Marilla J. Dickfos

Raman and infrared spectroscopic study of the anhydrous carbonate minerals shortite and barytocalcite

The Raman spectra of shortite and barytocalcite complimented with infrared spectra have been used to characterise the structure of these carbonate minerals. The Raman spectrum of barytocalcite shows a single band at 1086 cm(-1) attributed to the (CO3)(2-) symmetric stretching mode, in contrast to shortite where two bands are observed. The observation of two bands for shortite confirms the concept of more than one crystallographically distinct carbonate unit in the unit cell. Multiple bands are observed for the antisymmetric stretching and bending region for these minerals proving that the carbonate unit is distorted in the structure of both shortite and barytocalcite.

Raman spectroscopic study of the uranyl minerals vanmeersscheite U(OH)4[(UO2)3(PO4)2(OH)2]·4H2O and arsenouranylite Ca(UO2)[(UO2)3(AsO4)2(OH)2]·(OH)2·6H2O

Raman and infrared spectra of secondary uranyl phosphate vanmeersscheite and Raman spectrum of secondary uranyl arsenate arsenuranylite were recorded and interpreted, and the spectra related to the structure of the minerals. Observed bands were attributed to the stretching and bending vibrations of uranyl, phosphate and/or arsenate units and OH (H(2)O and OH(-)) units. Phosphuranylite sheet topology is characteristic for both minerals. U-O bond lengths in uranyl were calculated from the spectra and compared with those inferred for vanmeersscheite from the X-ray single crystal structure analysis. O-H...O hydrogen bonds in both minerals were also inferred using the Libowitzky empirical relation.

Characterisation of Ni silicate-bearing minerals by UV-vis-NIR spectroscopy Effect of Ni substitution in hydrous Ni-Mg silicates

Three Ni silicate-bearing pimelite, nepouite and pecoraite minerals, from Australia have been investigated by UV-vis-NIR spectroscopy to study the effect of Ni-Mg substitution. The observation of three major absorption bands at 9205-9095, 15,600-15,190 and 26,550-25,660 cm(-1) are the characteristic features of Ni(2+) in sixfold coordination. The effect of cation substitution like Mg(2+) for Ni(2+) on band shifts in electronic and vibrational spectra enable the distinction between the Ni-bearing silicates.

Raman spectroscopic study of the tellurite minerals : Carlfriesite and spiroffite

Raman spectroscopy has been used to study the tellurite minerals spiroffite and carlfriesite, which are minerals of formula type A(2)(X(3)O(8)) where A is Ca(2+) for the mineral carlfriesite and is Zn(2+) and Mn(2+) for the mineral spiroffite. Raman bands for spiroffite observed at 721 and 743 cm(-1), and 650 cm(-1) are attributed to the nu(1) (Te(3)O(8))(2-) symmetric stretching mode and the nu(3) (Te(3)O(8))(2-) antisymmetric stretching modes, respectively. A second spiroffite mineral sample provided a Raman spectrum with bands at 727 cm(-1) assigned to the nu(1) (Te(3)O(8))(2-) symmetric stretching modes and the band at 640cm(-1) accounted for by the nu(3) (Te(3)O(8))(2-) antisymmetric stretching mode. The Raman spectrum of carlfriesite showed an intense band at 721 cm(-1). Raman bands for spiroffite, observed at (346, 394) and 466 cm(-1) are assigned to the (Te(3)O(8))(2-)nu(2) (A(1)) bending mode and nu(4) (E) bending modes. The Raman spectroscopy of the minerals carlfriesite and spiroffite are difficult because of the presence of impurities and other diagenetically related tellurite minerals.

