Identification Characteristic of A New Ivory Imitation Material

A fantastic simulated products similar to ivory in appearance such as graining and texture have arised in Guangzhou jewelry wholesale market in recent years, bringing about new tasks for identification of ivory and related accessories.In this paper, three circular tags are used as test samples, and conventional physical property test, knife scratch, hot needle spine, microscopic observation of texture, infrared spectrum analysis have been studied. The author contrasts the differences in internal and external characteristics with the other imitations such as mammoth teeth, hippo teeth, nut ivory, animal bones, celluloid, plastic products and the real ivory.The routine test results showed that the simulated material has the physical parameters of refractive index 1.48(point measurement), relative index 1.22, and it emerges complete roll sheets while being scratched, and comes into hollow pinprick, granular powder residue, white colour while contacting with hot needle. Microscopic observation indicated that the grain lines arrange in a gradual transition by coarse, irregular to fine from the center to the edge on the circular samples' surface. The central is the rows of big wavy lines, and the middle layer is a rough concentric ripple, and the outer layer is fine concentric ripples. Each graining line changes from narrow to wide in width, and its boundaries are vague, extending in the curving and independent Z-shaped way. Furthermore, the texture and structure characteristics inside the simulated products are completely consistent with the outside, and lack of Retzius layers, cross-rhomb patterns and overall concentric structure of ivory. Infrared spectrometry indicated that the stimulated products has uniform material composition, without being coating. The main three strong infrared absorption peaks located at 2 920、1 728、1 278 cm^-1. None of vibration absorption spectrum peak is related to collagen amide linkage and PO₄^3-, and drasticly differs from ivory. In brief, this stimulated material is a kind of macromolecule alkyd resin. Compared with the previous imitations, this stimulated material is characterized with its unique texture such as gradual transition of thickness and density, clear hierarchy and incomplete concentric ripple layered structure. Furthermore, colour, luster, density and refractive index can be used as an auxiliary basis for identification.