Provides a complete coverage to the tremendous range of treatments available to enhance the colour and appearance of gemstones. This includes various types of irradiation and heat treatments, colourless impregnations, bleaching, dyeing, diffusion and other processes. Some of these processes date back at least 2000 years, others are of quite recent origin. This edition includes advances such as glass and plastic filling of diamonds and other gemstones, the large expansion in the use of both heat and irradiation treatments and the efforts to keep up identification procedures with the advances in treatments. The book is written for gemmologists to simplify their work: by knowing the details of the possible treatment techniques, the treatments that have been applied to the gemstone under study can be more readily recognized. Collectors, dealers, jewellers, appraisers, pawnbrokers and others interested in gemstones will also gain added insight from knowing the range of possible treatments.