The Gemological And Mineralogical Characteristics Of Serpentine Jade "Dongshi" In Liaoyang,Liaoning Province

Beigou Village,Manchu Township,Jidong Valley,Liaoyang City,Liaoning Province,is a new source of serpentine jade in China.A type of serpentine jade produced there is called“Dongshi”by locals.Based on field geological survey and indoor experiment analysis,by hand specimen observation and relative density,refractive index,hardness,basic gemological properties,ultraviolet fluorescence test using polarizing microscope and secondary electron phase observation and electron microprobe analysis,X-ray powder diffraction analysis to determine its mineral composition and structure characteristics,The mineralogical characteristics and genetic information of the“Dongshi”of serpentine jade in the new producing area of China were obtained by the systematic study of the spectral characteristics of infrared spectroscopy,Raman spectroscopy and X-ray fluorescence spectroscopy.The main color of“Dongshi”is bluish white,light yellowish green and yellowish white,with the outer skin of maroon,yellow and yellowish green.It is vitreous luster to grease luster,translucent to micro-transparent.The refractive index is 1.54?1.56(point measurement method),the relative density is 2.44?2.62,and the Mohs hardness is 3.61?4.78.The physical properties of“Dongshi”are mainly related to its composition and structure.Under normal conditions,“Dongshi”is inert in ultraviolet fluorescence under short and long waves.The main mineral of“Dongshi”is serpentine(antigorite),and the secondary minerals are magnesite,talc,limonite and so on.Most of the“Dongshi”show lepidoblastic texture with pilotaxitic texture and local metasomatic relict texture.The chemical composition analysis of the serpentines shows that the serpentines are rich in Si,Mg,Fe and Al.The white point mineral in“Dongshi”is magnesite.The infrared spectrum characteristic absorption peaks of“Dongshi”are 400cm^-1,437cm^-1,564cm^-1,623cm^-1,979cm^-1,1078cm^-1,3617cm^-1,3677cm^-1and 3697cm^-1,showing typical absorption peaks of antigorite.The Raman spectra of antigorite in“Dongshi”mainly include a series of characteristic absorption spectra located at 229cm^-1,375cm^-1,527cm^-1,633cm^-1,681cm^-1,1045cm^-1,3637cm^-1,3665cm^-1and 3697cm^-1.Raman spectral characteristic peaks of magnesite are located at 212cm^-1,330cm^-1,740cm^-1,1095cm^-1,1448cm^-1and 1764cm^-1.Microarea X-ray fluorescence spectrum analysis shows that the black dendritic inclusions in“Dongshi”are silicate minerals rich in Mn,and a large number of Fe elements are enriched in the maroon position at the internal cracks and veins.In addition,Si and Mg elements are evenly distributed in the“Dongshi”.The original rocks of“Dongshi”are dolomite marble and magnesite,and the ore-bearing strata provide the Mg source for the formation of“Dongshi”.The Si-rich mesothermal metamorphic hydrothermal metamorphism metasomatism of dolomite marble and magnesite caused Mg to combine with the Si and H₂O in the hydrothermal metamorphism and form the primary deposit of“Dongshi”in the favorable position.After that,the primary ore near the surface is weathered,and the surface water penetrates and oxidizes along the jade fissures to produce limonite,which presents a layer of reddish-brown skin with different shades of depth,and finally forms“Dongshi”.