Gemstone treatment

Color and clarity are two of the attributes that give gemstones used ia jewelry value. Gemstones deficient ia either color or clarity can be enhanced (1). Almost worthless material can at times be converted iato valuable-appeariag gemstones. An estimated two-thirds of all colored gemstones used ia jewelry have been treated. Accordingly the identification of the use of treatments and the disclosure of enhancements to the purchaser are important. Table 1 Hsts the materials discussed hereia. 

Some treatments are practiced so widely that untreated material is essentially unknown ia the jewelry trade. The heating of pale Fe-containing chalcedony to produce red-brown carnelian is one of these. Another example iavolves turquoise where the treated material is far superior ia color stabiUty. Such treatments have traditionally not been disclosed. Almost all blue sapphire on the market has been heat treated, but it is not possible to distinguish whether it was near-colorless comndum containing Fe and Ti before treatment, or whether it had already been blue and was only treated ia an attempt at marginal improvement. The irradiation of colorless topa2 to produce a blue color more iatense than any occurring naturally is, however, self-evident, and treatments used on diamond are always disclosed. 

The stabihty of a particular treatment is also important. The enhancement should survive during normal wear or display conditions. Whereas all the enhancements from heat treatments are stable, some produced by irradiation are not. There are also surface coatings which wear off, oilings which dry out, etc. 

It is convenient to discuss enhancements ia three groups heat treatments, irradiations, and other treatments (1). Several types of treatments are at least 3000 years old others, such as the filling of cracks with glass, arose only ia the late 1980s. 

Kirk-Othmer Encyclopedia of Chemical Technology (4th Edition) 

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Aquamarine [1327-51-1] [GEMSTONES - GEMSTONE MATERIALS] (Vol 12) [GEMSTONES - GEMSTONE TREATMENT] (Vol 12)... 

There are three types of gemstone materials as defined by the U.S. Federal Trade Commission (1) (/) natural gemstones are found in nature and at most are enhanced (see Gemstones, gemstone treatment) (2) imitation or simulated, fake, faux, etc, material resembles the natural material in appearance only and is frequendy only colored glass or even plastic and (3) synthetic material is the exact duplicate of the natural material, having the same chemical composition, optical properties, etc, as the natural, but made in the laboratory (2,3). Moreover, the word gem cannot be used for synthetic gemstone material. The synthetic equivalent of a natural material may, however, be used as an imitation of another, eg, synthetic cubic zirconia is widely used as a diamond imitation. 

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