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

赵思艺; 许博

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

赵思艺,
许博^,

中国地质大学(北京)珠宝学院，北京 100083

详细信息

作者简介:
赵思艺(1993-)，女，博士后，主要从事矿物学、宝石学方面的研究工作。E-mail: 2023700021@cugb.edu.cn

通讯作者:
许博(1988-)，男，教授，主要从事碰撞带深部过程与成矿，矿物微区分析和宝石学研究工作。E-mail: xubo@outlook.com.cn

计量
- 文章访问数: 84
- HTML全文浏览量: 39
- PDF下载量: 24
出版历程
- 收稿日期: 2024-07-14
- 刊出日期: 2024-10-30

Gemmological and Mineralogical Characteristics of Gem-Quality Green Kornerupine from Tanzania, Myanmar and Sri Lanka

ZHAO Siyi,
XU Bo^,

School of Gemmology, China University of Geosciences, Beijing 100083, China

摘要

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。
- 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
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 kornerupine 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 characteristics 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 gemmological characteristics, except for the inert ultraviolet fluorescence response of the Myanmar samples, which is attributed to higher iron content. Besides, all the kornerupine samples from the three origins displayed abundant fluid inclusions, needle-like inclusions and graphite inclusions with varying degrees of crystallization, indicating their metamorphic origin. The B element apfu (atoms per formula unit) serves as a crucial criterion for the classification of kornerupine mineral species. The testing results of B element using LA-ICP-MS indicate that kornerupine samples from Myanmar are predominantly classified as kornerupine, 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 identifying 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.
- kornerupine /
- origin identification /
- colouring element /
- chemical composition /
- Tanzania /
- Myanmar /
- Sri Lanka

HTML全文

图 1 12个产地海蓝宝石样品汇总

Figure 1. Overview of aquamarine samples from 12 different origins

下载: 全尺寸图片幻灯片

图 2 海蓝宝石样品的包裹体特征：(a)中国四川样品中的锯齿状三相流体包裹体；(b)中国云南样品中的短针状三相流体包裹体；(c)中国西藏样品中的带彩虹干涉色薄流体包裹体；(d)阿富汗样品中的原生电气石包裹体；(e)纳米比亚样品中的萤石包裹体；(f)尼日利亚样品中的大量磁黄铁矿包裹体

Figure 2. Inclusion characteristics of aquamarine samples: (a) jagged three-phase fluid inclusions in the sample from Sichuan Province, China; (b) short needle-like three-phase fluid inclusions in the sample from Yunnan Province, China; (c) thin fluid inclusions with rainbow interference colors in the sample from Xizang, China; (d) primary tourmaline inclusions in the sample from Afghanistan; (e) fluorite inclusions in the sample from Namibia; (f) numerous pyrrhotite inclusions in the sample from Nigeria

下载: 全尺寸图片幻灯片

图 1 宝石级柱晶石的产地(底图修改自Li, et al.^[5])

Figure 1. The origins of gem-quality kornerupines. The base figure is modified from Li, et al.^[5]

下载: 全尺寸图片幻灯片

图 2 缅甸、坦桑尼亚和斯里兰卡的宝石级绿色柱晶石样品.左边8颗斯里兰卡绿色样品及其4颗具有独特的猫眼效应；中间13颗坦桑尼亚苹果绿色样品原石及刻面型；右边3颗缅甸深绿色样品

Figure 2. Faceted, cabochon and raw kornerupine samples from Myanmar, Tanzania and Sri Lanka. The eight green samples from Sri Lanka on the left of the photo, four of them showing distinctive chatoyancy effect. The thirteen samples with apple green colour in the center of the photo are from Tanzania.The three precious emerald-colored gemstones on the right are from Myanmar

下载: 全尺寸图片幻灯片

参考文献(5)

[1]	Cooper M A, Hawthorne F C, Grew E S. The crystal chemistry of the kornerupine-prismatine series. I. Crystal structure and site populations[J]. The Canadian Mineralogist, 2009, 47(2): 233-262. doi: 10.3749/canmin.47.2.233
[2]	Grew E S, Anovitz L. Borosilicates (exclusive of tourmaline) and boron in rock-forming minerals in metamorphic environments[J]. Reviews in Mineralogy, 1996(33): 387-502.
[3]	Grew E S, Hystad G, Hazen R M, et al. How many boron minerals occur in Earth's upper crust[J]. American Mineralogist, 2017, 102(8): 1 573-1 587.
[4]	Sehgal A, Girma D. Cat's-eye kornerupine[J]. Gems & Gemology, 2017, 53(2): 1-3.
[5]	Shen J Q, Hu Z K, Cui S Y, et al. A study on beryl in the Cuonadong Be-W-Sn polymetallic deposit, Longzi county, Tibet, China[J]. Crystals, 2021, 11(777): 777.