CS Book 1_AS-5 Synthetic:Imitations .pdf

Synthetics and Imitations KEY CONCEPTS Knowing whether a gem is natural or synthetic is crucial when buying or selling colored stones. Imitations can be made of a variety of materials, including natural or synthetic versions of other gems. The process used to produce a synthetic gem can determine it...

Synthetics and Imitations KEY CONCEPTS Knowing whether a gem is natural or synthetic is crucial when buying or selling colored stones. Imitations can be made of a variety of materials, including natural or synthetic versions of other gems. The process used to produce a synthetic gem can determine its value. Pulling is important for sapphire synthesis because it produces extremely pure, high-quality crystals for technological and science applications. Solution processes are generally slower and more expensive than melt processes. Solution processes can synthesize gems that closely resemble natural gems. Advances in synthetic crystal growth have been driven mostly by industrial and research demands. Internal and external characteristics can help trained observers separate natural from synthetic gems. Most synthetic gem crystals are produced by either a melt or a solution process. Gemologists play an important role in ensuring that disclosure becomes the industry standard. Key Terms Assembled stone—Two or more separate pieces of material joined to form a unit. Melt process—A synthetic-crystal growth method in which the chemical mixture is melted, then recrystallized. Boule—A cylindrical synthetic crystal produced by a melt process. Pulling—A process in which the synthetic crystal grows from a seed that is dipped into a chemical melt, then pulled away as it gathers material. Ceramic process—A process in which finely ground powder is heated, sometimes under pressure, to produce a fine-grained solid material. Doublet—Two separate pieces of material fused or cemented together to form a single assembled stone. Flame fusion—A process in which powdered chemicals are dropped through a high-temperature flame onto a rotating pedestal to produce a synthetic crystal. Floating zone —A melt process where a heating unit passes over a rotating solid rod of chemicals until it forms a synthetic crystal. Flux growth—A process in which nutrients dissolve in heated chemicals, then cool to form synthetic crystals. Hydrothermal growth—A process in which nutrients dissolve in a water solution at high temperature and pressure, then cool to form synthetic crystals. Imitation gem—Any material that looks like a natural gem and is used in its place. Seed crystal—A tiny crystal used as a template to control the size, speed, or direction of growth and the shape of a growing synthetic crystal. Skull melt—A synthetic-crystal growth method that uses cooling pipes around an interior of melted chemical ingredients. Solution process—A growth method in which the synthetic crystal grows from a dissolved chemical mixture, sometimes at high temperature and pressure. Spontaneous nucleation—A synthetic-crystal growth method that starts without a seed crystal. Synthetic gem—A laboratory creation with essentially the same chemical composition, crystal structure, and properties as its natural counterpart. Triplet—A single assembled stone made from three separate pieces of material fused or cemented together, or from two pieces and a colored cement layer. 245