subject: Natural Gem stones [print this page] The use of high heat temperatures with chemical additives to a stone's surface is chemical diffusion. The process leads to a more intense color or a complete color change altogether. Because chemical diffusion often results in artificially altering a gemstone's color, it must be disclosed on documents and advertising of the gemstone on which it is used. Rubies, sapphires and green topaz are sometimes chemically diffused.
