Computerized X-ray micro tomography: A non-destructive insight into the internal structures of pearls

WEHRMEISTER, URSULA; JACOB, DORRIT E.; SOLDATI, ANALIA L.; HOFMEISTER, WOLFGANG

Bangkok and Kanchanaburi, Thailand

Conferencia; The 2nd International Gem & Jewelry Conference (GIT 2009); 2009

The determination of the nature of a pearl can be incrementally difficult and in some specimens only the combination of different methods can lead to a successful identification. For the differentiation of natural from cultured pearls the most promising methods are different radiographic investigations. These are often carried out with radiographs (X-ray shadow pictures), that enable visualization of the internal structures of a pearl and can show the presence of a manufactured nucleus. The recorded images are two-dimensional, while the structures occur at varying depths within the pearl. Therefore several radiographs are normally taken to get sufficient information about the internal growth structures. However, the identification is not always easy, because some radiographic features are common to both beadless cultured and natural pearls. The development and availability of tabletop X-ray tomographs offers a new exciting method, since computerized three-dimensional X-ray microtomography is capable of revealing the internal structure and some of the material properties of pearls at unprecedented resolution. Differences in material-specific transparency to X-rays (radiodensities) can be detected and, when combined with micro-Raman spectrometry, vaterite- containing areas can be identified .