湖北十堰绿松石中杂质矿物自然硒的谱学研究

近期在湖北绿松石市场上出现一种带有肉眼可见的灰黑色异形杂质的绿松石，于此种绿松石的研究甚少。故选取来自湖北省十堰的一块该种绿松石原石，蓝色绿松石基底上布满形态各异、大小不一的灰黑色杂质，放大观察可见灰黑色杂质矿物呈金属光泽。对灰黑色杂质采用激光剥蚀电感耦合等离子体质谱仪进行原位微区微量元素测试、背散射电子图像物相观察、主量化学成分测试采用能谱仪进行半定量测试和电子探针定量测试以及显微激光拉曼光谱仪测试。灰黑色杂质矿物的LA-ICP-MS测试激光剥蚀束斑直径及深度的影响，测试结果表现为灰黑色杂质矿物和少量绿松石的混合物的化学成分含量，灰黑色杂质矿物处Se含量为95 927～221 394 μg·g-1明显高于蓝色基底绿松石中Se的含量（146～212 μg·g-1），灰黑色杂质处的测试结果中CuO含量为7.47%～9.28%、Al₂O₃含量为28.1%～35.7%，P₂O₅含量为30.1%～37.8%为少量绿松石混杂产生；背散射电子图像表明杂质矿物结晶颗粒细小，细小的杂质矿物与绿松石混杂在一起，他形的杂质矿物为多个晶体集合在一起形成的集合体，能谱测试结果表明杂质矿物主要含有Al，P，Fe，Cu和Se，电子探针主量化学成分定量测试结果表明杂质矿物主要含有Se，含量为79.34%～87.97%，此外，由于杂质矿物结晶颗粒细小，杂质矿物集合体中可见杂质矿物与绿松石混杂，因此化学成分定量测试结果中还呈现有绿松石中的Al，P，Fe，Cu和Al含量约为0.93%～4.13%，Cu含量约为1.30%～2.04%，P含量约为0.66%～2.40%，Fe含量约为0.31%；杂质矿物的显微激光拉曼光谱峰为位于144和235 cm-1处的尖锐拉曼谱峰，结合化学成分谱学测试结果可鉴别该杂质矿物主要为自然硒。硒矿物是绿松石中新发现的杂质矿物，绿松石中杂质矿物自然硒的发现可以为珠宝从业者鉴别绿松石提供有效的鉴定依据。

Spectral Study on Natural Seleniumin Turquoise From Shiyan,Hubei Province

Recently, there is a kind of turquoise with gray black impurity in turquoise market of Hubei Province, which has been studied very little. This study selected a turquoise protolith from Shiyan, Hubei Province. Blue basal turquoise is covered with dark gray inclusions of different shapes and sizes. The magnified observation shows that dark gray inclusions minerals have a metallic luster. The dark gray inclusions have been measured by in situ micro-element analysis with LA-ICP-MS, phase observation with back scattering electron image, principal quantitative chemical composition analysis using EDS for semi-quantitative testing and EPMA for quantitative testing, and micro-laser Raman spectrometer testing. The test results show that: The LA-ICP-MS results of dark gray inclusion minerals are influenced by the diameter and depth of the laser ablation spot. The results show that the chemical composition is a mixture of dark gray inclusion minerals and a small amount of turquoise. Se in dark gray inclusion minerals content is 95 927～221 394 μg·g-1, which is obviously higher than that in blue basal turquoise (146～212 μg·g-1). The content of CuO in dark gray inclusion minerals is 7.47%～9.28%, the content of Al₂O₃ is 28.1%～35.7%, and the content of P₂O₅ is 30.1%～37.8%. In dark gray inclusion minerals CuO content is 7.47%～9.28%, Al₂O₃ content is 28.1%～35.7%, P₂O₅ content is 30.1%～37.8%, which are caused by a small amount of turquoise mixture. Backscatter electron images show that the crystalline particles of inclusion minerals are fine and mix with turquoise, and heteromorphic inclusion minerals are aggregates formed by multiple crystals. The results of EDS show that inclusion minerals mainly contain Al, P, Fe, Cu and Se. Quantitative analysis of principal chemical components by EPMA shows that inclusion minerals mainly contain Se, with a content of 79.34%～87.97%. In addition, due to the fine crystalline particles of inclusion minerals, in the aggregates, inclusion minerals are mixed with turquoise. Therefore, Al, P, Fe and Cu of turquoise can also be found in the quantitative determination of chemical composition. Al content is about 0.93%～4.13%, Cu content is about 1.30%～2.04%, P content is about 0.66%～2.40%, Fe content is about 0.31%. The micro-laser Raman spectra of inclusion minerals are sharp peaks at 144 and 235 cm-1. The inclusion mineral is mainly natural selenium, according to the results of chemical composition spectroscopy. Selenium minerals is a newly discovered inclusion mineral in turquoise. The discovery of natural selenium, an inclusion mineral in turquoise, can provide an effective basis for the identification of turquoise by jewelry practitioners.