Raman spectroscopic study of the mixed anion mineral yecoraite Bi5Fe3O9(Te4+O3)(Te6+O4)2·9H2O

Tellurates are rare minerals as the tellurate anion is readily reduced to the tellurite ion. Often minerals with both tellurate and tellurite anions are found. An example of such a mineral containing tellurate and tellurite is yecoraite. Raman spectroscopy has been used to study this mineral, the exact structure of which is unknown. Two Raman bands at 796 and 808 cm⁻¹ are assigned to the ν₁(TeO₄)²⁻ symmetric and ν₃(TeO₃)²⁻ antisymmetric stretching modes and Raman bands at 699 cm⁻¹ are attributed to the ν₃(TeO₄)²⁻ antisymmetric stretching mode and the band at 690 cm⁻¹ to the ν₁(TeO₃)²⁻ symmetric stretching mode. The intense band at 465 cm⁻¹ with a shoulder at 470 cm⁻¹ is assigned the (TeO₄)²⁻ and (TeO₃)²⁻ bending modes. Prominent Raman bands are observed at 2878, 2936, 3180 and 3400 cm⁻¹. The band at 3936 cm⁻¹ appears quite distinct and the observation of multiple bands indicates the water molecules in the yecoraite structure are not equivalent. The values for the OH stretching vibrations listed provide hydrogen bond distances of 2.625 Å (2878 cm⁻¹), 2.636 Å (2936 cm⁻¹), 2.697 Å (3180 cm⁻¹) and 2.798 Å (3400 cm⁻¹). This range of hydrogen bonding contributes to the stability of the mineral. A comparison of the Raman spectra of yecoraite with that of tellurate containing minerals kuranakhite, tlapallite and xocomecatlite is made. Copyright © 2009 John Wiley & Sons, Ltd.     

Raman spectroscopic study of the tellurite minerals: emmonsite Fe23+Te34+O9·2H2O and zemannite Mg0.5[Zn2+Fe3+(TeO3)3]4.5H2O

Raman spectroscopy has been used to study zemannite Mg_0.5[Zn²⁺Fe³⁺(TeO₃)₃]4.5H₂O and emmonsite Fe₂³⁺Te₃⁴⁺O₉·2H₂O. Raman bands for zemannite and emmonsite, observed at 740 and 650 cm⁻¹ and at 764 and 788 cm⁻¹, respectively, are attributed to the ν₁ (TeO₃)²⁻ symmetric stretching mode. The splitting of the symmetric stretching mode for emmonsite is in harmony with the results of X‐ray crystallography which shows three non‐equivalent TeO₃ units in the crystal structure. Two bands at 658 and 688 cm⁻¹ are assigned to ν₃ (TeO₃)²⁻ anti‐symmetric stretching modes. Raman bands observed at 372 and 408 cm⁻¹ for zemannite and 397 and 414 cm⁻¹ for emmonsite are attributed to the (TeO₃)²⁻ν₂(A₁) bending mode. The two Raman bands at 400 and 440 cm⁻¹ for emmonsite are ascribed to the ν₄(E) bending modes, while the band at 326 cm⁻¹ is due to the ν₂(A₁) bending vibration. Copyright © 2008 John Wiley & Sons, Ltd.     

