Gemmological Identification Characteristics of Natural Ageing and Artificial Aged Beeswax Amber

Beeswax amber is a kind of translucent to opaque amber with yellow to brown colour. The old beeswax amber refers to a kind of beeswax that has been worn, played or left in the natural environment for a certain period of time (tens to hundreds of years) and has been darkened by natural weathering, which is visually "old". Among them, natural old beeswax is greatly appreciated by certain collectors and the public due to its high cultural value and commercial value, and its price has always been high since its stock is limited. In recent years, there has been a large number of artificial aged beeswax amber through heating treatment of ordinary beeswax, controlling the processing parameters such as the heating rate and temperature difference, or overlapping other technologies, the artificial aged beeswax displays the appearance similar to that of natural ageing beeswax amber. At present, there is a lack of systematically academic research on the artificial aged beeswax amber. This article conducts a systematic study on the Qing Dynasty natural ageing beeswax amber and artificially aged beeswax amber via gemstone microscopy, infrared spectroscopy, photoluminescence spectroscopy, and ultraviolet visible near-infrared (UV-Vis-NIR) spectroscopy, and summarizes the identification characteristics of them. The main conclusions are as follows: (1) The surface of artificially aged beeswax amber is mostly smooth, and sometimes accompanied by black carbonization pits formed by rapid heating. However, the surface of naturally ageing beeswax amber is mostly rough, with an irregular and uneven appearance. Some manually made beeswax amber can also be artificially polished to create a more consistent uneven appearance; (2) There is only one set of turtle cracks can be made on the artificially aged beeswax amber, and the turtle cracks are more regular in shape than the natural ageing beeswax amber. The turtle cracks can be large, small, and shallow in depth; The morphology of turtle cracks in natural ageing beeswax amber is natural, uniform, and compact, generally divided into 2-3 levels. The first level main crack is deep and wide, and appears as a dark large crack under the microscope. The depth and width of the second level crack are smaller than the main crack, and the third level fine turtle cracks are distributed in small areas divided by the main or secondary cracks. The coexistence of Level 3 or Level 2 turtle cracks in naturally ageing beewax amber is a process that cannot be achieved by artificially aged beeswax amber, and it is also an important basis for identifying them; (3) The thickness of the ageing layer (≤ 0.2 mm) at the fracture surface of artificially aged beeswax amber is much smaller than that of naturally ageing beeswax amber (≥ 0.8 mm); (4) In the infrared spectrum, due to the rough surface of the naturally ageing beeswax amber, the infrared spectrum deformation is obvious, and the "Baltic shoulder" (1 260-1 160 cm^-1) is not significant. However, the characteristic peaks are more obvious in the artificially aged beeswax amber, which is related to the thin ageing layer. Secondly, the absorption peak at 1 566 cm^-1 has a higher probability of appearing in naturally aged beeswax amber, which is speculated to be related to the succinic acid generated after the ageing of Baltic amber. (5) The photoluminescence spectra of naturally ageing beeswax amber and artificially aged beeswax amber are similar, but the luminescence center intensity of both samples significantly decreases compared to that of the fracture (inner). There is a small difference in the characteristic spectral peak wavelength between these two, but which are easily affected by instrument accuracy and human operation, and the identification significance needs further statistical verification; (6) The UV-Vis-NIR spectra are basically consistent and have no identification significance. The research results of this article are of practical value for the identification of natural aging and artificially aged beeswax amber.