Editorial Feature

Akaganeite – Occurrence, Properties, and Distribution of Akaganeite

Akaganéite is a chlorine mineral/iron (III) oxide-hydroxide that is formed by the weathering pyrrhotite. Akaganeite is named after the Akagane mine in Iwate, Japan, where it was first discovered.

Properties of Akaganéite

The following are the key properties of Akaganeite:

  • Cell Data
    • Space Group: I2/m.
    • a = 10.561(4)
    • b = 3.031(1)
    • c = 10.483(4)
    • β = 90.63(4)°
    • Z = 8
  • Crystal Data
    • Monoclinic
    • Point group: 2/m
    • Tiny spindlelike quasi-single crystals are up to 5 µm in length; in bundles of such rods; commonly fine-grained massive to powdery.
    • X-ray powder pattern: synthetic FeO(OH). 3.333 (100), 2.5502 (55), 7.467 (40), 2.2952 (35), 1.6434 (35), 5.276 (30), 2.6344 (25)
  • Chemical Composition
    Elements Content 1 Content 2 Content 3
    Fe2O3 78.23 69.0 – 76.0 89.86
    H2O+ 10.20 - 10.14
    H2O- 4.96 - -
    SiO2 3.10 - -
    Al2O3 1.21 - -
    FeO 0.82 -
    Na2O 0.62 - -
    K2O 0.19 - -
    Cl - 3.6 – 6.3 -
    NiO - 0.4 – 5.6 -
    Total 99.33 100.00
  • Optical Properties
    • Optical Class: Biaxial.
    • α = n.d.
    • β = n.d.
    • γ = n.d.
    • 2V(meas.) = n.d.
  • Estimated Properties
    Electron density Bulk density (electron density)=3.64 g/cm3
    note: specific gravity of akaganeite =3.75 g/cm3
    Photoelectric PEAkaganeite = 18.39 barns/electron
    U=PEAkaganeite x ρElectron Density= 66.91 barns/cm3
    Fermion index Fermion index = 0.01
    Boson index = 0.99
    Radioactivity Akaganeite is not radioactive

How to Identify Akaganéite

Akaganeite can be identified in the field by its brown and rusty brown opaque appearance. It has an adamantine-metallic lusture with a brownish yellow streak. This mineral forms a loose and poorly-coherent pulverulent mass.

A piece of the mineral Akaganéite. Exhibit of the "Earth and Man" Museum in Sofia, Bulgaria. Discovered in Kaskasnyunchorr, Khibiny Massif, Kola Peninsula, Russia. Image Credit: Vassia Atanassova – Spiritia”

Global Distribution

Globally, akaganeite can be found in the following locations:

  • Japan- Akagane mine, Iwate Prefecture
  • Germany-Oberwolfach, Black Forest
  • England- Warham Marshes, Norfolk
  • Belgium- Richelle
  • USA- In Black Rock, Humboldt Co., Nevada
    -North of the Santa Ni˜no mine, Santa Cruz Co, Arizona
    -Questa, Taos Co., New Mexico
    -Duluth Gabbro complex, near Hibbing, St. Louis Co., Minnesota
    -Las Animas mine, La Mur, Trincheras, Sonora

Occurrence of Akaganéite and Useful Mineral Association

Akaganeite occurs in certain geothermal brines, oxidation zones of pyrrhotite-bearing iron sulphide deposits and sea-floor nodules. Akaganeite is formed as a corrosion product of some meteorites.

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G.P. Thomas

Written by

G.P. Thomas

Gary graduated from the University of Manchester with a first-class honours degree in Geochemistry and a Masters in Earth Sciences. After working in the Australian mining industry, Gary decided to hang up his geology boots and turn his hand to writing. When he isn't developing topical and informative content, Gary can usually be found playing his beloved guitar, or watching Aston Villa FC snatch defeat from the jaws of victory.


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