Raman spectroscopic study of the selenite mineral mandarinoite Fe2Se3O9·6H2O

Selenites and tellurites may be subdivided according to formula and structure. There are five groups, based upon the formulae (a) A(XO₃), (b) A(XO₃·) xH₂O, (c) A₂(XO₃)₃·xH₂O, (d) A₂(X₂O₅) and (e) A(X₃O₈). Of the selenites, molybdomenite is an example of type (a); chalcomenite, clinochalcomenite, cobaltomenite and ahlfeldite are minerals of type (b); mandarinoite Fe₂Se₃O₉·6H₂O is an example of type (c). Raman spectroscopy has been used to characterise the mineral mandarinoite. The intense, sharp band at 814 cm⁻¹ is assigned to the symmetric stretching (Se₃O₉)⁶⁻ units. Three Raman bands observed at 695, 723 and 744 cm⁻¹ are attributed to the ν₃ (Se₃O₉)⁶⁻ anti‐symmetric stretching modes. Raman bands at 355, 398 and 474 cm⁻¹ are assigned to the ν₄ and ν₂ bending modes. Raman bands are observed at 2796, 2926, 3046, 3189 and 3507 cm⁻¹ and are assigned to OH stretching vibrations. The observation of multiple OH stretching vibrations suggests the non‐equivalence of water in the mandarinoite structure. The use of the Libowitzky empirical function provides hydrogen bond distances of 2.633(9) Å (2926 cm⁻¹), 2.660(0) Å (3046 cm⁻¹), 2.700(0) Å (3189 cm⁻¹) and 2.905(3) Å (3507 cm⁻¹). The sharp, intense band at 3507 cm⁻¹ may be due to hydroxyl units. It is probable that some of the selenite units have been replaced by hydroxyl units. Copyright © 2008 John Wiley & Sons, Ltd.     

Raman spectroscopic study of the selenite mineral: ahlfeldite,NiSeO3·2H2O

Raman spectroscopy has been used to study the selenite mineral ahlfeldite. A comparison is made with the Raman spectra of chalcomenite, cobaltomenite and clinochalcomenite. Selenite minerals are characterised by the position of the symmetric stretching mode which is observed at higher wavenumbers than the anti‐symmetric stretching mode. The selenite ion has C_3v symmetry and four modes, 2A₁ and 2E. These modes are observed at 813, 472 cm⁻¹ (A₁) and 685, 710, 727 and 367 and 396 cm⁻¹ (E). Bands assigned to the water stretching vibrations are observed for ahlfeldite at 3385 cm⁻¹, for chalcomenite at 2953, 3184 and 3506 cm⁻¹ and for clinochalcomenite at 2909, 3193 and 3507 cm⁻¹. A comparison of the Raman spectra of chalcomenite, clinochalcomenite and cobaltomenite is made. The position of these bands enabled hydrogen bond distances in the selenite structure to be estimated. Hydrogen bond distances for ahlfeldite, chalcomenite and clinochalcomenite were determined to be similar. Copyright © 2008 John Wiley & Sons, Ltd.     

Raman spectroscopic study of the selenite minerals—chalcomenite CuSeO3·2H2O,clinochalcomenite and cobaltomenite

Raman spectroscopy has been used to study the dimorphous selenite minerals chalcomenite, cobaltomenite and clinochalcomenite. Selenite minerals are characterised by the position of the symmetric stretching mode that is observed at higher wavenumbers than the anti‐symmetric stretching mode. The selenite ion has C_3v symmetry and four modes, 2A₁ and 2E. These modes are observed at 813, 472 cm⁻¹ (A₁) and 685, 710, 727 and 367 and 396 cm⁻¹ (E). Bands assigned to the water stretching vibrations are observed for chalcomenite at 2953, 3184 and 3506 cm⁻¹ and for clinochalcomenite at 2909, 3193 and 3507 cm⁻¹. A comparison of the Raman spectra of chalcomenite, clinochalcomenite and cobaltomenite is made. The position of these bands enabled hydrogen bond distances in the selenite structure to be estimated. Hydrogen bond distances for chalcomenite and clinochalmenite were determined to be similar. Copyright © 2008 John Wiley & Sons, Ltd.     

Raman spectroscopy of hydrogen‐arsenate group (AsO3OH) in solid‐state compounds: copper mineral phase geminite Cu(AsO3OH)·H2O from different geological environments

