A comparison between the Raman spectra of glaucophane samples (three recorded spectra at different parameters) and one reference spectrum from the RRUFF project is illustrated in figure 9 (see reference paper¹ / above spectra). The minor discrepancies concern the shifted peaks in our spectra at: 1011 cm^-1, 1014 cm^-1 and 1010 cm^-1, respectively (for 4-1, 4-1 and 4-1), while in the glaucophane reference spectrum the band exhibits at 984 cm^-1. The interpretation of the spectra in the 200-650 cm^-1 region is generally based on the bands dominantly arising from the vibrations of the M-O (cation-oxygen; between 300 and 450 cm^-1) and bending vibrations of the main Si₄O₁₁ structural unit (between 450 and 615 cm^-1).

The dominant peak (385-388 cm^-1) of the lower spectral region is characteristic to glaucophane Raman spectra; if we look carefully, this band has a shoulder peak at 409-410 cm^-1 (in our spectra and in reference R050333). The bands below 300 cm^-1 may be assigned to the lattice mode. The highest-frequency peak, observed in the Raman spectra of glaucophane samples at 670 cm^-1, also present in the reference spectra at 669 cm^-1, is attributed to the symmetric stretching (ν₁) of the Si-O_b-Si bridges.

Also, the spectral lines around ~743 cm^-1 may be ascribed to the symmetric stretching vibration of the Si-O_b-Si bridges. The symmetric stretching (ν_s) of the O-Si-O linkage is represented by the bands between 774 cm^-1 and 895 cm^-1. As is visible in figure 9 (see reference paper¹), one band exhibits in all spectra around ~928 cm^-1, and may be assigned to the asymmetric stretching vibration of the O-Si-O group. The bands at 985 and 984 cm^-1 are shifted with ~30 cm^-1, in comparison with our spectra; the assignment of these bands remains questionable because they are probably the ν_as of the Si-O_b-Si, although the peak value is in the ν_as region of the O-Si-O linkage. The wavenumbers between 1000 and 1110 cm^-1 are assigned to the ν_as (asymmetric stretching) of the Si-O_b-Si bridges. The 1100 region of the 4-1 spectra presents a very low signal-to-noise ratio.

• The Mineralogy Database [link]

• Crystal data (.cif file) from the American Mineralogist Crystal Structure Database [link]

• ¹APOPEI A. I., BUZGAR N. (2010) - The Raman study of amphiboles. Anal. Şt. Univ. “Al. I. Cuza” Iaşi, Geologie, LVI/1 [link]

• Glaucophane spectrum from the RRUFF project [link]

• Downs, R. T. 2006. The RRUFF Project: an integrated study of the chemistry, crystallography, Raman and infrared spectroscopy of minerals. Program and Abstracts of the 19th General Meeting of the International Mineralogical Association in Kobe, Japan. O03-13.

• Huang, E. (2003) - Raman Spectroscopic Study of Amphiboles. PhD thesis in Chinese.