Pollucite

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Pollucite
Pollucite-193819.jpg
Euhedral, tabular crystal of colorless, translucent and lustrous pollucite with frosted crystal faces from Afghanistan (size: 2.7 x 2.4 x 1.2 cm)
General
Category Zeolite mineral
Formula
(repeating unit)
Cs(Si2Al)O6.nH2O
Strunz classification 9.GB.05
Dana classification 77.1.1.2
Crystal symmetry Isometric hexoctahedral
H-M symbol: (4/m32/m)
Space group: Ia3d
Unit cell a = 13.67 Å; Z=16
Identification
Color Usually colorless, also white, grey, pink, blue or violet
Crystal habit Usually massive, rare crystals are normally trapezohedral or cubic
Crystal system Isometric
Cleavage None observed
Fracture Conchoidal to uneven
Tenacity Brittle
Mohs scale hardness 6.5 to 7
Luster Vitreous to greasy
Streak White
Diaphaneity Transparent to translucent
Specific gravity 2.7 to 3.0
Optical properties Isotropic or very weakly anisotropic
Refractive index 1.508-1.528
Solubility Readily soluble in HF, dissolves with difficulty in hot HCL
Other characteristics Sometimes weakly fluorescent under SW and LW UV
References [1][2][3][4]

Pollucite is a zeolite mineral with the formula (Cs,Na)2Al2Si4O12·2H2O with iron, calcium, rubidium and potassium as common substituting elements. It is important as a significant ore of caesium and sometimes rubidium. It forms a solid solution series with analcime. It crystallizes in the isometric - hexoctahedral crystal system as colorless, white, gray, or rarely pink and blue masses. Well formed crystals are rare. It has a Mohs hardness of 6.5 and a specific gravity of 2.9. It has a brittle fracture and no cleavage.

Discovery and occurrence[edit]

Another sample of Pollucite Ore, held in the Royal Ontario Museum

It was first described by August Breithaupt in 1846 for occurrences on the island of Elba, Italy. It is named for Pollux, the twin of Castor on the grounds that it is often found associated with petalite (previously known as castorite).[5] The high caesium content was missed by the first analysis by Karl Friedrich Plattner in 1848,[6] but after the discovery of caesium in 1860 a second analysis in 1864 was able to show the high caesium content of pollucite.[7]

Its typical occurrence is in lithium-rich granite pegmatites in association with quartz, spodumene, petalite, amblygonite, lepidolite, elbaite, cassiterite, columbite, apatite, eucryptite, muscovite, albite and microcline.

About 82% of the world's known reserves of pollucite occur near Bernic Lake in Manitoba, Canada, where they are mined for their caesium content for use in caesium formate oil drilling assistance. [8] This ore is about 20% by weight caesium.


References[edit]

  1. ^ Gaines, et al. (1997) Dana's New Mineralogy, Wiley ISBN 978-0471193104
  2. ^ Pollucite on Mindat.org
  3. ^ Pollucite data on Webmineral
  4. ^ Handbook of Mineralogy
  5. ^ Breithaupt, August (1846). "Neue Mineralien". Annalen der Physik und Chemie 69 (11): 439–442. Bibcode:1846AnP...145..429B. doi:10.1002/andp.18461451111. 
  6. ^ Plattner, C. F. (1846). "Chemische Untersuchung zweier neuen, vom Herrn Prof. Breithaupt mineralogisch bestimmten Mineralien von der Insel Elba". Annalen der Physik und Chemie 145 (11): 443–447. Bibcode:1846AnP...145..443P. doi:10.1002/andp.18461451112. 
  7. ^ Pisani, F. (1864). "Étude chimique et analyse du pollux de l'ile d'Elbe". Comptes rendus 58: 714–716. 
  8. ^ http://www.encyclopedia.com/doc/1G1-75752682.html Original reference to Mining Journal, March 2, 2001, p 160. Accessed March 28, 2009