The participation of hydrogen‐arsenate group (AsO₃OH)²⁻ in solid‐state compounds may serve as a model example for explaining and clarifying the behaviour of As and other elements during weathering processes in natural environment. The mineral geminite, a hydrated hydrogen‐arsenate mineral of ideal formula Cu(AsO₃OH)·H₂O, has been studied by Raman and infrared spectroscopies. Two samples of geminite of different origin were investigated and the spectra proved quite similar. In the Raman spectra of geminite, six bands are observed at 741, 812, 836, 851, 859 and 885 cm⁻¹ (Salsigne, France), and 743, 813, 843, 853, 871 and 885 cm⁻¹ (Jáchymov, Czech Republic). The band at 851/853 cm⁻¹ is assigned to the ν₁ (AsO₃OH)²⁻ symmetric stretching mode; the other bands are assigned to the ν₃ (AsO₃OH)²⁻ split triply degenerate antisymmetric stretching mode. Raman bands at 309, 333, 345 and 364/310, 333 and 345 cm⁻¹ are attributed to the ν₂ (AsO₃OH)²⁻ bending mode, and a set of higher wavenumber bands (in the range 400–500 cm⁻¹) is assigned to the ν₄ (AsO₃OH)²⁻ split triply degenerate bending mode. A very complex set of overlapping bands is observed in both the Raman and infrared spectra. Raman bands are observed at 2289, 2433, 2737, 2855, 3235, 3377, 3449 and 3521/2288, 2438, 2814, 3152, 3314, 3448 and 3521 cm⁻¹. Two Raman bands at 2289 and 2433/2288 and 2438 cm⁻¹ are ascribed to the strong hydrogen bonded water molecules. The Raman bands at 3235, 3305 and 3377/3152 and 3314 cm⁻¹ may be assigned to the ν OH stretching vibrations of water molecules. Two bands at 3449 and 3521/3448 and 3521 cm⁻¹ are assigned to the OH stretching vibrations of the (AsO₃OH)²⁻ units. The lengths of the O H···O hydrogen bonds vary in the range 2.60–2.94 Å (Raman) and 2.61–3.07 Å (infrared). Two Raman and infrared bands in the region of the bending vibrations of the water molecules prove that structurally non‐equivalent water molecules are present in the crystal structure of geminite. Copyright © 2009 John Wiley & Sons, Ltd.     

Raman spectroscopic study of the hydrogen‐arsenate mineral pharmacolite Ca(AsO3OH)·2H2O—implications for aquifer and sediment remediation

The removal of arsenate anions from aqueous media, sediments and wasted soils is of environmental significance. The reaction of gypsum with the arsenate anion results in pharmacolite mineral formation, together with related minerals. Raman and infrared (IR) spectroscopy have been used to study the mineral pharmacolite Ca(AsO₃OH)· 2H₂O. The mineral is characterised by an intense Raman band at 865 cm⁻¹ assigned to the ν₁ (AsO₃)²⁻ symmetric stretching mode. The equivalent IR band is found at 864 cm⁻¹. The low‐intensity Raman bands in the range from 844 to 886 cm⁻¹ provide evidence for ν₃ (AsO₃) antisymmetric stretching vibrations. A series of overlapping bands in the 300‐450 cm⁻¹ region are attributed to ν₂ and ν₄ (AsO₃) bending modes. Prominent Raman bands at around 3187 cm⁻¹ are assigned to the OH stretching vibrations of hydrogen‐bonded water molecules and the two sharp bands at 3425 and 3526 cm⁻¹ to the OH stretching vibrations of only weakly hydrogen‐bonded hydroxyls in (AsO₃OH)²⁻ units. Copyright © 2009 John Wiley & Sons, Ltd.     

Raman spectroscopic study of the uranyl selenite mineral marthozite Cu[(UO2)3(SeO3)2O2]·8H2O

The mineral marthozite, a uranyl selenite, has been characterised by Raman spectroscopy at 298 K. The bands at 812 and 797 cm⁻¹ were assigned to the symmetric stretching modes of the (UO₂)²⁺ and (SeO₃)²⁻ units, respectively. These values gave the calculated U O bond lengths in uranyl of 1.799 and/or 1.814 Å. Average U O bond length in uranyl is 1.795 Å, inferred from the X‐ray single crystal structure analysis of marthozite by Cooper and Hawthorne. The broad band at 869 cm⁻¹ was assigned to the ν₃ antisymmetric stretching mode of the (UO₂)²⁺ (calculated U O bond length 1.808 Å). The band at 739 cm⁻¹ was attributed to the ν₃ antisymmetric stretching vibration of the (SeO₃)²⁻ units. The ν₄ and the ν₂ vibrational modes of the (SeO₃)²⁻ units were observed at 424 and 473 cm⁻¹. Bands observed at 257, and 199 and 139 cm⁻¹ were assigned to OUO bending vibrations and lattice vibrations, respectively. O H···O hydrogen bond lengths were inferred using Libowiztky's empirical relation. The infrared spectrum of marthozite was studied for complementation. Copyright © 2008 John Wiley & Sons, Ltd.     

