Barbertonite – Occurrence, Properties, and Distribution

Barbertonite was named after the Barberton district in South Africa, where it first occurred. It forms a dimorphous series with stitchtite. This mineral belongs to Manasseite group.

Properties of Barbertonite

The following are the key properties of barbertonite:

  • Cell Data
    • a = 6.17
    • c = 15.52
    • Z = 1

  • Crystal Data
    • Hexagonal
    • As plates, flattened on {0001}, in fibrous matted masses, and as cross-fiber veinlets

  • Chemical Composition
    • It is difficult to determine the chemical composition of barbertonite as it is intimately mixed with stichtite

  • Optical Properties
    • Transparent
    • Color: intense violet to rose-pink; violet to pale rose-pink in transmitted light
    • Streak: very pale violet to white
    • Luster: Waxy to pearly
    • Pleochroism: weak; O = dark rose-pink to violet; E = pale rose-pink to violet
    • Optical Class: Uniaxial (-), may be biaxial due to strain
    • ω = 1.557(3); ε = 1.529(3); 2V(meas) = small

  • Estimated Properties
    Electron density Bulk density (electron density) = 2.14 g/cm3
    note: Specific gravity of barbertonite = 2.10 g/cm3
    Photoelectric PEBarbertonite = 4.01 barns/electron
    U = PEBarbertonite x ρ electron density = 8.59 barns/cm3
    Fermion index Fermion index = 0.03
    Boson index = 0.97
    Radioactivity
    Barbertonite is not radioactive

How to Identify Barbertonite

The color of barbertonite varies from intense violet to rose-pink, and it appears violet to pale rose-pink in transmitted light. It is flexible in nature but not elastic. It has a greasy feel upon touching.

Global Distribution

Barbertonite is distributed in the following locations:

  • South Africa – from the Kaapsehoop asbestos mine, Kaapse Hoop in the Barberton district
  • Australia – from Adelaide Ag-Pb mine in Dundas Tasmania
  • Scotland – from Hoo field, Cunningsburgh, Shetland Islands

Occurrence of Barbertonite and Useful Mineral Association

Barbertonite occurs as an alteration product of chromite in serpentinite.

It is associated with minerals such as stitchtite, chromite, and antigorite.

References

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