A Raman spectroscopic study of the ‘cave’ mineral ardealite Ca₂(HPO₄)(SO₄)·4H₂O

Abstract

The mineral ardealite Ca 2 (HPO 4 )(SO 4 )·4H 2 O is a 'cave' mineral and is formed through the reaction of calcite with bat guano. The mineral shows disorder and the composition varies depending on the origin of the mineral. Raman spectroscopy complimented with infrared spectroscopy has been used to characterise the mineral ardealite. The Raman spectrum is very different from that of gypsum. Bands are assigned to SO 4 2− and HPO 4 2− stretching and bending modes.

ASb2(SO4)2(PO4) (A = H3O+, K, Rb): Layered Structure Containing Ordered Sulfate and Phosphate Anions

“…In infrared spectra, bands ranged from 2930 to 3436 cm –1 are attributed to this stretching mode. The band at 1621 cm –1 is assigned to H–O–H bending mode 36. All these signals confirm the existence of H 2 O and [H 3 O] + in (H 3 O)Sb 2 (SO 4 ) 2 (PO 4 ) structure 37.…”

“…In Raman spectra (Figure 6), an intense band at 986 cm –1 and weak intensity band at 887 cm –1 are assigned to v 1 SO 4 2– and PO 4 3– symmetry stretching vibration 36,38. Overlapping bands at 980, 1006, 1050 cm –1 and weak bands at 880 and 898 cm –1 in infrared spectra are ascribed to this vibration mode.…”

“…Overlapping bands at 980, 1006, 1050 cm –1 and weak bands at 880 and 898 cm –1 in infrared spectra are ascribed to this vibration mode. In Raman spectra ( λ = 785 nm), a very weak band at 1080 cm –1 for all compounds, a single sharp band at 1112 cm –1 [(H 3 O)Sb(SO 4 ) 2 (PO 4 )], both weak bands at 1110 and 1134 cm –1 , and a moderately intense band at 1046 cm –1 are attributed to v 3 SO 4 2– and PO 4 3– asymmetric stretching mode 36,39. Infrared spectra for (H 3 O)Sb(SO 4 ) 2 (PO 4 ), KSb 2 (SO 4 ) 2 (PO 4 ), and RbSb 2 (SO 4 ) 2 (PO 4 ) can be viewed at series overlapping bands at 1198 and 1228 cm –1 ,1178 and 1274 cm –1 , and 1174 and 1232 cm –1 , respectively.…”

Recent advances in linear and nonlinear Raman spectroscopy. Part VI

“…Cornette and co‐workers used vibrational spectra of rhombohedral TeO 3 compared with those of ReO 3 ‐like proto‐phase and TeO 2 (paratellurite) to study their lattice dynamic and crystalline chemistry properties . Frost and various co‐workers reported the vibrational properties for a variety of minerals . Hoang et al .…”