中国南疆和田玉戈壁料的宝石学特征

Gemmological Characteristic of Gobi Nephrite from Southern Xinjiang, China

和田玉戈壁料是按和田玉产状分类的一种重要品种,是原生矿经风化剥落搬运至戈壁滩,暴露于地表经历长期风化吹蚀形成的,表面凹凸不平,油脂光泽极强,产自新疆南疆地区。选取了36件产自南疆和田玉戈壁料样品为研究对象,采用常规宝石学测试、激光剥蚀电感耦合等离子体质谱仪、红外光谱,拉曼光谱等现代测试手段对其宝石矿物学及谱学特征作系统研究。结果表明,和田玉戈壁料样品的主要化学成分为SiO2、MgO及CaO,其中SiO2的质量分数为57.6%—59.6%,MgO的质量分数为23.4%~25.2%,CaO的质量分数为13.9%~15.1%,与标准的透闪石质量分数一致;超景深显微镜观察结果显示,和田玉戈壁料表面具独特的凹凸不平形貌,高低起伏大,风蚀凹坑与裂隙中有杂质矿物沉积,暗色杂质矿物可能为含锰钡化合物;红外光谱显示了位于900~1150cm-1和400~760cm-1范围内的吸收谱带,拉曼光谱主要出现在3672,1061,1030,932,675,530,417,395,372,225,179,123cm-1处,与和田玉山料的一致。

Gobi nephrite is a significant type of nephrite. After weathering, exfoliation and transportation processing, the original deposit mines were carried to the Gobi Desert, and the surface of Gobi nephrite was uneven with intense greasy luster through long-term weathering. The major producing regions are in southern Xinjiang.36 pieces of Gobi nephrite samples from southern Xinjiang were chosen as research objects. Conventional testing, LA-ICP-MS, FTIR spectrum and Raman spectrum were applied to obtain gemmology, mineralogy and spectroscope characteristics.From the relative test results, LA-ICP-MS tests showed that the main chemical compositions of Gobi nephrite were SiO 2 ,MgO and CaO. The content of SiO 2 was 57.6%-59.6%, MgO was 23.4%-25.2% and CaO was 13.9%-15.1%,which were basically consistent with the theoretical content of tremolite. The microscopic characteristics on the surface of Gobi nephrite observed by the high resolution digital image technique showed that the surface of Gobi nephrite presented a distinctively uneven and undulating appearance.Impurity minerals were often deposited in weathering pits and fissures. Infrared spectra displayed the typical tremolite absorption between 900-1 150 cm -1 and 400- 760 cm -1 . Raman spectra demonstrated peaks at 3 672,1 061,1 030,932,675,530,417,395, 372, 225,179,123 cm -1 , which is in accordance with mountainous nephrite.