Beryl – Occurrence, Properties, and Distribution

Beryl was named after the Greek word beryllos. The original significance of the name is unknown, but it may refer to the blue-green stones in the mineral.

Properties of Beryl

The following are the key properties of beryl:

  • Cell Data
    • Space group: P6/mcc
    • a = 9.205-9.274
    • c = 9.187-9.249
    • Z = 2

  • Crystal Data
    • Hexagonal
    • Point group: 6/m2/m2/m
    • Crystals prismatic to tabular, with {1010}, {0001}, and {1120}
    • May be complexly terminated by pyramids, to 18m and 180t
    • Also radial, trapiche, columnar
    • Granular to compact
    • Twinning: On {hkil} forms, rarely
    • X-ray powder pattern: 2.867 (100), 3.254 (95), 7.98 (90), 4.60 (50), 3.99 (45), 3.015 (35), 2.523 (30)

  • Chemical Composition
    Elements Content 1 Content 2 Content 3
    SiO2 65.59 63.29 67.07
    Al2O3 18.25 17.76 18.97
    BeO 13.46 10.79 13.96
    Cs2O - 3.79 -
    Li2O - 1.30 -
    FeO 1.16 - -
    Na2O 0.26 1.23 -
    LOI 0.70 1.10 -
    Rb2O - 0.05 -
    Total 99.42 99.31 100.00

  • Optical Properties
    • Optical class: Biaxial (-)
    • Pleochroism: Weak to distinct; O = colorless, yellowish-green, light blue, yellowish-red; E = sea-green, blue, purplish-red
    • ω = 1.567-1.610
    • ε = 1.565-1.599

  • Estimated Properties
    Electron density Bulk density (electron density) = 2.74 g/cm3
    note: Specific gravity of beryl = 2.77 g/cm3
    Photoelectric PEBeryl = 1.55 barns/electron
    U = PEBeryl x ρ electron density = 4.24 barns/cm3
    Fermion index Fermion index = 0.06
    Boson index = 0.94
    Radioactivity
    Beryl is not radioactive

How to Identify Beryl

Beryl can be identified in the field by its color variations, such as green, blue, yellow, and pink. It is sometimes colorless. Its transparent to sub-translucent form has {0001} imperfect cleavage. This mineral has a vitreous - resinous luster, with white streak. The fracture on this mineral is brittle - conchoidal.

The density of beryl is 2.63 - 2.9 g/cm3, with a hardness of 7.5 to 8. It is non-fluorescent.

Global Distribution

Beryl is distributed in the following places:

  • Russia, in the Mursinka - Alabashka area, near Yekaterinburg (Sverdlovsk), Ural Mountains, and from Nerchinsk south to Borzya, Adun-Chilon Mountains, Siberia
  • Ukraine - At Volhynia
  • Mozambique - In the Muiane pegmatite, Alto Ligonha district
  • Nigeria - In the Ran-Gabas Hills, near Jos
  • Zimbabwe - In the Sandawana-Belingwe area, Mweza Range
  • Madagascar - Especially around Mt. Bity, south of Antsirabe, with giant crystals from the Malakialina district
  • USA - From the Pala and Rincon districts, San Diego Co. California; at Hiddenite, Alexander Co. North Carolina; Fine red crystals in the Wah Wah Mountains, Beaver Co. Utah; on Mt. Antero, Chaee Co. Colorado; and in the Sawtooth Mountains area of Idaho
  • Colombia - Exceptional green crystals from the Muzo and Chivor districts, Boyaca Province
  • Brazil - From Minas Gerais, in large districts around Teolo Otoni, Governador Valadares, Conselheiro Pena, and Itabira
  • Pakistan - Around Mingora, Swat district; from Dassu and the Skardu district; at Kunar and Nagar, near Karimabad, Hunza district
  • Afghanistan - Around Khenj, Panjshir Valley

Occurrence of Beryl and Useful Mineral Association

Beryl occurs in granites and granite pegmatites, and, rarely, in nepheline syenites. It may occur in mafic metamorphic rocks, low to high temperature hydrothermal veins, and in vugs in rhyolite.

It is often associated with minerals such quartz, topaz, feldspar, lepidolite, spodumene, muscovite, amblygonite, cassiterite, columbite, tantalite, and tourmaline.

References

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