Chemistry:Bertrandite

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Bertrandite
Bertrandite-38545.jpg
Bertrandite from the Golconda pegmatite, Minas Gerais, Brazil
General
CategorySorosilicate
Formula
(repeating unit)
Be4Si2O7(OH)2
Strunz classification9.BD.05
Crystal systemOrthorhombic
Crystal classPyramidal (mm2)
H-M symbol: (mm2)
Space groupCcm21
Unit cella = 8.7135(4) Å,
b = 15.268(1) Å,
c = 4.5683(3) Å; Z = 4
Identification
ColorColorless to pale yellow
Crystal habitThin tabular, prismatic to needle-like crystals commonly in radial clusters
TwinningCommon on {011} or {021} forming heart- or V-shaped twins
CleavagePerfect on {001}; distinct on {100}, {010} and {110}
Mohs scale hardness6–7
|re|er}}Vitreous, pearly on cleavage surfaces
DiaphaneityTransparent
Specific gravity2.59–2.60
Optical propertiesBiaxial (−)
Refractive indexnα = 1.591 nβ = 1.605 nγ = 1.614
Birefringenceδ = 0.023
2V angleMeasured: 73° to 81°
References[1][2][3]

Bertrandite is a beryllium sorosilicate hydroxide mineral with composition: Be4Si2O7(OH)2. Bertrandite is a colorless to pale yellow orthorhombic mineral with a hardness of 6–7.

It is commonly found in beryllium rich pegmatites and is in part an alteration of beryl. Bertrandite often occurs as a pseudomorphic replacement of beryl. Associated minerals include beryl, phenakite, herderite, tourmaline, muscovite, fluorite and quartz.[1]

It, with beryl, are ores of beryllium.

It was discovered near Nantes, France in 1883 and named after France mineralogist, Emile Bertrand (1844–1909).[1][2][3]

One of the world's largest deposits of bertrandite is Spor Mountain, Thomas Range, Utah which is currently the source of most of the world's beryllium production.[5][6]

See also

References

  1. 1.0 1.1 1.2 Handbook of Mineralogy
  2. 2.0 2.1 Bertrandite on Mindat.org
  3. 3.0 3.1 Bertrandite on Webmineral
  4. Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine 85 (3): 291–320. doi:10.1180/mgm.2021.43. Bibcode2021MinM...85..291W. 
  5. Fact Sheet 2016–3081 (October 2016). "Beryllium—A Critical Mineral Commodity—Resources, Production, and Supply Chain" (in English) (Article). pubs.usgs.gov: USGS. pp. 4. https://pubs.usgs.gov/fs/2016/3081/fs20163081.pdf. Retrieved 16 May 2017. 
  6. Shawe, Daniel (1968). Ridge, John. ed. Geology of the Spor mountain Beryllium District, Utah, in Ore deposits of the United States, 1933–1967. New York: The American Institute of Mining, Metallurgical, and Petroleum engineers, Inc.. pp. 1148–1161.