绿松石颜色成因及分级研究现状  

Research Status of Turquoise Color Causing and Grading

作　　者：王雪丁 WANG Xueding(School o f 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1期28-35,共8页China Gems & Jades

摘　　要：绿松石是一种含水的铜铝磷酸盐矿物,纯净状态下呈天蓝色,因常见复杂类质同象而呈现出丰富多变的颜色外观.绿松石颜色成因可由晶体场理论解释,其天蓝色由Cu2+配位八面体的局域对称性及其在晶格中的结构位置决定;Fe3+和V3+的综合作用导致蓝色绿松石中绿色调的出现;Fe3+含量的增多会使得蓝色绿松石向土黄、棕色转变.绿松石中存在氢键较强的羟基(Al-OH)、氢键相对较弱的[Cu(H2O)4]2+和充填在孔隙或微裂隙中的吸附水,其中羟基和结晶水的热损失会对绿松石颜色产生破坏性的影响,而吸附水含量的增加仅对绿松石颜色的明度和饱和度产生积极作用.绿松石结构致密性影响着绿松石吸附水的赋存,疏松绿松石吸水前后的色差大于致密绿松石吸水前后的色差.目前针对绿松石颜色分级的研究方法可分为理论建模型和规律总结型两类,前者基于CIE 1976 L*a*b*颜色体系,以L*、a*和b*颜色参数为独立变量进行聚类分析和判别分析,将单一色调内的绿松石颜色分成差异性极显著的不同类别,从而根据明度和彩度进行具体级别的描述;后者基于HSB表色体系,实现绿松石颜色空间内的可视化表征,总结绿松石分布规律并结合肉眼观察特征,并以色相分级、明度分级和饱和度分级构成绿松石颜色分级的全部内容.Turquoise is a hydrated copper aluminum phosphate, which appears as blue as sky in the pure state and has various and changable color due to the complicated isormophism. The color causing of turquoise can be explained by crytal field theory. The blue is determined by the local symmetry of the Cu2+ coordination octahedron and its position in the lattice;The combited effects of Fe3+ and V3+ result in the appearance of green tones in blue turquoise, while the increasing of Fe3+ content may turn turquoise blue into yellow and brown. There are hydroxyl groups(Al-OH) with strong hydrogen bonds, [Cu(H2O)4]2+ with relatively weak hydrogen bonds and adsorbed water filled in pores or micro-cracks in turquoise. Heat loss from hydroxyl and crystal water can have a devastating effect on turquoise color;the increase in adsorbed water content only has a positive effect on the lightness and chroma of turquoise color. The compactness of turquoise structure affects the occurrence of turquoise adsorbed water and there are more color difference between dry turquoise to watering turquoise, especially for the loose. The current research methods for turquoise color grading can be divided into two types: theoretical models and regular summary. The former takes cluster analysis and discriminant analysis by L*, a*and b* as idicators based on the CIE 1976 L*a*b* color system to classify the turquoise colors into different types with extremely significant differences in a single hue, so that specific levels are described according to lightness and chroma;the latter depends on the visual characterization of turquoise and summarizes the distribution of turquoise color based on the HSB color system to achieve turquoise color space. According to the characteristics in the naked eyes, the quality evaluation of turquoise color is explained with hue, lightness and saturation grading.

关 键 词：绿松石 颜色成因 晶体场理论 颜色分级 

分 类 号：P574.2[天文地球—矿物学]