Magi Application Note

Determining color origin of cultured freshwater pearls

Feb. 24. 2013 Mikko Åström & Alberto Scarani

Cultured fresh water pearls (CFWP) are frequently dyed with various substances for creating greater diversity and fulfilling the modern taste demand of colored pearls. Many colors look obviously unnatural to the eyes of experienced gemologist. Still enormous portion of production is only moderately dyed. Raman/PL spectrometer can be used for detecting organic polyene compounds which give the color of naturally colored freshwater pearls.
TIP: Pearls may exhibit very strong fluorescence masking all Raman features when initially exposed to green laser. This fluorescence may be reduced by usign built-in Photo-Bleaching feature of GemmoRaman software. Usually a less than one minute photo-bleaching procedure reduces general fluorescence enough for allowing better resolution of Raman peaks.


Danilo Bersani, Pier Paolo Lottici: Applications of Raman spectroscopy to gemology, Analytical and Bioanalytical Chemistry (2010)

Further reading

Karampelas, Fritsch, Sklavounos, Soldatos: Identification of treated-color freshwater cultured pearls

Laura Bergamonti, Danilo Bersani and Pier Paolo Lottici: Raman spectroscopy in corals and pearls