坦桑尼亚、缅甸和斯里兰卡宝石级绿色柱晶石的宝石矿物学特征
Gemmological and Mineralogical Characteristics of Gem-Quality Green Kornerupine from Tanzania,Myanmar and Sri Lanka
赵思艺 1许博1
作者信息
- 1. 中国地质大学(北京)珠宝学院,北京 100083
- 折叠
摘要
柱晶石(Kornerupine)是一种复杂的含水镁-铁-铝硼硅酸盐,颜色有无色、黄色、绿色、棕色和蓝色等,其中以宝石级绿色柱晶石最为珍贵,在市场上备受追捧.然而,由于其稀有性,人们对该类柱晶石的宝石矿物学特征及产地信息知之甚少.本研究采用常规的宝石学测试方法、谱学测试、EMPA以及LA-ICP-MS对产自坦桑尼亚、缅甸和斯里兰卡绿色柱晶石样品进行了表征.这三个产地的柱晶石样品均表现了相似的折射率和相对密度等基础宝石学特征,坦桑尼亚和斯里兰卡样品短波下显示黄色荧光,而缅甸柱晶石样品因含铁量较高致其紫外荧光惰性.三个产地的绿色柱晶石样品均表现出丰富的流体包裹体、针状包裹体和不同结晶程度的石墨包裹体,表明其变质成因.B元素的apfu(每分子式单位原子数)是鉴定柱晶石矿物种类的重要标准,利用LA-ICP-MS对缅甸绿色柱晶石样品中的B元素进行分析,结果表明缅甸柱晶石样品主要被归为kornerupine,而坦桑尼亚和斯里兰卡绿色柱晶石样品主要被归为prismatine.由于微量元素组成的差异,缅甸柱晶石样品的宝石学特征与其他两个产地的来源不同.V-Cr-Mn和Fe-Mn-V是鉴定坦桑尼亚、缅甸和斯里兰卡绿色柱晶石的产地来源的微量元素"指纹".根据紫外-可见-近红外光谱和痕量元素分析的综合观察,V元素是来自坦桑尼亚和斯里兰卡绿色柱晶石的主要致色元素,导致其具有黄绿色,Cr是缅甸柱晶石的主要致色元素.
Abstract
Kornerupine is a complex hydrous magnesia-iron-aluminum borosilicate that ranges in colour from colourless to yellow,green,brown and blue,etc.The gem-grade green korne-rupine is the most precious and popular in the gemstone market now.Nonetheless,due to its rarity,the information about the origins and gemmological characteristics of the gem-quality green kornerupine is little known.In this paper,the gemmological and mineralogical charac-teristics of the kornerupine samples from Tanzania,Myanmar,and Sri Lanka respectively were studied by conventional gemmological methods,UV-Vis-NIR,Raman spectroscopy,EMPA and LA-ICP-MS.Kornerupine samples from the three origins exhibited similar gem-mological characteristics,except for the inert ultraviolet fluorescence response of the Myan-mar samples,which is attributed to higher iron content.Besides,all the kornerupine sam-ples from the three origins displayed abundant fluid inclusions,needle-like inclusions and graphite inclusions with varying degrees of crystallization,indicating their metamorphic ori-gin.The B element apfu(atoms per formula unit)serves as a crucial criterion for the classi-fication of kornerupine mineral species.The testing results of B element using LA-ICP-MS indicate that kornerupine samples from Myanmar are predominantly classified as korne-rupine,whereas those samples from Tanzania and Sri Lanka are primarily identified as prismatine.Due to differences of trace element compositions,the gemmological properties of kornerupine samples from Myanmar were different compared to the other two origins.The V-Cr-Mn and Fe-Mn-V are trace elements"fingerprints"that provide a useful tool for identi-fying the provenance of kornerupines from Tanzania,Myanmar,and Sri Lanka.V3+is the predominant colouring element of kornerupines from Tanzania,and Sri Lanka,giving rise to more yellowish green colour.Chromium is the predominant chromophore of kornerupine from Myanmar,according to the combined observations from UV-Vis-NIR spectroscopy and trace element analyses.
关键词
柱晶石/产地鉴别/致色元素/化学成分/坦桑尼亚/缅甸/斯里兰卡Key words
kornerupine/origin identification/colouring element/chemical composition/Tanzania/Myanmar/Sri Lanka引用本文复制引用
出版年
2024
NETL
NSTL
万方数据