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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