广西合浦养殖珍珠的宝石学特征

合浦养殖珍珠的结构可分为珍珠层型、棱柱层型及复合型三类。化学成分主要为碳酸钙，其次为有机质和水，此外含有多种微量元素。矿物成分是由碳酸钙的两种矿物相－文石和方解石组成，文石为主要组成矿物，文石与方解石含量的比值愈高，珍珠质量愈好，反之，愈差。珍珠中的微量元素没有以类质同像方式参与到矿物晶格中，水是以吸附态存在。珍珠的颜色以白色、淡黄色为主，密度２．６５～２．７６ｇ／ｃｍ３，维氏硬度１６３～１８３ｋｇ／ｍｍ２，折光率１．５３３～１．６９０，珍珠形态以圆形为主，大小一般在４～７ｍｍ，珍珠工艺性能的评价通常采用“光、重、圆、大”四字标准。

Characteristics of Gemology of Marine-cultured Pearls in Hepu,Guangxi

The structure of the Hepu marine-cultured pearls is divided into three types:pearl layer,prismatic layer and compound layer. The chemical compositions are mainly calcium carbonate, supplemented by organic matter and adsorptive water, and with minor amounts of microelements. The major mineral constituents are composed of dimorphous mineral faciesaragonite to calcite, the quality of Hepu pearls increases with the ratio of aragonite and calcite. The microelements in Hepu pearls are not in the form of isomorphism and they are not entering the mineral crystal lattice. Hepu pearls are well-rounded, have an elegant pearly luster, and are 2.65~2.76 g/cm³ in density, 163~183 kg/mm² in hardness, 4~7 mm in mean diameter, 1.533~1.690 in refractive index, the appreciative standards of the pearls are luster, weight, shape and size.