Synthetic diamonds and gemstones

Naturally occurring zircon is in demand as a gemstone. It is polished, cut, and used for jewelry and art. Natural zircon often includes uranium, thorium, and other radioactive elements. The ptesence of these elements often gives a zircon a special brilliance and fire-like quality, resembling fine diamonds. Synthetic diamonds and gemstones, known as cubic zirconia, are produced from zirconium oxide. 

Until World War II, the diamond business was relatively simple, consisting only of natural diamond. The great majority of the market was gemstones and industrial applic2rtions were limited. The advent of synthetic diamond and the rapid rise of industrial applications have drastically altered the industry, and more changes will undoubtedly take place in the future such as the development of CVD diamond (Ch. 13). The challenge and potential impact of this new technology are well understood by the dieimond producers. 

Table 3. Properties of Diamond and Synthetic Gemstone Materials ...

The applications of natural and high-pressure synthetic diamond were reviewed in Ch. 12. Although these eipplications have a very large market, particularly in gemstones, they are limited because of the small size and... 

In the introductory laboratory, the Raman spectroscopy of diamond and pearl, which is predominantly calcium carbonate, has been used to introduce the concept of the vibrational spectrum as a qualitative identifier [9]. The Raman spectra of the authentic gemstones are compared to the spectra of common costume jewelry substitutes, faux pearl and cubic zirconia, respectively. Synthetic calcium carbonate is used as a reference material for pearl. The pearl, faux pearl, and reference spectra are shown in Fig. 3. 

Diamond is supreme among natural gemstones ia H, RI, and DISP. Table 3 shows the steady improvement ia the sequence of diamond imitations, the aim being to produce a colorless, adequately hard material having closely matching optical properties. The iatroduction of synthetic cubic 2irconia ia 1976 brought about a sufficiently close match. 

Several gemstone species occur in various colors, depending on the presence of impurities or irradiation-induced color centers. Examples are the beryl, comndum, and quart2 families. Quart2 has poor optical properties (RI = 1.55, DISP = 0.013), but becomes of gemological interest when it exhibits attractive colors. Any material can have its color modified by the addition of various impurities synthetic mby, sapphires, and spinel are produced commercially in over 100 colors (2). Synthetic cubic 2irconia has been made in essentially all colors of the spectmm (11), but only the colorless diamond imitation is produced commercially in any quantity. 

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. 

Scapolite has a complicated crystal structure and is formed by the alteration of plagioclase feldspars. Incidentally, diamond, sapphire, and ruby all fluoresce, but as with the materials above, the color depends on the UV wavelength used. A given specimen can also show different colors depending on the distribution of impurities. Trace elements can be included in synthetic gemstones to make them fluoresce and thus be easily identifiable. 

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