Polarized micro-Raman spectra of a single large crystal of Keokuk kaolinite were recorded in the OH-stretching region with the laser beam directed along the different crystal axes. The Raman spectra are characterized by five OH-stretching bands at 3694, 3683, 3668, 3650 and 3620 cm−1 labeled A, Z, B, C and D, respectively. The relative intensities of these five bands depend on the orientation of the crystal and the scattering geometry. The spectra agree with the assertion that bands A and Z arise from out-of-plane vibrations, whereas band D corresponds to an in-plane vibration. The area ratios of the various bands were calculated from fitted curves of spectra recorded with the electric vector of the laser beam parallel to different crystallographic planes. The increments in the relative areas of bands B and C were parallel to those of bands A and Z and it appears that out-of-plane vibrations made considerable contributions to these bands also. From the change of area ratios with the change in the direction of the electric vector of the laser beam, bands A and Z were attributed to LO and TO frequencies of one inner-surface hydroxyl vibration. Bands A + Z, B, C and D were attributed to the vibrations of the hydroxyls assigned by Bish (1993) as OH(3), OH(4), OH(2) and OH(1), respectively. These observations were supported by photoacoustic and transmission IR spectra.

The high-pressure behaviour (up to 30 kbar) of dehydrated analcime, Na[AlSi2O6), has been studied in detail using polarized microscopy and Raman micro-spectroscopy. Samples were compressed using a diamond anvil cell in a quasi-hydrostatic medium (glycerol or water-ice). Two transitions at 3.7 and 11 kbar were observed.

At the first transition, phase II is observed under cross polarized light as a contrasting black zone, moving from the edge to the centre of the sample. At this transition the strong Raman doublet at ∼480 and 500 cm−1 transforms discontinuously to a singlet, which is similar to that of quasi-cubic natural analcime. This transition, with an increase of effective symmetry, seems unusual on increasing pressure.

The analcime framework may be thought of as an array of four-, six-, or eight-membered interconnected rings. Phase transitions in the analcime group are considered in the literature in terms of deformations of the six-membered rings. However, the present work shows that these phase transitions should be associated with deformations of the four-membered rings (as the minimum size secondary building units) by rotation of rigid TO4 units. The strongest Raman band frequency is correlated with the mean T-O-T angle inside the four-membered ring: a rate of 4.5 cm−1/degree was found for analcimes and leucites. Using this correlation, one can estimate from Raman data the possible deformation of four-membered rings at the phase transitions.

Arhbarite was described in 1982 as a new copper arsenate, Cu2(OH)AsO4·6H2O, from the Arhbar mine, Morocco. Due to the very small grain size no crystallographic data other than the X-ray powder diffraction data could be given. Reinvestigation of the type material and of new finds from the El Guanaco mine, Chile, is based on Rietveld refinement of X-ray powder data, electron microprobe investigations, optical studies as well as infrared and Raman spectra. The main results are: (1) arhbarite has the ideal formula Cu2Mg(AsO4)(OH)3 with magnesium oxide as an additional constituent and (2) arhbarite is isotypic with gilmarite, Cu3(AsO4)(OH)3. Arhbarite is triclinic, space group P1 (no. 1), unit-cell parameters (type material; refined from powder data) a= 5.315(4), b= 5.978(6), c= 5.030(6)Å, α = 113.58(6), β = 97.14(7), γ = 89.30(8)°, V= 145.2(1)Å3, Z= 1. Microprobe analyses of the type material gave MgO 10.20, CuO 47.46, NiO 0.20, CoO 0.24, As2O5 33.85, SiO2 0.10, H2O 7.58 (calc.), total 99.63 wt.%. The empirical formula is Cu1.98(Mg0.88Cu0.09Ni0.01Co0.01)S0.99(AsO4)1.02(OH)2.92, based on 7 O atoms. The Chilean arhbarite shows a slightly higher Cu content than the type material; it has the formula Cu1.99(Mg0.73Cu0.25Zn0.01)∑0.99[(AsO4)1.01(SiO4)0.01]∑1.02(OH)2.92. The formal redefinition of arhbarite has been approved by the CNMMN of the IMA.

