Gemmological Characteristic Comparison of Aquamarines from Four Different Origins
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摘要: 采用常规宝石学测试、电子探针、电感耦合等离子体质谱仪、红外光谱仪、拉曼光谱仪等现代测试技术方法对来自巴基斯坦、坦桑尼亚、越南及纳米比亚4个不同产地的11块海蓝宝石样品的基本性质、化学成分及谱学特征等进行对比分析研究。常规测试结果发现，巴基斯坦海蓝宝石的折射率及相对密度较高，越南海蓝宝石具有鲜艳的蓝色；电子探针测试结果表明，巴基斯坦海蓝宝石中碱金属Na质量分数明显高于其他产地的海蓝宝石；电感耦合等离子体质谱测试结果表明，各样品Li、Mn、Zn、Rb、Cs等质量分数较高，4个产地的海蓝宝石在微量元素质量分数上差别较大，巴基斯坦海蓝宝石含有较高的Mn、Zn，坦桑尼亚海蓝宝石含有较高质量分数的Li、Cs，纳米比亚海蓝宝石则含有最高质量分数的Cs；红外光谱显示，各产地海蓝宝石在1 200~400 cm-1谱峰相对一致，为绿柱石结构振动峰，其中巴基斯坦海蓝宝石在这一范围内的谱峰较其他产地海蓝宝石谱峰有所偏移，近红外8 000~4 000 cm-1内发现4个产地海蓝宝石在不同方向上水的吸收存在明显差别，垂直c轴方向才会出现6 816 cm-1的吸收峰；拉曼光谱显示仅巴基斯坦海蓝宝存在明显的I型水（3 608 cm-1）与Ⅱ型水（3 598 cm-1）的谱峰，另外3个产地则仅见明显的I型水（3 608 cm-1）吸收峰。Abstract: Eleven aquamarine samples from four different origins including Pakistan, Tanzania, Vietnam and Namibia were tested in this paper. Conventional gemmological tests, electron microprobe, ICP-MS, infrared spectroscopy and Raman spectroscopy were studied to analyze differences of basic characteristics, chemical constituents as well as spectral features of aquamarines from four different origins. Conventional gemmological tests revealed samples from Pakistan are of comparatively higher refractive indexes and specific gravities, and the colour of Vietnam aquamarine samples is deeper than others. High content of alkalis-Na was measured in Pakistan aquamarine and the Fe content in Vietnam aquamarine is the highest among all the samples. The results of ICP-MS showed obvious amount of Li, Mn, Zn, Rb and Cs, which were different among samples from different origins, including higher content of Mn, Zn in Pakistan aquamarine and the highest content of Cs in Namibia samples. The infrared spectra displayed consistent peaks among 1 200-400 cm-1 of all the samples except spectra shifting of Pakistani aquamarine. Different absorption peaks of water were also found in different directions through near-infrared spectra. Raman spectra indicated coexistence of both type I water (3 608 cm-1) and type Ⅱ water (3 598 cm-1) in Pakistani aquamarine.
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Keywords:
- aquamarine /
- different origin /
- chemical characteristic /
- infrared spectrum /
- Raman spectrum
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