Vibrational spectroscopic study of the antimonate mineral bindheimite Pb2Sb2O6(O,OH)

Raman spectroscopy complimented with infrared spectroscopy has been used to characterise the antimonate mineral bindheimite Pb₂Sb₂O₆(O,OH). The mineral is characterised by an intense Raman band at 656 cm⁻¹ assigned to SbO stretching vibrations. Other lower intensity bands at 664, 749 and 814 cm⁻¹ are also assigned to stretching vibrations. This observation suggests the non-equivalence of SbO units in the structure. Low intensity Raman bands at 293, 312 and 328 cm⁻¹ are assigned to the OSbO bending vibrations. Infrared bands at 979, 1008, 1037 and 1058 cm⁻¹ may be assigned to δOH deformation modes of SbOH units. Infrared bands at 1603 and 1640 cm⁻¹ are assigned to water bending vibrations, suggesting that water is involved in the bindheimite structure. Broad infrared bands centred upon 3250 cm⁻¹ supports this concept. Thus the true formula of bindheimite is questioned and probably should be written as Pb₂Sb₂O₆(O,OH,H₂O).     

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 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 and mid‐IR spectroscopic study of the magnesium carbonate minerals—brugnatellite and coalingite

Two hydrated hydroxy magnesium carbonate minerals brugnatellite and coalingite with a hydrotalcite‐like structure were studied by Raman spectroscopy. Intense bands are observed at 1094 cm⁻¹ for brugnatellite and at 1093 cm⁻¹ for coalingite attributed to the CO₃²⁻ν₁ symmetric stretching mode. Additional low intensity bands are observed at 1064 cm⁻¹. The existence of two symmetric stretching modes is accounted for in terms of different anion structural arrangements. Very low intensity bands at 1377 and 1451 cm⁻¹ are observed for brugnatellite, and the Raman spectrum of coalingite displays two bands at 1420 and 1465 cm⁻¹ attributed to the (CO₃)²⁻ν₃ antisymmetric stretching modes. Very low intensity bands at 792 cm⁻¹ for brugnatellite and 797 cm⁻¹ for coalingite are assigned to the CO₃²⁻ out‐of‐plane bend (ν₂). X‐ray diffraction studies by other researchers have shown that these minerals are disordered. This is reflected in the difficulty of obtaining Raman spectra of reasonable quality and explains why the Raman spectra of these minerals have not been previously or sufficiently described. A comparison is made with the Raman spectra of other hydrated magnesium carbonate minerals. Copyright © 2008 John Wiley & Sons, Ltd.     

A near-infrared and Raman spectroscopic study of the mineral richelsdorfite Ca2Cu5Sb[Cl|(OH)6|(AsO4)4]·6H2O

Raman spectroscopy has enabled insights into the molecular structure of the richelsdorfite Ca(2)Cu(5)Sb[Cl|(OH)(6)|(AsO(4))(4)]·6H(2)O. This mineral is based upon the incorporation of arsenate or phosphate with chloride anion into the structure and as a consequence the spectra reflect the bands attributable to these anions, namely arsenate or phosphate and chloride. The richelsdorfite Raman spectrum reflects the spectrum of the arsenate anion and consists of ν(1) at 849, ν(2) at 344 cm(-1), ν(3) at 835 and ν(4) at 546 and 498 cm(-1). A band at 268 cm(-1) is attributed to CuO stretching vibration. Low wavenumber bands at 185 and 144 cm(-1) may be assigned to CuCl TO/LO optic vibrations.     

A Raman spectroscopic study of the different vanadate groups in solid‐state compounds—model case: mineral phases vésigniéite [BaCu3(VO4)2(OH)2] and volborthite [Cu3V2O7(OH)2·2H2O]

Raman spectroscopy has been used to study vanadates in the solid state. The molecular structure of the vanadate minerals vésigniéite [BaCu₃(VO₄)₂(OH)₂] and volborthite [Cu₃V₂O₇(OH)₂·2H₂O] have been studied by Raman spectroscopy and infrared spectroscopy. The spectra are related to the structure of the two minerals. The Raman spectrum of vésigniéite is characterized by two intense bands at 821 and 856 cm⁻¹ assigned to ν₁ (VO₄)³⁻ symmetric stretching modes. A series of infrared bands at 755, 787 and 899 cm⁻¹ are assigned to the ν₃ (VO₄)³⁻ antisymmetric stretching vibrational mode. Raman bands at 307 and 332 cm⁻¹ and at 466 and 511 cm⁻¹ are assigned to the ν₂ and ν₄ (VO₄)³⁻ bending modes. The Raman spectrum of volborthite is characterized by the strong band at 888 cm⁻¹, assigned to the ν₁ (VO₃) symmetric stretching vibrations. Raman bands at 858 and 749 cm⁻¹ are assigned to the ν₃ (VO₃) antisymmetric stretching vibrations; those at 814 cm⁻¹ to the ν₃ (VOV) antisymmetric vibrations; that at 508 cm⁻¹ to the ν₁ (VOV) symmetric stretching vibration and those at 442 and 476 cm⁻¹ and 347 and 308 cm⁻¹ to the ν₄ (VO₃) and ν₂ (VO₃) bending vibrations, respectively. The spectra of vésigniéite and volborthite are similar, especially in the region of skeletal vibrations, even though their crystal structures differ. Copyright © 2011 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.     

A Review of the Vibrational Spectroscopic Studies of Arsenite,Antimonite, and Antimonate Minerals

Abstract

This review focuses on the vibrational spectroscopy of the compounds and minerals containing the arsenite, antimonite, and antimonate anions. The review collects and correlates the published data.     

Raman spectroscopic study of the antimonate mineral lewisite (Ca,Fe, Na)2(Sb,Ti)2O6(O,OH)7

The mineral lewisite, (Ca, Fe, Na)₂(Sb, Ti)₂O₆(O, OH)₇, an antimony-bearing mineral, has been studied by Raman spectroscopy. A comparison is made with the Raman spectra of other minerals, including bindheimite, stibiconite, and roméite. The mineral lewisite is characterised by an intense sharp band at 517 cm^?1 with a shoulder at 507 cm^?1 assigned to SbO stretching modes. Raman bands of medium intensity for lewisite are observed at 300, 356, and 400 cm^?1. These bands are attributed to OSbO bending vibrations. Raman bands in the OH stretching region are observed at 3200, 3328, 3471 cm^?1, with a distinct shoulder at 3542 cm^?1. The latter is assigned to the stretching vibration of OH units. The first three bands are attributed to water stretching vibrations. The observation of bands in the 3200–3500 cm^?1 region suggests that water is involved in the lewisite structure. If this is the case then the formula may be better written as (Ca, Fe²⁺, Na)₂(Sb, Ti)₂(O, OH)₇ xH₂O.