Infrared spectroscopic study of modern and ancient ivory from sites at Jinsha and Sanxingdui, China

Abstract

Ancient ivory, from the Chengdu Jinsha and Guanghan Sanxingdui sites in China, has been buried for several thousand years. In order to determine the degradation mechanisms and to provide a scientific basis for protecting them, these ancient ivory samples have been compared with modern ivory using infrared spectroscopy in the frequency range 400À4000 cm À1 . By combining chemical analysis data we compare the crystallinity and crystal chemistry of the apatite component, as well as the structural characteristics of the ivory. These investigations showed that the ancient ivory consists almost entirely of hydroxyl-carbonate apatite as the predominant phase. Compared with the modern ivory, the PO 4 3À and CO 3 2À bands are stronger, the PO 4 RF values are obviously greater, and an extra OH À band at 3569 cm À1 is observed in the ancient ivory. These results indicate that there is a greater degree of apatite crystallinity in the ancient ivory and also imply that there has been incorporation and recrystallization of CO 3 2À in the apatite during burial. Positive correlations have been found between the apatite crystallinity, CO 3 2À and OH À ion contents, and burial time. The organic matter in ancient ivory has been lost or decomposed as the organic bands (e.g. at 1238 cm À1 and 1337 cm À1 ) have disappeared. This may be the main reason that ancient ivory is easily dewatered and readily friable after being unearthed.

Differentiation of archaeological ivory and bone materials by micro-PIXE/PIGE with emphasis on two Upper Palaeolithic key sites: Abri Pataud and Isturitz, France

“…The extent to which the exchange of chemical species takes place depends on the environmental conditions. In general, a loss of magnesium and an enrichment of calcium were observed for the samples analyzed in this study (see also Wang et al, 2007). Obviously, the calcium ions replace the magnesium ions within the hydroxyapatite lattice as indicated by the elemental distribution profile (Fig.…”

“…Relatively few studies focused on ivory diagenesis. Chemical and structural changes in dentine of elephant and mammoth tusks as well as tooth due to diagenetic processes were studied by chemical, structural and morphological analyses (Godfrey et al, 2002;Wang et al, 2007;Edwards et al, 2005). Alterations in archaeological antler have been studied by Chadefaux et al (2008).…”

F-content variation in mammoth ivory from Aurignacian contexts: Preservation, alteration, and implications for ivory-procurement strategies

“…The apatite crystals in proboscidean ivory are smaller than those in bone and in the dentine that forms the cheek-teeth of proboscideans (Su and Cui, 1997). Some studies have been conducted on changes in ivory crystallinity with prolonged burial time (Fan et al, 2006;Reiche et al, 2002;Wang et al, 2007). As in bone and other variations of dentine, deterioration of the organic phase and processes of recrystallization lead to an overall higher crystallinity in ancient ivories.…”

“…The vast majority of such research has been conducted on bone, and sometimes dentine. With some exceptions little chemical research has been undertaken on processes of diagenetic alteration of elephant (Albéric et al, 2014;Wang et al, 2007) and mammoth (Edwards et al, 2005;Müller and Reiche, 2011;Sastri et al, 2013) ivory, which is a highly altered variation of dentine with specific chemical and structural characteristics. Non-destructive chemical analysis is a promising avenue of research in the study of ivory artefacts and is essential for determining "whether chemical indicators can be used as a source of information about diet, climate, genetics and dating or whether they record post-mortem transformation of original biominerals" (Guido et al, 2012: 180).…”

Approche analytique pour l’étude des ivoires archéologiques. Les défenses d’éléphant du site de Jinsha (1200-650 BC, Sichuan, Chine)

“…Cette altération est certainement en partie due à l'activité des microorganismes, mais aussi à un mécanisme complexe de dissolution-recristallisation de l'hydroxylapatite qui intervient sur la phase minérale avec généralement pour ef et une augmentation de la cristallinité. Wang et al (2007) [20] ont déjà réalisé une première étude d'ivoires d'éléphant de Jinsha utilisant la spectroscopie IR-TF avec une référence moderne. Ils montrent une augmentation de la cristallinité de la phase minérale des échantillons archéologiques ainsi que l'introduction de carbonates dans la matrice apatique, concluant à leur recristallisation.…”