Gemological Mineralogy Of Dushan Jade In Henan Province

Dushan jade is a zoisitized plagioclase,which has high gemstone technology value and scientific research value.At present,there are abundant research data on the genesis,metallogenic characteristics,petrological characteristics and mineral composition of the deposit,but relatively few studies on its spectral characteristics.Therefore,on the basis of detailed observation of mineral assemblage,fabric characteristics and symbiotic relationship in Dushan jade samples,combined with XRD and other testing methods,this paper systematically summarized the conventional gemological characteristics of Dushan jade in Nanyang City,Henan Province,and further distinguished the differences of mineralogical characteristics of Dushan jade with different colors through mineral chemical composition and infrared spectral reflection peak.The color systems of this batch of Dushan jade samples include pink,green,yellow,brown,purple and flower colors.The following conclusions are obtained:translucent to opaque,with a relative density of 2.75～2.97,and a refractive index of 1.55～1.61.The pink Dushan jade has a birefringence phenomenon.Under the optical microscope,the main mineral composition of Dushan jade is plagioclase（70%is anorthite）,followed by zoisite,diopside,sphene,mica group minerals（mostly muscovite and biotite）,calcite,epidote,chlorite and a small amount of opaque minerals（mainly magnesite and magnetite）.The mineral assemblages and relative contents of Dushan jades with different colors vary greatly.The mineral texture types include metasomatic residual texture,restorative texture,granular texture,etc.,reflecting that they have experienced multiple magmatic hydrothermal activities during the crystallization process,mainly hydrothermal metasomatism and dynamic metamorphism.In addition,the fabric characteristics of Dushan jade can be reflected by conventional gemological parameters such as refractive index and relative density.On the basis of previous studies,through the analysis of chemical composition differences and spectrograms of Dushan jades with different colors,it is determined that the chromogenic mineral of Huang Duyu is sphene,the chromogenic mineral of Celestial Blue Duyu is Cr containing muscovite,and the green Duyu is Fe containing diopside.A large amount of diopside and zoisite are found under the mirror of the powder alone jade.The electron probe data show that the content of Mn²⁺is high.It is speculated that the colouring minerals of the powder alone jade may be related to the diopside and zoisite containing Mn²⁺.