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A piece of the mineral akaganeite. Exhibit of the "Earth and Man" Museum in Sofia, Bulgaria. Discovered in Kaskasnyunchorr, Khibiny Massif, Kola Peninsula, Russia
CategoryOxide mineral
(repeating unit)
Strunz classification4.DK.05
Crystal systemMonoclinic
Crystal classPrismatic (2/m)
(same H-M symbol)
Space groupI2/m
Unit cella = 10.561, b = 3.031
c = 10.483 [Å]; β = 90.63°; Z = 1
ColorYellowish brown, rusty brown
StreakBrownish yellow
DiaphaneityTransparent, translucent
Specific gravity3.52

Akaganeite is an iron(III) oxide-hydroxide / chloride mineral with formula: Fe3+O(OH,Cl) e.g.; β-FeO(OH). It is formed by the weathering of pyrrhotite (Fe1−xS). Nickel also has been reported in the structure. It has a monoclinic crystal structure, a metallic luster and a brownish yellow streak. It is named after the Akagane mine in Iwate, Japan, in which it was discovered. It has also been found in widely dispersed locations around the world and in rocks from the Moon that were brought back during the Apollo Project. The occurrences in meteorites and the lunar sample are thought to have been produced by interaction with Earth's atmosphere. It has been detected on Mars through orbital imaging spectroscopy [1].

It was described by the Japanese mineralogist Matsuo Nambu in 1968[2] but named as early as 1961[3]. The name comes from the topotype, the Akagane Mine in Iwate Prefecture, Japan.

See also[edit]

List of minerals