Raman spectroscopic study of the tellurite minerals : mackayite and quetzalcoatlite

Tellurites may be subdivided according to formula and structure. There are five groups based upon the formulae: (a) A(XO(3)), (b) A(XO(3)).xH(2)O, (c) A(2)(XO(3))(3).x(2)O, (d) A(2)(X(2)O(5)) and (e) A(X(3)O(8)). Raman spectroscopy has been used to study mackayite and quetzalcoatlite are examples of tellurites containing OH units Raman bands for mackayite observed at 732, 782 and 579, 635cm(-1) are assigned to the nu(1) (Te(2)O(5))(2-) symmetric stretching and nu(3) (Te(2)O(5))(2-) antisymmetric stretching modes. The Raman spectral profile of quetzalcoatlite is more complex with a considerable number of overlapping bands. Two bands may be resolved at 719 and 754cm(-1) which may be attributed to nu(1) (Te(2)O(5))(2-) symmetric stretching mode. The two Raman bands of quetzalcoatlite at 602 and 606cm(-1) are accounted for by the nu(3) (Te(2)O(5))(2-) antisymmetric stretching mode. Raman bands for mackayite, observed at 306, 349, 379 and 424, 436cm(-1) are assigned to the (Te(2)O(5))(2-) nu(2) (A(1)) bending mode and nu(4) (E) bending modes. This research shows that Raman spectroscopy may be applied to tellurite minerals successfully.

Raman spectroscopic study of the tellurite minerals: Rajite and denningite

Tellurites may be subdivided according to formula and structure. There are five groups based upon the formulae (a) A(XO3), (b) A(XO3).xH2O, (c) A2(XO3)3.xH2O, (d) A2(X2O5) and (e) A(X3O8). Raman spectroscopy has been used to study rajite and denningite, examples of group (d). Minerals of the tellurite group are porous zeolite-like materials. Raman bands for rajite observed at 740, and 676 and 667 cm(-1) are attributed to the nu1 (Te2O5)(2-) symmetric stretching mode and the nu3 (TeO3)(2-) antisymmetric stretching modes, respectively. A second rajite mineral sample provided a more complex Raman spectrum with Raman bands at 754 and 731 cm(-1) assigned to the nu1 (Te2O5)(2-) symmetric stretching modes and two bands at 652 and 603 cm(-1) are accounted for by the nu3 (Te2O5)(2-) antisymmetric stretching mode. The Raman spectrum of dennigite displays an intense band at 734 cm(-1) attributed to the nu1 (Te2O5)(2-) symmetric stretching mode with a second Raman band at 674 cm(-1) assigned to the nu3 (Te2O5)(2-) antisymmetric stretching mode. Raman bands for rajite, observed at (346, 370) and 438 cm(-1) are assigned to the (Te2O5)(2-)nu2 (A1) bending mode and nu4 (E) bending modes.

An Application of near Infrared and Mid-Infrared Spectroscopy to the Study of Uranyl Selenite Minerals: Derriksite, Demesmaekerite, Guilleminite and Haynesite

The near infrared (NIR) spectra of the natural uranyl selenite minerals that include derriksite, demesmaekerite, guilleminite and haynesite are examined as a potential indicator of uranium occurring geologic materials at the earths surface. NIR analysis, complimented with mid-IR studies, was used to investigate the co-ordination of UO22+ and Cu2+ in the uranyl selenites. Bands obtained from the infrared spectra of selenites are interpreted in terms of the stretching vibrations of uranyl, selenite units and OH groups and bending modes. NIR spectra of the uranyl selenite minerals exhibit distinctive characteristics of uranyl ion (UO2)2+ absorptions over the range of 11,500–8000 cm−1. The high- range NIR spectrum of Cu-bearing uranyl derriksite is resolved into two bands, UO22+ 8070 cm−1 and Cu2+ 7175 cm−1. The effect of lead in demesmaekerite leads to distortion of the spectrum and the NIR bands are observed for uranyl ion at 11,305 cm−1 and 8475 cm−1 and for Cu2+ at 7430 cm−1. The δ U–OH bending vibrations are characterised by a strong absorption feature centred at 1015 cm−1 in haynesite. A significant shift for UOH bending vibrations and the absence of ν1 and ν3 vibrations of UO22+ at the expense of Cu2+ are reflected in the spectrum of derriksite. The complexity of bands with shifts to low wavenumbers could take place due to the additional cations of Pb and Cu in the structure of demesmaekerite. NIR spectroscopy has proven to be a most useful tool for the identification of and distinction between different uranyl selenite minerals.