The Study On The Characteristics Of Chinese Northern Pearl

China's freshwater-cultured pearl is mainly produced in Zhejiang,Jiangsu and other southern places of China.With the improving of the cultivation techniques,pearls have been successfully cultured in the northern area of our country,which fills the blank of that the northern are unable to produce pearl.Chinese northern pearl produced in Liaoning areas can be divided into white,pink and purple classes according their body colors.The shape of pearl is round,oval and flat round,and the size of round shape pearl ranges from 4 to 10 mm.Moh's hardness of the pearl is ranging from 3 to 4,and the refractive index is ranging from 1.52 to 1.55.Luminescence properties under long wave ultraviolet light are non-fluorescence to yellow and blue fluorescent.The relative density of Chinese northern pearl is 2.704 to 2.730,and the relative density of the Chinese southern pearl produced from Zhuji of Zhejiang is 2.675 to 2.699.The characteristics of component and inner structure of Chinese northern pearl are investigated,with the help of X-ray powder diffraction,Fourier Transform Infrared Spectroscopy,X Ray Fluorescence,Scanning Electron Microscope,polarizing microscope and Transmission Electron Microscope.The components of Chinese northern pearl are aragonite,organic matter and water,and the highest content is aragonite.The main elements are Ca,Na,Sr,S,Fe,and containing a small amount of Zr,Mo,P,Mg,Si,Al and Cu.The amino acid content of Chinese northern pearl is 1.72 g/100 g,and that in Chinese southern pearl is 1.40 g/100 g.The North Pearl Chinese is made up of irregular cystidium and the lamellar nacre.The thickness of the nacre is gradually thinning from center to outside.The nacre is composed of aragonite and the accumulation mode of aragonite is brick-mortar type.The aragonite layer is composed by aragonite particles whose shapes are irregular.The organic matter is exists in the around of aragonite particles,aragonite layer and nacre.The internal structure of Chinese northern pearl and Chinese southern pearl are similar,but the thickness of the nacre that belong to Chinese northern pearl is smaller.For the different structure,the Vickers hardness of Chinese northern pearl is ranging from 1.83 GPa to 2.15 GPa,but the Vickers hardness of Chinese southern pearl is 1.75 GPa to 2.02 GPa.