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| Akaganeite | |
|---|---|
 A piece of the mineral akaganeite. Exhibit of the "Earth and Man" Museum in Sofia, Bulgaria. Discovered in Kaskasnyunchorr, Khibiny Massif, Kola Peninsula, Russia | |
| General | |
| Category | Oxide mineral |
| Formula (repeating unit) | Fe3+O(OH,Cl) |
| IMA symbol | Akg[1] |
| Strunz classification | 4.DK.05 |
| Crystal system | Monoclinic |
| Crystal class | Prismatic (2/m) (same H-M symbol) |
| Space group | I2/m |
| Unit cell | a = 10.561, b = 3.031 c = 10.483 [Å]; β = 90.63°; Z = 1 |
| Identification | |
| Color | Yellowish brown, rusty brown |
| Luster | Earthy |
| Streak | Brownish yellow |
| Diaphaneity | Transparent, translucent |
| Specific gravity | 3.52 |
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).
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]
- ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
- ^ Ernst A.J. Burke (2008): "Tidying up Mineral Names: an IMA-CNMNC Scheme for Suffixes, Hyphens and Diacritical marks". Mineralogical Record, volume 39, issue 2.
- ^ Jongsik Kim and Clare P. Grey (2010), "Li Solid-State MAS NMR Study of Local Environments and Lithium Adsorption on the Iron(III) Oxyhydroxide, Akaganeite (β-FeOOH)". Chemistry of Materials, volume 22, pages 5453–5462. doi:10.1021/cm100816h
- ^ a b C. Rémazeilles and Ph. Refait (2007): "On the formation of β-FeOOH (akaganéite) in chloride-containing environments". Corrosion Science, volume 49, issue 2, pages 844-857. doi:10.1016/j.corsci.2006.06.003
- ^ "Mineral 314-687: Akaganeite". Mindat.org database, accessed on 2019-02-12.