Editorial Feature

Celadonite – Occurrence, Properties, and Distribution

Celadonite was named after the French word ‘celadon’, meaning sea green, in allusion to its color.

Properties of Celadonite

The following are the key properties of celadonite:

  • Cell Data
    • Space group: C2/m or C2
    • a = 5.23(2)
    • b = 9.06(1)
    • c = 10.13(2)
    • β = 100°55 (10)’
    • Z = 2
  • Crystal Data
    • Monoclinic
    • Point group: 2/m or 2
    • As minute micaceous scales or earthy aggregates
    • X-ray powder pattern: 2.580 (100), 4.53 (85), 3.635 (80), 3.087 (80), 2.678 (75), 2.402 (75), 3.318 (70)
  • Chemical Composition
    Elements Content 1
    SiO2 55.61
    Fe2O3 17.19
    K2O 10.03
    MgO 7.26
    H2O 4.88
    FeO 4.02
    Al2O3 0.79
    CaO 0.21
    Na2O 0.19
    MnO 0.09
    Total 100.27
  • Optical Properties
    • Optical class: Biaxial (-)
    • Pleochroism: Yellow-green, blue-green
    • α = 1.606-1.625; β = n.d.; γ= 1.579-1.661
    • 2V(meas.) =5°- 8°
  • Estimated Properties
    Electron density Bulk density (electron density) = 2.97 g/cm3
    note: Specific gravity of celadonite = 3.00 g/cm3
    Photoelectric PE Celadonite = 6.26 barns/electron
    U=PE Celadonite x ρ electron density= 18.60 barns/cm3
    Fermion index Fermion index = 0.02
    Boson index = 0.98
    Radioactivity
    Celadonite is radioactive (barely detectable)

How to Identify Celadonite

Celadonite can be identified in the field by its color variations, such as gray-green and bluish-green. Its translucent to opaque form has {001} perfect cleavage. This mineral has an earthy luster with greenish white streaks. The density of celadonite is 2.95 - 3.05 g/cm3, with a hardness of 2 – approximate to gypsum. It has clay-like fractures.

Global Distribution

Celadonite is distributed in the following places:

  • Italy - On Mt. Baldo, near Verona, Vicenza, and at Val di Fassa, Trentino-Alto Adige
  • Scotland - At Scuir Mohr
  • Austria - In the Zillertal, Tirol
  • Faeroe Islands - From Streymoy and Suduroy
  • Nicaragua - On the Pearl Islands
  • Japan - In the Hosokura mine, Miyagi Prefecture; at Toyoura, Yamagata Prefecture; Nishikata, Tochigi Prefecture; Kamogawa, Chiba Prefecture
  • USA - In the John Day Formation, Grant Co. Oregon; in Mt. Rainier National Park, Pierce Co. Washington; and from Red Rock Canyon, Kern Co. California

Occurrence of Celadonite and Useful Mineral Association

Celadonite replaces primary ferromagnesian silicate minerals in altered intermediate to mafic volcanic rocks. It occurs under low-grade zeolite facies metamorphism; and as amygdule fillings in basalts or andesites. It is often associated with minerals such as montmorillonite, calcite, clinoptilolite, laumontite, prehnite, heulandite, chlorite, and quartz.

References

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