Unusual Characteristics of FTIR Spectra of Aragonites from Nacreous Layers of Pearls and Bivalve Shells

The FTIR spectra of aragonites from different origins, which include aragonites from nacreous layers of pearls and bivalve shells, coral skeletons and natural inorganic aragonites, are measured and comparatively analyzed. The results show that the ν₂ vibrational frequency of aragonites from nacreous layer has the mean value of 863.6 cm⁽-1 )which is about 7.9 cm^-1and 9.1 cm^-1, higher than that of aragonite from coral skeleton and natural inorganic aragonite respectively. The unusual characteristics of ν₂ vibrational frequency of aragonites from nacreous layer is probably resulted from the low crystallinity, crystal lattice distortion and nanometer size of aragonites.