Gemmological and Mineralogical Characteristics and Genesis of “Dengguangdong” in Qingtian Stone

The "Dengguangdong" samples,a precious variety of Qingtian stone,are studied by using the X-ray powder diffraction(XRD) and electron paramagnanetic resonance(EPR) methods.The results show that the mineral component of the "Dengguangdong" samples is pyrophyllite.Its polymorphism is 2M,but containing rare 1TC,with a high degree-order structure and poor aluminum and rich silicon of the chemical composition.The edge of the sample is quartzification.Fe³⁺ in the "Dengguangdong" samples is located in octahedron interstice.The "Dengguangdong" sample is colourated by Fe³⁺,Ti⁴⁺ and hole center of Si-O^--Al.The pyrophyllite crystal in the sample is irregular bladed,uniform size and curved-platy aggregate structure.