Study On The Gemological And Mineralogical Characteristics Of Red Serpentine Jade In Liaoyang,liaoning Province

The red serpentine jade from Beigou Village,Jidong Manchu Town,Liaoyang County,Liaoyang City,Liaoning Province,is a newly discovered serpentine jade variety in recent years,and is characterized by a highly saturated red appearance.This paper systematically studies the red serpentine jade through modern instrument testing techniques such as conventional gemological testing,X-ray fluorescence spectroscopy and ultraviolet-visible light spectroscopy,polarized light microscope and scanning electron microscope,electron probe and X-ray powder crystal diffraction,infrared spectroscopy and laser Raman spectroscopy.The gem mineralogical characteristics of serpentine jade,a preliminary quality classification system is proposed,and its coloring mechanism and causes are discussed.The color of Liaoyang red serpentine jade covers light red,deep red,brilliant red,,maroon,etc.,with sub-glass to glass luster,slightly transparent to opaque.The refractive index is 1.56?1.57(point measurement).The relative density is 2.56?2.57,and the Mohs hardness is 4.8?5.0,and it is inert under ultraviolet fluorescence.The red serpentine jade has a cryptocrystalline structure,and the main mineral is antigorite,which contains a small amount of lizardite.Observed under the microscope,its structure mainly includes scale-like metamorphic structure,leaf-like metamorphic structure,felt-like structure and metasomatism Mesh structure and so on.Electron probe and X-ray powder crystal diffraction show that the secondary minerals are magnesite,pyrite,goethite,and magnetite,and the surrounding rocks include calcite,apatite,and pyrrhotite.Dry red serpentine jade contains a small amount of talc.The infrared spectrum characteristic peaks of red serpentine jade are 3674,1203,1076,994,642,622,562,452 cm^-1,and the common peaks in the Raman spectrum are 231,375,457,682,1047,3666,3697cm^-1,all indicate that it is mainly antigorite.Only a few specimens have the Raman characteristic peak of lizardite at 1092 cm^-1,and the intensity is weak,indicating that some samples contain less lizardite.This result is consistent with X-ray powder crystal diffraction analysis.Observed under the microscope,the red serpentine appears densely distributed red-brown minerals.Raman spectroscopy confirms that the red-brown mineral is hematite.In ultraviolet-visible spectroscopy analysis,the yellow serpentine has a peak near 430nm,which is the first-order characteristic peak of goethite.In addition to the characteristic peak of goethite,the red serpentine also has hematite near 570nm.The first-order characteristic peak indicates that the yellow serpentine is colored by goethite,and the red serpentine is colored by both goethite and hematite,and hematite plays a leading role.X-ray fluorescence spectroscopy further shows that the color of serpentine is closely related to iron.According to the color and pattern characteristics,the Liaoyang red serpentine jade is divided into four characteristic jade varieties:red,red plus green,dry red and‘waterweed'.The five aspects of color,texture,clarity,transparency,and craftsmanship are discussed and the preliminary quality grading system for Liaoyang red serpentine jade is proposed.The red serpentine jade is produced in the middle and lower parts of the third member of the Dashiqiao Formation in the Proterozoic Yuliaohe Group.The original rocks of the ore body are magnesite and dolomite marble.Serpentine and calcite were formed under hydrothermal metasomatism of dolomite in the early original rock,and the surrounding rock was serpentinized.Later,hydrothermal fluid containing Si O₂ metabolized the magnesite to form serpentine.Iron-containing chromogenic minerals are formed under the oxidizing environment after the formation of serpentine,and they are distributed in a disseminated manner or immersed along the cracks,which is a post-generation cause.