Figure 6 (see reference paper¹) shows the Raman spectra of two samples of nephrite minerals (on this page), one sample of smaragdite and, finally, one of uralite (with a spectrum of quartz, see further discussion). All these samples are varieties of actinolite; in general, discussions regarding the vibrations and assignments of samples of these varieties are the same with discussions regarding actinolite (see Actinolite Raman spectrum and vibrations intepretation page).

The wavenumbers of 2-4 and 2-5 (nephrite samples) are found in column 1 and 2 of the below table. The third and fourth columns of that table contain the wavenumbers reported in the literature (Shurvell et al., 2001; Huang, 2003). The Raman spectra of nephrite samples, like those of actinolite, are dominated by a very strong sharp band at 674 cm^-1; these bands are assigned to the symmetric stretching (ν_s) of Si-O_b-Si bridges. The bands between 745-747 cm^-1 are difficult to assign (see discussion of actinolite). Nevertheless, we consider these bands tentative assignments of Si-O_b-Si bridges (also, this assignment is valid for samples of smaragdite and uralite). The main peak of this region – 928 cm^-1 (around 920-950 cm^-1) and one overlapped – 946 cm^-1 (these values are identical in both spectra) may be ascribed to the ν_s (symmetric stretching) of the O-Si-O linkage. The asymmetric stretching region of the O-Si-O linkage (950-1000 cm^-1) shows (at least for sample 2-4) a peak with a very low intensity. In the case of the 1027 cm^-1 peak and 1059 cm^-1 highest peak (in comparison with the 1027 cm^-1 one; in both spectra of nephrite samples), they may be ascribed to the ν_as (asymmetric stretching) of the Si-O_b-Si bridges.

In the external vibration region, a group of five peaks (for 2-4: 349, 369, 392, 413, 435 cm^-1 and for 2-5: 350, 368, 392, 412, 434 cm^-1) centred on a band at 392 cm^-1 (in both spectra of nephrite samples) are shown in the spectral domain assigned to M-O vibration. Shurvell et al. (2001) state that these Raman bands are characteristic for nephrite, in comparison with the jadeite mineral. The peaks between 210-300 cm^-1 may be ascribed to lattice modes. For 2-4, two bands, namely at 483 cm^-1 (low intensity) and 527 cm^-1, respectively, may be assigned to the deformation mode of the Si₄O₁₁ group. In another sample of nephrite (2-5), only one peak appears, at 525 cm^-1, which is assigned to the same deformation mode of the Si₄O₁₁ group.

The Raman spectrum of smaragdite (2-6) is slightly different from those recorded on samples of actinolite (the same thing may be said about the Raman spectrum of the uralite sample, but this will be discussed separately). The wavenumbers and assignments of smaragdite and uralite samples (quartz included) are found in table (see above links of smaragdite and uralite) of smaragdite and uralite webpage in comparison with (2-2) actinolite, in order to emphasize small differences between them.

In the case of nephrite samples, in Shurvell et al. (2001) there are two bands in the spectrum of nephrite, at 1114 cm^-1 and 1140 cm^-1, respectively, which are assigned to OH^- bending modes. In our samples (2-4 and 2-5), however, these bands do not appear.

• 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]

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

• Shurvell, H. F., Rintoul, L., Fredericks, P. M. (2001) - Infrared and Raman spectra of jade and jade minerals. Internet Journal of Vibrational Spectroscopy, (www.ijvs.com) 5, 5, 4.