On the deep origin of the depressed rings on pearl surface illustrated from Polynesian Pinctada margaritifera (Linnaeus 1758) |
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| Authors: | Jean‐Pierre Cuif Alberto Perez‐Huerta Cédric Lo Oulfa Belhadj Yannicke Dauphin |
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| Institution: | 1. CR2P: Centre de recherche sur la paléodiversité et les paléoenvironnements, UMR 7207, Museum National d'Histoire Naturelle CNRS, Paris, France;2. Department of Geological Sciences, The University of Alabama, Tuscaloosa, AL, USA;3. Direction des Ressources Marines & Minières, Papeete Tahiti, Polynésie fran?aise;4. Centre de recherche sur la conservation (CRC, USR 3224), Sorbonne Universités, Muséum national d'Histoire naturelle, Ministère de la Culture et de la Communication, CNRS CP21, Paris, France;5. ISYEB: Institut de systématique, Evolution, Biodiversité, UMR 7205 CNRS MNHN UPMC, EPHE Muséum national d'Histoire naturelle, Paris, France |
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| Abstract: | Among the various defects that contribute to depreciate the commercial value of pearls, the occurrence of depressed rings is the most spectacular. Through a series of structural, physical and chemical characterizations of the pearl layer, this paper reveals that the origin and initial stages of these essentially superficial defects are to be found in the earliest stages of pearl formation. The disturbance in growth of the nacreous envelopes is the physical cause of the occurrence of these depressed areas. Attention is also drawn on the unexpected relationship between these large morphological alterations of the pearl surfaces and more punctual defects primarily well visible in the strongly coloured Polynesian pearls. An understanding of the actual origin of these very negative patterns opens the way to reduce their statistical occurrence by paying attention to the grafting practice. |
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| Keywords: | biomineralization electron back‐scattered diffraction nacreous tablets ringed pearls scanning electron microscope |
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