The Study On Gemological And Mineralogical Characteristics Of Fluorite In Wuyi,Zhejiang

In this paper,the gemological and mineralogical properties of fluorite in Wuyi,Zhejiang Province were systematically studied by infrared spectroscopy,ultraviolet-visible absorption spectroscopy,Raman spectroscopy,electron probe,LA-ICP-MS and other modern testing techniques.The fluorite in Wuyi area is rich in color,such as green,purple and colorless fluorites,and the ribbon type is developed.It can be characterized by crossed ribbons and flat ribbons.The fluorites usually have good transparency.The crystal form of fluorites is intact,mostly cubic,or interspersed with twin or crystal clusters,and some crystals are symbiotic with quartz.The micro Vickers hardness is 180.44 to 189.1,the Mohs hardness is 3.81 to 3.87,and the relative density is 3.13 to 3.15.The refractive index is 1.431 to 1.437.It has strong fluorescence under ultraviolet fluorescence,usually blue-violet,and long-wave is stronger than short-wave,and the cathode glow color is bright blue-violet.The fluorite interior is rich in inclusions,including initial cleavage,irregular vein-like associated mineral inclusions,various forms of healing fissures,and pyramidal,conformal native inclusions.These native inclusions are confirmed by Raman spectroscopy,which are the combination of solid BaSO₃ and gases CO₂,H₂S,CH₄ and water vapor.The chemical composition of fluorite in this area is relatively pure,the content of Ca changes from 50.92%to 52.16%,and the content of F changes from 46.12%to47.51%.Other major impurity elements are S,Si,Fe,Cu,Ni,Zn and rare earth elements.Combined with the study of UV-Vis spectroscopy,it is confirmed that these elements are related to the coloration of fluorite,in which Sm²⁺color center is relate to green,colloidal calcium color is related to purple,colloidal calcium and F color center are associate with dark blue.Fluorites with color change effect are due to the difference in color excitability of different light sources in pyramidal cells in the human eyes.In the infrared spectrum,the fingerprint region shows that the characteristic absorption peak of fluorite is near 1080cm^-1.In addition to the characteristic peak position,the infrared spectrum of fluorite in Wuyi area also contains the free CO₃^2-ion absorption peak around 1378cm^-1.Except that,the O-H stretching vibration peak near3428cm^-1 confirmed the participation of water in the mineralization process.Raman spectroscopy confirmed that the associated minerals of Wuyi fluorite are quartz and magnetite.Combined with the data of rare earth distributions in this paper and the predecessors,it can be inferred that the fluorite mineralization in Wuyi area has undergone hydrothermal leaching mainly based on REE element adsorption and mineralization mainly based on REE element complexation.