• Antiques in Oxford

Synthetic gemstones.

In 1873 Auguste Verneuil, who was based at the Museum of Natural History in Paris, began to work to synthesise corundum. In 1876, after many experiments, ruby synthesis was understood and repeatable. It was not understood how sapphire, called “bug juice” synthesis took place. The blue corundum colour that was created was not a fine blue colour and the process could not be repeated.

About 1890, synthetic ruby was created by using a process called “flame fusion.” By taking a blowtorch to powdered corundum, he created a boule or ball of material that was then shaped into a cylinder that could be cut and faceted to form gemstones. Exhibited at the 1900 Paris Exposition, synthetic rubies nearly caused a riot among jewellers. The stones had been very successfully faceted and mounted and transformed into attractive jewellery. Synthetic gemstones made in a laboratory have the same chemical, optical and physical characteristics as their naturally occurring counterparts. Synthetic sapphire and ruby are both corundum, with different mineral or colour additives used to create their distinctive hues. The colour comes from isotopes and by adding other materials, you can change the colour of the corundum. In some gemstones, such as with colour-change Alexandrite, the colour is also a clue to its laboratory origin. It displays a colour change from greyish blue-green to purple-pink instead of the green-to-red colour change that a natural stone exhibits. Synthetic Alexandrite was used frequently in 1950s jewellery and is actually synthetic sapphire. Regardless of colour, synthetic ruby or sapphire has the same durability or hardness as a natural stone and often possesses little or no inclusions. It is important to note that imitation gemstones are different from synthetic in that they can be made from any material, such as glass or crystal, and generally do not possess the characteristics of a natural gemstone.

The advantage of using synthetic stones was purely economic. Verneuil rubies sold for pennies a carat. Jewellery designers used them for achieving perfect aesthetics. They could be cut in odd shapes, such as kite, square or triangle. Jack Ogden, chief executive of the Gemmological Association and Gem Testing Lab of Great Britain (GAGTL) cautions that “synthetics look better and quite often, if a sapphire looks too good to be true, that’s because it’s synthetic.” Another advantage was availability of gemstone material. This was particularly true during World War II when gemstones and precious metals were scarce. Synthetic ruby was used in great numbers during the war period. The signature look in the 1940s was rose gold and ruby. Most of the rubies used then in jewellery were synthetic. Synthetic stones are often used in 1920s and Art Deco bracelets. Synthetic stones weren’t always cheaper because French-cut stones could be expensive. The jewellers were looking for consistency in colour and matching the stones was easier. When jewellers started using calibre-cut synthetic sapphires in the 1920s, it was more cost effective to use synthetics because the stones would frequently break while being set. Although synthetic sapphire was widely available, the use of synthetic Blue Spinel was far more common. This was created in 1900 and was a brighter and prettier material, so they used it in place of sapphire. In addition to ruby and sapphire, synthetic emerald is another gemstone frequently found in period jewellery. The process for developing synthetic emerald was discovered by San Francisco scientist Carroll F. Chatham in 1936. To this day, Chatham’s process is a closely held family secret. The conditions under which an emerald will grow are complex which makes the process expensive. While the gemstones retailed for much less than comparable natural emeralds they were always intended for jewellery. Unlike synthetic corundum, Chatham Created Emeralds aren’t flawless. They have inclusions but the cut and polished stones are so identical to natural ones that special tests must be performed to positively identify them as synthetic. The company also asserts that Chatham Created Emeralds aren’t enhanced or treated like many natural emeralds. The types of jewellery found to have synthetic stones runs the gamut from very fine, high-end pieces to less-pedigreed examples. So a fine bracelet from the 1920s could easily have synthetic sapphires. Sometimes the stones are mixed, where you have 60 percent synthetic and 40 percent natural. If the jewellery is an original period piece, having synthetic stones in it isn’t a deterrent for buying it. Synthetic gemstones are very convincing to a lay person. There really isn’t any way for the average person to know the difference. Smith says that a synthetic will look flawless to the naked eye but that under a loupe you will observe curved striation in the stone and the stones fluoresce. A black light will make the stones stand out dramatically. Colour can also be an indication of a synthetic stone. Synthetic ruby is bright stop-sign red and they glow. With sapphire, it’s a little more difficult to tell the difference. Lines in a synthetic sapphire are curved. Lines in a natural sapphire are straight. As technology for creating synthetic gemstones has improved, so has the need for accurate identification, which is always easier when the manufacturer takes on this responsibility. Judith Osmer’s Ramaura Cultured Ruby was created in the 1970s, originally for laser use. For example, in scanners used at supermarket check-out counters, the little red light is created by the laser passing through a synthetic ruby. It was such a beautiful material, however, that jewellers began purchasing it for jewellery. When several top gemmologists couldn’t detect its synthetic manufacture, Osmer found a way to make the gemstone identifiable. By adding an ingredient that would make the synthetic gemstone fluoresce in a characteristic way, the Ramaura Cultured Ruby can be easily recognized. In fact older synthetics are easier to discern than modern ones. For more recent synthetics, you need a microscope and even then you still need quite sophisticated equipment, such as a spectroscope, to tell the difference. In the last ten to 20 years, the technology has become far more complicated. Also, beware as the practice of swapping out important stones in older pieces and replacing them with synthetics is now commonplace.

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