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Near-field fluorescent spectroscopy was used to characterize the grain boundary of Cr-doped polycrystalline alumina. The results show that the peak widths in near-field spectra are narrower than in spectra obtained by conventional microspectrometry, and this is attributed to the difference in spatial resolution of the two methods. The R-line peaks of [Cr.sup.3+] fluorescence were observed to shift to a lower wavelength at the grain boundary compared to the bulk crystal, which is attributed to stress relief at the crystal boundary. This peak shift at the boundary decreases as a function of the time a polycrystal is annealed at 1700[degrees]C.

Significant amounts of boron in both trigonal and tetrahedral coordination have been found through [sup.11]B magic-angle-spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy of natural olenite (aluminum-rich tourmaline) from Stoffhutte, Koralpe, Styria, Austria. The [sup.11]B MAS NMR spectrum consists of a superposition of two quadrupolar MAS peaks. A broad peak with [[delta].sub.iso] = 18.3 ppm, [v.sub.Q] = 1410 KHz, and [eta] = 0.11 demonstrates the trigonal-planar environment of the B[O.sub.3] group (relative area ratio = 80%). The narrow symmetrical peak ([[delta].sub.iso] = 0.0 ppm, [v.sub.Q] = 300 KHz, [eta] = 0.00) represents tetrahedral B[O.sub.4] groups (relative area ratio = 20%). An infrared spectrum shows hydroxyl stretching bands at low wavenumbers indicating that underbonded O atoms of the hexagonal ring (due to a partial replacement of [sup.[4]][Si.sup.4+] by [sup.[4]][B.sup.3+]) form relatively strong hydrogen bonds with the protons of the hydroxyl groups. A [sup.29]Si MAS NMR spectrum shows a peak consisting of a main signal at -90 ppm and a shoulder at about -85 ppm. The main signal originates from Si atoms connected (via oxygen bridges) to two other Si atoms in the hexagonal ring, and the minor signal is from Si atoms connected to one Si and one B atom. No signal corresponding to [sup.[6]]Si was detected in this natural olenite sample.

Raman spectra of [Fe.sub.2][O.sub.3] were measured to 62 GPa in a diamond anvil cell. All group theoretically predicted Raman-active phonon modes were detected to 54 GPa. In addition, some high-pressure spectra show an IR-active [E.sub.u], mode (-660 [cm.sup.-1]), possibly induced by surface defects or stress. This mode is related by a factor of two to a mode at 1320 [cm.sup.-1]. The assignment of the 1320 [cm.sub.-1] mode has been controversial (two-magnon scattering or two-phonon scattering), and our observation supports the phonon assignment. All Raman-active phonons show nonlinear pressure-induced shifts. The mode Gruneisen parameters and their logarithmic volume dependences for two low-frequency phonons, [A.sub.1g] and [E.sub.g], become negative and infinite, respectively, near 50 GPa as a result of the instability of the corundum structure at this pressure. Using the observed Raman-active phonons together with acoustic phonons previously measured by ultrasonics, and Kieffer's model, we calculate the phonon contribution to the thermodynamic parameters of hematite. Comparison with experimentally measured values allows an estimation of an upper bound to the magnon contribution to the heat capacity at ambient pressure. This increases continuously above the Morin temperature and reaches a maximum at the Neel temperature (~37%). The Raman spectra change dramatically at pressures greater than 54 GPa as indicated by the appearance of new peaks and a significant increase in background. Although direct structural analysis is not possible due to the low signal-to-background ratio and the lack of polarization information, we were able to examine the consistency of our Raman observation with the corundum-to-perovskite phase transformation using the results for an analog system: MgSi[O.sub.3] ilmenite (ordered corundum type) and perovskite. This analysis shows that observed new features in [Fe.sub.2][O.sub.3] Raman spectra may not be consistent with the GdFe[O.sub.3] perovskite structure.

Samples of wadsleyite ([beta]-[Mg.sub.2]Si[O.sub.4]) containing a range of dissolved water concentrations up to 1.5 wt% were synthesized at 1300 [degrees] C and 15 GPa. The samples were studied using [sup.1]H MAS NMR and FTIR spectroscopy to determine the ordering of OH within the structure. As the [sup.1]H NMR chemical shift and O-H stretching frequency are both known to be correlated with the O-H ... O distances in silicate and other materials, the spectroscopic data were compared with O ... O distances calculated from the published crystal structure of hydrous wadsleyite. Using this approach we show that the hydroxyl ions in wadsleyite containing 0.8-1.5 wt% [H.sub.2]O are highly disordered, occupying at least 14 of the 17 possible O-H ... O environments, including some with strong hydrogen bonding. In contrast, for low water concentrations ( It is probable that the degree of disorder will increase with increasing temperature, so it should be taken into account when predicting phase equilibria involving hydrous wadsleyite and when extrapolating data on density and elastic properties from room temperature measurements.

