Differences on Growth Microstructure and FTIR Absorption Spectra between Mammoth Teeth and Ivory

Mammoth is the ancient vertebrate and most of the existing mammoth teeth often exists as semi-fossil.The difference characteristics between mammoth teeth and ivory in the growth microstructure and collagen are studied by using the analysis and testing instruments like SEM and FTIR.The results show that the ivory and mammoth teeth are primarily composed of collagen and hydroxyl calcium phosphate.The infrared absorption spectra with the characteristics of the amido bond of the collagen are located at 1 663 cm^-1(ν_C-0), 1 558 cm^-1(ν_C-H) and 1 240 cm^-1(δ_N-H).The fossilization leads to the damage of the amido bond of the collagen to some extent and the intensities of the infrared absorption spectra of the collagen in the mammoth teeth are reduced gradually.There is the obvious difference between the ivory and mammoth teeth in the maximum included angle of the Retzius pointing to the center.The maximum angle of the former is larger than 120° while the maximum angle of the latter is smaller than 95°.The Retzius layer of the ivory has the fibrous interlocking texture with dense, solid and delicate structure.The Retzius layer of the mammoth teeth has the leaf-shaped structure with less collagen fibers and loose structure.The texture is dry and the size of the hole is larger.With the growth of the microfracture, the toughness will become weak.