Raman spectroscopic study of the uranyl mineral pseudojohannite Cu6.5[(UO2)4O4(SO4)2]2(OH)5·25H2O

Raman spectra of pseudojohannite were studied and related to the structure of the mineral. Observed bands were assigned to the stretching and bending vibrations of (UO₂)²⁺ and (SO₄)²⁻ units and of water molecules. The published formula of pseudojohannite is Cu_6.5(UO₂)₈[O₈](OH)₅[(SO₄)₄]·25H₂O. Raman bands at 805 and 810 cm⁻¹ are assigned to (UO₂)²⁺ stretching modes. The Raman bands at 1017 and 1100 cm⁻¹ are assigned to the (SO₄)²⁻ symmetric and antisymmetric stretching vibrations. The three Raman bands at 423, 465 and 496 cm⁻¹ are assigned to the (SO₄)²⁻ν₂ bending modes. The bands at 210 and 279 cm⁻¹ are assigned to the doubly degenerate ν₂ bending vibration of the (UO₂)²⁺ units. U O bond lengths in uranyl and O H···O hydrogen bond lengths were calculated from the Raman and infrared spectra. Copyright © 2009 John Wiley & Sons, Ltd.     

Raman microscopy of haidingerite Ca(AsO3OH)·H2O and brassite Mg(AsO3OH)·4H2O

Raman spectroscopy has been used to study the arsenate minerals haidingerite Ca(AsO₃OH)·H₂O and brassite Mg(AsO₃OH)·4H₂O. Intense Raman bands in the haidingerite spectrum observed at 745 and 855 cm⁻¹ are assigned to the (AsO₃OH)²⁻ν₃ antisymmetric stretching and ν₁ symmetric stretching vibrational modes. For brassite, two similarly assigned intense bands are found at 809 and 862 cm⁻¹. The observation of multiple Raman bands in the (AsO₃OH)²⁻ stretching and bending regions suggests that the arsenate tetrahedrons in the crystal structures of both minerals studied are strongly distorted. Broad Raman bands observed at 2842 cm⁻¹ for haidingerite and 3035 cm⁻¹ for brassite indicate strong hydrogen bonding of water molecules in the structure of these minerals. OH···O hydrogen‐bond lengths were calculated from the Raman spectra based on empirical relations. Copyright © 2009 John Wiley & Sons, Ltd.     

Raman spectroscopic study of the mineral finnemanite Pb5(As3+O3)3Cl

The arsenite mineral finnemanite Pb₅(As³⁺ O₃)₃Cl has been studied by Raman spectroscopy. The most intense Raman band at 871 cm⁻¹ is assigned to the ν₁(AsO₃)³⁻ symmetric stretching vibration. Three Raman bands at 898, 908 and 947 cm⁻¹ are assigned to the ν₃(AsO₃)³⁻ antisymmetric stretching vibration. The observation of multiple antisymmetric stretching vibrations suggest that the (AsO₃)³⁻ units are not equivalent in the molecular structure of finnemanite. Two Raman bands at 383 and 399 cm⁻¹are assigned to the ν₂(AsO₃)³⁻ bending modes. Density functional theory enabled calculation of the position of AsO₃²⁻ symmetric stretching mode at 839 cm⁻¹, the antisymmetric stretching mode at 813 cm⁻¹ and the deformation mode at 449 cm⁻¹. Raman bands are observed at 115, 145, 162, 176, 192, 216 and 234 cm⁻¹ as well. The two most intense bands are observed at 176 and 192 cm⁻¹. These bands are assigned to PbCl stretching vibrations and result from transverse/longitudinal splitting. The bands at 145 and 162 cm⁻¹ may be assigned to Cl Pb Cl bending modes. Copyright © 2009 John Wiley & Sons, Ltd.     

