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 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 uranyl mineral natrouranospinite (Na2,Ca)[(UO2)(AsO4)]2· 5H2O

Raman spectra of natrouranospinite complemented with infrared spectra were studied and related to the structure of the mineral. Observed bands were assigned to the stretching and bending vibrations of (UO₂)²⁺ and (AsO₄)³⁻ units and of water molecules. 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 spectroscopy of hydrogen‐arsenate group (AsO3OH) in solid‐state compounds: cobalt mineral phase burgessite Co2(H2O)4[AsO3OH]2·H2O

Raman spectrum of burgessite, Co₂(H₂O)₄[AsO₃OH]₂· H₂O, was studied, interpreted and compared with its infrared spectrum. The stretching and bending vibrations of (AsO₃) and As‐OH units, as well as the stretching, bending and libration modes of water molecules and hydroxyl ions were assigned. The range of O H···O hydrogen bond lengths was inferred from the Raman and infrared spectra of burgessite. The presence of (AsO₃OH)²⁻ units in the crystal structure of burgessite was proved, which is in agreement with its recently solved crystal structure. Raman and infrared spectra of erythrite inferred from the RRUFF database are used for comparison. Copyright © 2010 John Wiley & Sons, Ltd.     

Raman spectroscopic study of the hydroxy‐arsenate‐sulfate mineral chalcophyllite Cu18Al2(AsO4)4(SO4)3(OH)24·36H2O

The mixed anion mineral chalcophyllite Cu₁₈Al₂(AsO₄)₄(SO₄)₃(OH)₂₄·36H₂O has been studied by using Raman and infrared spectroscopies. Characteristic bands associated with arsenate, sulfate and hydroxyl units are identified. Broad bands in the OH stretching region are observed and are resolved into component bands. Estimates of hydrogen bond distances were made using a Libowitzky function. Both short and long hydrogen bonds were identified. Two intense bands at 841 and ∼814 cm⁻¹ are assigned to the ν₁ (AsO₄)³⁻ symmetric stretching and ν₃ (AsO₄)³⁻ antisymmetric stretching modes. The comparatively sharp band at 980 cm⁻¹ is assigned to the ν₁ (SO₄)²⁻ symmetric stretching mode, and a broad spectral profile centred upon 1100 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 © 2010 John Wiley & Sons, Ltd.     

Raman spectroscopic study of the multi‐anion uranyl mineral schroeckingerite

Raman spectroscopy complemented with infrared (IR) spectroscopy has been used to study the mineral schroeckingerite. The mineral is a multi‐anion mineral and has (UO₂)²⁺, (SO₄)²⁻ and (CO₃)²⁻ units in its structure, and bands attributed to these vibrating units are readily identified in the Raman spectra. Symmetric stretching modes at 815, 983 and 1092 cm⁻¹ are assigned to (UO₂)²⁺, (SO₄)²⁻ and (CO₃)²⁻ units, respectively. The antisymmetric stretching modes of (UO₂)²⁺, (SO₄)²⁻ are not observed in the Raman spectra but may be readily observed in the IR spectrum at 898 and 1180 cm⁻¹. The antisymmetric stretching mode of (CO₃)²⁻ is observed in the Raman spectrum at 1374 cm⁻¹, as is also the ν₄ (CO₃)²⁻ bending modes at 742 and 707 cm⁻¹. No ν₂ (CO₃)²⁻ bending modes are observed in the Raman spectrum of schroeckingerite. All the spectroscopic evidence points to a highly ordered structure of this mineral. Copyright © 2007 John Wiley & Sons, Ltd.     

Raman spectroscopic study of the uranyl mineral metauranospinite Ca[(UO2)(AsO4)]2·8H2O

Raman spectra of metauranospinite Ca[(UO₂)(AsO₄)]₂·8H₂O complemented with infrared spectra were studied. Observed bands were assigned to the stretching and bending vibrations of (UO₂)²⁺ and (AsO₄)³⁻ units and of water molecules. 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 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.     

A Raman spectroscopic study of bukovskýite Fe2(AsO4)(SO4)(OH)· 7H2O,a mineral phase with a significant role in arsenic migration

The Raman spectrum of bukovskýite [Fe³⁺₂(OH)(SO₄)(AsO₄)· 7H₂O] has been studied and compared with that of an amorphous gel containing specifically Fe, As and S, which is understood to be an intermediate product in the formation of bukovskýite. The observed bands are assigned to the stretching and bending vibrations of (SO₄)²⁻ and (AsO₄)³⁻ units, stretching and bending vibrations and vibrational modes of hydrogen‐bonded water molecules, stretching and bending vibrations of hydrogen‐bonded (OH)⁻ ions and Fe³⁺ (O,OH) units. The approximate range of O H···O hydrogen bond lengths was inferred from the Raman spectra. Raman spectra of crystalline bukovskýite and of the amorphous gel differ in that the bukovskýite spectrum is more complex, the observed bands are sharp and the degenerate bands of (SO₄)²⁻ and (AsO₄)³⁻ are split and more intense. Lower wavenumbers of δ H₂O bending vibrations in the spectrum of the amorphous gel may indicate the presence of weaker hydrogen bonds compared to those in bukovskýite. Copyright © 2011 John Wiley & Sons, Ltd.     

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 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.     

