Diamond imitations

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. 

Cubic Zirconia. As of this writing, cubic zirconia [1314-23 ], is the best diamond imitation available (Table 3). It is marketed under... 

Drilling diamonds using a focused laser beam to bum out dark inclusions or make the inclusions accessible to a chemical treatment is a frequent enhancement. In a potential deception, a cubic zirconia diamond imitation was laser drilled to make it more convincing (15). 

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. 

Cubic Zirconia. As of this writing, cubic zirconia [1314-23-4], Zr02, is the best diamond imitation available (Table 3). It is marketed under such names as CZ, Cerene, Cubic zirconium, Diamonair II, Diamonique III, Fianite, etc, and grown by the skull melting technique (2,5,13). Pure Zr02 is... 

Carnets. Both YAG, yttrium aluminum garnet. YjAIsOi3, and GGG, gadolinium gallium garnet. GdiGa 0,2. have the garnet structure and were used al one time as diamond imitations. These have been supplanted by cubic zirconia. 

Rutile. Rutile, a form of TiCb, was at one lime used as a rather poor diamond imitation. Related is strontium titanaie, SrTiOj. now more properly called synthetic tausonite. 

The original rhinestones were pieces of clear crystalline quartz found near the Rhine River. These stones were faceted and used in imitation of diamonds. They became very popular in costume jewelry, to the point where there was not enough raw material to keep up with the growing demand. Clear glass was gradually substituted, and the term rhinestone came to mean any colorless diamond imitation, regardless of its composition (see Figure 2.5). 

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