Raman spectroscopic study of the antimonate mineral bottinoite Ni[Sb2(OH)12]·6H2O and in comparison with brandholzite Mg[Sb5+2(OH)12]·6H2O

Raman spectroscopy was used to study the mineral bottinoite and a comparison with the Raman spectra of brandholzite was made. An intense sharp Raman band at 618 cm⁻¹ is attributed to the SbO symmetric stretching mode. The low intensity band at 735 cm⁻¹ is ascribed to the SbO antisymmetric stretching vibration. Low intensity Raman bands were found at 501, 516 and 578 cm⁻¹. Four Raman bands observed at 1045, 1080, 1111 and 1163 cm⁻¹ are assigned to δ SbOH deformation modes. A complex pattern resulting from the overlapping band of the water and hydroxyl units is observed. Raman bands are observed at 3223, 3228, 3368, 3291, 3458 and 3510 cm⁻¹. The first two Raman bands are assigned to water stretching vibrations. The two higher wavenumber Raman bands observed at 3466 and 3552 cm⁻¹ and two infrared bands at 3434 and 3565 cm⁻¹ are assigned to the stretching vibrations of the hydroxyl units. Observed Raman and infrared bands are connected with O H···O hydrogen bonds and their lengths 2.72, 2.79, 2.86, 2.88 and 3.0 Å (Raman) and 2.73, 2.83 and 3.07 Å (infrared). Copyright © 2010 John Wiley & Sons, Ltd.     

Dussertite BaFe3+3(AsO4)2(OH)5—a Raman spectroscopic study of a hydroxy‐arsenate mineral

The mineral dussertite, a hydroxy‐arsenate mineral with formula BaFe³⁺₃(AsO₄)₂(OH)₅, has been studied by Raman spectroscopy complemented with infrared spectroscopy. The spectra of three minerals from different origins were investigated and proved to be quite similar, although some minor differences were observed. In the Raman spectra of the Czech dussertite, four bands are observed in the 800–950 cm⁻¹ region. The bands are assigned as follows: the band at 902 cm⁻¹ is assigned to the (AsO₄)³⁻ν₃ antisymmetric stretching mode, the one at 870 cm⁻¹ to the (AsO₄)³⁻ν₁ symmetric stretching mode, and those at 859 and 825 cm⁻¹ to the As‐OM^{2 + /3+} stretching modes and/or hydroxyl bending modes. Raman bands at 372 and 409 cm⁻¹ are attributed to the ν₂ (AsO₄)³⁻ bending mode and the two bands at 429 and 474 cm⁻¹ are assigned to the ν₄ (AsO₄)³⁻ bending mode. An intense band at 3446 cm⁻¹ in the infrared spectrum and a complex set of bands centred upon 3453 cm⁻¹ in the Raman spectrum are attributed to the stretching vibrations of the hydrogen‐bonded (OH)⁻ units and/or water units in the mineral structure. The broad infrared band at 3223 cm⁻¹ is assigned to the vibrations of hydrogen‐bonded water molecules. Raman spectroscopy identified Raman bands attributable to (AsO₄)³⁻ and (AsO₃OH)²⁻ units. Copyright © 2010 John Wiley & Sons, Ltd.     

Raman spectroscopic study of the mineral gerstleyite Na2(Sb,As)8S13·2H2O and comparison with some heavy‐metal sulfides

The mineral gerstleyite is described as a sulfosalt as opposed to a sulfide. This study focuses on the Raman spectrum of gerstleyite Na₂(Sb,As)₈S₁₃·2H₂O and makes a comparison with the Raman spectra of other common sulfides including stibnite, cinnabar and realgar. The intense Raman bands of gerstleyite at 286 and 308 cm⁻¹ are assigned to the SbS₃E antisymmetric and A₁ symmetric stretching modes of the SbS₃ units. The band at 251 cm⁻¹ is assigned to the bending mode of the SbS₃ units. The mineral stibnite also has basic structural units of Sb₂S₃ and SbS₃ pyramids with C_3v symmetry. Raman bands of stibnite Sb₂S₃ at 250, 296, 372 and 448 cm⁻¹ are assigned to Sb S stretching vibrations and the bands at 145 and 188 cm⁻¹ to S Sb S bending modes. The Raman band for cinnabar HgS at 253 cm⁻¹ fits well with the assignment of the band for gerstleyite at 251 cm⁻¹ to the S Sb S bending mode. Raman bands in similar positions are observed for realgar AsS and orpiment As₂S₃. Copyright © 2010 John Wiley & Sons, Ltd.     

