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Strüverite.
ОглавлениеFeO,(Nb,Ta)₂O₅,4TiO₂. TiO₂ = 69-71%.
Tetragonal; angles very close to those of rutile.
G = 5·0. H = 6-7. Black; opaque.
Craveggia, Piedmont, Italy; and in Madagascar.