“爱迪生”淡水有核珍珠的鉴定特征

Identification Characteristic of Freshwater Cultured Nucleated “Edison” Pearl

作为大颗粒、圆度好、光泽亮丽、色彩丰富的淡水有核珍珠的代名词,"爱迪生"珍珠越来越受到人们的关注,其特有的紫色和金属色品种更是深受消费者的喜爱。但与此同时,"爱迪生"珍珠的颜色成因受到各方面的质疑,且其染色仿制品也逐渐流入市场。为了更好地鉴别"爱迪生"珍珠,准确地将其与染色仿制品进行区分,笔者通过放大观察、珠层厚度、发光图像、紫外-可见吸收光谱及拉曼光谱等测试方法,对15粒不同颜色品种的"爱迪生"珍珠样品进行了系统的宝石学特征研究,并重点对比分析了"爱迪生"珍珠与染色仿制品以及紫色淡水无核珍珠的颜色成因。研究发现,彩色"爱迪生"珍珠的拉曼光谱中出现与天然色素多烯(聚乙炔)化合物有关的1 121~1 132cm^(-1)和1 503~1 524cm^(-1)处吸收峰,可作为"爱迪生"珍珠颜色成因的主要鉴定依据。而染色样品可通过放大观察、异常的荧光发光图像以及染料的紫外-可见吸收光谱特征峰与其进行区分。

＂Edison＂pearls as a type of large,rounded,shiny and colourful freshwater cultured nucleated pearls,are getting more and more attention.Their unique purple and bronze colours with metallic luster are deeply loved by people.However,the cause of colour in＂Edison＂pearls has been questioned,and the dyed imitations gradually appear in the market.In order to identify the ＂Edison＂pearl and its imitations accurately,the authors collected 15 pieces of＂Edison＂pearl samples with different colours and applied systematic tests on the gemmological characteristics including magnification observation,the thickness of the nacre layer,fluorescent images,UV-Vis absorption spectroscopy and Raman spectroscopy.The cause of colour in the＂Edison＂pearls,dyed imitations,and purple freshwater cultured non-nucleated pearls were analyzed.In Raman spectra of＂Edison＂pearl,peaks at 1 121—1 132cm^（-1）and 1 503—1 524cm^（-1） related to the natural pigments of polyenic（polyacetylenic）compounds were regarded as the major evidence on the cause of colour.Dyed imitations could be distinguished by magnification observation,abnormal fluorescent images and UV-Vis ab-sorption spectroscopy.