Hydroxyferroroméite, ideally (Fe2+1.50.5)Sb5+2O6(OH), is a new secondary mineral from the Correc d’en Llinassos, Oms, Pyrénées-Orientales Department, France. Hydroxyferroroméite occurs as yellow to yellow-brown powdery boxwork replacements up to about 50 μm across after tetrahedrite in a siderite–quartz matrix. No distinct crystals have been observed. The empirical formula (based on 7 (O + OH) per formula unit, pfu) is (Fe2+1.07Cu2+0.50Zn0.03Sr0.03Ca0.010.36)Ʃ2(Sb5+1.88Si0.09Al0.02As0.01)Ʃ2O6((OH)0.86O0.14). X-ray photoelectron spectroscopy was used to determine the valence states of Sb, Fe and Cu. Hydroxyferroroméite crystallises in the space group Fd3¯m with the pyrochlore structure and hence is a new Fe2+-dominant member of the roméite group of the pyrochlore supergroup. It has the unit-cell parameters: a = 10.25(3) Å, V = 1077(6) Å3 and Z = 8. A model, based on bond-valence theory, for incorporation of the small Fe2+ cation into a displaced variant of the A site of the pyrochlore structure is proposed.

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