Gemological Characteristics Of Serpentine Jade "Jinxiang Jade" In Hanzhong,Shaanxi Province

Based on field investigation and laboratory analysis,Utilizing the modern testing techniques such as polarizing microscopes,scanning electron microscopes,electron probe analysis,X-ray powder diffraction,infrared spectroscopy,laser Raman spectroscopy,UV-Vis spectrophotometer,this thesis systematically studied the geology,basic gemological characteristics,mineralogical characteristics and spectral characteristics of the serpentine jade“Jinxiang jade”in Hanzhong,Shaanxi Province,leading to a quality grading evaluation system for quality evaluation of gold and jade.“Jinxiang jade”is waxy to oily,sub-transparent to opaque.Using the spot measurement method,it has a refractive index of 1.56?1.57,a density of 2.45?2.54,a Mohs hardness of 3?4,a strong absorption band of 460 nm,and is inert under both long and short waves.The main constituent mineral of“Jinxiang jade”is lizardite,and the secondary minerals are calcite,diopside and magnetite.Its structure types mainly include:microfibrillar crystal structure,leaf-like crystal structure,columnar crystal structure,scaly crystal structure and etc.Based on differential thermal-thermogravimetric analysis,it is shown that the serpentine structure is stable when the temperature is lower than 500?;When the temperature rises,the dehydrogenation begins;When the temperature reaches at 600?800?,the structure is destroyed and the structural water is dehydrated;at about 825?,the sample is completely dehydroxylated,and the structure is completely destroyed,leading to a new phase.The infrared characteristic peak of"Jinxiang jade"is 441cm^-1,560cm^-1,610cm^-1,960cm^-1,1076cm^-1,3647cm^-1,3665cm^-1,3689cm^-1,3703cm^-1,and the characteristic absorption peak of Raman spectra is 125cm^-1,200cm^-1,225cm^-1,343cm^-1,380cm^-1,618cm^-1,685cm^-1,1098cm^-1,3649cm^-1,3669cm^-1,3680cm^-1,3680cm^-1,3689cm^-1,3698cm^-1,3703cm^-1.There are serpentines formed in different stages in“Jinxiang Jade”.The chrysotile is arranged in the parallel direction,and they are interspersed in the early serpentines like a fine vein.By infrared spectroscopy and Raman spectroscopy,we can quickly distinguish the serpentine subspecies of the different structures of lizardite and chrysotile in“Jinxiang jade”.Ultraviolet-visible spectroscopy reveals that the the chromogenic principle is due to the d-d electronic transition of Fe³⁺ ions and the charge transfer from Fe²⁺ to Fe³⁺,The color of"Jinxiang Jade"is related to the content of TFeO.The quality evaluation of“Jinxiang jade”has been carried out in five aspects:color,transparency,texture,clarity,blockness and craftsmanship.Based on that,the quality classification of the“Jinxiang Jade”is preliminarily determined,and its corresponding history cultural value is discussed in depth.Finally,the associated development prospects are forecasted.