IMA 2017-064 = silesiaite

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Marco E. Ciriotti
Messaggi: 31675
Iscritto il: ven 25 giu, 2004 11:31
Località: via San Pietro, 55 I-10073 Devesi/Cirié TO - Italy
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IMA 2017-064 = silesiaite

Messaggio da Marco E. Ciriotti » mer 25 gen, 2023 21:32

Prossima pubblicazione.

Referenza:
▪ Pieczka, A., Zelek-Pogudz, S., Gołębiowska, B., Stadnicka, K.M., Kristiansen, R. (2023): Silesiaite, ideally Ca2Fe3+Sn(Si2O7)(Si2O6OH), a new species in the kristiansenite group: crystal chemistry and structure of holotype silesiaite from Szklarska Poręba, Poland, and Sc-free silesiaite from Häiviäntien, Finland. Mineralogical Magazine, 87, (in press).

Abstract:
Two silesiaite crystals, one from Szklarska Poręba, Poland (type locality), and the other from Häiviäntien (Finland), were studied with electron-probe microanalysis, Raman spectroscopy and single-crystal X-ray diffraction. The crystals have the following compositions normalised to 13 O2– + 1 (OH)–anions: Ca2.001(2[(Sn1.105(6)Zr0.009(1))Σ1.114(Fe3+0.523(78)Sc0.185(62)Al0.070(14))Σ0.779(Fe2+0.065(12)Mn2+0.041(5)Mg0.003(3))Σ0.110]Σ2.003(Si3.997(2)O13OH), and Ca2.006(8[(Sn1.110(18)Ti0.006(3))Σ1.107(Fe3+0.648(50)Al0.063(11))Σ0.710(Fe2+0.140(30)Mn2+0.011(3)Mg0.005(2))Σ0.155(Nb0.020(6)Ta0.011(3))Σ0.040]Σ2.009(Si3.991(14)O13OH), respectively. The structure of the crystals was refined in the triclinic system with unconventional space-group symmetry C1 to R1 = 2.02% and 3.56%, respectively. The crystals’ unit cells were found to be a = 10.0080(2), b = 8.3622(1), c = 13.2994(2) Å, α = 89.987(1), β = 109.095(2), gamma = 89.978(1)°, V = 1051.77(3) Å3 for the silesiaite from Szklarska Poręba, and a = 9.9985(3), b = 8.3446(2), c = 13.2760(4) Å, α = 89.986(3), β = 109.122(2), gamma = 90.020(2)°, V = 1046.55(5) Å3 for silesiaite from Häiviäntien. In both crystals, the Ca sites are solely occupied by calcium and Si sites by silicon atoms. Optimised occupancies of the four M sites indicated slightly different site fillings. In the Szklarska Poręba silesiaite, the M1 site is predominantly occupied by trivalent Fe + Sc and the M2-M4 sites by Sn. In contrast, in the Häiviäntien silesiaite, the M1-M3 sites are Sn-dominant, while Fe3+ predominantly occupies the M4 site. The differences can be considered a result of an evolution of the M1-M4 site occupancies following a decrease of the <M–O> distance. Among the minerals of the kristiansenite group, Sc-free silesiaite from the Häiviäntien pegmatite has the smallest average radius of M-site cations and a unit-cell volume that increases proportionally to the (Fe2+ ± Sc) content. The hydrogen atoms form moderate hydrogen bonds between disilicate groups (Si2O7and Si2O6OH) linked in rows along [101], indicating the presence of one hydroxyl in the formula calculated for Z = 4. All three kristiansenite-group species, i.e. silesiaite, kozłowskiite and kristiansenite, are isostructural.
Marco E. Ciriotti

«Things are interesting only in so far as they relate themselves to other things»

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Marco E. Ciriotti
Messaggi: 31675
Iscritto il: ven 25 giu, 2004 11:31
Località: via San Pietro, 55 I-10073 Devesi/Cirié TO - Italy
Contatta:

Re: IMA 2017-064 = silesiaite

Messaggio da Marco E. Ciriotti » mar 16 mag, 2023 15:13

Pubblicazione effettuata.

Referenza:
▪ Pieczka, A., Zelek-Pogudz, S., Gołębiowska, B., Stadnicka, K.M., Kristiansen, R. (2023): Silesiaite, ideally Ca2Fe3+Sn(Si2O7)(Si2O6OH), a new species in the kristiansenite group: crystal chemistry and structure of holotype silesiaite from Szklarska Poręba, Poland, and Sc-free silesiaite from Häiviäntien, Finland. Mineralogical Magazine, 87, 271-283.
Marco E. Ciriotti

«Things are interesting only in so far as they relate themselves to other things»

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