Characterization of “Green Amber” With Infrared and Nuclear Magnetic Resonance Spectroscopy
A peridot-like bright greenish yellow to green gem material called “green amber” has recently appeared in the gem market. It is produced by treating natural resin (amber or copal) with heat and pressure in two stages in an autoclave. Differences in molecular structure between untreated amber and copal as compared to treated “green amber” were studied by FTIR and 13C NMR spectroscopy, using powdered samples. Regardless of the starting material, the FTIR spectrum of “green amber” showed an amber pattern but with a characteristic small absorption feature at 820 cm-1. Solid-state 13C NMR spectroscopy of the treated material indicated a significantly lower volatile component than in the untreated natural resin, evidence that the treatment can actually “artificially age” copal. A new absorption observed near 179 ppm in the NMR spectra of all the treated samples also separated them from their natural-color counterparts.
FTIR and NMR Spectra
Table DD-1: FTIR Spectral Features of Amber and Copal Before and After Heat Treatment
Table DD-2: Chemical Shift (ppm) of 13C NMR Spectral Features of Amber and Copal Before and After Heat Treatment
Parameters Used for NMR Spectroscopy