Both Raman and infrared spectroscopy have been used to characterise the three phase-related minerals -dreyerite (tetragonal BiVO 4 ), pucherite (orthorhombic BiVO 4 ) and clinobisvanite (monoclinicBiVO 4 ) -and a comparison of the spectra is made with that of the minerals namibite (Cu(BiO 2 )VO 4 (OH)), schumacherite (Bi 3 O(OH)(VO 4 ) 2 ) and pottsite (PbBiH(VO 4 ) 2 ·2H 2 O). Pucherite, clinobisvanite and namibite are characterised by VO 4 stretching vibrations at 872, 824 and 846 cm −1 . The Raman spectrum of dreyerite shows complexity in the 750 to 950 cm −1 region with two intense bands at 836 and 790 cm −1 assigned to the symmetric and antisymmetric VO 4 modes. The minerals schumacherite and pottsite are characterised by bands at 846 and 874 cm −1 . In both the infrared and Raman, spectra bands are observed in the 1000-1100 cm −1 region which are attributed to the antisymmetric stretching modes. The Raman spectra of the low wavenumber region are complex. Bands are identified in the 328 to 370 cm −1 region and in the 404 to 498 cm −1 region and are assigned to the n 2 and n 4 bending modes. The minerals namibite and schumacherite are characterised by intense bands at 3514 and 3589 cm −1 assigned to the symmetric stretching vibrations of the OH units. Importantly, Raman spectroscopy enables new insights into the chemistry of these bismuth vanadate minerals. Raman spectroscopy enables the identification of the bismuth vanadate minerals in mineral matrices where paragenetic relationships exist between the minerals.

A comparative study of a suite of natural oxalates including weddellite, whewellite, moolooite, humboldtine, glushinskite, natroxalate and oxammite was undertaken using Raman spectroscopy at 298 and 77 K. Oxalates are found as films on host rocks as a result of heavy metal expulsion by primitive plants such as lichens and fungi. The minerals are characterized by the Raman position of the CO stretching vibration, which is cation sensitive. The band is observed at 1468 cm−1 for weddellite, 1464 cm−1 for whewellite, 1489 cm−1 for moolooite, 1489 cm−1 for humboldtine, 1471 cm−1 for glushinskite, 1456 cm−1 for natroxalate and 1473 cm−1 for oxammite. Except for oxammite, the infrared and Raman spectra are mutually exclusive, indicating that the minerals are bidentate and planar. Significant differences are observed in the CC stretching region and in the OCO bending region centred upon 910 and 860 cm−1, respectively. The significance of this work rests with the ability of Raman spectroscopy to identify oxalates which often occur as a film on a host rock. As such, Raman spectroscopy has the potential to identify the existence or pre‐existence of life forms on planets such as Mars. Copyright © 2003 John Wiley & Sons, Ltd.

Raman spectroscopy has been used to study the molecular structure of a series of selected uranyl silicate minerals including uranophane, sklodowskite, cuprosklodowskite, boltwoodite and kasolite. Raman spectra clearly show well resolved bands in the 750 to 800 cm -1 region and in the 950 to 1000 cm -1 region assigned to the ν 1 modes of the (UO 2 ) 2+ units and to the (SiO 4 ) 4-tetrahedra. Sets of Raman bands in the 200 to 300 cm -1 region are assigned to ν 2 δ (UO 2 ) 2+ and UO ligand vibrations. Multiple bands indicate the non-equivalence of the UO bonds and the lifting of the degeneracy of ν 2 δ (UO 2 ) 2+ vibrations. The (SiO 4 ) 4-tetrahedral are characterized by bands in the 470 to 550 cm -1 and in the 390 to 420 cm -1 region. These bands are attributed to the ν 4 and ν 2 (SiO 4 ) 4-bending modes. The minerals show characteristic OH stretching bands in the 2900 to 3500 cm -1 and 3600 to 3700 cm -1 region ascribed to water stretching and SiOH stretching vibrations. The high wavenumber position of the δH 2 O bands indicate strong hydrogen bonding of water in these uranyl silicates. Bands in the 1400 to 1550 cm -1 region are attributed to δSiOH modes. The Raman spectroscopy of uranyl silicate minerals enabled separation of the bands attributed to distinct vibrational units. This enabled definitive assignment of the bands. The spectra are analysed in terms of the molecular structure of the minerals.

Raman and infrared spectra of five uranyl oxyhydroxide hydrates, becquerelite, billietite, curite, schoepite and vandendriesscheite, are reported. The observed bands are attributed to the (UO 2 ) 2+ stretching and bending vibrations, U-OH bending vibrations and H 2 O and (OH) − stretching, bending and libration modes. The U-O bond lengths in uranyls and the O-H· · ·O bond lengths are calculated from the wavenumbers assigned to the stretching vibrations. They are close to the values inferred and/or predicted from the X-ray single-crystal structure. The complex hydrogen-bonding network arrangement was proved in the structures of all the minerals studied. This hydrogen bonding contributes to the stability of these uranyl minerals.

Raman and infrared spectroscopy has been used to study the structure of selected vanadates including pascoite, huemulite, barnesite, hewettite, metahewettite, hummerite. Pascoite, rauvite and huemulite are examples of simple salts involving the decavanadates anion (V10O28)6-. Decavanadate consists of four distinct VO6 units which are reflected in Raman bands at the higher wavenumbers. The Raman spectra of these minerals are characterised by two intense bands at 991 and 965 cm(-1). Four pascoite Raman bands are observed at 991, 965, 958 and 905 cm(-1) and originate from four distinct VO6 sites. The other minerals namely barnesite, hewettite, metahewettite and hummerite have similar layered structures to the decavanadates but are based upon (V5O14)3- units. Barnesite is characterised by a single Raman band at 1010 cm(-1), whilst hummerite has Raman bands at 999 and 962 cm(-1). The absence of four distinct bands indicates the overlap of the vibrational modes from two of the VO6 sites. Metarossite is characterised by a strong band at 953 cm(-1). These bands are assigned to nu1 symmetric stretching modes of (V6O16)2- units and terminal VO3 units. In the infrared spectra of these minerals, bands are observed in the 837-860 cm(-1) and in the 803-833 cm(-1) region. In some of the Raman spectra bands are observed for pascoite, hummerite and metahewettite in similar positions. These bands are assigned to nu3 antisymmetric stretching of (V10O28)6- units or (V5O14)3- units. Because of the complexity of the spectra in the low wavenumber region assignment of bands is difficult. Bands are observed in the 404-458 cm(-1) region and are assigned to the nu2 bending modes of (V10O28)6- units or (V5O14)3- units. Raman bands are observed in the 530-620 cm(-1) region and are assigned to the nu4 bending modes of (V10O28)6- units or (V5O14)3- units. The Raman spectra of the vanadates in the low wavenumber region are complex with multiple overlapping bands which are probably due to VO subunits and MO bonds.