Heat treatment, gemstones

A very different type of application based on the use of LA-MC-ICP-MS, among other techniques, was reported recently by Fontaine et al., who investigated whether colored andesines (silicate gemstones) originating from Tibet were authentic or were produced from colorless andesines by Cu diffusion under heat treatment [99]. The authors analyzed laboratory-diffused samples and proved that, owing to... 

Nassau, Kurt (1984) Gemstone Enhancement Heat, Irradiation, Impregnation, Dyeing and Other Treatments Which Alter the Appearance of Gemstones, and the Detection of Such Treatments, Butterworth Heine-mann, London. Appendix A is a brief and clearly written description of the different types of furnaces often encountered in ceramics laboratories. 

Two methods that are widely used to enhance the color of gemstones are irradiation and heating, usually in that sequence. Table 36.11 summarizes some of the heat and irradiation treatments that have been used. The reason for treating (processing) gemstones is invariably to enhance their appearance and thus increase their value. We will review the general features of the different treatments and the science behind them, but refer discussion of the details to the sections on particular materials. All irradiated samples will be heated. 

An important field in gemmology is the determination of gemstone treatments to enhance their appearance. These treatments range from heating the stones to improve their color, filling fissures or impregnating stones with colorless substances to improve their clarity and color, to dyeing. Some of these treatments are accepted by the trade others are not. 

---