Gemmological and Spectral Characteristics of Emerald from Panjsher Valley, Afghanistan
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摘要:
品质和产地是影响祖母绿价格的重要因素，而不同产地祖母绿的宝石学特征是其产地溯源的重要依据之一。本文以阿富汗潘杰希尔(Panjsher)矿区祖母绿样品为研究对象，运用了光学显微镜、红外光谱仪、显微紫外-可见-近红外光谱仪、拉曼光谱仪等大型仪器对样品的宝石矿物学特征、内部包裹体特征、化学成分和颜色成因等进行了测试分析。结果显示，该地区祖母绿样品的颜色为浅绿色-深绿色，常见晶形为六方短柱状或板状晶体，外部可见黑色、褐色伴生矿物，查尔斯滤色镜下除个别样品外均局部变红。祖母绿样品的主要包裹体多为长针状、梭状或长管状的含岩盐-钾盐的多相流体包裹体以及固相矿物包裹体。拉曼光谱对包裹体测试后发现其多相包裹体中液相成分多为H2O，固体相成分多为方解石和赤铁矿，矿物包裹体主要成分多为赤铁矿、方解石、无定形碳、石英、碳质和磷灰石等；LA-ICP-MS的化学成分结果显示，该产地祖母绿样品的主要化学成分为BeO、Al2O3、SiO2，微量元素主要有Ca、Mg、Ti、Li、Na、K、Rb、Cs、Cr、V；红外光谱的测试结果显示该产地祖母绿样品含有Ⅰ型水和Ⅱ型水，且Ⅱ型水的红外吸收峰强度大于Ⅰ型水，以Ⅱ型水为主，与LA-ICP-MS测试结果中碱金属的含量高相一致；紫外-可见光谱结果显示，Cr3+和V3+为阿富汗潘杰希尔矿区祖母绿样品的主要致色离子。综上，阿富汗潘杰希尔矿区祖母绿的宝石学特征、谱学特征和化学成分可为其产地溯源提供一定的参考依据。
Abstract:Quality and origin are important factors affecting the price of emerald. Emeralds from different origins have their own gemmological characteristics, which are important basis to trace their hometown. This study takes the emerald samples from the Panjshir mining area in Afghanistan as the research objects, and uses large-scale instruments such as optical microscopy, infrared spectroscopy, micro ultraviolet visible near-infrared spectroscopy, Raman spectroscopy, etc. to conduct study on their gemmological characteristics, internal inclusion characteristics, chemical compositions, and colour genesis. The colour of emerald samples from Afghanistan is light green to dark green, and the common crystal form is hexagonal short columnar or tabular crystal. Black and brown associated minerals can be seen outside. Under the Charles filter, all except a few samples showed localized redness. The main inclusions of emerald samples from Afghanistan are long needle-like, shuttle-like or long tube-like multiphase fluid inclusions containing rock salt and potassium salt and solid mineral inclusions. Raman spectrum tests on inclusions found that the liquid component of multiphase inclusions in emerald samples from Afghanistan is mostly H2O, and the solid component is mostly calcite and hematite. In addition, mineral inclusions contained in emerald are mainly composed of hematite, calcite, amorphous carbon, quartz, carbonaceous, apatite, etc. LA-ICP-MS was used to test the chemical compositions of the emerald samples from Afghanistan, the result indicated that the main chemical compositions of the emerald samples are BeO, Al2O3, SiO2, and trace elements including Ca, Mg, Ti, Li, Na, K, Rb, Cs, Cr, V. Through infrared spectroscopy test, it is known that emerald from Afghanistans contain typeⅠand typeⅡwater, and the infrared absorption peak intensity of type Ⅱ water is greater than that of typeⅠwater, indicating that emerald samples from Afghanistans are mainly composed of type Ⅱ water. The alkali metal content in general beryl (and emerald) is positively correlated with type Ⅱ water content. The infrared test results mainly show type Ⅱ water, which is consistent with the high alkali metal content in LA-ICP-MS test results. The UV visible spectrum tests show that Cr3+ and V3+ are the chromogenic ions of emerald from Afghanistan. The gemmological, spectral and chemical composition characteristics of emeralds samples from Afghanistan will provide the basis for tracing their origin.
