Editorial Feature

Iowaite - Occurrence, Properties, and Distribution

Iowaite is a trigonal-hexagonal scalenohedral mineral, composed of oxygen, magnesium, iron, hydrogen, and chlorine. It is a member of the hydrotalcite group.

The mineral was named after Sioux County, Iowa, where it was first discovered.

Properties of Iowaite

The following are the key properties of Iowaite:

  • Cell Data
    • Space Group: R3m
    • a = 3.1183(9)
    • c = 24.113(8)
    • Z = 3/8

  • Crystal Data
    • Hexagonal
    • Point Group: 3 2/m
    • As platy crystals, to 2.5cm, in masses in veins
    • X-ray Powder Pattern: 8.109 (100), 4.047 (40), 2.363 (27), 2.019 (23), 2.639 (17), 1.530 (13), 1.560 (8)

  • Chemical Composition
    Elements Content 1 Content 2
    MgO 35.3 35.95
    Fe2O3 24.6 23.74
    H2O200°C 11 -
    Cl 7.0 10.54
    H2O - 32.14
    CO2 0.4 -
    -O = Cl2 - 2.37

  • Optical Properties
    • Optical Class: Uniaxial (–); Commonly anomalously biaxial
    • Pleochroism: Intense; O = pale yellow; E = deep blue-green
    • ω = 1.543–1.561
    • ε = 1.533–1.543
    • 2V(meas.) = 5°

  • Estimated Properties
    Electron density Bulk density (electron density) = 1.94 g/cm3
    note: Specific gravity of Iowaite = 1.90 g/cm3
    Photoelectric PEIowaite = 5.25 barns/electron
    U = PEIowaite x ρElectron density = 10.17 barns/cm3
    Fermion index Fermion index = 0.02
    Boson index = 0.98
    Radioactivity
    Iowaite is not radioactive

How to Identify Iowaite

Iowaite is a transparent mineral, having different variations, from honey-yellow to bluish-green and greenish-white. It has a greasy luster, white streak, and perfect cleavage.

The average density of iowaite is 2.09 g/cm3, and its relative hardness is 1.5.

Global Distribution

Iowaite is distributed in the following places:

  • Precambrian basement of Sioux Co. Iowa, USA
  • Phalaborwa mine, Transvaal, South Africa
  • Komsomolsk mine, Talnakh, Noril’sk region, western Siberia, Russia
  • Almalyk district, Uzbekistan
  • Sea floor sediments in the Bonin-Mariana area, Pacific Ocean
  • Mount Keith nickel deposit, 400km north-north-west of Kalgoorlie, Western Australia

Occurrence of Iowaite and Useful Mineral Association

Iowaite occurs as an alteration product of serpentine.

The minerals that are closely associated with iowaite include dolomite, calcite, antigorite, celestine, apatite, fluoborite, phlogopite, hydrotalcite, brucite, clinochlore, chondrodite, magnetite, pyroaurite, pyrite, magnesite, and chrysotile.

References

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