Gemmological and Spectral Characteristics of Amber from Ethiopia
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摘要: 本文收集了产自埃塞俄比亚的绿黄色琥珀原石样品，对其宝石学特征和谱学特征进行了测试分析。测试结果表明，埃塞俄比亚琥珀的折射率为1.54~1.55（点测），密度为1.022~1.058 g/cm3, 长波紫外线下琥珀基体呈强蓝白色荧光，褐红色氧化层呈中等强度绿色荧光, 显微镜下可见琥珀中具有水胆、气泡、黑色团絮物、“翅果”状包体等内含物，以及由树脂多期次堆覆导致的层状或波状纹理; 红外光谱和拉曼光谱均呈现琥珀典型的脂肪族基团和氧化基团的组合，同时也含有少量不饱和组分，振动谱带峰位特征与豆科植物的石化树脂较为相似; 拉曼光谱中指示琥珀成熟度的I1 650 cm-1/1 442 cm-1值落在0.69~0.75范围，与多米尼加琥珀接近; 绿黄色埃塞俄比亚琥珀的紫外-可见-近红外光谱具以630 nm为中心的平缓吸收宽带，是其绿色调的主要成因。
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关键词:
- 琥珀 /
- 红外光谱 /
- 拉曼光谱 /
- 紫外-可见-近红外光谱
Abstract: Specimens of greenish-yellow amber from Ethiopia were collected and tested for their gemmological and spectroscopic characteristics. The test results showed that amber from Ethiopia has a refractive index of 1.54-1.55(point measurement) and a density of 1.022~1.058 g/cm3. Wave-like anomalous extinction was visible under crossed polarizer. The amber matrix showed a strong blue fluorescence under long-wave ultraviolet light, while after a long period of natural oxidation in the air, the fluorescence turned to blue-green with a slightly lower intensity.The maroon oxidized surface showed a green fluorescence in medium intensity. In the transitional zone from the oxidized surface to the inner matrix, the body colour showed gradient transition from brownish red to yellow, however the long-wave ultraviolet fluorescence image showed a clear boundary of the transitional zone. Observed by microscope, the amber contained inclusions such as gas-liquid two-phase inclusions, gas bubbles, black flocs, "samara-like" inclusions, and lamellar or wave-like patterns caused by multiple stages of resin accumulation. Both IR and Raman spectra showed a combination of aliphatic and C=O functional groups typical of amber, with small amount of unsaturated components.The vibration spectral characteristics were similar to those of fossilized resins from Leguminosae plants. The value of I1 650 cm-1/1 442 cm-1 in the Raman spectra indicating the maturity of amber fell in the range of 0.69-0.75, which was rather close to that of amber from Dominica. The UV-Vis-NIR spectra of greenish-yellow amber from Ethiopia showed a broad band centered at 630 nm, causing the unique greenish tint of its body colour.-
Keywords:
- amber /
- infrared spectrum /
- Raman spectrum /
- UV-Vis-NIR spectrum
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图 1 危地马拉绿色翡翠(“玛雅绿”)代表性样品Figure 1. Representative Feicui samples from Guatemala ("Maya green")![]()
图 2 代表性翡翠样品的红外反射光谱Figure 2. Infrared reflection spectra of representative green Feicui samples -
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图 1 埃塞俄比亚琥珀的主要开采露头[1]
(a)位于非洲大陆东部的埃塞俄比亚联邦民主共和国; (b, c)棕黄色区域为埃塞俄比亚中部的NorthShewa地区, 该地区横跨两州, 东半部属Amhara州, 西半部属Oromiya州棕黄色区域中的黑色曲线为两州州界。首都亚的斯亚贝巴(AddisAbaba)位于NorthShewa南端, 即图中黑色卵形区域; (d)图 1c中黑框区域放大, 比例尺=20 km, 数字1~4为目前已知的4处琥珀开采露头，其中1为AlemKetema; 2为Jema; 3为Woll; 4为Fiche镇附近露头, 详细地点未知
Figure 1. Geographical maps showing the location of amber outcrops in Ethiopia[1]
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图 3 埃塞俄比亚琥珀样品EA-2与EA-4的异常消光现象
(a)白光下的图像；(b)正交偏光图像
Figure 3. Anomalous extinction of the amber samples EA-2 and EA-4 from Ethiopia
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图 4 埃塞俄比亚琥珀样品的长波紫外荧光特征
(a)样品EA-1在白光下图像，视域5.26 mm；(b)样品EA-1长波紫外荧光图像，过渡带与内部基体间可见清晰边界，视域5.26 mm；(c)样品EA-2新鲜断面(上)与自然氧化断面(下)的荧光对比，视域24.81 mm
Figure 4. Long-wave ultraviolet fluorescence images of the amber samples from Ethiopia
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图 5 埃塞俄比亚琥珀样品EA-3的围岩及相关内含物特征
(a)样品表面附着的围岩物质，可见磨圆石英颗粒、灰白色胶结物和浅黄色土状物，视域5.92 mm；(b)图 5a的原位长波紫外荧光图像，视域5.92 mm；(c)样品中包裹的同时期沉积物，其间散布有白色丝状纤维。1为浅黄色土状物；2为褐色泥土，被包裹在琥珀内部时表面呈灰白色；3为黑褐色团状物，可见似植物根茎组织残余物夹杂其中，推测为腐殖质。视域6.03 mm；(d)在样品断面处出露表面的内含物，箭头指向处为磨圆石英颗粒，其右下方为浅黄色土状物，有定向排列的纤维夹杂其中，视域2.99 mm
Figure 5. Host rock and associated sediment inclusions of amber sampe EA-3 from Ethiopia
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图 6 埃塞俄比亚琥珀样品的显微内含物
