Raman microscopy of some natural pseudo‐alums: halotrichite, apjohnite and wupatkiite, at 298 and 77 K

Raman spectroscopy of halotrichite from Jaroso, Spain

“…In the 77 K spectrum four bands are found at 435.2, 466.7, 481.7 and 534.1 cm -1 . A previous study showed halotrichite showed two bands at 468 and 424 cm -1 for halotrichite [13]. Halotrichites are known for forming a continuous solid solution with pickingerite.…”

“…As with the infrared spectra, Raman spectra of alums are based on the combination of the spectra of the sulphate and water. Sulphate typically is a tetrahedral oxyanion with Raman bands at 981 (ν 1 ), 451 (ν 2 ), 1104 (ν 3 ) and 613 (ν 4 ) cm -1 [13]. Some sulphates have their symmetry reduced through acting as monodentate and bidentate ligands [13].…”

“…Sulphate typically is a tetrahedral oxyanion with Raman bands at 981 (ν 1 ), 451 (ν 2 ), 1104 (ν 3 ) and 613 (ν 4 ) cm -1 [13]. Some sulphates have their symmetry reduced through acting as monodentate and bidentate ligands [13]. In the case of bidentate behaviour both bridging and chelating ligands are known.…”

Raman spectroscopic study of the basic copper sulphates—implications for copper corrosion and ‘bronze disease’

“…26 Further, the molecular structure of some naturally occurring pseudo-alums has been determined. 27,28 Recently, the Raman spectroscopy of the vivianite phosphates and sulphates has been undertaken. Raman spectroscopy has proven extremely powerful for studying hydrated (such as the vivianite minerals), hydroxylated (basic copper sulphates and phosphates) and sulphated (natural alums) minerals.…”

Natural halotrichites—an EDX and Raman spectroscopic study

“…Sulphate typically is a tetrahedral oxyanion with Raman bands at 981 (ν 1 ), 451 (ν 2 ), 1104 (ν 3 ) and 613 (ν 4 ) cm -113 . Some sulphates have their symmetry reduced through acting as monodentate and bidentate ligands 13 . In the case of bidentate behaviour both bridging and chelating ligands are known.…”