The Study On Colour Causing Mechanism And Ameliorate Conditions Of Lulong Red Corundum

In the thesis the red corundums which are exploritated from Lulong Qinhuangdao are studied. Firstly, the desposit of the red corundum is reconnoitred, samples of the corundums and the wall rocks are collected. Secondly, the geologic environment of the corundum and the principle of colour are studied. Thirdly, we ameliorated its colour with the heat treatment method and then studied its changeness of colour, transparency and the gemological characters before and after the heat treatment. The main instruments and the equipments used in the experiment are polarized microsope, XRF, XRD, ultraviolet-visible light spectrophotometer and high temperature finance and so on.The results reveal that the red corundum in Lulong Qinhuangdao is rooted in aluminum-bearing gneiss. The corundum formed in two generations. Corundums formed in the first generation are small and xenomorphic. The fashion of geologic action is area metamorphose. The geologic action to form the corundums in the second generation is commix lithification. The corundums are larger and more inerratic.The colour of the red corundum exploitated in Lulong is low-end and motley. The Cr³⁺ makes the corundum red. With the reduce of the Cr³⁺, the intensity of the red hue become weaken. The transfer of electon betten Fe2+-Fe³⁺ and Fe2+-Ti4+ is the causation which brings the blue hue into the corundum. Appearance of the blue hue makes the colour of red corundum motley. A little amount of Ti³⁺ execited in the corundum lead to purple hue. The course of yellow and green hue is the contation of Fe³⁺.In order to ameliorate the colour of the red corundum, we use the mothod of heat treatment. The temperature which is appropriated with the heat treatment of dark red-red corundum is 1200℃. Corundum with gray hue had better to use higher treatment temperature. The velocity of calefaction should be as slow aspossible. The time of heat preservation makes little infection to the outcome of the heat treatment. The method of heat treatment get rid of the excrescent hue in the red corundum effectively. The transparency of the corundum become worse. Other gemological characters do not have much change generally.