Raman spectroscopic study of the magnesium carbonate mineral hydromagnesite (Mg5[(CO3)4(OH)2]· 4H2O)

Magnesium minerals are important for understanding the concept of geosequestration. One method of studying the hydrated hydroxy magnesium carbonate minerals is through vibrational spectroscopy. A combination of Raman and infrared spectroscopy has been used to study the mineral hydromagnesite. An intense band is observed at 1121 cm⁻¹, attributed to the CO₃²⁻ν₁ symmetric stretching mode. A series of infrared bands at 1387, 1413 and 1474 cm⁻¹ are assigned to the CO₃²⁻ν₃ antisymmetric stretching modes. The CO₃²⁻ν₃ antisymmetric stretching vibrations are extremely weak in the Raman spectrum and are observed at 1404, 1451, 1490 and 1520 cm⁻¹. A series of Raman bands at 708, 716, 728 and 758 cm⁻¹ are assigned to the CO₃²⁻ν₂ in‐plane bending mode. The Raman spectrum in the OH stretching region is characterized by bands at 3416, 3516 and 3447 cm⁻¹. In the infrared spectrum, a broad band is found at 2940 cm⁻¹, which is assigned to water stretching vibrations. Infrared bands at 3430, 3446, 3511, 2648 and 3685 cm⁻¹ are attributed to MgOH stretching modes. Copyright © 2011 John Wiley & Sons, Ltd.     

Raman spectroscopy of gallium‐based hydrotalcites of formula Mg6Ga2(CO3)(OH)16· 4H2O

Insight into the unique structure of hydrotalcites has been obtained using Raman spectroscopy. Gallium‐containing hydrotalcites of formula Mg₄Ga₂(CO₃)(OH)₁₂· 4H₂O (2:1 Ga‐HT) to Mg₈Ga₂(CO₃)(OH)₂₀· 4H₂O (4:1 Ga‐HT) have been successfully synthesized and characterized by X‐ray diffraction and Raman spectroscopy. The d(003) spacing varied from 7.83 Å for the 2:1 hydrotalcite to 8.15 Å for the 3:1 gallium‐containing hydrotalcite. Raman spectroscopy complemented with selected infrared data has been used to characterize the synthesized gallium‐containing hydrotalcites of formula Mg₆Ga₂(CO₃)(OH)₁₆· 4H₂O. Raman bands observed at around 1046, 1048 and 1058 cm⁻¹ are attributed to the symmetric stretching modes of the CO₃²⁻ units. Multiple ν₃ CO₃²⁻ antisymmetric stretching modes are found at around 1346, 1378, 1446, 1464 and 1494 cm⁻¹. The splitting of this mode indicates that the carbonate anion is in a perturbed state. Raman bands observed at 710 and 717 cm⁻¹ assigned to the ν₄ (CO₃²⁻) modes support the concept of multiple carbonate species in the interlayer. Copyright © 2009 John Wiley & Sons, Ltd.     

Raman spectroscopic study of the phosphate mineral churchite‐(Y) YPO4·2H2O

Raman spectroscopy has been used to study the rare‐earth mineral churchite‐(Y) of formula (Y,REE)(PO₄) ·2H₂O, where rare‐earth element (REE) is a rare‐earth element. The mineral contains yttrium and, depending on the locality, a range of rare‐earth metals. The Raman spectra of two churchite‐(Y) mineral samples from Jáchymov and Medvědín in the Czech Republic were compared with the Raman spectra of churchite‐(Y) downloaded from the RRUFF data base. The Raman spectra of churchite‐(Y) are characterized by an intense sharp band at 975 cm⁻¹ assigned to the ν₁ (PO₄³⁻) symmetric stretching mode. A lower intensity band observed at around 1065 cm⁻¹ is attributed to the ν₃ (PO₄³⁻) antisymmetric stretching mode. The (PO₄³⁻) bending modes are observed at 497 cm⁻¹ (ν₂) and 563 cm⁻¹ (ν₄). Some small differences in the band positions between the four churchite‐(Y) samples from four different localities were found. These differences may be ascribed to the different compositions of the churchite‐(Y) minerals. Copyright © 2009 John Wiley & Sons, Ltd.     

