Editorial Feature

Cesbronite: Occurrence and Properties

Cesbronite is a copper tellurite mineral that was first discovered in 1974 from Bambollita mine, Moctezuma, Sonora, Mexico. It was named after Fabien Cesbron, French mineralogist, Bureau de Recherches Geologiques et Miniere, Orleans. France.

Chemical Formula – Cu5(Te4+O3)2(OH)6 •2H2O

Properties of Cesbronite

The following are the key properties of Cesbronite:

Cell Data

  • Space Group: Pbcn
  • a = 8.624(16)
  • b = 11.878(16)
  • c = 5.872(16)
  • Z = 2

Crystal Data

  • Orthorhombic
  • Point Group: 2/m 2/m 2/m
  • As chisel-shaped dipyramidal crystals, to 0.5 mm, showing dominant and striated {103}, with {180}, {001}, and {010}; as hollow crusts of radiating crystals and fanlike aggregates
  • X-ray Powder Pattern: 5.934 (100), 3.490 (92), 4.889 (71), 2.358 (70), 2.379 (38), 1.592 (34), 2.156 (28)

Chemical Composition

Elements Content 1 Content 2
CuO 49.95 49.29
TeO2 38.92 39.55
H2O 11 11.16
Total 99.87 100

 

Optical Properties

  • Optical Class: Biaxial (+)
  • Pleochroism: Distinct; X = pale bluish green; Y = dark yellow-green; Z = dark emerald-green. Orientation: X = a; Y = c; Z = b
  • Dispersion: r > v; moderate
  • Absorption: Z ? Y>>X
  • α = 1.880(8)
  • β = 1.928(8)
  • γ = 2.029(8)
  • 2V(meas.) = n.d
  • 2V(calc.) = 72°

Estimated Properties

Electron density Bulk density (electron density)=4.10 g/cm3
note: Specific gravity of Cesbronite =4.46 g/cm3
Photoelectric PECesbronite = 123.60 barns/electron
U= PECesbronite x ρ Electron density= 506.84 barns/cm3
Fermion index Fermion index = 0.02
Boson index = 0.98
Radioactivity
Cesbronite is not radioactive

How to Identify Cesbronite

Cesbronite is a translucent green mineral having subadamantine luster, non-fluorescent luminescence, and a light green streak. It exhibits good cleavage and brittle fractures. It can be formed as spherical rounded aggregates. The density of cesbronite is 4.45 g/cm3, and its hardness is 3 on the Mohs scale, akin to calcite.

Occurrence of Cesbronite and Useful Mineral Association

Cesbronite occurs as a secondary mineral in an oxidized Cu–Te–Pb sulfide deposit. It is closely associated with hematite, jensenite, leisingite, utahite, xocomecatlite, carlfriesite, teineite and argentian gold.

Sources and Further Reading

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