• journal_title：Mineralogical Magazine
• Contributor：F. Bellatreccia ; G. Della Ventura ; G. D. Gatta ; M. Cestelli Guidi ; S. Harley
• Publisher：Mineralogical Society of Great Britain and Ireland
• Date：2012-
• Format：text/html
• Language：en
• Identifier：10.1180/minmag.2012.076.4.07
• journal_abbrev：Mineralogical Magazine
• issn：0026-461X
• volume：76
• issue：4
• firstpage：903
• section：Articles

d="p-1">We report a single-crystal Fourier-transform infrared (FTIR) study of a sample of pollucite from Maine, USA. Prior to our work, the sample had been characterized by single-crystal X-ray diffraction, neutron diffraction and electron-probe microanalysis. It is cubic Ia3İd, with a crystal-chemical formula Na_1.93(Cs_10.48Rb_0.31K_0.04)_Σ=10.83(Al_14.45Si_33.97)_Σ=48.42O₉₆·3.92H₂O, and an H₂O content, determined by thermogravimetric analysis, of 1.6 wt.%. The single-crystal FTIR spectrum has a doublet of intense bands at 3670 and 3589 cm⁻¹, which are assigned to the ν₃ and ν₁ stretching modes of the H₂O molecule, respectively. A very intense and sharp peak at 1620 cm⁻¹ is assigned to the ν₂ bending vibration. In the near-infrared region there is a relatively intense peak at 5270 cm⁻¹, which is assigned to a combination (ν₂ + ν₃) mode of H₂O, and a weak but well defined doublet at 7118 and 6831 cm⁻¹, which is assigned to the first overtones of the fundamental stretching modes. A relatively weak but extremely sharp peak at 2348 cm⁻¹ shows that the pollucite contains CO₂ molecules in structural cavities. Mapping the sample using FTIR indicates that both H₂O and CO₂ are homogeneously distributed. Secondary ion mass spectrometry yielded an average CO₂ content of 0.09 0.02 wt.%. On the basis of this value, we determined the integrated molar absorption coefficient for the spectroscopic analysis of CO₂ in pollucite to be ε_iCO2 = 11,000±3000 l mol⁻¹ cm⁻²; the linear molar absorption coefficient for the same integration range is ε_lCO2= 1600±500 l mol⁻¹ cm⁻¹.