Editorial Feature

Cebollite: Occurrence and Properties

Cebollite was named after the Cebolla Creek in Colorado, USA, where the mineral was first located.

Chemical Formula – Ca5Al2Si3O12(OH)4

Properties of Cebollite

The following are the key properties of cebollite:

Cell Data

  • Space group: n.d. i.e. the symmetry group of a configuration in three-dimensional space
  • Z = n.d.

Crystal Data

  • Orthorhombic
  • Point group: n.d. i.e. how the orientation of a crystal can be changed without altering the position of its atoms
  • As compact masses of minute radiating fibers
  • X-ray powder pattern: 2.73 (100), 2.88 (90), 2.59 (70), 1.62 (60), 3.01 (50), 2.90 (40), 2.45 (40)

Chemical Composition

Elements Content 1 Content 2 Content 3
CaO 29.27 35.75 41.06
SiO2 27.06 33.05 31.07
Insol. 18.05 - -
Al2O3 11.49 14.03 18.48
H2O 5.13 6.27 [7.75]
MgO 3.84 4.69 -
Fe2O3 2.81 3.43 -
Na2O 2.10 2.57 0.28
FeO 0.17 0.21 1.36
K2O trace - -
Total 99.92 [100.00] [100.00]

 

Optical Properties

  • Optical class: Biaxial (+)
  • Dispersion: r > v, weak
  • α = 1.592-1.595; β = 1.597-1.60; γ = 1.628-1.630
  • 2V(meas.) =~58°

Estimated Properties

Electron density Bulk density (electron density) = 2.97 g/cm3
note: Specific gravity of cebollite =2.96 g/cm3
Photoelectric PE Cebollite = 4.90 barns/electron
U=PE Cebollite x ρ electron density= 14.55 barns/cm3
Fermion index Fermion index = 0.0072311321
Boson index = 0.9927688679
Radioactivity
Cebollite is not radioactive

How to Identify Cebollite

Cebollite can be identified in the field by its color variations such as greenish grey, white, and light brown. It is sometimes colorless. Its sub-translucent to opaque form has no cleavage. This mineral has a vitreous – dull luster with a white streak. The density of cebollite is 2.96 g/cm3 with a hardness of 5 on the Mohs scale – approximate to apatite, a pale green to purple mineral consisting of calcium phosphate with chlorine and fluorine. It is non-fluorescent as well as non-magnetic.

Occurrence of Cebollite and Useful Mineral Association

Cebollite occurs as an alteration product of melilite in a carbonatite; along a diabase-chalk contact; in zeolitized plagioclase-rich gneiss, amphibolite, and basalt xenoliths; and as a late-stage primary igneous mineral. It is often associated with minerals such as melilite, diopside, natrolite, phlogopite, vesuvianite, garnet, and calcite.

Sources and Further Reading

This article was updated on 3rd February, 2020.

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