A Raman spectroscopic study of selected minerals of the rosasite group

Journal of Raman Spectroscopy (Impact Factor: 2.67). 09/2006; 37(9). DOI: 10.1002/jrs.1521
Source: OAI


Minerals in the rosasite mineral group namely rosasite, glaucosphaerite, kolwezite, mcguinnessite, nullaginite and pokrovskite have been studied by Raman spectroscopy at 298 and 77 K and complimented with infrared spectroscopy. The spectral patterns for the minerals rosasite, glaucosphaerite, kolwezite and mcguinnessite are similar to that of malachite implying the structure is the same as malachite i.e. monoclinic. A comparison is made with the spectra of malachite. The symmetry of the carbonate anion in the rosasite mineral group is C2v or Cs and is composition dependent. Two (CO3)2- symmetric stretching modes are observed for the rosasite minerals at 1060 and 1090 cm-1. Two hydroxyl stretching modes are observed for the rosasite mineral group. The position of these bands is determined to be a function of the hydrogen bond lengths. Hydrogen bond distances for rosasite are calculated as 2.867, 2.799 and 2.780 Å whereas for pokrovskite the distances are 3.280 and 2.999 Å. The effect of lowering the temperature from ambient to 77 K results in a decrease of the hydrogen bond distances by 5%. Multiple Raman bands are observed in the 800 to 850 cm-1 and the 720 to 750 cm-1 regions and are attributed to ν2 and ν4 bending modes confirming the reduction of the carbonate anion in the rosasite structure.

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    • "In particular the sample 3702 (Figure 6(a)) belongs to the rosasite group, while the other three samples (3524, 3708 and 3714) in Figure 6(b) belong to the aurichalcite group. In both groups we can observe the band at 1073 cm –1 ; that is the (CO 3 ) 2– symmetric stretching mode, typical of the carbonate block [6] [7]. The bands at 140 and 167 cm –1 are assigned to the CuO and ZnO bending vibrations. "
    Journal of Analytical Sciences, Methods and Instrumentation 01/2012; 2(01):42-47. DOI:10.4236/jasmi.2012.21009
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    ABSTRACT: In this endeavour near-infrared spectroscopy studies show an evidence for variable composition in aurichalcite minerals of zinc copper carbonate hydroxides. The observation of a broad feature in the electronic part of the spectrum around 11500 cm-1 (0.87 µm) is a strong indication of Cu2+ substitution for Zn2+ in the mineral. Overtones of OH vibrations in the spectra from 7250 to 5400 cm-1 (1.38 to 1.85µm) show strong hydrogen bonding in these carbonates. A band common to spectra of all carbonates appears near 5400 cm-1 (1.85 µm) due to the combination of both OH-stretching and HOH-bending vibrations, may be attributed to adsorbed water by the minerals. Aurichalcite minerals display a spectral sequence of five absorpton bands with variation of both band positions and intenities and this is the chief spectral feature observed in the range 5200 -5100 cm-1 (1.92 - 2.38 µm) due to vibrational processes of the carbonate ion. The frequency shifts of carbonate bands suggest the effect of divalent cations and or variations of Zn/Cu ratio in aurichalcite minerals.
    Journal of Near Infrared Spectroscopy 01/2007; 15(2). DOI:10.1255/jnirs.722 · 1.25 Impact Factor
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    ABSTRACT: The Cu–ZnO catalyst precursors with variable Cu:Zn ratio, between Zn-rich and Cu-rich compositions have been investigated by a combination of electronic and vibrational spectroscopy. Synthesized catalyst precursors exhibit two d–d transition bands of Cu2+ ions in a distorted octahedral symmetry, at 7,600 and 12,900cm−1 (1,315 and 775nm). The effect of structural cation substitution (Zn2+ and Cu2+) on band shifts is observed in the spectra of the synthetic catalyst precursors. The observation of two broad features at ∼7,600 and 12,900cm−1 (1,315 and 775nm) is a strong indication for Zn2+ substitution by Cu2+ ions. The result of multiple bands in the symmetric stretching and bending regions confirms the reduction of symmetry from D 3h to C 2v /C s for (CO3)2− ion in aurichalcite. The synthetic aurichalcite may be used as a standard for identification of spectral properties of naturally occurring anhydrous carbonate minerals.
    Transition Metal Chemistry 04/2007; 33(3):331-339. DOI:10.1007/s11243-007-9044-9 · 1.31 Impact Factor
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