Brianite - Occurrence, Properties, and Distribution

Brianite is a phosphate mineral that was first identified in an iron meteorite.

The mineral was named in honor of Brian Harold Mason, a New Zealandic-American meteoriticist, mineralogist, and geochemist.

Properties of Brianite

The following are the key properties of Brianite:

  • Cell Data
    • Space Group: P21/a
    • a = 13.36(5)
    • b = 5.23(2)
    • c = 9.13(3)
    • β = 91.2(2)°
    • Z = 4

  • Crystal Data
    • Monoclinic
    • Point Group: 2/m
    • As anhedral grains, to 0.2mm
    • Twinning: Polysynthetic on {100}, showing a lamellar structure in polarized light
    • X-ray Powder Pattern: 2.625 (10), 3.734 (9), 2.679 (9), 1.875 (9), 2.718 (8), 3.344 (7), 2.230 (7)

  • Chemical Composition
    Elements Content 1 Content 2
    P2O5 46.9 47.27
    Na2O 22.1 20.64
    CaO 18.8 18.67
    MgO 12.6 13.42
    FeO 0.5 -
    Total 100.9 100.00

  • Optical Properties
    • Optical Class: Biaxial (–)
    • Orientation: Extinction ^ lamellae ≈ 2°–3°
    • α = 1.598(1)
    • β = 1.605(1)
    • γ = 1.608(1)
    • 2V(meas.) = 63°–65°
    • 2V(calc.) = 66°

  • Estimated Properties
    Electron density Bulk density (electron density) = 3.09 g/cm3
    note: Specific gravity of Brianite = 3.13 g/cm3
    Photoelectric PEBrianite = 3.06 barns/electron
    U = PEBrianite x ρElectron density = 9.43 barns/cm3
    Fermion index Fermion index = 0.0084
    Boson index = 0.9915
    Radioactivity
    Brianite is not radioactive

How to Identify Brianite

Brianite is colorless, with vitreous luster, and white streak.

It has a transparent appearance, with a density of 3 g/cm3, and a relative hardness ranging from 4 to 5.

Global Distribution

Brianite is widely distributed in the Dayton finest (very fine-grained) octahedrite meteorite.

Occurrence of Brianite and Useful Mineral Association

Brianite occurs as a very rare component in phosphate nodules in an iron meteorite.

The minerals that are closely associated with brianite include troilite, sphalerite, graphite, taenite, kamacite, schreibersite, enstatite, albite, whitlockite, and panethite.

References

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