莫桑比克天河石的宝石学特征

Gemmological Characteristic of Amazonite from Mozambique

以莫桑比克宝石级艳蓝绿色天河石为研究对象,利用偏光显微镜、拉曼光谱、电感耦合等离子体质谱仪和环境扫描电镜等测试技术对其宝石学特征进行测试与分析。莫桑比克天河石样品主要由钾长石和钠长石两种矿物组成;其中蓝绿色区域主要是钾长石,白色区域主要是钠长石;钾长石和钠长石有规律的交生在一起;依据近代宝石学颜色成因理论,天河石的颜色成因主要有两种观点:(1)Rb和Cs以类质同象替代晶体结构中的K产生色心致色;(2)Pb以类质同象替代晶体结构中的K产生色心致色。通过ICP-MS测试发现莫桑比克天河石中蓝绿色区域和白色区域Rb、Cs、Pb在含量上存在明显差异,推测天河石的致色原因可能是Rb、Cs、Pb中的某一种或者两种元素以类质同象替代天河石晶体结构中的K,从而引起结构缺陷,产生色心而形成蓝绿色。

In the paper, the gemmological characteristics of gem grade blue-green amazonite sample from Mozambique were tested by using the polarizing microscope, Raman spectrum, inductively coupled plasma mass spectrometer and environmental scanning electron microsco-py. The result showed that the amazonite sample from Mozambique is primarily composed of potassium feldspar and albite. The blue-green part of amazonite is mainly composed of potas-sium feldspar and the white part is mainly composed of albite. Potassium feldspar and albite intergrowth together regularly. Based on the theory of modern gemmology colour formation, there are two main views about the colour cause of amazonite. （1） Rb and Cs elements take the place of K element, which form colour heart; （2） Pb element takes the place of K ele-ment which form colour heart. Though ICP-MS,we found that the content of Rb、 Cs、 Pb el-ements in the blue-green part and the white part of amazonite sample from Mozambique are different. The colour cause of amazonite sample from Mozambique was discussed that one or two elements of Rb、 Cs、Pb take the place of K element which is such quality as alternative in the crystal structure of amazonite, leading to structural defects, forming colour heart.