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Keywords:
- emerald /
- spectral characteristic /
- inclusion /
- Panjsher, Afghanistan
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图 1 本文研究的祖母绿矿床位于阿富汗东北部潘杰希尔山谷和科尔贡(拉格曼省)附近的位置(左图)；祖母绿矿区位于Khenj村上游，距喀布尔约115 km(右图为左图红色框中放大的三维地貌图)[6]
Figure 1. Location of the emerald deposit near Panjshir Valley and Korgon (Laghman Province) in northeast Afghanistan (left figure); emerald mining area is located in the upstream of Khenj village, about 115 kilometers away from Kabul (the right picture is an enlarged three-dimensional geomorphic map in the red box on the left)
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图 3 阿富汗祖母绿样品的外观特征：(a-b)褐色伴生矿物；(c-d)垂直于c轴的平行包裹体及颜色分布；(e)晶面凹坑；(f)黄色色块
Figure 3. External characteristics of emerald samples from Afghanistan: (a-b)brown associated minerals of emerald enclaves; (c-d) the parallel inclusion and colour distribution perpendicular to the c axis; (e)the pit on the crystal surface; (f)the yellow colour block
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图 4 阿富汗祖母绿样品在查尔斯滤色镜下特征
Figure 4. Characteristics of emerald samples observed under Chelsea filter
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图 5 阿富汗祖母绿样品中的流体包裹体: (a)长针状两相包裹体；(b)尖状包裹体；(c)短柱状流体包裹体；(d-e)三相流体包裹体；(f)长管状两相包裹体
Figure 5. Fluid inclusions in emerald samples from Afghanistan: (a)long needle-like two-phase inclusion; (b)sharp inclusions; (c)short columnar fluid inclusion; (d-e)three-phase fluid inclusion; (f)long tubular two-phase inclusion
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图 6 阿富汗祖母绿样品的矿物包裹体：(a-b)黑色矿物及无色矿物包裹体；(c)褐色矿物包裹体；(d-e)为黑色无定形矿物包裹体；(f)褐色和黑色矿物包裹体
Figure 6. Mineral inclusions in emerald samples from Afghanistan: (a-b)black and colourless mineral inclusions; (c)brown mineral inclusions; (d-e)black amorphous mineral inclusions; (f) brown and black mineral inclusions
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图 9 阿富汗祖母绿样品的紫外-可见光谱(⊥c和//c)
Figure 9. UV-Vis spectra of some emerald samples from Afghanistan(⊥c and //c)
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图 11 阿富汗祖母绿样品ENAFGH06中流体包裹体的拉曼光谱
Figure 11. Raman spectra of the fluid inclusions of emerald sample ENAFGH06 from Afghanistan
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图 12 阿富汗祖母绿样品中固体包裹体的拉曼光谱
(a)样品ENAFGEE08中的赤铁矿；(b)样品ENAFGWM中的磷灰石；(c)样品ENAFGSPOST.0中的无定形碳和ENAFGWM中的碳质
Figure 12. Raman spectra of the solid inclusions in emerald samples from Afghanistan
表 1 阿富汗祖母绿样品的基本特征
