Akaganeite
Akaganeite
Iron(III) oxide-hydroxide mineral
Akaganeite, also written as the deprecated Akaganéite,[2] is a chloride-containing iron(III) oxide-hydroxide mineral, formed by the weathering of pyrrhotite (Fe1−xS).
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Akaganeite is often described as the β phase of anhydrous ferric oxyhydroxide FeOOH, but some chloride (or fluoride) ions are normally included in the structure,[3] so a more accurate formula is FeO
0.833(OH)
1.167Cl
0.167.[4]
Nickel may substitute for iron, yielding the more general formula (Fe3+
,Ni2+
)
8(OH,O)
16Cl
1.25[5]
Akaganeite has a metallic luster and a brownish yellow streak. Its crystal structure is monoclinic and similar to that of hollandite BaMn
8O
16, characterised by the presence of tunnels parallel to the c-axis of the tetragonal lattice. These tunnels are partially occupied by chloride anions that give to the crystal its structural stability.[4]