Cultured pearl with unconventional bead material

by Dr. M.S. Krzemnicki, first published in Facette 28 (May 2023)

Figure 1: Cultured pearl of 24 mm diameter. The X-ray tomography section (right) reveals the unconventional bead material (dark grey) of this cultured pearl. Photo: SSEF

Recently, we received a round pearl for testing which exhibited an excellent surface quality and a remarkable size of 24 mm in diameter. Interestingly, its weight of 60 ct was rather low for such a pearl (resulting in a calculated specific gravity of approx. 1.61 instead of 2.715 considered standard for a pearl). Using radiography and micro X-ray tomography, its identity as a beaded cultured pearl and the reason for this low weight was quickly revealed.

The saltwater cultured pearl contained an unconventional organic bead material, possibly similar to those described in 2013 in an article in the Australian Gemmologist (Cartier & Krzemnicki, 2013: New developments in cultured pearl production: use of organic and baroque shell nuclei.)

The Australian Gemmologist, Vol. 25, No. 1, pp. 6-13), accessible from the online library on the SSEF website. Nearly transparent to X-rays, this bead material showed no internal structure except a fine granular texture and some empty cavities (black) along the bead/nacre interface. The cultured pearl was undrilled, so the identity of the bead material could not be further tested.

In terms of market acceptance, it might be interesting to see if more such cultured pearls arrive on the market in future. For us, it was the only one in the past few months. Another interesting aspect would be to see the long-term stability of such organic bead material, specifically if the pearl would be drilled and strung on a necklace.

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