Table 1 Basic characteristics of emerald samples from Afghanistan
样品编号 颜色 色带 透明度 晶形 晶面特征 查尔斯滤色镜 RI DR ENAFGEE01 绿色 色带不明显，可见黄色色块 透明 板状 晶面纵纹较明显，平行于c轴 局部变红 1.575~1.584 0.009 ENAFGEE08 绿色 色带不明显 半透明 板状 晶面纵纹很明显，平行于c轴 局部变红 1.576~1.584 0.008 ENAFGEE02 绿色 色带不明显 透明 厚板状 晶面纵纹较明显，平行于c轴 局部变红 1.580~1.589 0.009 ENAFGH06 浅绿色 具较明显⊥ c轴六边形色带 透明 六方柱状 可见色带，晶面纵纹较明显，平行于c轴 局部变红 1.570~1.578 0.008 ENAFGH01 深绿色 色带不明显 半透明 不规则块状 晶面纵纹较明显，平行于c轴 局部变红 1.570~1.580 0.010 ENAFGHAZ03 浅绿色 色带不明显 透明 六方柱状 晶面纵纹较明显，平行于c轴 不变红 1.570~1.576 0.006 ENAFGLU11 绿色 色带不明显 透明 六方柱状 晶面纵纹较明显，平行于c轴 局部变红 1.575~1.583 0.008 ENAFGX09 浅绿色 色带不明显 透明 六方短柱 晶面纵纹很明显，平行于c轴 局部变红 1.578~1.585 0.007 ENAFGSPOST.0 绿色 色带不明显，可见黑色色团 透明 六方短柱 晶面纵纹较明显，平行于c轴 局部变红 1.572~1.580 0.008 ENAFGWM 深绿色 色带不明显 透明 六方短柱 晶面纵纹很明显，平行于c轴 局部变红 1.579~1.585 0.006 ENAFGEE04 深绿色 色带不明显 透明 六方短柱 晶面纵纹较明显，平行于c轴 局部变红 1.584~1.590 0.006 
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表 2 阿富汗祖母绿样品的主要化学成分
Table 2 Main chemical compositions of emerald samples from Afghanistan
wB/% 样品号 BeO Al2O3 SiO2 ENAFGHAZ03 13.30 16.34 67.33 ENAFGEE01 13.12 16.54 67.57 ENAFGEE02 13.49 15.46 66.63 ENAFGEE04 13.62 16.07 66.86 ENAFGEE08 13.46 14.66 66.95 ENAFGH01 13.64 14.44 66.41 ENAFGH06 14.01 18.04 66.62 ENAFGWM 13.46 15.35 66.89 ENAFGLU11 13.68 16.77 66.67 ENAFGSPOST.0 13.73 17.33 66.64 ENAFGX09 13.39 15.81 66.75
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表 3 阿富汗祖母绿样品的微量元素含量
Table 3 Contents of trace elements of emerald samples from Afghanistan
样品号 Li/10-6 Na/10-6 K/10-6 Rb/10-6 Cs/10-6 Cr/10-6 V/10-6 CaO/% MgO/% TiO2/% FeO/% ENAFGHAZ03 83.47 7 546.60 349.45 20.92 29.54 1 803.93 1 263.32 0.018 1.182 0.003 0.185 ENAFGEE01 88.69 5 996.35 233.70 15.35 25.64 2 188.68 3 405.49 0.140 0.940 0.003 0.160 ENAFGEE02 70.11 9 316.62 596.60 40.02 42.58 4 442.92 6 209.68 0.019 1.513 0.003 0.315 ENAFGEE04 74.36 6 410.87 410.62 27.72 34.64 5 273.58 2 266.29 0.031 1.042 0.003 0.140 ENAFGEE08 73.92 9 574.06 586.82 54.05 56.35 5 481.08 3 254.69 0.016 1.564 0.004 0.266 ENAFGH01 79.03 10 313.18 935.08 63.91 69.73 5 207.00 3 639.83 0.014 1.826 0.005 0.302 ENAFGH06 60.85 3 638.14 89.24 5.04 9.21 230.66 298.14 0.006 0.543 0.002 0.129 ENAFGWM 76.84 8 207.29 490.56 35.35 39.03 5 864.35 2 571.99 0.019 1.386 0.004 0.190 ENAFGLU11 80.67 7 006.60 323.90 21.80 29.78 2 059.39 1 164.69 0.009 1.125 0.003 0.130 ENAFGSPOST.0 90.09 5 531.77 215.95 13.86 31.62 1 042.03 1 036.68 0.012 0.852 0.003 0.221 ENAFGX09 81.48 7 872.26 504.31 33.90 44.67 6 034.85 1 956.40 0.014 1.259 0.003 0.247
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