Introduction; The history of treatments; Heat treatments; Irradiation treatments; Other treatments; Identification and disclosure; Specific gemstone treatments; Amber, Anglesite, Anzurite, Beryl, Corundum, Chalcedony, Diamond, Grossular, Feldspar group, Jade group, Lapiz lazuli, Malachitte, Opal, Pearl, Quartz, Spodumene, Topaz, Tourmaline, Turquoise, Zircon; Appendices: More on heating, More on irradiation, Colour, Purveyors.