Raman spectroscopic study of the arsenite minerals leiteite ZnAs2O4, reinerite Zn3(AsO3)2 and cafarsite Ca5(Ti,Fe,Mn)7(AsO3)12·4H2O

The selected arsenite minerals leiteite, reinerite and cafarsite have been studied by Raman spectroscopy. Density functional theory (DFT) calculations enabled the position of the AsO₂²⁻ symmetric stretching mode at 839 cm⁻¹, the antisymmetric stretching mode at 813 cm⁻¹ and the deformation mode at 449 cm⁻¹ to be calculated. The Raman spectrum of leiteite shows bands at 804 and 763 cm⁻¹ assigned to the As₂O₄²⁻ symmetric and antisymmetric stretching modes. The most intense Raman band of leiteite is the band at 457 cm⁻¹ and is assigned to the ν₂ As₂O₄²⁻ bending mode. A comparison of the Raman spectrum of leiteite is made with the arsenite minerals reinerite and cafarsite. Copyright © 2009 John Wiley & Sons, Ltd.     

Raman spectroscopic study of the antimonate mineral brandholzite Mg[Sb2(OH)12]·6H2O

Raman spectra of brandholzite Mg[Sb₂(OH)₁₂]·6H₂O were studied, complemented with infrared spectra, and related to the structure of the mineral. An intense Raman sharp band at 618 cm⁻¹ is attributed to the SbO symmetric stretching mode. The low‐intensity band at 730 cm⁻¹ is ascribed to the SbO antisymmetric stretching vibration. Low‐intensity Raman bands were found at 503, 526 and 578 cm⁻¹. Corresponding infrared bands were observed at 527, 600, 637, 693, 741 and 788 cm⁻¹. Four Raman bands observed at 1043, 1092, 1160 and 1189 cm⁻¹ and eight infrared bands at 963, 1027, 1055, 1075, 1108, 1128, 1156 and 1196 cm⁻¹ are assigned to δ SbOH deformation modes. A complex pattern resulting from the overlapping band of the water and hydroxyl units is observed. Raman bands are observed at 3240, 3383, 3466, 3483 and 3552 cm⁻¹; infrared bands at 3248, 3434 and 3565 cm⁻¹. The Raman bands at 3240 and 3383 cm⁻¹ and the infrared band at 3248 cm⁻¹ are assigned to water‐stretching vibrations. The two higher wavenumber Raman bands observed at 3466 and 3552 cm⁻¹ and two infrared bands at 3434 and 3565 cm⁻¹ are assigned to the stretching vibrations of the hydroxyl units. Observed Raman and infrared bands in the OH stretching region are associated with O‐H···O hydrogen bonds and their lengths 2.72, 2.79, 2.86, 2.88 and 3.0 Å (Raman) and 2.73, 2.83 and 3.07 Å (infrared). Copyright © 2009 John Wiley & Sons, Ltd.     

Raman spectroscopic study of the mixed anion sulphate–arsenate mineral parnauite Cu9[(OH)10|SO4|(AsO4)2]·7H2O

The mixed anion mineral parnauite Cu₉[(OH)₁₀|SO₄|(AsO₄)₂]·7H₂O has been studied by Raman spectroscopy. Characteristic bands associated with arsenate, sulphate and hydroxyl units are identified. Broad bands are observed and are resolved into component bands. Two intense bands at 859 and 830 cm⁻¹ are assigned to the ν₁ (AsO₄)³⁻ symmetric stretching and ν₃ (AsO₄)³⁻ antisymmetric stretching modes. The comparatively sharp band at 976 cm⁻¹ is assigned to the ν₁ (SO₄)²⁻ symmetric stretching mode and a broad‐spectral profile centered upon 1097 cm⁻¹ is attributed to the ν₃ (SO₄)²⁻ antisymmetric stretching mode. A comparison of the Raman spectra is made with other arsenate‐bearing minerals such as carminite, clinotyrolite, kankite, tilasite and pharmacosiderite. Copyright © 2009 John Wiley & Sons, Ltd.