Magazine |
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| Authors | Škoda, Radek | Author |
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| Plášil, Jakub | Author |
| Jonsson, Erik | Author |
| Čopjaková, Renata | Author |
| Langhof, Jörgen | Author |
| Galiová, Michaela Vašinová | Author |
| Year | 2015 (August) | Volume | 79 |
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| Issue | 4 |
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| Publisher | Mineralogical Society |
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| DOI | doi:10.1180/minmag.2015.079.4.07Search in ResearchGate |
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| Generate Citation Formats |
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| Mindat Ref. ID | 244678 | Long-form Identifier | mindat:1:5:244678:7 |
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| GUID | 0 |
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| Full Reference | Škoda, Radek, Plášil, Jakub, Jonsson, Erik, Čopjaková, Renata, Langhof, Jörgen, Galiová, Michaela Vašinová (2015) Redefinition of thalénite-(Y) and discreditation of fluorthalénite-(Y): A re-investigation of type material from the Österby pegmatite, Dalarna, Sweden, and from additional localities. Mineralogical Magazine, 79 (4) 965-983 doi:10.1180/minmag.2015.079.4.07 |
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| Plain Text | Škoda, Radek, Plášil, Jakub, Jonsson, Erik, Čopjaková, Renata, Langhof, Jörgen, Galiová, Michaela Vašinová (2015) Redefinition of thalénite-(Y) and discreditation of fluorthalénite-(Y): A re-investigation of type material from the Österby pegmatite, Dalarna, Sweden, and from additional localities. Mineralogical Magazine, 79 (4) 965-983 doi:10.1180/minmag.2015.079.4.07 |
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| Abstract/Notes | AbstractUsing type material from the Österby pegmatite in Dalarna, Sweden, the chemical composition and structural parameters of thalénite-(Y) [ideally Y3Si3O10(OH)] were examined by wavelength dispersive spectroscopy electron microprobe (WDS EMP) analysis and single-crystal X-ray diffraction. High contrast back-scatter electron images of the Österby material show at least two generations of thalénite-(Y). The formula of the primary thalénite-(Y) normalized to 11 anions is (Y2.58Dy0.11Yb0.09Gd0.06Er0.06Ho0.02Sm0.02Tb0.02Lu0.02Nd0.01Tm0.01)Σ3.00Si3.01O10F0.97OH0.03. The secondary thalénite-(Y), replacing the primary material, is weakly enhanced in Y and depleted in the lightest and the heaviest rare-earth elements, yielding the formula (Y2.63Dy0.12Yb0.06Gd0.06Er0.05Ho0.02Sm0.02Tb0.02Tm0.01Nd0.01Lu0.01)Σ3.00Si3.01O10F0.98OH0.02. Structural data for thalénite-(Y) from Österby clearly indicate the monoclinic space group P21/n, with a = 7.3464(4), b = 11.1726(5), c = 10.4180(5) Å, β = 97.318(4)°, V = 848.13(7) Å3, Z = 4, which is consistent with previous investigations. The structure was refined from single-crystal X-ray diffraction data to R1 = 0.0371 for 1503 unique observed reflections, and the final chemical composition obtained from the refinement, (Y2.64Dy0.36)Σ3.00F0.987[Si3O10], Z = 4, is in good agreement with the empirical formula resulting from electron microprobe (EMP) analysis. Both techniques reveal a strong dominance of F over OH, which means that the type material actually corresponds to the fluorine analogue. Moreover, new EMP analyses of samples of thalénite-(Y) from an additional seven localities (Åskagen and Reunavare in Sweden; White Cloud and Snow Flake in Colorado, USA; the Guy Hazel claim in Arizona, USA; Suishoyama and Souri in Japan) clearly show the prevalence of F over OH as well. Based on these observations, the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association has recommended a redefinition of the chemical composition of thalénite-(Y) to represent the F-dominant species with the ideal formula Y3Si3O10F, as it has historical priority. Consequently, the later described fluorthalénite-(Y) has to be discredited. |
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