The (010) surfaces of forsterite ([FO.sub.100]) and natural forsteritic olivine ([FO.sub.90]) single crystals have been studied by Rutherford backscattering spectrometry (RBS). Spectra were collected either in channeling geometry with the incident beam parallel to the [010] zone axis, or in a random orientation. In both materials, two surface preparations were examined: (1) mechanical polishing and (2) chemical etching by hydrofluoric acid after mechanical polishing. Composition profiles extending to several hundreds of nanometers below the surface were probed by RBS in random mode. Simulations of all the spectra indicated constant major element compositions, equal to the bulk compositions of the crystals. Characteristics of the few top atomic layers were probed by RBS in channeling mode. The crystalline quality of the surface of chemically etched samples has been evaluated quantitatively and is shown to be much better than that of mechanically polished samples. Given the energy resolution, we estimate that the bulk crystalline quality is perturbed for more than 40 nm below the surface in the case of mechanical polishing whereas disorder is limited to a topmost layer thinner than 1 nm in the case of chemical etching. On average, for the chemically etched samples, less than one atom per [010] atomic row is displaced from its mean crystallographic position. The bulk stoichiometry is preserved in the topmost layer of pure forsterite whereas a slightly higher Fe/Mg ratio is detected at the surface of chemically etched [FO.sub.90]. A method for the quantitative assessment of surface quality of olivine is thus proposed, constituting a useful preliminary step before any study of surface modifications of olivine subjected to various geological conditions.

Raman spectra of syngenetic majoritic garnets were obtained from the Brazilian Sao-Luiz diamond suite. These garnets have a low majoritic content ( 3) have a characteristic signature in the frequency region of the Si[O.sub.4]-Si[O.sub.6] stretching vibrations. This vibration gives a broad peak between 800 and 900 [cm.sup.-1] just before an intense band (900-930 [cm.sup.-1]) classically assigned to Si-O stretching vibrations of the SiO4 tetrahedra in all known garnets. This broad band is also present in non-majoritic garnets (Si = 3) that result from the transformation, within the diamonds, of majoritic garnets into low-pressure garnet + pyroxene intergrowths. We show that the presence of significant Ti[O.sub.2] content in these normal garnets leads to Raman spectra mimicking those of majoritic garnets. The occurrence of a broad shoulder between 800 and 900 [cm.sup.-1] as well as broad bands near 960 and 1030 [cm.sup.-1] in the Raman spectra are no longer diagnostic features indicative of a majoritic garnet when the Ti[O.sub.2] content of the garnets is high (>1 wt%) as is the case for the Sao Luiz diamonds. The full width at half maximum (FWHM) of the strong Raman mode near 910 [cm.sup.-1] is the only reliable signature that discriminates Si = 3 from Si > 3 garnets. The frequency of the diamond Raman mode used as an in-situ piezometer shows that the actual pressure of the garnet inclusions is between 0.5 and 0.8 GPa.

Energy-dispersive X-ray powder diffraction spectra have been collected for aragonite (CaC[O.sub.3]) and dolomite [CaMg[(C[O.sub.3]).sub.2]] at high pressure and high temperature, using synchrotron radiation and a cubic multi-anvil apparatus. Unit-cell volumes were measured up to 7 GPa and 1073 K along several isothermal paths. This study has confirmed previously determined but still debated values of the bulk incompressibilities at 298 K [65.4(5) GPa for aragonite and 90.7(7) GPa for dolomite] and thermal expansivities at 1 bar [[.sub.298-1000 K] = 6.7(5) [10.sup.-5] [K.sup.-1] for aragonite and [.sub.298-1000 K] = 4.1(5) [10.sup.-5] [K.sup.-1] for dolomite]. In addition, new equation-of-state parameters were measured: [([Delta]K/[Delta]T).sub.P] [-0.013(2) and -0.025(4) GPa/K for aragonite and dolomite, respectively] and [K[prime].sub.0] [2.7(7) and 2.3(5) for aragonite and dolomite, respectively!. We suggest that these equation-of-state parameters could be used in the calculation of high-temperature, high-pressure thermodynamic properties of these carbonates. At pressures exceeding 5 GPa, we observed that dolomite breaks down to aragonite and magnesite. We used the equation-of-state parameters measured in this study to calculate the position of the equilibrium curve: dolomite [approaches] aragonite + magnesite. This reaction could be important in the ultra-high-pressure metamorphism of carbonates. This decomposition reaction also provides a useful test of thermodynamic data sets of carbonates at high pressures and temperatures.

