Agrellite – Occurrence, Properties, and Distribution

Agrellite was named after Professor Stuart Olof Agrell, an eminent petrologist from Cambridge University in Cambridge, England.

Properties of Agrellite

The following are the key properties of Agrellite:

  • Cell Data
    • Space group: P1
    • a = 7.759(2)
    • b = 18.946(3)
    • c = 6.986(1)
    • α = 89.88(2) °
    • β = 99.61°
    • γ = 94.2(2)°
    • Z = 4

  • Crystal Data
    • Triclinic
    • Point group: 1
    • Elongated || [001], to 10cm
    • Platy aggregates
    • X-ray powder pattern: 3.19 (vs), 3.14 (vs), 3.44 (s), 3.33 (s), 2.58 (s), 2.31 (s), 2.04 (ms)

  • Chemical Composition
    Elements Content 1 Content 2
    SiO2 57.79 60.92
    CaO 25.70 28.43
    Na2O 7.90 7.86
    F 4.45 4.82
    RE 2.57 -
    -O = F2 1.87 2.03
    Al2O3 1.32 -
    H2O+ 0.4 -
    MnO 0.25 -
    K2O 0.22 -
    ZrO2 0.18 -
    SrO 0.16 -
    Fe2O3 0.11 -
    BaO 0.06 -
    MgO 0.02 -
    TiO2 0.01 -
    Total 99.27 100.00

  • Optical Properties
    • Optical class: Biaxial (-)
    • α = 1.567; β = 1.579; γ = 1.581

  • Estimated Properties
    Electron density Bulk density (electron density) = 2.84 g/cm3
    note: Specific gravity of Agrellite = 2.86 g/cm3
    Photoelectric PEAgrellite = 3.71 barns/electron
    U = PEAgrellite x ρ electron density = 10.54 barns/cm3
    Fermion index Fermion index = 0.01
    Boson index = 0.99
    Radioactivity
    Agrellite is not radioactive

How to Identify Agrellite

Agrellite can be identified in the field by its color variations, such as white, grayish-white, and greenish-white. Its translucent form has {110} perfect, {110} perfect, {010} poor cleavage. This mineral has a vitreous–pearly luster, with a white streak.

The density of agrellite is 2.88 to 2.9 g/cm3, with a hardness of 5.5 – approximate to a knife blade.

Global Distribution

Agrellite is distributed in the following places:

  • USA - In the Wausau complex, Marathon Co. Wisconsin
  • Canada - From the Sheffield Lake complex, Kipawa River, Villedieu Township, Quebec
  • Tajikistan - In the Dara-i-Pioz massif, Alai Range, Tien Shan
  • Russia - From the Murun massif, south-west of Olekminsk, Yakutia

Occurrence of Agrellite and Useful Mineral Association

Agrellite occurs in pegmatite lenses and pods, and in mafic gneisses in a regionally metamorphosed agpaitic alkalic rock complex.

It is often associated with minerals such as mosandrite, britholite, hiortdahlite, vlasovite, calcite, fluorite, norbergite, zircon, biotite, clinohumite, gittinsite, phlogopite, miserite, aegirine, galena, eudialyte, quartz, and miserite.

References

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