不同产地欧泊的宝石矿物学特征  

The Gemological and Mineralogical Characteristics of Opals from Different Origins

作　　者：钟媛媛 ZHONG Yuanyuan(School of Gemmology,China University of Geosciences(Beijing),Beijing 100083)

机构地区：[1]中国地质大学(北京)珠宝学院,北京100083

出　　处：《中国宝玉石》2020年第2期34-41,共8页China Gems & Jades

摘　　要：澳大利亚、埃塞俄比亚及墨西哥是欧泊的主要产地,所产欧泊的外观、结构、成分等存在明显差异,本文总结了这三个产地的欧泊的宝石矿物学特征。澳大利亚欧泊通常透明度较差,变彩色斑呈二维片状,色斑之间边界模糊,过渡自然;埃塞俄比亚欧泊透明度较好,色斑立体,色斑之间边界明显;墨西哥产出的火欧泊通常呈橙红色至红色,透明度好,变彩少。根据Ca、Sr和Ba的含量可以区分三个产地的欧泊,相应元素的含量规律为:埃塞俄比亚欧泊>澳大利亚欧泊>墨西哥欧泊。澳大利亚欧泊属非晶态的Opal-A型欧泊,埃塞俄比亚和墨西哥欧泊属结晶程度较高的Opal-CT型欧泊。Opal-A型欧泊在红外光谱790cm-1附近的吸收峰位于796~800cm-1处,Opal-CT型的欧泊在该处的吸收峰则较低,位于788~792cm-1处。澳大利亚欧泊中二氧化硅小球的直径约为150~300nm,球体排列规律;埃塞俄比亚欧泊中二氧化硅小球的直径一般为30nm,球体排列无规律;而墨西哥火欧泊的结构当中没有真正的二氧化硅球体。There are obvious differences in the appearance, structure and composition of opals produced in Australia, Ethiopia and Mexico, which are main origins of opal. This article summarizes the gemological and mineralogical characteristics of opals from different origins. Opal from Australia is usually poor in transparency, and the boundaries between the color spots are blurred;opal from Ethiopia has better transparency, and the boundaries between the color spots are obvious;the fire opal from Mexico is usually orangered to red, with good transparency and less play-of-color. According to the content of Ca, Sr and Ba, the opals of the three origins can be distinguished, and the content of Ca, Sr and Ba in the opals of three places is as follows: Ethiopian opal> Australia opal> Mexico opal. Opal from Australia(non-crystalline Opal-A) has an absorption peak at 796~800 cm-1 in the infrared spectrum, while opal from Ethiopia and Mexico(micro-crystalline Opal-CT) has lower frequencies that located at 788~792 cm-1. The diameters of silica spheres in opal from Australia are the largest(about 150~300 nm), and the spheres are regularly arranged;the silica spheres in opal of Ethiopia are generally 30 nm in diameter and irregularly arranged while there is no real silica sphere in the structure of Mexican opal.

关 键 词：欧泊 产地 微量元素 红外光谱 扫描电镜 

分 类 号：P584[天文地球—岩石学]