一种“冻地”鸡血石相似玉石的宝石学及谱学研究

研究对象是一种与“冻地”鸡血石外观高度相似的玉石，该种玉石半透明“地”中含有橙红色矿物。利用X射线粉晶衍射仪、扫描电子显微镜、红外光谱仪、拉曼光谱仪对该玉石的宝石学及谱学特征进行研究。结果表明：该玉石“地”的主要组成矿物为有序度较高的地开石、橙红色矿物为雄黄；地开石晶体为自形假六边形片状，约15～20 μm，厚2～4 μm，粒径均一且形态一致，集合体在三维空间无序排列；部分样品“地”中含有少量黄铁矿、萤石、石英、方解石等矿物。“地”的红外光谱指纹区具有高岭石族矿物的主要特征峰，分别位于430，470，540，698，755，795，913，937，1 002，1 034和1 118 cm-1；官能团区以3 622，3 653和3 706 cm-1处的吸收峰为特征，3 622 cm-1吸收峰由内羟基OH1的面内伸缩振动引起，3 653 cm-1归属于内表面羟基OH2和OH4的同相伸缩振动；从高频峰到低频峰强度依次增大，且内表面羟基OH3伸缩振动引起的吸收峰位于3 706 cm-1，表明“地”为有序地开石；拉曼光谱测试表明“血”为雄黄，具有186，222，235，273，346和355 cm-1的特征拉曼位移，其中186和222 cm-1归属于S-As-S的弯曲振动，346和355 cm-1由As-S的伸缩振动引起；拉曼光谱同样可用于“地”的矿物组成研究，低频区具有133，241，266，336，436，463，747，792和914 cm-1的高岭石族矿物的特征位移，高频区可见三个与红外光谱相似的阶梯状谱峰，3 624 cm-1强度最大，归属于OH1的伸缩振动，次强峰3 646 cm-1由OH2和OH4的同相伸缩振动引起，归属于OH3的伸缩振动峰强度最小且位于3 706 cm-1，高频区拉曼位移特点指示“地”为地开石，且有序度较高，与红外光谱测试结论一致。尽管研究样品的“地”与“冻地”鸡血石的主要组成矿物相同，为地开石，且具有外观细腻、温润等特点，但其“血”并非辰砂而是雄黄，所以不应与鸡血石混淆，其正确的珠宝玉石名称应为“粘土矿物质玉”。

Gemmological and Spectroscopic Studies of the Jade Looked Like “Frozen Matrix” Chicken-Blood Stone

The object of this study is a kind of jade that is similar to “Frozen Matrix” Chicken-Blood Stone. There are orange-red minerals in its semitransparent “Matrix”. Using X-ray powder diffraction spectrometer (XRD), scanning electron microscopy (SEM), infrared spectrometer (IR), and laser Raman spectroscopy(LRM) to analyze the gemological and spectroscopic characteristics of the jade. The results are as follow: the “Matrix” of the jade is mainly composed of ordered dickite, and the part in orange-red is realgar. The crystals are self-shaped hexagonal-plate. The length diameter of dickite is 15～20 μm, and the thickness is 2～4 μm. There is no obvious directionality in the aggregation of dickite. Some samples contain minerals like pyrite, fluorite, quartz, and calcite. The fingerprint region of FTIR spectra of “Matrix” has the main characteristic peaks of kaolinite minerals, which are located at 430, 470, 540, 698, 755, 795, 913, 937, 1 002, 1 034 and 1 118 cm-1; the functional areais characterized by the absorption peak at 3 622, 3 652 and 3 706 cm-1. The absorption peak of 3 622 cm-1 is caused by the in-plane stretching vibration of the inner hydroxyl OH1, and 3 653 cm-1 is attributed to the in-phase stretching vibration of the inner surface hydroxyl OH2 and OH4. The high-frequency peak is weak, while the low-frequency peak is strong. The absorption peak caused by the stretching vibration of hydroxyl OH3 on the inner surface is located at 3 706 cm-1. The result of FTIR spectra shows that the “Matrix” is a highly ordered dickite. Raman spectra showed that the “Blood” of the jade is realgar with the characteristic Raman shift at 186, 222, 235, 273, 346 and 355 cm-1. Among them, 186 and 222 cm-1 is attributed to the bending vibration of S-As-S, while the stretching vibration of As-S causes 346 and 355 cm-1. The Raman spectra of “Matrix” shows that the low-frequency region has the characteristic shift of kaolinite minerals of 133, 241, 266, 336, 436, 463, 747, 792 and 914 cm-1. In the high-frequency region, three stepped spectral peaks similar to the infrared spectra can be seen. The maximum strength of 3 624 cm-1 is attributed to the stretching vibration of OH1. The sub-strong peak 3 646 cm-1 is caused by the in-phase stretching vibration of OH2 and OH4. The peak strength of stretching vibration attributed to OH3 is the lowest and located at 3 706 cm-1. The characteristics of Raman shift in the high-frequency region indicate that“Matrix” is highly ordered dickite, which is consistent with the conclusion of FTIR spectra. Although the “Matrix” of the jade share the same composition of “Frozen Matrix” Chicken-blood stone, its’ “blood” is not cinnabar but realgar. Therefore, this study’s object is not Chicken-blood stone, and it should be called “Clay minerals jade”.