This second edition of Nassau"s important work on the methods of modifying and enhancing gemstones has been thoroughly updated, encompassing all the major developments of the 1980s. "Gemstone Enhancement" provides a complete coverage of 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 such. Some of these processes date back at least two thousand years, others are of quite recent origin. The new edition covers such advances as: glass and plastic filling of diamonds and other gemstones; expansion in the use of both host and irradiation treatments; and efforts to keep up identification procedures with the advances in treatments. All the fundamental concepts are covered, so only a general knowledge of gems is required of the reader.