Larnite - Occurrence, Properties, and Distribution

Topics Covered

Introduction to Larnite
Properties of Larnite
How to Identify Larnite
Global Distribution
Occurrence of Larnite and Useful Mineral Association
References

Introduction to Larnite

Chemical Formula – Ca2SiO4

Larnite is a member of olivine group of minerals. It is a high temperature, monoclinic polymorph of calico-olivine. The mineral was first discovered from Scawt Hill, near Larne, Co., Antrim, Ireland in 1929. It was named after its locality.

Properties of Larnite

The following are the key properties of Larnite:

  • Cell Data
    • Space Group: P21/n
    • a = 5.502(1)
    • b = 6.745(1)
    • c = 9.297(1)
    • β = 94:59(2)°
    • Z = 4
  • Crystal Data
    • Monoclinic
    • Point Group: 2/m
    • As anhedral grains flattened on {010}; subhedral interlocking grains; granular, massive. Twinning: Common, polysynthetic || {100}; a second set may be ⊥ the first
    • X-ray Powder Pattern: 2.795 (100), 2.744 (95), 2.780 (90), 2.608 (65), 2.188 (65), 2.731 (40), 2.716 (40)
  • Chemical Composition
    Elements Content 1 Content 2 Content 3
    CaO 64.98 65.56 65.12
    SiO2 31.00 33.89 34.88
    Al2O3 1.12 - -
    CO2 0.82 - -
    MgO 0.69 - -
    FeO 0.64 - -
    H2O+ 0.61 - -
    Na2O - 0.36 -
    P2O - 0.32 -
    Fe2O3 trace - -
    Total 99.86 100.13 100.00
  • Optical Properties
    • Optical Class: Biaxial (+)
    • Orientation: Z = b
    • X ^ c = 13°-14°
    • Dispersion: r < v; weak.
    • α = 1.700-1.715
    • β = 1.715-1.723
    • γ = 1.725-1.740
    • 2V(meas.) = 60°-63°
  • Estimated Properties
    Electron density Bulk density (electron density)=3.34 g/cm3
    note: Specific gravity of Larnite =3.34 g/cm3
    Photoelectric PELarnite = 6.32 barns/electron
    U= PELarnite x ρElectron density= 21.09 barns/cm3
    Fermion index Fermion index = 0.008
    Boson index = 0.99
    Radioactivity Larnite is not radioactive

How to Identify Larnite

Larnite is either colorless or gray in color. It has transparent to translucent appearance, white streak, good cleavage and vitreous luster. It generally forms anhedral to subhedral crystals in matrix. The relative hardness of larnite is 6, and its density is 3.28 g/cm3.

Global Distribution

Larnite is distributed in the following places:

  • Scawt Hill and Ballycraigy, near Larne, Co. Antrim, Ireland
  • Camas Mµor, Isle of Muck, Scotland
  • Camphouse, Ardnamurchan, Argyllshire, Scotland
  • Bellerberg volcano, two km north of Mayen, Eifel district, Germany
  • Hatrurim Formation,Israel
  • Rehia, and in Golden Gully, Tokatoka district, about 150 km north of Auckland, New Zealand
  • Gosse Pile, Tomkinson Ranges, and in the Deering Hills, South Australia
  • Marble Canyon, Culberson Co., Texas, USA.

Occurrence of Larnite and Useful Mineral Association

Larnite occurs in contact metamorphic terranes involving sedimentary carbonate rocks. It is closely associated with spurrite, melilite, mayenite, brownmillerite, hydrogrossular, scawtite, kilchoanite, rankinite, wollastonite, perovskite, merwinite and gehlenite.

References


Tell Us What You Think

Do you have a review, update or anything you would like to add to this article?

Leave your feedback
Submit