The Raman spectra of aegirine (see above spectrum) are characterized by lower frequencies of the bands, compared with the rest of the clinopyroxenes. In the stretching region of Si-O_nbr, bands were observed at 866 cm^-1, 952 cm^-1, 971 cm^-1, 1041 cm^-1 and 1132 cm^-1 in the 5805 sample; and 866 cm^-1, 953 cm^-1, 1044 cm^-1 and 1130 cm^-1 in the 5820 sample. The stretching modes of Si-O_br are observed at 544 cm^-1, 678 cm^-1, ~757 cm^-1 and a weak shoulder at 558 cm^-1 in the 5805 sample. The bending modes of Si-O are located at ~466 cm^-1 and ~497 cm^-1. Below 400 cm^-1, the bands are assigned to the vibrations of M-O bonds (see below table).

In the spectrum of the 5805 sample (see above spectrum), the higher intensity bands corresponding to the Si-O stretch are present as doublets. In the case of orthopyroxenes, these splits of the bands were attributed to the vibrations of two different tetrahedra. In aegirine, this is probably caused by the substitution of Na⁺ with Ca²⁺ in the M2 sites, and implicitly, Fe³⁺ with Fe²⁺ in M1 sites. These subtitutions lead to the distortion of the tetrahedra chain, creating two types of Si tetrahedra. In the previous literature, no discussion on the Raman spectrum of aegirine was reported. A study on Li-aegirine (LiFeSi₂O₆) was made by Pommier et al. (2005) in order to follow the phase transition under pressure from the C2/c to P21/c structure.

• The Mineralogy Database [link]

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

• ¹BUZATU A., BUZGAR N. (2010) - The Raman study of single-chain silicates. Anal. Şt. Univ. “Al. I. Cuza” Iaşi, Geologie, LVI/1. [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. (www.rruff.info).

• Pommier, C.J.S., Downs, R.T., Stimpfl, M., Redhammer, G.J., Denton, M.B., (2005) - Raman and X-ray investigations of LiFeSi₂O₆ pyroxene under pressure. Journal of Raman Spectroscopy, 36, 864–871.