(a)样品EA-6中的异形气泡和黑色团絮物，视域2.77 mm；(b)样品EA-4中的水胆包体，视域1.79 mm；(c)样品EA-4中的“翅果”状包体，视域4.02 mm
Figure 6. Micro inclusions of the amber samples from Ethiopia
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图 7 埃塞俄比亚琥珀样品EA-6中的树脂多期次堆覆构造
(a)散射照明图像，视域5.65 mm；(b)长波紫外荧光图像，视域5.65 mm
Figure 7. Multi-stage stacking structure of resin in amber sample EA-6 from Ethiopia
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图 8 埃塞俄比亚琥珀样品的红外吸收光谱(反射法，经K-K变换)
Figure 8. Infrared absorption spectra of the amber samples from Ethiopia (reflection method with K-K transformed)
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图 9 埃塞俄比亚琥珀样品EA-2自然氧化断面和新鲜断面的红外光谱对比(反射法，经K-K变换，峰位标注基于样品EA-2新鲜断面光谱)
Figure 9. Comparison of infrared spectra of naturally oxidized section and fresh section of amber sample EA-2 from Ethiopia(reflection method with K-K transformed, peak annotations based on the spectrum of sample EA-2 Fresh)
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图 11 绿黄色埃塞俄比亚琥珀的紫外-可见-近红外吸收光谱(内反射法)
Figure 11. UV-Vis-NIR spectra of the greenish yellow amber samples from Ethiopia(internal reflection method)
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图 12 埃塞俄比亚琥珀与相似品种的红外光谱对比(反射法，经K-K变换，峰位标注基于样品EA-2光谱)
Figure 12. Comparison of infrared spectra of amber sample from Ethiopia with similar natural resin varieties (reflection method with K-K transformed, peak annotations based on the spectrum of sample EA-2)
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图 13 埃塞俄比亚琥珀与相似品种的拉曼光谱对比(峰位标注基于样品EA-2光谱)
Figure 13. Comparison of Raman spectra of amber sample from Ethiopia with similar natural resin varieties (peak annotations based on the spectrum of sample EA-2)
表 1 埃塞俄比亚琥珀样品的常规宝石学测试结果
Table 1 Conventional test results of the amber samples from Ethiopia
测试项目 EA-1 EA-2 EA-3 EA-4 EA-5 EA-7 折射率(点测) 1.54 1.54 1.55 1.55 1.54 1.55 密度/g·cm-3 1.058 1.058 1.022 1.057 1.053 1.057 
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[1] Bouju V, Feldberg K, Kaasalainen U, et al. Mioceneamber from Ethiopia: A new source of fossil cryptogams[J]. Journal of Systematics and Evolution, 2022, 60(4): 23.
[2] Bouju V, Perrichot V. A review of amber and copal occurrences in Africa and their paleontological significance[J]. Bulletin de la Societe Geologique de France, 2020, 191(17).
[3] Coty D, Lebon M, Nel A, et al. When phylogeny meets geology and chemistry: Doubts on the dating of Ethiopian amber[J]. Annales de la Societe Entomologique de France, 2016, 52(3): 161-166. doi: 10.1080/00379271.2016.1230477
[4] 王雅玫, 李妍, 石兆彤, 等. 琥珀的宝石学研究综述[J]. 宝石和宝石学杂志(中英文), 2022, 24(5): 55-68. Wang Y M, Li Y, Shi Z T, et al. A review for the gemmological research on amber[J]. Journal of Gems & Gemmology, 2022, 24(5): 55-68. (in Chinese)
[5] 涂彩, 汤红云, 招博文, 等. 缅甸琥珀及半石化树脂的谱学特征[J]. 上海计量测试, 2018, 45(5): 5. Tu C, Tang H Y, Zhao B W, et al. Spectrum characterization of Burma amber and subfossil resin[J]. Shanghai Measurement and Testing, 2018, 45(5): 5. (in Chinese)
[6] 邢莹莹, 亓利剑, 麦义城, 等. 不同产地琥珀FTIR和13C NMR谱学表征及意义[J]. 宝石和宝石学杂志(中英文), 2015, 17(2): 9. https://www.cnki.com.cn/Article/CJFDTOTAL-BSHB201502003.htm Xing Y Y, Qi L J, Mai Y C, et al. FTIR and 13CNMR spectrum characterization and significance of amber from different origins[J]. Journal of Gems & Gemmology, 2015, 17(2): 9. (in Chinese) https://www.cnki.com.cn/Article/CJFDTOTAL-BSHB201502003.htm
[7] 杨一萍, 王雅玫. 琥珀与柯巴树脂的有机成分及其谱学特征综述[J]. 宝石和宝石学杂志(中英文), 2010, 12(1): 7. https://www.cnki.com.cn/Article/CJFDTOTAL-BSHB201001006.htm Yang Y P, Wang Y M. Summary on organic components and relevant spectral characteristics of amber and copal[J]. Journal of Gems & Gemmology, 2010, 12(1): 7. (in Chinese) https://www.cnki.com.cn/Article/CJFDTOTAL-BSHB201001006.htm
[8] 吴文杰, 王雅玫. 琥珀的激光拉曼光谱特征研究[J]. 宝石和宝石学杂志(中英文), 2014, 16(1): 6. https://www.cnki.com.cn/Article/CJFDTOTAL-BSHB201401008.htm Wu W J, Wang Y M. Study on Raman spectrum characteristics of amber[J]. Journal of Gems & Gemmology, 2014, 16(1): 6. (in Chinese) https://www.cnki.com.cn/Article/CJFDTOTAL-BSHB201401008.htm
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