Synthetic Gemstones are made in laboratories or factories, not in rocks. They have virtually the chemical composition and crystal structure as natural gemstones, so their optical and physical properties are very similar. However they can usually be identified by the differences in their inclusions. Many gemstones have been synthesized in the laboratory, but only a few are produced commercially – generally for industries and scientific purposes.
Man has tried to replicate gemstones for thousands of years, but it was not until the late 1800s than any substantial success was achieved. In 1877 French chemist Edmond Fremy grew the first gem – quality crystals of reasonable size and the around 1900 August Verneuil devised his technique to manufacture ruby. With a few modifications, the Verneuil “flame – fusion” method is still in use today. The powered ingredients are dropped into a furnace and melt as the fall through a flame hotter than 2,000°C (3,630°F), fusing into liquid drops. These drip on to a pedestal and crystallize. As the pedestal is withdraw, along, cylindrical crystal, which is known as a boule, forms.
Shapes and Colors:
Because of the way they are made, synthetic gems may show subtle differences in shape and color they help to distinguish them from their natural counterparts. For instance, corundum produced by flame – fusion has curved growth lines, rather than straight ones, because the ingredients have not mixed together fully. Some synthetic gems may also suffer from uneven color distribution. Flame – fusion spinel is manufactured to initiate gems such as ruby, sapphire, aquamarine, peridot, blue sapphire, tourmaline and chrysoberyl.
Synthetic gems have different inclusions from natural gems, so often the best way to tell them apart is to examine them with a loupe or a microscope. Synthetic inclusions may be typical of a process, or of a synthetic gem spices. For instant, in Verneuil rubies, gas bubbles have well – defined outlines; in flux – melt emeralds, characteristic “veil” and “feather” patterns form.
Lapis Lazuli, turquoise and coral produced by the French manufacturer, Gilson are similar to their natural counterparts, but are not true synthetic because their optical and physical properties differ from the natural gems. Gilson lapis lazuli, for example, is more porous and has a lower specific gravity.