Hydroxycalciomicrolite, Ca1.5Ta2O6(OH) is a new microlite-group mineral found in the Volta Grande pegmatite, Nazareno, Minas Gerais, Brazil. It occurs as isolated octahedral and as a combination of octahedral and rhombic dodecahedral crystals, up to1.5 mm in size. The crystals are yellow and translucent, with a white streak and vitreous to resinous lustre. The mineral is brittle, with a Mohs hardness of 5–6. Cleavage is not observed and fracture is conchoidal. The calculated density is 6.176 g cm–3. Hydroxycalciomicroliteis isotropic, ncalc. = 2.010. The infrared and Raman spectra exhibit bands due to O–H stretching vibrations. The chemical composition determined from electron microprobe analysis (n = 13) is (wt.%): Na2O 0.36(8), CaO 15.64(13), SnO2 0.26(3),Nb2O5 2.82(30), Ta2O5 78.39(22), MnO 0.12(2), F 0.72(12) and H2O 1.30 (from the crystal structure data), O = F –0.30, total 99.31(32), yielding an empirical formula, (Ca1.48Na0.06Mn0.01)∑1.55(Ta1.88Nb0.11Sn0.01)∑2.00O6.00[(OH)0.76F0.20O0.04].Hydroxycalciomicrolite is cubic, with unit-cell parameters a = 10.4205(1) Å, V = 1131.53(2) Å3 and Z = 8. It represents a pyrochlore supergroup, microlite-group mineral exhibiting P4332 symmetry, instead of Fd3m. Thereduction in symmetry is due to long-range ordering of Ca and vacancies on the A sites. This is the first example of such ordering in a natural pyrochlore, although it is known from synthetic compounds. This result is promising because it suggests that other species with P4332or lower-symmetry space group can be discovered and characterized.

Raman scattering experiments of natural FeS2 pyrite were performed at simultaneous high-pressure and high-temperature conditions up to 675 K and 2100 MPa using a hydrothermal diamond anvil cell combined with micro-Raman spectroscopy. Four out of five Raman active modes [Eg, Ag, Tg(1) and Tg(3)] were resolved at ambient conditions, the remaining Tg(2) [∼377 cm–1] mode was weak and unresolved occurring ∼2 cm–1 from the intense Ag [379 cm–1] mode. The frequency shifts of the Eg [343 cm–1] and Ag [379 cm–1] modes were determined to be quadratic functions of pressure and temperature: ν343 = 343.35 – 0.0178 × ΔT – 8.4E – 6 × (ΔT)2 + 0.00367 × Δp 3.7E–7 × (Δp)2 + 1.0E–6 × ΔT × Δp and ν379 = 379.35 – 0.0295 × ΔT – 9.0E–6 × (ΔT)2 + 0.00460 × Δp – 5.3E–7 × (Δp)2 + 7.0E–7 × ΔT × Δp. The positive pressure dependence of both modes indicates stress-induced contraction of S–S and Fe–S bonds, whereas the negative temperature dependence shows temperature-induced expansion of them. The Raman spectra of pyrite were used to derive its bulk modulus at high temperatures, thermal expansion coefficient at high pressures and anharmonic parameters at high-pressure and high-temperature conditions.

Diamond-like carbon films were synthesized by electro-deposition technique from an organic liquid (a solution of alpha- and beta-pinenes in n-hexane) on silicon substrate at room temperature and at room pressure. The x-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectra, Raman spectra, photoluminescence (PL), and x-ray absorption near edge structure (XANES) spectra analysis were used to study the properties of the diamond-like carbon (as-deposited and annealed) films. The XRD measurement indicated that the film contains some diamond-crystalline phases whereas Raman spectra did not show any prominent diamond-like peak. PL intensity as higher for the as-deposited film and decreased with high-temperature vacuum annealing. FTIR spectra showed the presence of sp3 hybridization C–H bonds and their intensity decreases at higher annealing temperature. C and O K-edge XANES spectra showed that π* (sp2) intensity significantly decreases when the annealing temperature is 600 °C.