| Even though there were a few early hard works, | | | | synthetic diamonds, colorless or near colorless |
| successful gem synthesis began in the late 1800s | | | | imitation materials are much more abundant. |
| with the development of synthetic ruby by the | | | | Over the years, a number of natural gem |
| flame-fusion method. The need for a variety of | | | | minerals and synthetic materials have been used |
| high-quality crystals for a range of industrial | | | | to imitate colorless diamond. Cubic zirconium oxide |
| applications (i.e. optics components, laser crystals | | | | (cubic zirconium or CZ) is the most widespread |
| and other uses), and the increased awareness of | | | | stimulant because of its low cost and similar |
| crystal growth mechanisms, have since combined | | | | appearance to a polished diamond. It (and most |
| to yield the production of a wide variety of | | | | other stimulants) can be readily distinguished from |
| crystals, some of which are synthetic | | | | diamond on the basis of a difference in heat |
| counterparts of natural gemstones. A synthetic | | | | conduction, which can be detected with a simple |
| gem material has the similar chemical composition | | | | gemological test instrument. Within the past two |
| and crystal structure as a natural gem mineral. In | | | | years, a new material, synthetic moissanite (silicon |
| contrast, a gem stimulant or imitation has the | | | | carbide), has been marketed for jewelry |
| appearance of a natural gemstone, but has a | | | | purposes. It has caused some serious identification |
| different chemical composition, physical properties, | | | | problems among jewelry, because it cannot be |
| and crystal structure. Both synthetic and stimulant | | | | distinguished from diamond by the heat |
| gem materials almost always possess gemological | | | | conduction test mentioned earlier. However, |
| properties that allow them to be distinguished | | | | synthetic moissanite displays optical features due |
| from the corresponding natural gemstones. | | | | to its anisotropic optical character (seen as an |
| Current methods used for gem synthesis fall into | | | | optical doubling when viewed with magnification) |
| two general categories: crystallization from a fluid | | | | which allow it to be easily recognized by trained |
| of different composition (such as a flux or | | | | gemologists. |
| aqueous hydrothermal solution), and crystallization | | | | Among colored stones, the most important |
| from a melt with roughly the same chemical | | | | synthetics are synthetic corundum (sapphire and |
| composition as the crystal being grown. Synthetic | | | | ruby), emerald, spinal and amethyst. As indicated |
| diamonds, grown from a metallic flux at high | | | | they are produced by both solution and melt |
| temperatures and pressures, have evoked | | | | crystallization techniques. In the marketplace, |
| concern in the jewelry trade ever since the first | | | | flame-fusion and crystal-pulled synthetics are |
| production of gem quality crystals in the early | | | | relatively less expensive and therefore are more |
| 1970s. However, due to the growth conditions | | | | abundant than the flux and hydrothermal |
| involved, as well as the great expense and | | | | synthetics. Solution-grown synthetic amethyst falls |
| restricted availability of the growth equipment | | | | into the same less-expensive category because |
| used, the actual number of gem-quality synthetic | | | | of the existing large-scale production facilities for |
| diamonds continues to be limited. Those that are | | | | synthetic quartz for use in the electronics industry. |
| encountered in the jewelry trade are mainly | | | | In contrast, hydrothermal- and flux-grown ruby, |
| brownish-yellow crystals, weighing 1 carat or less | | | | sapphire and emerald are considered as |
| (1 carat = 0.2 g), which can yield faceted pieces | | | | ‘luxury’ synthetics that command higher |
| of 0.5 carat or smaller in size. In contrast to | | | | prices. |