X-Ray Computed Microtomography: Distinguishing Natural Pearls from Beaded and Non-Beaded Cultured Pearls

X-Ray Computed Microtomography Applied to Pearls: Methodology, Advantages, and Limitations

“…More structures in natural and cultured pearls observed with µ-CT are well illustrated by Krzemnicki et al (2010), in the G&G Data Depository, and at www.gubelingemlab.ch. …”

“…The best structural visualization of the samples is revealed by the 3D µ-CT images. In addition to producing superior image quality, microtomography allows the user to scroll through a pearl virtually by combining the single CT sections into a "movie," enabling the dynamic recognition of internal structures that are difficult to interpret when observing single CT sections or radiographs (see G&G Data Depository for this article and for Krzemnicki et al, 2010). All the beaded cultured pearls as well as all but two of the non-beaded cultured pearls and natural pearls in this study could be identified by radiography.…”

Age Determination of Pearls: A New Approach for Pearl Testing and Identification

“…However, accidentally, this bead may be rejected or fall out of the mollusk tissue ("pearl-sac"), thus forming a cultured pearl with no bead inside. Such beadless cultured pearls may eventually show internal structures in radiographies (and X-ray µ-tomography) that are very similar to the ones of natural pearls (Hänni 2006;Krzemnicki 2010;Krzemnicki et al 2010). In recent years, such cultured pearls were even produced on purpose, partly by introducing natural pearls as beads, to mimic the appearance and structures of natural pearls, with the evident reason to deceive the buyer.…”

“…As there is commonly a large price gap between natural pearls and cultured pearls, the trade relies on specialized gemmological laboratories to identify pearls and to distinguish natural from cultured pearls. Identification if a pearl grew as natural or cultured pearl is commonly based on radiography, X-ray luminescence, and X-ray computed µ-tomography, combined with X-ray fluorescence (EDXRF), Raman microspectrometry, UV-Vis-NIR reflectometry and meticulous microscopic examinations (Anderson 1931;Elen 2002;Hänni 2006;Barnard and de Waal 2006;Sturman 2009;Krzemnicki et al 2010). Recently, radiocarbon dating appeared as a new approach in pearl testing (Hänni 2008;Krzemnicki 2010;Hainschwang et al 2010).…”

The Brremangurey pearl: A 2000 year old archaeological find from the coastal Kimberley, Western Australia

“…The use of x-ray technology allows differences in density to be clearly defined and mapped through the differential blocking and absorption of x-rays . The abilities and non-destructive nature of μ-CT make it ideal for studying pearls and the structures and layers of which they are composed Krzemnicki et al 2010).…”