Raman spectroscopic study of the multi‐anion mineral dixenite CuMn²⁺₁₄Fe³⁺(AsO₃)₅(SiO₄)₂(AsO₄)(OH)₆

Abstract

The mixed anion mineral dixenite has been studied by Raman spectroscopy, complemented with infrared spectroscopy. The Raman spectrum of dixenite shows bands at 839 and 813 cm −1 assigned to the (AsO 3 ) 3− symmetric and antisymmetric stretching modes. The most intense Raman band of dixenite is the band at 526 cm −1 and is assigned to the ν 2 AsO 3 3− bending mode. DFT calculations enabled the calculation of the position of AsO 2 2− symmetric stretching mode at 839 cm −1 , the antisymmetric stretching mode at 813 cm −1 , and the deformation mode at 449 cm −1 . The Raman bands at 1026 and 1057 cm −1 are assigned to the SiO 4 2− symmetric stretching vibrations and those at 1349 and 1386 cm −1 to the SiO 4 2− antisymmetric stretching vibrations. Both Raman and infrared spectra indicate the presence of water in the structure of dixenite. This brings into question the commonly accepted formula of dixenite as CuMn 2+ 14 Fe 3+ (AsO 3 ) 5 (SiO 4 ) 2 (AsO 4 )(OH) 6 . The formula may be better written as CuMn 2+ 14 Fe 3+ (AsO 3 ) 5 (SiO 4 ) 2 (AsO 4 )(OH) 6 ·xH 2 O.

Recent advances in linear and nonlinear Raman spectroscopy. Part V

“…Vibrational analyses of the following minerals have been carried out by Frost and coworkers using Raman scattering and other related techniques: the arsenite mineral finnemanite Pb 5 (As 3+ O 3 ) 3 Cl; the multi‐anion mineral dixenite, CuMn 2+ 14 Fe 3+( AsO 3 ) 5 (SiO 4 ) 2 (AsO 4 )(OH) 6 ; vajdakite, [(Mo 6+ O 2 ) 2 (H 2 O) 2 As 2 3+ O 5 ]‐H 2 O; triclinic cejkaite Na 4 [UO 2 (CO 3 ) 3 ] and its synthetic trigonal analog; the arsenite minerals leiteite ZnAs 2 O 4 , reinerite Zn 3 (AsO 3 ) 2 and cafarsite Ca 5 (Ti,Fe,Mn) 7 (AsO 3 ) 12 ‐4H 2 O; the antimonate mineral bahianite Al 5 Sb 5+ 3 O 14 (OH) 2 , a semi‐precious gemstone; the antimonate mineral bottinoite Ni[Sb 2 (OH) 12 ]‐6H 2 O and in comparison with brandholzite Mg[Sb 5+ 2 (OH) 12 ]‐6H 2 O; haidingerite Ca(AsO 3 OH)‐H 2 O and brassite Mg(AsO 3 OH)‐4H 2 O; the kaolinite‐like phyllosilicate minerals bismutoferrite BiFe 3+ 2 Si 2 O 8 (OH) and chapmanite SbFe 3+ 2 Si 2 O 8 (OH); the hydrogen‐arsenate mineral pharmacolite Ca(AsO 3 OH)‐2H 2 O with implications for aquifer and sediment remediation; the mineral gerstleyite Na 2 (Sb,As) 8 S 13 ‐2H 2 O and in comparison with some heavy‐metal sulfides; synthetic reevesite and cobalt substituted reevesite (Ni,Co) 6 Fe 2 (OH) 16 (CO 3 )‐4H 2 O; the mineral euchroite, a mineral involved in a complex set of equilibria between the copper hydroxy arsenates: euchroite Cu 2 (AsO 4 )(OH)‐3H 2 O‚ olivenite Cu 2 (AsO 4 )(OH)‚ strashimirite Cu 8 (AsO 4 ) 4 (OH) 4 ‐5H 2 O and arhbarite Cu 2 Mg(AsO 4 )(OH) 3 ; the mixite mineral BiCu 6 (AsO 4 ) 3 (OH) 6 ‐3H 2 O from the Czech Republic; the gallium‐based hydrotalcites of formula Mg 6 Ga 2 (CO 3 )(OH) 16 ‐4H 2 O; the indium‐based hydrotalcites of formula Mg6In 2 (CO 3 )(OH) 16 ‐4H 2 O; the hydroxy‐arsenate‐sulfate mineral chalcophyllite Cu 18 Al 2 (AsO 4 ) 4 (SO 4 ) 3 (OH) 24 ‐36H 2 O; the phosphate mineral churchite‐(Y) YPO 4 ‐2H2O; the synthesis of sodium hexatitanate from sodium trititanate was characterized by Raman spectroscopy, XRD and high‐resolution TEM; a Raman spectroscopic study on the allocation of ammonium‐adsorbing sites on H2Ti3O7 nanofibre and its structural derivation during calcination; and hydrogen‐arsenate group (AsO 3 OH) in solid‐state compounds: copper mineral phase geminite Cu(AsO 3 OH)‐H2O from different geological environments . Gomez et al .…”

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

“…Raman spectroscopy has proved very useful for the study of minerals 12–25. Indeed Raman spectroscopy has proved most useful for the study of diagentically related minerals as often occurs with minerals containing sulfate and phosphate groups.…”

Single‐crystal Raman spectroscopy of natural leiteite (ZnAs2O4) and comparison with the synthesised mineral

“…A review of the vibrational spectroscopy of arsenite and antimonite minerals has been undertaken 10. Some recent studies of arsenite minerals have been published by the authors 11–14. Although Raman studies on aqueous solutions of arsenic trioxide have spanned several decades, few spectroscopic investigations have been undertaken on other arsenite minerals and none to date on leiteite 14.…”