Gemological Characteristic And Quality Influencing Factors Of Freshwater Nucleated Cultured Pearls

Pearl is round and plump, has pastel colors, is a beautiful and precious jewelry without over processing. Known as the "Queen of gems", people loved pearls for a long time. With the improvement of technology of Chinese freshwater nucleated cultured pearls, many new colors and new varieties of pearls have introduced and shown on global market, and the quality is as good as seawater pearls. In the paper, the author discussed the composition, structure and surface characteristics of freshwater nucleated pearls, and compared with other pearls by using various of microscopes, OCT, EMPA, XRD, Infrared and Raman spectrum, etc. The results as follows:The basic properties of gemology have slightly differences between different kinds of pearls, such as color, luster, density, RI, Luminescence. The main component of the freshwater nucleated pearls is aragonite. Sometimes with a small amount of vaterite, but without calcite. Vaterite is point-like and plaque-like, with a bright red fluorescence under a cathode ray. Vaterite can exist in a variety of color and luster of freshwater nucleated pearls, between different nacres and on the surface of pearl. The content and distribution of vaterite can affect pearls’ luster and surface perfection. The color is mainly affected by the type and content of colored organics, while the metal elements assistant.By using various of microscopes, the author recommend the special growth structure and surface characteristics of freshwater nucleated pearls. And discussed the influence of shape, luster, surface perfection from dense degree of nacres, the content of organic matter, the surface layer structure, the shape of aragonite. In particular author observed the relationships between aragonite prismatic layer and nacre.In the paper, the author recommend the enhancing processes of freshwater pearls, such as Sorting, Punching, Puffing, Dehydration, Lightening, Bleaching, Whitening, Polishing, etc. The enhancing processes of freshwater pearls can improve the color and luster of pearl, extend the life of pearl jewelry. Most of the pearls are enhanced on the market, and the consumers are generally accepted.By national standard of cultured pearl grading, we evaluate the quality of pearls mainly from color, size, shape, luster, surface perfection, nacre thickness, matching attribute. The author analysis the influence factors of quality from internal and external cause, which can improve the quality of Chinese freshwater nucleated cultured pearls.