The Spectra and Mineralogy Study of Changbai Colored Jade
CAO Miao-cong1, CHEN Tao2*, QIN Hong-yu1, LIU Rui1, ZHANG Hai-jun3, GU Zhong-yuan1
1. Changchun Institute of Technology, Changchun 130021, China
2. Gemmological Instiute, China University of Geosciences, Wuhan 430074, China
3. Wuhan Center, China Geological Survey, Wuhan 430205, China
Abstract：Changbai jade is a high-quality seal stone produced in Changbai County, Jilin Province. It has rich reserves and high economic value. X-ray diffractometer, infrared spectrum, Raman spectrum, scanning electron microscope and EDS were used to study the varieties of Changbai coloredjade which is one variety of Changbai jade. XRD test results show that in addition to dickite type, Changbaicolord jade also has kaolinite, nacrite-dickite, forsterite-serpentine, brucite and talc type. The impurity components include pyrite, hematite, brucite, serpentine, calcite and dolomite; Through the full peak fitting (WPF) and Rietveld fine fitting calculation, it is found that forsterite accounts for 49%, serpentine accounts for 23%, dolomite accounts for 15%, brucite accounts for 13% in sample CB9, and the main mineral composition in other samples accounts for more than 90%. Combined with the analysis of gemological characteristics: the color of the kaolinite group is mainly gray, dark gray, red, light yellow and brown, with a hardness of 2~3, fine texture and good knife feeling; Forsterite serpentine is green, and brucite is yellow green and light gray; Except for the Changbai coloredjade of kaolinite group, the hardness of other types is low, ranging from 1 to 2, with poor toughness and poor carving knife feeling. Infrared spectrum analysis verifies the XRD test results, and distinguishes the polytypics of kaolinite in Changbai colord jade. It is considered that CB1 is disordered kaolinite, CB15 is nacrite, CB6, CB11 and CB14 are orderly dickite, and the degree of order is CB14>CB6>CB11. Combined with the characteristics of Raman spectroscopy and EDS element analysis, it is inferred that the red of Changbai jade is related to cryptocrystalline hematite, the black is related to large-scale crystalline hematite, and the gray, gray black and black are also related to the existence of amorphous carbon. The serpentine leads to the green and yellow green of Changbai colord jade; The existence of brucite increases the transparency of Changbai jade, and fine and dense pyrite reduces the transparency of Changbai jade. The analysis of Microscopic morphology is considered that the dickitetype is a flake, heteromorphic, semi automorphic, and locally visible, the flakes are closely stacked, and the crystalline particles are large, ranging from a few microns to more than ten microns; the Kaolinite type is flaky, uneven in size and disorderly distributed in three-dimensional space; Brucite type is in the form of large scale lamination, sharp edges, flake crystals up to tens of microns, and the lamella is very thin; Serpentine is fibrous and combined with flake brucite; Forsterites are in dense, massive structure.