A Raman spectroscopic study of copiapites Fe2+Fe3+(SO4)6(OH)2 · 20H2O: environmental implications

Raman spectroscopy has been used to study selected mineral samples of the copiapite group. Copiapite (Fe²⁺Fe³⁺(SO₄)₆(OH)₂ · 20H₂O) is a secondary mineral formed through the oxidation of pyrite. Minerals of the copiapite group have the general formula AFe₄(SO₄)₆(OH)₂ · 20H₂O, where A has a + 2 charge and can be either magnesium, iron, copper, calcium and/or zinc. The formula can also be B_2/3Fe₄(SO₄)₆(OH)₂ · 20H₂O, where B has a + 3 charge and may be either aluminium or iron. For each mineral, two Raman bands are observed at around 992 and 1029 cm⁻¹, assigned to the (SO₄)²⁻ν₁ symmetric stretching mode. The observation of two bands provides evidence for the existence of two non‐equivalent sulfate anions in the mineral structure. Three Raman bands at 1112, 1142 and 1161 cm⁻¹ are observed in the Raman spectrum of copiapites, indicating a reduction of symmetry of the sulfate anion in the copiapite structure. This reduction in symmetry is supported by multiple bands in the ν₂ and ν₄(SO₄)²⁻ spectral regions. Copyright © 2010 John Wiley & Sons, Ltd.     

Raman spectroscopy of hydrogen arsenate group (AsO3OH)2− in solid‐state compounds: cobalt‐containing zinc arsenate mineral,koritnigite (Zn,Co)(AsO3OH)·H2O

Raman spectra of two well‐defined types of koritnigite crystals from the Jáchymov ore district, Czech Republic, were recorded and interpreted. No substantial differences were observed between both crystal types. The observed Raman bands were attributed to the (AsO₃OH)²⁻ stretching and bending vibrations as well as stretching and bending vibrations of water molecules and hydroxyl ions. The non‐interpreted Raman spectra of koritnigite from the RRUFF database and the published infrared spectra of cobaltkoritnigite were used for comparison. The O H···O hydrogen bond lengths in the crystal structure of koritnigite were inferred from the Raman spectra and compared with those derived from the X‐ray single‐crystal refinement. The presence of (AsO₃OH)²⁻ units in the crystal structure of koritnigite was proved from the Raman spectra, which supports the conclusions of the X‐ray structure analysis. Copyright © 2010 John Wiley & Sons, Ltd.     

Raman spectroscopic study of the antimonate mineral bahianite Al5Sb35+O14(OH)2

Raman spectroscopy has been used to characterize the antimonate mineral bahianite Al₅Sb₃⁵⁺O₁₄(OH)₂, a semi‐precious gemstone. The mineral is characterized by an intense Raman band at 818 cm⁻¹ assigned to Sb₃O₁₄¹³⁻ stretching vibrations. Other lower intensity bands at 843 and 856 cm⁻¹ are also assigned to this vibration, and this concept suggests the non‐equivalence of SbO units in the structure. Low‐intensity Raman bands at 669 and 682 cm⁻¹ are probably assignable to the OSbO antisymmetric stretching vibrations. Raman bands at 1756, 1808 and 1929 cm⁻¹ may be assigned to δ SbOH deformation modes, while the bands at 3462 and 3495 cm⁻¹ are assigned to AlOH stretching vibrations. The complexity in the low wave number region is attributed to the composition of the mineral. 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 microscopy of the mixite mineral BiCu6(AsO4)3(OH)6·3H2O from the Czech Republic

Raman microscopy of the mixite mineral BiCu₆(AsO₄)₃(OH)₆·3H₂O from Jáchymov and from Smrkovec (both Czech Republic) has been used to study their molecular structure. The presence of (AsO₄)³⁻, (AsO₃OH)²⁻, (PO₄)³⁻ and (PO₃OH)²⁻ units, as well as molecular water and hydroxyl ions, was inferred. O H···O hydrogen bond lengths were calculated from the Raman and infrared spectra using Libowitzky's empirical relation. Small differences in the Raman spectra between both samples were observed and attributed to compositional and hydrogen‐bonding network differences. 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 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.     

Synthesis and Raman spectroscopic characterisation of the oxalate mineral wheatleyite Na2Cu2+(C2O4)2·2H2O

The mineral wheatleyite has been synthesised and characterised by Raman spectroscopy complimented with infrared spectroscopy. Two Raman bands at 1434 and 1470 cm⁻¹ are assigned to the ν_{(C O)} stretching mode and implies two independent oxalate anions. Two intense Raman bands observed at 904 and 860 cm⁻¹ are assigned to the ν(C C) stretching mode and support the concept of two non‐equivalent oxalate units in the wheatleyite structure. Two strong bands observed at 565 and 585 cm⁻¹ are assigned to the symmetric CCO in plane bending modes. The Raman band at 387 cm⁻¹ is attributed to the CuO stretching vibration and the bands at 127 and 173 cm⁻¹ to OCuO bending vibrations. A comparison is made with Raman spectra of selected natural oxalate bearing minerals. Oxalates are markers or indicators of environmental events. Oxalates are readily determined by Raman spectroscopy. Thus, deterioration of works of art, biogeochemical cycles, plant metal complexation, the presence of pigments and minerals formed in caves can be analysed. Copyright © 2008 John Wiley & Sons, Ltd.