Chemical Composition Analysis of Emeralds from the Mingora Region, Pakistan: Insights into Formation Mechanisms

doi:10.19657/j.geoscience.1000-8527.2025.008

Abstract

Abstract:

The emeralds from the Swat region of Pakistan are notable for their unique color and exceptional crystal quality; however, the chemical composition of Mingora emeralds in this area has not been systematically studied. This research employs Electron Probe Microanalysis (EMPA) and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) techniques to conduct a comprehensive chemical composition analysis of emerald samples from the Mingora deposit, aiming to explore their chemical properties and uncover the geological environmental influences during their formation. The results indicate that the average degree of isomorphous substitution in Mingora emeralds is 12.79%, primarily occurring at the tetrahedral T2 site of beryllium (Be), classifying them as “tetrahedral-type” emeralds. Additionally, the channel structure of these emeralds contains a rich concentration of alkali metal ions, with estimated H₂O content ranging from 2.28% to 2.41%. Notably, the projection of Mingora emeralds in the Cr-V content diagram shows that the chromium (Cr) content is consistently higher than 4,500×10^-6, which is significantly higher than that of emeralds from other global sources. Through comparative analysis of trace elements such as rubidium (Rb), cesium (Cs), scandium (Sc), and lithium (Li), this study provides essential scientific supports and new insights for the provenance determination of emeralds.

Key words: Pakistan, Mingora, Emerald, chemical composition, trace element

CLC Number:

P575.3

ZHAO Hongxing, CAI Jingkun, XU Yingxin, LI Yuxuan, LIU Yingxin. Chemical Composition Analysis of Emeralds from the Mingora Region, Pakistan: Insights into Formation Mechanisms[J]. Geoscience, 2025, 39(01): 209-223.

