Gemological Feature And Color-Forming Mechanism Of Yunxian Turquoise In Hubei Province

The gemological feature and color-forming mechanism of Yunxian turquoise in Hubei province is studied comprehensively in this paper.The characteristics of the deposits geological feature, mineral feature and rocky feature are analyzed, also compared with Maanshan turquoise. The components and strcture of turquoise are studied deliberately through electron probe, x-rays powder diffraction and differential thermal analysis(DTA).Through Charoma theory and metal-bearing ores' color index analysis, the color of the turquoise is quantitated. Crystal field spectra of Cu2+ ion have been analysed and compared with the oretical calculations, the results show that the basic color of turquoise (azure) is related to the existence of Cu2+ octahedron. In this charpter, quantum mineralogy theory is used in quantity.The ralationship between the color of turquoise and its composition andstructure is studied, That is, the variation from blue through green to brownyellow is dependent on the amount of iron. Absorped water, crystalline waterand hydroxyls lose from turquoise when it is heated, therefore its structureis destroied and its color also becomes green,yellow from azure.Besides, the calture, treatment and identifying ways, quality and vauling of turquoise are studied in the paper.