Raman spectroscopy of different types of Mexican copal resins

Dispersive Raman spectra of six copal resins, that were purchased in local markets in Mexico, are presented. The spectra were interpreted and compared with each other. For all these spectra, the relative intensity of the Raman band at approximately 1645 cm(-1), attributed to the exomethylene nu(C=C) stretching vibration, was rather low, especially as fresh samples are involved. In one resin, viz. Incienso, CaCO3 was detected. Probably this inorganic pigment was added as a whitener. In the spectrum of Lágrima a starch fraction was present. Raman spectra of a sample from an Aztec figurine were recorded. It was shown that its composition was inhomogeneous at the micrometer level. Here, too, CaCO3 was observed. It was not possible to identify the resin applied in the antique figurine due to material degradation by age and environmental exposure.