Experiments in using atypical ‘beads’ and mantle interference in the production of cultured pearls with Australian Pinctada maxima
Since approximately 2010 a practice has been developed of using low quality natural pearls as the substrates for cultured nacre growth – natural pearls used as ‘beads’ in the production of ‘bead’ cultured pearls. This practice involves the placing of these low-quality natural pearls into the gonads of Pinctada maxima along with a piece of donor mantle tissue, or in some cases into the cultured pearl sacs created by first or subsequent operations, in order to facilitate the growth of cultured nacre on to their surfaces.
Given that gem laboratories by normal practice examine the internal micro structures of pearls by x-rays to determine natural or cultured origins the use of natural pearls as ‘beads’ in the cultured process is clearly designed to deceive the gemmologist, the pearling industry and from there potentially the public.
With numerous examples of these deceptions already on the market in 2011, the authors initially conducted mainly nondestructive and a few destructive examinations of 100 reported atypical bead cultured pearls (aBCPs) that were provided by Umit Koruturk of Australian Pure Pearls, Sharjah. These examinations were by RTX (Real-time microradiography) and μCT (micro-computed x-ray tomography).
Following the results of the examination of the 100 reported aBCPs the authors began ninety one controlled experiments in order to gain a better understanding of the processes used and the results likely to be obtained from the use of unconventional culturing techniques and then comparing these with known natural and cultured pearl growth data. The authors used Australian Pinctada maxima; seventy five of the experiments consisted of the insertion of various types of atypical ‘beads’ (natural abalone, scallop, Pteria sterna and Pinna, and assumed caracol panocha “Astrea (Megastrea) turbanica” aka “wavy turban shell” pearls, partially drilled coral ‘beads’, faceted sapphire ‘beads’ of various colors, freshwater non-bead cultured pearls, various shells and rough coral and an assortment of plastic, glass, quartz and agate ‘beads’), while sixteen consisted of irritating, folding, or inserting tissue into the mantle of Pinctada maxima.
Each of the atypical ‘beads’ used in the experiments were examined, photographed, weighed and had microradiographs recorded prior to the experimentation date. Of the ninety one experiments performed only twenty three resulted in cultured nacre growth over the atypical ‘beads’ and formed ‘bead’ cultured pearls (Table 1), nevertheless the authors were able to record the limitations of the processes and the resulting twenty three cultured pearls provided excellent data for future comparisons with natural pearl structures. No whole pearls resulted from the sixteen irritating, folding, or tissue insertion experiments detailed in Table 2, although in two cases shell blisters appeared.
Details of the experiments along with the results are presented along with RTX and μCT images of some of the successful operations. In most instances the atypical ‘beading’ could be identified with either RTX or μCT imaging although the identification process is not without its challenges.Download pdf