Raman spectroscopic vibrational analysis of the complex iron sulfates clairite, metavoltine, and voltaite from the burning coal dump Anna I, Alsdorf, Germany

Abstract

Vibrational spectroscopy has been used to characterize the three uncommon complex iron sulfates clairite, (NH4)2Fe3(SO4)4(OH)3 3H2O, metavoltine, Na6K2Fe2+Fe3+6(SO4)12O2·18H2O, and voltaite, K2Fe2+5Fe3+3Al(SO4)12 18H2O. The investigated specimens were formed at the burning coal dump Anna I (Alsdorf, Germany) due to alteration processes connected with the subsurface thermal activity. It is found that all three minerals display complex Raman spectra with an extensive proliferation of bands attributed to the sulfate vibrational modes. Both clairite and metavoltine show extraordinary strong Raman bands in the low‐wavenumber region, which can be attributed to the FeO stretching modes. Clairite and metavoltine show a very similar spectral shape; it can be concluded that both minerals can exhibit a similar crystal structure. In comparison, voltaite represents a different structural type; therefore, a distinct Raman spectrum is observed.

Application of a handheld Raman spectrometer for the screening of colored secondary sulfates in abandoned mining areas—The case of the São Domingos Mine (Iberian Pyrite Belt)

“…Such spectral shapes are characteristic of some complex iron sulfates, probably metavoltine (Na 6 K 2 FeFe 6 (SO 4 ) 12 O 2 Á18H 2 O) or another similar phase. [33] Pickeringite and a metavoltine-like phase with an admixture of other sulfates (probably rozenite or alunogen) were also confirmed by the laboratory Raman instrument ( Figure S2). Albeit not detected by the handheld instrument, the Raman spectrum of coquimbite [34] was identified within collected spectra ( Figure S2).…”

“…It can be assigned to the M─O vibration. Such spectral shapes are characteristic of some complex iron sulfates, probably metavoltine (Na 6 K 2 FeFe 6 (SO 4 ) 12 O 2 ·18H 2 O) or another similar phase 33 …”

Infrared and Raman Spectroscopy of Ammoniovoltaite, (NH4)2Fe2+5Fe3+3Al(SO4)12(H2O)18

“…The Raman spectrum of ammoniovoltaite obtained in this work is compared to very recently published spectra of voltaite [34] and tschermigite, (NH 4 )Al(SO 4 ) 2 •12H 2 O, the latter is an ammonium alum [35], but it is chemically related to voltaites since it is hydrated ammonium sulphate ( Table 6). The Raman spectrum of voltaite from Iron Mountain Mine Superfund Site (Redding, CA, USA) has also been reported previously [22]; however, in the cited work, the inverse problem of identifying minerals by spectra without their detailed chemical characteristics is solved.…”

“…The main difference between Raman spectra of ammoniovoltaite and voltaite [34] is in the shape of the 3400 cm −1 to 2800 cm −1 region. The spectra of ammoniovoltaite has a very intensive and distinctive band centered at 3194 cm −1 , although the spectrum of voltaite has a band with similar Raman shift, 3209 cm −1 , the shape of the spectra in this region is evidently different.…”

GeoRaman

“…The correct chemical formula for nesquehonite (Mg (HCO 3 )OHÁ2H 2 O) have been determined by Skliros et al [4] studying its thermal behaviour by means of Raman spectroscopy in combination with Fourier-transform infrared and X-ray diffraction. Košek et al [5] collected and assigned the Raman spectra of three uncommon complex iron sulfate minerals: clairite, metavoltine and voltaite. Clairite and metavoltine show a very similar spectra and hence similar crystal structure, while in comparison, voltaite has a distinct spectrum, thus represents a different structural type.…”