Thermal Property of the Apatite Pseudomorphic Turquoise
CHEN Quan-li1,QI Li-jian1,YUAN Xin-qiang1,CHEN Jing-zhong21.Gemmological Institute,China University of Geosciences,Wuhan 430074,China2.Faculty of Material Science and Chemical Engineering,China University of Geosciences,Wuhan 430074,China
The study of the apatite pseudomorphic turquoise's thermal property plays a significant role in the investigation of the coloring mechanism and the structural characteristics of water in turquoise.In this paper,thermal property of the apatite pseudomorphic turquoise from Maanshan,Anhui Province,has been studied by using the thermogravimetric and thermal analysis(TG-DSC),infrared(IR)spectrum and X-ray powder(XRD)diffraction.From room temperature to 1 100 ℃,its thermal phase transformation can be divided into six stages:100-200 ℃,the removal of the absorption water;250-330 ℃,the release of the hydroxyl and lattice water;330-750 ℃,the formation of non-crystalline structure;about 750 ℃,a new phase formed;750-1 100 ℃,the generation of aluminum phosphate with tridymite structure,and 1 100 ℃,the degree of crystalline order of aluminum phosphate is improved.The color of pseudomorphic turquoise is controlled by the structure,the existence form and total amount of water,together with the binding mode of water molecules.
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