Spectroscopic (micro FTIR, Raman, MAS NMR) and mass spectroscopic techniques have been used to examine, on both single-crystal and powder samples, the behavior of [H.sub.2]O and C[O.sub.2] molecules in the structural channels of an alkali-poor, volatile-rich beryl from Brazil. Polarized single-crystal FTIR and Raman spectra were obtained on oriented wafers of isolated crystals. Location and orientation of [H.sub.2]O and C[O.sub.2] molecules were determined from IR spectra. The proton-proton vectors of type-I and type-II [H.sub.2]O are parallel and perpendicular to the c axis, respectively; the molecular axis of the C[O.sub.2] molecule is perpendicular to the c axis. Relative proportions of both types of [H.sub.2]O were determined from their respective IR absorption-band intensities and were found to be nearly equivalent. There is, contrary to what is generally claimed in the literature, no relation between alkali and type-II [H.sub.2]O contents. Absorptivity coefficients for [H.sub.2]O and C[O.sub.2] were computed for every specific orientation. A 1H MAS NMR spectrum resolved as a 'Pake' doublet seems to confirm the absence of any anisotropic movement of the [H.sub.2]O molecules from one orientation to the other on the NMR time scale. Mass discrimination of volatiles released by pyrolysis under vacuum confirms the weak mobility of [H.sub.2]O and C[O.sub.2] molecules in the channel sites, although the plugging effect of alkalis in the channels can be neglected for such an alkali-poor beryl. The volatile vs. alkali content ratio in beryl could possibly be used as an environmental indicator.

The oscillatory zoning patterns (OZP) in crystals with respect to self-affine fractals are described by a quantitative method yielded by spectroscopic studies. The fractal dimension, a quantitative calculation of the nonrandom behavior of the pattern, characterizes the OZP, and are the quantitative characteristics along with compositional variations. These quantitative characteristics are reproduced by the oscillatory crystallization. The fractal dimensions of the OZP crystals are similar to the spectral patterns of the crystals.

A X-ray photoelectron Fe [2p.sub.3/2] spectrum of a pristine pyrite fracture surface was collected using synchrotron radiation with the source tuned to 800 eV. Comparison of this highly surface sensitive Fe 2p spectrum with Fe 2p spectra collected by conventional means (1487 eV A1K[Alpha] source) reveals that the high binding energy tail of the pyrite Fe [2p.sub.3/2] line results primarily from Fe surface state contributions. The three major contributions to the spectrum are interpreted to be: (1) [Fe.sup.2+] resident on bulk sites; (2) [Fe.sup.2+] resident on surfaces, edges and corners; (3) [Fe.sup.3+] surface states produced during fracture by an auto-redox reaction involving Fe and S. The intense main peak is ascribed to the bulk state, whereas the high binding energy tail of the spectrum is composed primarily of [Fe.sup.2+] and [Fe.sup.3+] surface state contributions. [Fe.sup.2+] on bulk sites is octahedrally coordinated ([O.sub.h] symmetry). All valence electrons of Fe on bulk sites are paired (diamagnetic) and a singlet photopeak at 707 eV is consequently produced. Fracture produces [Fe.sup.2+] surface states with lower coordination than bulk sites. [Fe.sup.2+] located at surfaces, edges and corners experiences modified Ligand Field Stabilization Energies (LFSE) which results in stabilization of the [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] orbital and destabilization of the [d.sub.xy] orbital. Promotion of a [d.sub.xy] electron to the [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] orbital makes surface [Fe.sup.2+] surface states paramagnetic resulting in multiplet splitting of their associated photopeaks. The [Fe.sup.3+] surface state is necessarily paramagnetic and its photoemissions are consequently multiply split. Analysis of photopeak structures and binding energy splittings of [Fe.sup.2+] and [Fe.sup.3+] surface states demonstrates that they are located at the appropriate binding energies, and span the appropriate energy range, to satisfactorily explain the high binding energy tail on of the Fe [2p.sub.3/2] spectrum.