2026

Old cultured pearl necklaces

By Dr. Michael S. Krzemnicki, first published in Facette 30 (March 2026)
Recently, the SSEF received three pearl necklaces for testing. Each necklace had a clasp containing diamonds and what appeared to be a sapphire. The pearls were graduated in size, with a small knot separating each one. These pearl necklaces therefore appeared to be a classic example of natural pearls, which are found in good supply on the market (Figure 1).
Figure 1: Three cultured pearl necklaces submitted to SSEF. Photo: L. Phan, SSEF.

However, radiography and X-ray luminescence quickly revealed that all of the pearls were beaded cultured pearls (saltwater), also known as Akoya cultured pearls in the trade. Based on their setting style, size grading, and rather thick nacre layer, we assume these cultured pearls and pearl necklaces to be from an early production period of Akoya cultured pearls.

We were further surprised when we checked the three clasps. What appeared to be sapphires in each of them were found to be three different stones: an unheated Sri Lankan sapphire in one, a Verneuil synthetic sapphire in the next, and a garnet-topped doublet (blue glass base and pyrope garnet top) in the third necklace (see Figure 2).

Figure 2: Clasp with diamonds and a blue garnet-topped doublet. The microphotos clearly reveal the distinct difference in reflectivity between the blue glass (lower reflectivity) and the thin garnet top (higher reflectivity), as well as the air bubbles trapped between the glassy base and the garnet top of this doublet. Photos and microphotos (50x magnification): M. S. Krzemnicki, SSEF.

In conclusion, what initially appeared to be a very common series of natural pearl necklaces with sapphire clasps ultimately proved to be three cultured pearl necklaces with interesting and unique blue stones in their clasps.