Figures/Tables 17

References 27

[1]	余晓艳. 有色宝石学教程[M]. 2版. 北京: 地质出版社, 2016: 151-160.
[2]	GIULIANI G, GROAT L, MARSHALL D, et al. Emerald deposits: A review and enhanced classification[J]. Minerals, 2019, 9(2): 105-168.
[3]	王长秋, 张丽葵. 珠宝玉石学[M]. 北京: 地质出版社, 2017: 347-365.
[4]	AURISICCHIO C, FIORAVANTI G, GRUBESSI O, et al. Reappraisal of the crystal chemistry of beryl[J]. American Mineralogist, 1988, 73: 826-837.
[5]	郑育宇. 云南大丫口祖母绿的通道水谱学特征和产地溯源[D]. 北京: 中国地质大学(北京), 2020.
[6]	郭鸿舒, 余晓艳, 郑育宇. 祖母绿的致色元素和微量元素特征对产地的指示意义[C]. 国家珠宝玉石质量监督检验中心(National Gemstone Testing Center),中国珠宝玉石首饰行业协会, 2019: 147-150.
[7]	GROAT L A, GIULIANI G, MARSHALL D D, et al. Emerald deposits and occurrences: A review[J]. Ore Geology Reviews, 2008, 34(1/2): 87-112.
[8]	AURISICCHIO C, CONTE A M, MEDEGHINI L, et al. Major and trace element geochemistry of emerald from several deposits: Implications for genetic models and classification schemes[J]. Ore Geology Reviews, 2018, 94: 351-366.
[9]	ARIF M, HENRY D J, MOON C J. Host rock characteristics and source of chromium and beryllium for emerald mineralization in the ophiolitic rocks of the Indus Suture Zone in Swat, NW Pakistan[J]. Ore Geology Reviews, 2011, 39(1/2): 1-20.
[10]	GUO H S, YU X Y, ZHENG Y Y, et al. Inclusion and trace element characteristics of emeralds from swat valley, Pakistan[J]. Gems & Gemology, 2020, 56(3): 336-355.
[11]	曹素巧, 戴慧, 王朝文, 等. 巴基斯坦Swat矿区祖母绿的宝石学及谱学特征[J]. 光谱学与光谱分析, 2022, 42(11): 3533-3540.
[12]	KAZMI A H, LAWRENCE R D, ANWAR J, et al. Mingora emerald deposits (Pakistan); suture-associated gem mineralization[J]. Economic Geology, 1986, 81(8): 2022-2028.
[13]	刘建栋, 李五福, 王国良, 等. 北祁连东段柏木峡—门岗峡地区蛇绿岩的识别及其区域构造意义[J]. 现代地质, 2022, 36(1): 244-258.
[14]	郭鸿舒, 余晓艳, 韩浩宇. 巴基斯坦祖母绿的宝石学特征[J]. 宝石和宝石学杂志, 2018, 20(2): 1-10.
[15]	鲍珮瑾, 陈全莉, 吴燕菡, 等. 巴基斯坦斯瓦特山谷祖母绿的谱学特征研究[J]. 光谱学与光谱分析, 2023, 43(1): 213-219.
[16]	黎介, 刘宁强, 龚庆杰, 等. 基于微量元素岩性地球化学基因的构建与检验[J]. 现代地质, 2021, 35(5): 1459-1470.
[17]	张红雨, 杨立明, 苏犁, 等. LA-ICP-MS独居石的U(Th)-Pb年龄精确测定方法及地质意义探究[J]. 现代地质, 2023, 37(2): 443-462.
[18]	张文兰, 汤志敏, 胡欢, 等. 含超轻元素Be矿物的电子探针定量分析——测试条件的约束[J]. 岩石学报, 2022, 38(7): 1879-1889.
[19]	乔鑫. 非伟晶岩型祖母绿的矿物学特征及其成矿环境指示意义: 以哥伦比亚Eastern Cordillera和巴基斯坦Swat Valley祖母绿对比为例[D]. 上海: 同济大学, 2020.
[20]	MARSHALL D, DOWNES P, ELLIS S, et al. Pressure-temperature-fluid constraints for the Poona emerald deposits, western Australia: Fluid inclusion and stable isotope studies[J]. Minerals, 2016, 6(4): 130-152.
[21]	MARSHALL D, PARDIEU V, LOUGHREY L, et al. Conditions for emerald formation at Davdar, China: Fluid inclusion, trace element and stable isotope studies[J]. Mineralogical Magazine, 2012, 76(1): 213-226.
[22]	GAVRILENKO E V, DASHEVSKY D M. Peculiarities of emeralds of different genesis and their diagnostic meaning[J]. Zap Vser Mineral Obshchest, 1998, 127(1):47-57.
[23]	郭鸿舒. 阿富汗和巴基斯坦袓母绿的产地特征对比研究[D]. 北京: 中国地质大学(北京), 2021.
[24]	DE ARAÚJO NETO J F, DE BRITO BARRETO S, CARRINO T A, et al. Mineralogical and gemological characterization of emerald crystals from Paraná deposit, NE Brazil: A study of mineral chemistry, absorption and reflectance spectroscopy and thermal analysis[J]. Brazilian Journal of Geology, 2019, 49(3):1-15.
[25]	曹素巧, 戴慧, 于露, 等. 赞比亚祖母绿的宝石学特征及颜色成因[C]. 国家珠宝玉石质量监督检验中心(National Gemstone Testing Center),中国珠宝玉石首饰行业协会, 2019: 150-156.
[26]	徐錞. 云南麻栗坡高钒祖母绿的宝石矿物学特征研究[D]. 北京: 中国地质大学(北京), 2017.
[27]	华剑阳, 狄敬如. 巴西Bahia矿区祖母绿成分及谱学特征研究[J]. 宝石和宝石学杂志(中英文), 2022, 24(5): 109-117.

样本	ME-01	ME-02	ME-03	ME-04	ME-05	ME-06	ME-07	ME-08
颜色	浅绿色	浅绿色	浅绿色	绿色	绿色	深绿色	深绿色	深绿色
Ne	1.588	1.583	1.588	—	1.589	1.585	1.583	1.583
No	1.600	1.588	1.600	—	1.592	1.599	1.586	1.589
DR	0.002	0.005	0.002	—	0.003	0.014	0.003	0.006
SG	2.69	2.86	2.74	2.77	2.79	2.76	2.73	2.79

样本	ME-01	ME-02	ME-03	ME-04	ME-05	ME-06	ME-07	ME-08
颜色	浅绿色	浅绿色	浅绿色	绿色	绿色	深绿色	深绿色	深绿色
Ne	1.588	1.583	1.588	—	1.589	1.585	1.583	1.583
No	1.600	1.588	1.600	—	1.592	1.599	1.586	1.589
DR	0.002	0.005	0.002	—	0.003	0.014	0.003	0.006
SG	2.69	2.86	2.74	2.77	2.79	2.76	2.73	2.79

