Study On The Gemological And Mineralogical Characteristics Of Colored Sphalerite

As the coming of the era of Industry 4.0,the demand for rare earth,rare and scattered metal elements in key minerals has increased strategically.It has become one of the hottest researching topics.Sphalerite is one of the most common and important sulfide minerals in lead-zinc polymetallic sulfide deposits.It is also the target mineral for searching for rare elements such as cadmium,indium,germanium,gallium,thallium and selenium.As a rare gemstone,the study of its gemological characteristics is not deep enough,especially the date of colored sphalerite.In this paper,the gemological and mineralogical Characteristics of pale yellow,greenish yellow,orange and black sphalerite is studied.The properties difference among four kinds of color of sphalerite were also studied by means of X-ray fluorescence spectrometer（XRF）,electron probe micro-analyzer（EPMA）,Laser denudation inductive coupled plasma mass spectrometer（LA-ICP-MS）,X-ray powder diffractometer（XRD）,Miniature fiber optic spectrometer and Raman spectrometer（Raman）.The results are as follows:Pale yellow and greenish-yellow sphalerites are anhedral crystals,with diamond to grease luster;Orange sphalerites are automorphic rhombic dodecahedron,with glass luster and rhom bohedral cleavage;Black ones are automorphic tetrahedral,with diamond luster.By the plane-polarized light observing that the pale yellow,greenish yellow and orange samples are yellow brown,while the black are red.By the crossed-polarized light observing that all the samples are completely extinction.The reflected color is gray.The average density and hardness increased with the color deepening.The main mineral composition o f sphalerite was ZnS,which contained a little of impurity elements such as Fe,Mn,Cd and In.Pale yellow and greenish yellow sphalerites are rich in Cd,Mn,In;Orange samples are rich in Cd,In,while deficient in Mn;And the black samples are rich in Fe,Mn,Cu,Cd,In and Sn.XRD shows that all the samples are typical Blende-type structure.And the lattice parameters increase with the content.of Fe.The absorption peak of Raman activity included 271cm^-1,297cm^-1,330cm^-1 and 349cm^-1 reflect to the Zn-S bond and Fe-S bond.And the replacement of Fe results in the increase of wave number.It can be seen that the color of the absorption band near 410nm,500nm and 700nm is related to the electronic transition of Fe,Cu and Co.Based on the comparison of the typical deposits and the comprehensive composition of samples,it is considered that the pale yellow and greenish yellow series sphalerite has the characteristics of both magmatic hydrothermal and stratabound deposits（mainly stratabound）,and the mineralization temperature is relatively low.Black sphalerites may be related to magmatic hydrothermal deposits,while orange sphalerite ones are formed in completely different metallogenic environments.The former may be close to magmatic hydrothermal genesis,whil e the latter is mainly characterized by stratabound type.