IMA 2015-G - Revision of the formulas of wernerbaurite and schindlerite

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Marco E. Ciriotti
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IMA 2015-G - Revision of the formulas of wernerbaurite and schindlerite

Messaggio da Marco E. Ciriotti » mer 22 mar, 2017 19:20

Prossima pubblicazione.

Referenza:
▪ Kampf, A.R., Hughes, J.M., Nash, B.P., Marty, J., Cooper, M.A., Hawthorne, F.C., Karpenko, V.Y., Pautov, L.A., Agakhanov, A.A. (2016): Revision of the formulas of wernerbaurite and schindlerite: ammonium- rather than hydronium-bearing decavanadate minerals. Canadian Mineralogist, 54, (in press).
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: 23136
Iscritto il: ven 25 giu, 2004 11:31
Località: via San Pietro, 55 I-10073 Devesi/Cirié TO - Italy
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Re: IMA 2015-G - Revision of the formulas of wernerbaurite and schindlerite

Messaggio da Marco E. Ciriotti » mer 05 apr, 2017 8:06

Pubblicazione avvenuta.

Referenza:
▪ Kampf, A.R., Hughes, J.M., Nash, B.P., Marty, J., Cooper, M.A., Hawthorne, F.C., Karpenko, V.Y., Pautov, L.A., Agakhanov, A.A. (2016): Revision of the formulas of wernerbaurite and schindlerite: ammonium- rather than hydronium-bearing decavanadate minerals. Canadian Mineralogist, 54, 555-558.

Abstract:
Wernerbaurite (IMA 2012–064) and schindlerite (IMA 2012–063) from the St. Jude mine, Slick Rock district, San Miguel County, Colorado, USA, were described as hydronium-bearing decavanadate minerals with the formulae {[Ca(H2O)7]2(H2O)2(H3O)2}{V10O28} and {[Na2(H2O)10](H3O)4}{V10O28}, respectively. Because these phases correspond to known synthetic phases with these formulae, the presence of NH4 in these minerals was not considered. Recent investigations of a similar phase discovered at a vanadium locality in the Fergana Valley of Kyrgyzstan showed it to contain NH4, leading us to reanalyze the original electron-microprobe mounts of wernerbaurite and schindlerite, specifically seeking N; those analyses confirmed the presence of sufficient NH4 to replace the originally assigned H3O. With the additional H sites included and O replaced by N at the NH4 sites, the structure refinement residual improved for wernerbaurite from R1 = 3.41% to R1 = 3.26% and for schindlerite from R1 = 3.99% to R1 = 3.70%. The newly assigned NH4 sites exhibited normal NH4–O bond distances and coordination and reasonable bond-valence sums. The H3O synthetic equivalents of both phases had been reported, as well as the NH4 synthetic equivalent of schindlerite. Subsequent to the publication of the original description of the minerals, the NH4 equivalent of wernerbaurite has also been reported.
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