Spectral Reflectance and Fluorescence Characteristics of Natural-Color and Heat-Treated "Golden" South Sea Cultured Pearls

PEARLS GEMS & GEMOLOGY SUMMER 2001first marketed in 1993 with full disclosure that they were treated (Vock, 1997).Details of the proprietary process are not known, but it has been reported that the treatment, which is believed to be stable, is applied to undrilled cultured pearls and involves the use of heat without the application of dyes or bleaching (Vock, 1997).Inasmuch as the report did not exclude chemicals other than bleach, it is possible that chemicals also may be involved in the treatment.It is probable that other companies are treating "golden" pearls using a similar process.The challenge for the gem and jewelry industry is to separate natural-color cultured pearls, of any color, from treated ones (Sheung, 1998).Although, as noted above, drilled treated cultured pearls generally can be distinguished from natural-color cultured pearls by microscopy (Hargett, 1989), undrilled cultured pearls-especially in the absence of obvious visual features-are much