Posts of : H.A. Haenni

Alumosilicates: Andalusite, Kyanite, Sillimanite

Alumosilicates: Andalusite, Kyanite, Sillimanite. Published in Journal of Gemmological Association of Hong Kong GAHK, 2014, 34, 22-23.

Author(s): H.A. Haenni

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DNA Fingerprinting of Pearls to Determine their Origins

Abstract: We report the first successful extraction of oyster DNA from a pearl and use it to identify the source oyster species for the three major pearl-producing oyster species Pinctada margaritifera, P. maxima and P. radiata. Both mitochondrial and nuclear gene fragments could be PCR-amplified and sequenced. A polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay in the internal transcribed spacer (ITS) region was developed and used to identify 18 pearls of unknown origin. A micro-drilling technique was developed to obtain small amounts of DNA while maintaining the commercial value of the pearls. This DNA fingerprinting method could be used to document the source of historic pearls and will provide more transparency for traders and consumers within the pearl industry.

Author(s): J.B. Meyer, L.E. Cartier, E.A. Pinto-Figueroa, M.S. Krzemnicki, H.A. Haenni, B.A. McDonald

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Appearance of new bead material in cultured pearls

Abstract: A range of different materials has already been used as cores in beaded cultured pearls, and now two new alternative options, baroque shaped shell beads and Chinese freshwater cultured pearls, are being used. Experiments with beads of the latter, approximately 6.5 mm across, have been carried out with marine Pinctada maxima and Pinctada margaritifera oysters. After 13 months, nearly 200 pearls of each kind were harvested. Cross sections and further observations of resulting pearls are described. X-radiographs and X-ray microtomography are found to generally deliver clear evidence for identification. These pearls have beenfound to be very suitable for subsequent drilling. Natural pearls also have been used as nuclei for producing cultured pearls. The material used is either non-nacreous, brown or of an unattractive appearance. This new kind of cultured pearl is diffi cult to identify, because the radiographic structures of the natural cores are masking these cultured pearls.

Journal of Gemmology (2010)

Author(s): H.A. Haenni, M.S. Krzemnicki, L.E. Cartier

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X-ray computed microtomography: distinguishing natural pearls from beaded and non-beaded cultured pearls

Abstract: The distinction of natural from cultured pearls traditionally has been based on X-radiography. X-ray computed microtomography (μ-CT) has recently been applied to gain more insight into pearl structures. Using this technique, this article presents features observed in a selection of natural pearls and beaded and non-beaded cultured pearls. Based on these observations, μ-CT is shown to be a powerful tool for pearl identification.

Gems & Gemology (2010)

Author(s): H.A. Haenni, M.S. Krzemnicki, P. Chalus, S. Karampelas, S.D. Friess

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