样品	Na₂O	K₂O		Cs₂O		MgO		CaO		TiO₂		P₂O₅		V₂O₃		Cr₂O₃		MnO		FeO		Al₂O₃		SiO₂		BeO	Total
ME-01	1.38	0.02		0.11		1.34		0.02		0.00		0.03		0.32		0.51		0.02		0.48		17.14		64.25		13.61	99.23
ME-02	1.44	0.07		0.15		1.34		0.06		0.00		0.01		0.31		0.50		0.00		0.65		16.74		64.66		12.76	98.68
ME-03	1.50	0.06		0.07		1.35		0.03		0.04		0.00		0.31		0.54		0.02		0.50		17.06		64.63		12.58	98.69
ME-04	1.37	0.04		0.06		1.33		0.03		0.00		0.01		0.33		0.57		0.00		0.04		17.46		65.18		13.20	99.61
ME-05	1.33	0.04		0.03		1.34		0.00		0.01		0.01		0.33		0.53		0.05		0.07		17.55		64.69		13.85	99.83
ME-06	1.34	0.02		0.06		1.33		0.00		0.01		0.01		0.38		0.52		0.00		0.07		17.44		65.64		12.83	99.66
ME-07	1.18	0.03		0.04		1.30		0.00		0.00		0.01		0.30		0.51		0.05		0.14		17.14		64.65		14.17	99.51
ME-08	1.35	0.03		0.08		1.33		0.00		0.00		0.00		0.37		0.52		0.01		0.56		17.05		65.22		13.14	99.65
平均值	1.36	0.04		0.07		1.33		0.02		0.01		0.01		0.33		0.52		0.02		0.31		17.20		64.87		13.27	99.36
样品	Na⁺		K⁺		Cs⁺		Mg²⁺		Ca²⁺		Ti⁴⁺		P⁵⁺		V³⁺		Cr³⁺		Mn²⁺		Fe²⁺		Al³⁺		Si⁴⁺			Be²⁺
ME-01	0.246		0.003		0.004		0.183		0.001		-		0.002		0.024		0.037		0.001		0.037		1.852		5.890			2.996
ME-02	0.258		0.008		0.006		0.185		0.006		-		0.001		0.023		0.037		-		0.050		1.825		5.980			2.834
ME-03	0.268		0.007		0.003		0.187		0.003		0.001		-		0.023		0.039		0.002		0.039		1.859		5.977			2.794
ME-04	0.242		0.004		0.002		0.181		0.003		-		0.001		0.024		0.041		0		0.003		1.876		5.942			2.891
ME-05	0.235		0.005		0.001		0.181		-		-		-		0.024		0.038		0.004		0.005		1.879		5.877			3.023
ME-06	0.237		0.003		0.002		0.181		-		-		0.001		0.028		0.037		-		0.005		1.874		5.985			2.811
ME-07	0.209		0.004		0.001		0.176		-		-		0.001		0.022		0.036		0.004		0.011		1.837		5.881			3.096
ME-08	0.240		0.004		0.003		0.181		-		-		-		0.027		0.037		-		0.043		1.836		5.959			2.884
平均值	0.242		0.005		0.003		0.182		0.002		-		0.001		0.024		0.038		0.001		0.024		1.855		5.936			2.916

