Mechanism of Irradiation Inducing Colouration and Colour Change of Topaz

Topaz appears in various colours, and the price of topaz with different colours differs greatly. The colour can be changed by irradiation. The colour of natural topaz is systematically described and the achievements in colouration by irradation of topaz are discussed. The mechanism of colouration by irradiation of topaz is also discussed here, suggesting that the colour is induced by integrated effect of impurity elements, impurity ion center and electron hole center.