The Study On Gemstone Mineralogical Characteristics Of Xiuyu Of Different Color Systems In Liaoning Province

Xiuyu,produced in Xiuyan County,Anshan City,Liaoning Province,is a popular traditional jade.There are still some deficiencies in the previous studies on jade,and the identification and evaluation system is not perfect.In this paper,different colors of jade are selected as the research object,and the similarities and differences of Liaoning jade of various color series are systematically sorted out by means of polarizing microscope,X powder diffraction analysis,electron probe analysis and various spectral analysis,so as to find out the internal relationship between the color of jade and its mineral composition and chemical composition.The main research results are as follows:The gemological characteristics of jade with different colors are different.According to the appearance characteristics,it is divided into seven color systems:white,yellow-green,light green,green,dark green,red and black.The refractive index of the jade samples with different colors has little change,all of which are 1.54-1.56.The higher hardness and density of the white sample is due to the presence of tremolite inside,the higher density of the green sample is affected by the pyrite inside,and the higher hardness and density of the dark green sample is closely related to the density of the tremolite or the structure inside.The mineral composition and structural characteristics of jade with different colors are different.The main minerals are antigorite and a small amount of chrysotile is found in the green samples.In terms of minor minerals,tremolite,calcite and apatite are found in both white and yellow-green samples.The light green samples contain dolomite;The green samples contain dolomite,apatite and pyrite.The dark green samples contain tremolite,calcite and pyrrhotite.The red samples contain magnesite,hematite and apatite.The black samples contain pyrrhotite,siderite,sideronite and so on.In the aspect of structure,the main structure is fibrous morphic structure.In addition,scales and petal-like crystal structures were found in the yellow-green samples.In the green samples,there was a blade-like crystal structure.Dark green samples are delicate and felt-like in texture.The black samples showed fine mesh veins.The chemical composition of jade with different colors is different.According to the electron probe analysis,the main chemical components of serpentine in different color jade samples are Si O₂and Mg O.The content of Si O₂is 43.941%～45.553%,which is higher than the theoretical value,and the content of Mg O is 38.423%～41.817%,which is lower than the theoretical value.The contents of K₂O,Ti O₂,Na₂O and Ca O are all low and have little difference.However,the content of Fe O and Al₂O₃is higher and the change is obvious.Among them,the Fe O content in green samples is the highest,which is related to the pyrite inside.The Fe O content of dark green samples is higher because of the pyrrhotite inside.Red samples have higher Fe O content due to hematite.Black samples have high Fe O content due to pyrrhotite and siderite.The color of Liaoning Xiuyu is related to the mineral assemblage inside.The whiteness of jade is related to tremolite and calcite;The red color of Xiuyu is caused by its internal hematite,which is related to Fe³⁺;The black color of Xiuyu is caused by the late immersion of black iron-containing hydrothermal materials,including pyrrhotite,siderite,sideronium and so on.