Gemstone enhancement

One of the important tasks of the gemologist is to identify treatments which may have been used to modify the colour or appearance of the gemstones being examined. The book is written for gemologists, to explain the details of possible treatment techniques. An historical account of treatments is given in chapter 2, general accounts of heat treatments in chapter 3, irradiations in chapter 4 and miscellaneous techniques (including impregnation and dyeing) in chapter 5. Chapter 6 is a brief discussion of the identification techniques used to reveal treatments. In chapter 7 the various gemstone materials are considered alphabetically, by groups. The irradiation treatments considered in chapter 4 start by summarising and explaining the rays and particles used for the irradiation of gemstones. The major colour changes that occur on irradiation are tabulated. Colour centres are explained. Colour-centre-like colour changes are mentioned. Finally, radioactive gemstones are considered. (UK)