Pollucite

Pollucite
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
CategoryZeolite mineral
Formula
(repeating unit)
Cs(Si2Al)O6·nH2O
IMA symbolPol[1]
Strunz classification9.GB.05
Dana classification77.1.1.2
Crystal systemIsometric
Crystal classHexoctahedral (m3m)
H-M symbol: (4/m 3 2/m)
Space groupIa3d
Unit cella = 13.67 Å; Z = 16
Identification
ColorUsually colorless; also white, grey, pink, blue or violet
Crystal habitUsually massive; rare crystals are normally trapezohedral or cubic
CleavageNone observed
FractureConchoidal to uneven
TenacityBrittle
Mohs scale hardness6.5 to 7
LusterVitreous to greasy
StreakWhite
DiaphaneityTransparent to translucent
Specific gravity2.7 to 3.0
Optical propertiesIsotropic or very weakly anisotropic
Refractive index1.508–1.528
SolubilityReadily soluble in HF; dissolves with difficulty in hot HCl
Other characteristicsSometimes weakly fluorescent under SW and LW UV
References[2][3][4][5][6]

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, with a brittle fracture and no cleavage.

  1. ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. ^ Mineralienatlas
  3. ^ Gaines, et al. (1997) Dana's New Mineralogy, Wiley ISBN 978-0471193104
  4. ^ Pollucite on Mindat.org
  5. ^ Pollucite data on Webmineral
  6. ^ Handbook of Mineralogy