Bromargyrite – Occurrence, Properties, and Distribution

Bromargyrite was named after BROMine and the Greek word argyros, meaning silver, which is present in its composition.

Properties of Bromargyrite

The following are the key properties of bromargyrite:

  • Cell Data
    • Space group: Fm3m
    • a = 5.7745
    • Z = 4

  • Crystal Data
    • Cubic
    • Point group: 4/m 3 2/m
    • Crystals cubic, with {111} and {011}, to 1cm
    • In parallel or sub-parallel groups
    • Commonly as crusts and coatings, massive
    • Twinning: {111}, rare
    • X-ray powder pattern: 2.886 (100), 2.041 (55), 1.667 (16), 1.291 (14), 1.1787 (10), 3.33 (8), 1.444 (8)

  • Chemical Composition
    Elements Content 1 Content 2
    Ag 57.56 65.16
    Br 42.44 24.13
    Cl - 10.71
    Total 100.00 100.00

  • Optical Properties
    • Optical Class: Isotropic
    • n = 2.253

  • Estimated Properties
    Electron density Bulk density (electron density) = 5.66 g/cm3
    note: Specific gravity of bromargyrite = 6.48 g/cm3
    Photoelectric PEBromargyrite = 188.51 barns/electron
    U=PEBromargyrite x ρ electron density = 1,066.92 barns/cm3
    Fermion index Fermion index = 0
    Boson index = 1
    Radioactivity
    Bromargyrite is not radioactive

How to Identify Bromargyrite

Bromargyrite can be identified in the field by its color variations, such as greenish-brown, gray-green, grayish-yellow, yellow, and olive green. Its transparent to translucent form has no cleavage. This mineral has an adamantine-greasy luster with gray streak. The fracture on this mineral is conchoidal and uneven.

The density of bromargyrite is 5.8 to 6 g/cm3 with a hardness of 1.5 to 2 - between talc and gypsum.

Global Distribution

Bromargyrite is distributed in the following places:

  • France - From Huelgoet, Finistere
  • Germany - At the Schone Aussicht mine, near Dernbach, and at Bad Ems,
  • Rhineland-Palatinate
  • Mexico - From Charcas, San Luis Potosi; Plateros, Zacatecas
  • Chile - At Chanarcillo, south of Copiapo, Atacama
  • Australia - From Broken Hill, New South Wales
  • USA - At Bisbee, Tombstone, and the Commonwealth mine, Pearce, Cochise Co. Arizona; from the Silver City district, Grant Co. and elsewhere in New Mexico; at Silver Cli, Custer Co. and on Horse Mountain, 13km south of Eagle, Eagle Co. Colorado.

Occurrence of Bromargyrite and Useful Mineral Association

Bromargyrite occurs in a rare secondary mineral in the oxidation zones of silver deposits, notably in arid regions.

It is often associated with minerals such as silver, smithsonite, iodargyrite, and Fe–Mn oxides.

References

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