Polarized IR spectra of synthetic smoky quartz

Abstract

Abstract. Polarized IR spectra of planeparallel (0001) plates of synthetic smoky quartz, with E rotating around [0001], show that the absorption figures of OH-related absorption bands at 3380 (room temperature), 3365 and 3305 cm-1 (liquid nitrogen temperature, -196 ~ C) are strongly anisotropic and violate the trigonal symmetry of low quartz. This effect is correlated with a non-uniform substitution of Si by A1 on the three symmetrically equivalent Si sites, as revealed by EPR measurements. Random distribution of A1 over the three Si sites, obtained by dry annealing of the samples in air, yields isotropic absorption figures in the (0001) plates. It is thus experimentally evident that the absorption bands at 3380, 3365 and 3305cm -1 are caused by the OHstretching vibrations coupled with A1 substituting for Si. For each experimentally determined integral absorption coefficient of the three absorption bands a theoretical absorption coefficient was calculated, based on the symmetry of low quartz and the given A1 distribution. This was done for various orientations of the OH-dipoles with respect to the a axes of low quartz. By comparing the experimentally determined and calculated absorption coefficients, the orientation of the corresponding OH-dipoles with respect to the a axes could be determined.

The infrared absorption band at 3596 cm−1 of the recrystallized quartz from Mt. Takamiyama, southwest Japan

“…amethyst, synthetic quartz, or in synthetic quartz which has been reported previously (e.g. Chakraborty and Lehmann, 1976a, b;Rovetta et al, 1989;Kats, 1962;Pankrath, 1991). Here we report that the naturally recrystallized quartz from the granite has a strong absorption band at 3596 cm 1 This granite experienced its first deformation due to the …”

“…Figure 8 shows the plot of the trace elements of Li, Na, A1, K and Fe (atom/106Si) in the quartz previously reported (Kats, 1962;Kronenberg et al, 1986;Rovetta et al, 1989;Pankrath, 1991) vs the absorbance of the 3596 cm -1 band. Although there seems to be no correlation between the trace element content and the absorbance, all the samples have low A1 contents.…”

“…An absorption band at 3596 cm -1 has been observed in amethyst (Chakraborty and Lehmann, 1976a, b;Rovetta et al, 1989), clear Brazilian single crystals (Kronenberg et al, 1986), chalcedony (Frondel, 1982), synthetic quartz crystals (Kats, 1962;Chakraborty and Lehmann, t976a,b) and in synthetic smoky quartz (Pankrath, 1991). In these cases, the 3596 cm -1 bands were either very weak or faint.…”

“…4 upper) and the smoky coloured quartz was bleached to transparent, Throughout these experiments the 3596 cm -1 band does not show any detectable change in shape of spectrum, intensity or peak shift. Pankrath (1991) examined the effect of y-irradiation on the IR absorption bands of the synthetic crystal of smoky quartz at around 3400 cm -1 and showed that the 3596 cm 1 absorption band and other bands at around 3600 cm -1 disappeared after 6~ Niimi et al (1995) examined the same recrystallized quartz as used in the present study and reported that the absorption band at 3476 cm l, associated with Li (Kats, 1962), disappeared at room temperature during X-ray irradiation with a …”

Water redistribution in experimentally deformed natural milky quartz single crystals—Implications for H2O‐weakening processes

“…At room temperature these bands tend to merge toward a single peak, which overlaps with the broad absorption band of molecular water. The distinct sharp bands around 3400 cm −1 are commonly assigned to OH defects in the quartz structure, associated with aluminum (coupled substitution of Al 3+ and H + for Si 4+ [ Kats et al, ; Brunner et al, ; Chakraborty and Lehmann, , ; Pankrath , ]).…”