Editorial Feature

Natrosilite - Occurrence, Properties, and Distribution

Natrosilite is a monoclinic-prismatic mineral, containing sodium, silicon, and oxygen. It was first discovered in Mt. Karnasurt, Lovozero massif, and also in Khibiny massif, Kola Peninsula, Russia.

It was named for the natrium or sodium, oxygen and silicon in its composition.

Properties of Natrosilite

The following are the key properties of Natrosilite:

  • Cell Data
    • Space Group: P21/a
    • a = 12.30(2)
    • b = 4.88(1)
    • c = 8.27(3)
    • β = 104°14'
    • Z = 4

  • Crystal Data
    • Monoclinic
    • Point Group: 2/m
    • Thick tabular pseudohexagonal crystals, to 6cm; granular
    • X-ray Powder Pattern: 6.06 (10), 2.98 (9), 3.97 (8), 2.435 (8), 3.64 (7), 4.17 (6), 4.28 (5)

  • Chemical Composition
    Elements Content 1 Content 2
    SiO2 66.03 65.97
    Na2O 33.96 34.03
    K2O 0.01 -
    H2O- 0.06 -
    Total 100.06 100.00

  • Optical Properties
    • Optical Class: Biaxial (-)
    • Orientation: Y ^ c = -12° to 2°
    • Dispersion: r < v
    • α = 1.507
    • β = 1.517
    • γ = 1.521
    • 2V(meas.) = 49°-64°
  • Estimated Properties
    Electron density Bulk density (electron density) = 2.48 g/cm3
    note: Specific gravity of Natrosilite = 2.51 g/cm3
    Photoelectric PENatrosilite = 1.58 barns/electron
    U = PENatrosilite x ρElectron density = 3.92 barns/cm3
    Fermion index Fermion index = 0.01
    Boson index = 0.99
    Natrosilite is not radioactive

How to Identify Natrosilite

Natrosilite can be either colorless or white. It has perfect cleavage, transparent appearance, and white streak.

The density of natrosilite is 2.48 g/cm3.

Global Distribution

Natrosilite is distributed in the following places:

  • Mt. Karnasurt, Lovozero massif
  • Khibiny massif, Kola Peninsula, Russia
  • Mont Saint-Hilaire, Quebec, Canada

Occurrence of Natrosilite and Useful Mineral Association

Natrosilite occurs in sodalite xenoliths associated with an intrusive alkalic gabbro-syenite complex (Mont Saint-Hilaire, Canada), and in pegmatites in nepheline syenites in differentiated alkalic massifs (Kola Peninsula, Russia).

It is closely associated with revdite, eudialyte, cancrinite, sodalite, aegirine, aenigmatite, vuonnemite, ussingite, lomonosovite, natrolite, analcime, and microcline.


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