样品	Na₂O	K₂O		Cs₂O		MgO		CaO		TiO₂		P₂O₅		V₂O₃		Cr₂O₃		MnO		FeO		Al₂O₃		SiO₂		BeO	Total
ME-01	1.38	0.02		0.11		1.34		0.02		0.00		0.03		0.32		0.51		0.02		0.48		17.14		64.25		13.61	99.23
ME-02	1.44	0.07		0.15		1.34		0.06		0.00		0.01		0.31		0.50		0.00		0.65		16.74		64.66		12.76	98.68
ME-03	1.50	0.06		0.07		1.35		0.03		0.04		0.00		0.31		0.54		0.02		0.50		17.06		64.63		12.58	98.69
ME-04	1.37	0.04		0.06		1.33		0.03		0.00		0.01		0.33		0.57		0.00		0.04		17.46		65.18		13.20	99.61
ME-05	1.33	0.04		0.03		1.34		0.00		0.01		0.01		0.33		0.53		0.05		0.07		17.55		64.69		13.85	99.83
ME-06	1.34	0.02		0.06		1.33		0.00		0.01		0.01		0.38		0.52		0.00		0.07		17.44		65.64		12.83	99.66
ME-07	1.18	0.03		0.04		1.30		0.00		0.00		0.01		0.30		0.51		0.05		0.14		17.14		64.65		14.17	99.51
ME-08	1.35	0.03		0.08		1.33		0.00		0.00		0.00		0.37		0.52		0.01		0.56		17.05		65.22		13.14	99.65
平均值	1.36	0.04		0.07		1.33		0.02		0.01		0.01		0.33		0.52		0.02		0.31		17.20		64.87		13.27	99.36
样品	Na⁺		K⁺		Cs⁺		Mg²⁺		Ca²⁺		Ti⁴⁺		P⁵⁺		V³⁺		Cr³⁺		Mn²⁺		Fe²⁺		Al³⁺		Si⁴⁺			Be²⁺
ME-01	0.246		0.003		0.004		0.183		0.001		-		0.002		0.024		0.037		0.001		0.037		1.852		5.890			2.996
ME-02	0.258		0.008		0.006		0.185		0.006		-		0.001		0.023		0.037		-		0.050		1.825		5.980			2.834
ME-03	0.268		0.007		0.003		0.187		0.003		0.001		-		0.023		0.039		0.002		0.039		1.859		5.977			2.794
ME-04	0.242		0.004		0.002		0.181		0.003		-		0.001		0.024		0.041		0		0.003		1.876		5.942			2.891
ME-05	0.235		0.005		0.001		0.181		-		-		-		0.024		0.038		0.004		0.005		1.879		5.877			3.023
ME-06	0.237		0.003		0.002		0.181		-		-		0.001		0.028		0.037		-		0.005		1.874		5.985			2.811
ME-07	0.209		0.004		0.001		0.176		-		-		0.001		0.022		0.036		0.004		0.011		1.837		5.881			3.096
ME-08	0.240		0.004		0.003		0.181		-		-		-		0.027		0.037		-		0.043		1.836		5.959			2.884
平均值	0.242		0.005		0.003		0.182		0.002		-		0.001		0.024		0.038		0.001		0.024		1.855		5.936			2.916

10^-6	ME-02	ME-03	ME-04	ME-05	ME-06	ME-07	ME-08	平均值
Li	406.092	412.057	668.929	208.514	321.818	257.364	344.145	374.132
Be	62681.734	55852.584	60428.915	53482.591	56613.642	57312.628	55799.814	57453.130
Na	18017.527	15564.226	18341.198	12751.093	14753.056	18582.547	15410.915	16202.924
K	-	-	61.356	44.589	-	102.015	44.129	36.013
Mg	19852.577	17187.883	20261.544	13842.919	16460.485	18361.850	16430.799	17485.437
Ca	701.771	243.028	-	329.012	514.024	349.524	313.578	350.134
Al	90790.700	83627.802	87548.355	76869.164	79560.711	78997.052	79798.997	82456.111
Si	267653.813	291009.260	274050.682	297681.156	288251.097	284641.439	290254.605	284791.722
Ti	44.797	-	809.506	7.424	46.745	53.712	43.088	143.610
Sc	1450.996	175.236	545.874	452.541	957.437	1433.636	804.146	831.409
V	783.112	243.856	684.005	130.738	650.461	713.564	447.744	521.926
Cr	5544.258	4978.415	6151.801	8059.077	13208.353	10250.583	11138.985	8475.925
Mn	9.874	8.027	2.459	0.468	5.292	5.360	4.395	5.125
Fe	8137.899	4172.877	5715.235	11632.990	3896.542	5569.400	4257.951	6197.556
Cs	198.909	140.905	665.849	238.524	75.717	104.661	93.495	216.866
Ni	14.703	15.699	34.041	9.549	5.041	9.816	8.459	13.901
Cu	0.293	-	0.326	0.295	2.181	0.346	-	0.492
Zn	1.445	4.196	5.010	2.752	3.425	2.836	3.380	3.292
Ga	9.956	7.046	8.344	3.633	8.388	7.444	8.319	7.590
Ge	-	-	1.289	0.258	1.139	2.785	-	0.782
Rb	10.334	12.346	16.295	5.303	11.527	14.016	10.427	11.464
Sn	0.831	0.684	3.984	2.960	3.738	2.042	2.890	2.447
Nb	0.105	0.161	0.117	0.053	0.071	0.109	0.116	0.105