Editorial Feature

Bromellite: Occurrence and Properties

Bromellite, BeO was named after Magnus von Bromell (1679–1731), a Swedish physician and mineralogist. The oxide mineral is found in manganese-iron deposits but has been made synthetically for over 40 years as it rarely occurs naturally. It has many uses, such as in ceramic-based electronics, or as a moderator for fast neutrons in nuclear reactors. As an additive, it can enhance mechanical strength and thermal properties.

Properties of Bromellite

The following are the key properties of bromellite:

Cell Data

  • Space group: P63mc (this describes the symmetry group of a configuration in three-dimensional space)
  • a = 2.6983(4)
  • c = 4.3776(4)
  • Z = 2

Crystal Data

  • Hexagonal – it forms dihexagonal pyramidal crystals
  • Point group: 6mm
  • As prismatic crystals, elongated along [0001], to 1 mm, showing pyramidal hemimorphism, with {0001} and {1010} well developed, {1011} small
  • May be tabular || {0001}
  • In randomly inter-grown rosette-like aggregates; cleavage fragments, to 10 cm.
  • X-ray powder pattern: 2.061 (100), 2.337 (91), 2.189 (61), 1.349 (29), 1.238 (24), 1.598 (22), 1.1482 (16)

Chemical Composition

  • The chemical composition of bromellite is BeO, although it often has impurities of aluminum, boron, barium, calcium, iron, magnesium and silicon. It is highly toxic, and contact with the skin should be avoided.

 

 

Elements Content 1 Content 2
BeO 98.02 93.2
SiO2 - 0.7
Al2O3 0.17 1.2
B2O3 - 1.4
Fe2 O3 - 0.1
Sb2O3 0.29 -
MgO 0.07 -
CaO 1.03 0.1
BaO 0.55 -
LOI 0.85 3.4
MnO Trace -
Total 100.98 100.1

 

Optical Properties

  • Optical Class: Uniaxial (+)
  • ω = 1.705–1.719
  • ε = 1.733

Estimated Properties

Electron density Bulk density (electron density) =2.89 g/cm3
note: Specific gravity of bromellite = 3.02 g/cm3
Photoelectric PEBromellite = 0.31 barns/electron
U=PEBromellite x ρ electron density= 0.90 barns/cm3
Fermion index Fermion index = 0.36
Boson index = 0.64
Radioactivity
Bromellite is not radioactive

How to Identify Bromellite

Bromellite can be identified in the field by its white color. Its transparent to translucent form has {1010} distinct cleavage – meaning it has a recognizable, distinct cleavage surface. This mineral has a vitreous luster with a white streak. The density of bromellite is 3.017 g/cm3 with a hardness of 9 on the Mohs Scale – approximate to corundum, an extremely hard crystallized alumina.

Occurrence of Bromellite and Useful Mineral Association

Bromellite occurs in hydrothermal calcite veins and veinlets in hematite skarn and skarnized limestones. For something to have undergone skarnization, it has been chemically and mineralogically altered by hot, chemically active fluids. It’s also present in vugs in natrolite, hydrothermally altered from nepheline; and in syenite pegmatite. It is often associated with minerals such as swedenborgite, richterite, diaspore, manganophyllite, natrolite, and chamosite.

Sources and Further Reading

This article was updated on 3rd February, 2020.

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