Gemological Characteristics And Heat Treatment Of Australian Sapphire

Sapphires are produced all over the world,the most famous of which are Kashmiri sapphires.Sapphires are also found in Laos,Myanmar,Thailand,Madagascar,the United States,Vietnam,China,Cambodia,and other countries,including Laos,Myanmar,Thailand,Madagascar,the United States,Vietnam,China,Cambodia and other countries.Australian sapphire appeared in the field of vision as early as the mid-19th century.Geologists have done detailed research on the geological output of Australian sapphire,but there are few studies on the gemological characteristics of Australian sapphire in China.The Australian sapphire is dark in color,mainly dark blue,dark green,dark blue green and different shades of brown,unlike Myanmar.Sapphires in Sri Lanka and Thailand are bright and showy,affecting their commercial and aesthetic values.The subject of this paper is the gemological characteristics and heat treatment of Australiansapphire.First of all,the background knowledge of mineralogy and gemmology characteristics,color origin and the research status of heat treatment color-changing technology of modern sapphire is expounded.The purpose of this study is to describe the detailed gemological characteristics of Australian sapphire and to provide a set of heat treatment schemes for Australian dark blue sapphire.The Gemological characteristics of Australian sapphire are mainly studied by conventional gemology instruments,Ultraviolet-Visible-Near Infrared spectrometer,Fourier infrared spectrometer,Laser Raman spectrometer and Laser Ablation-Inductively Coupled Plasma Mass Spectrometry.Their conventional gemological parameters,geological origin,color genesis and other information have been obtained.Australian sapphire inclusions are rich in negative crystals,zircons,amphibole,corundum,rutile,elemental sulfur,niobium iron ore,diaspore,diopside and so on.Niobium ore indicates that sapphire experienced hydrothermal metasomatism in the late growth stage.Infrared absorption peaks of 3310 cm^-1 and the characteristics of microelements show that they are produced in alkaline basalt,and the intensity of infrared absorption peak of 3310 cm^-1 increases with the increase of sapphire blue tone.The chromogenic origin of sapphire is directly related to the Fe³⁺d-d transition,Fe²⁺-Ti⁴⁺and Fe²⁺-Fe³⁺ion pair charge transfer,and the 700-1100nm strong absorption band related to Fe²⁺-Fe³⁺ion pair charge transfer is the main cause of the sapphire dark blue hue.The dichroism of sapphire is related to the number and overlap degree of Fe²⁺-Ti⁴⁺and Fe²⁺-Fe³⁺ion pairs in vertical and parallel C axis.The heat treatment technology of Australian dark blue sapphire is mainly to change the valence state,quantity or occupation of trace element ions in sapphire lattice by changing the heat treatment parameters such as constant temperature,heat treatment atmosphere and additives,etc.So as to explore the best heat treatment process.The experimental study of heat treatment shows that the temperature of 600?-800?for12 hours is not beneficial to the improvement of the dark blue tone of sapphire.The deep blue hue of sapphire can be improved by adding carbon powder or open environment for 12 hours at 600-1300?.When the heat treatment temperature is higher than 1400?,The tone of stone dark blue is enhanced,but the atmosphere environment created by toner is difficult to control.When Al?OH?₃ and TiO₂ powder were added in open environment for 12 hours at 1300?,the improvement effect was the most obvious.The dark blue tone of sapphire was obviously weakened and the color became brighter.