Department of Earth Sciences, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada
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The ideal formula of fluoro-potassic-magnesio-arfvedsonite [Can. Mineral.44 2006, 289] should have been recorded as KNa2(Mg4Fe3+)Si8O22F2. This formula agrees with the analytical data reported for samples 1070, 1093 and 1094 in the first description of the species [Can. Mineral.25 1987, 739–753]. The formula given in the 2006 article is in error. Apologies to amphibole afficionados.