Ever since the art of alchemy began, there have been attempts to produce precious metals and gemstones from base metals and ordinary ingredients. Over the decades techniques have been developed which have made possible synthetic gemstones which are identical physically and chemically to the natural gemstones and test as such. Seen in jewels in the 1920's/30's when they caused great excitement, presenting rarely found top quality gemstones for a fraction of the price of a mined one, we also see them in pieces from the 1960's/70's and have had a number in our collections. There is a fabulous display of these synthetic gemstones in the Natural History Museum, London.
The Ruby, a favourite and prized gem since time immemorial, was always a candidate for attempts to synthesise due to their scarcity. The first gem to be synthesised on an industrial scale; the famous name associated with synthetic Rubies is Auguste Verneuil a Parisian chemist whose name the technique takes.
The first documented attempts were in 1817, when a larger ruby was formed by melting two smaller rubies together and in 1837 when the first microscopic crystals were created in a laboratory. Sparking imaginations across Europe to experiment with methods until chemist Edmond Frémy devised an effective method for commercial ruby manufacture in 1877, using molten baths of aluminium oxide (or alumina), yielding the first gemstone-quality synthetic stones.
The Parisian chemist Auguste Verneuil collaborated with Frémy on developing the method, but soon went on to independently develop the flame fusion process, which would eventually come to bear his name and is still used today. One of Verneuil's main sources of inspiration was the appearance of some synthetic rubies sold by an unknown Genevan merchant in 1880. It was after examining the Geneva rubies that Verneuil concluded that it could be possible to recrystallise finely ground aluminium oxide into a large gemstone. This realisation, along with the availability of the recently developed oxyhydrogen torch and a world shortage of real Rubies, led him to design the Verneuil furnace, where finely ground purified alumina and chromium oxide were melted by a flame of at least 2,000 °C (3,630 °F), and recrystallised on a support below the flame, creating a large crystal.
He announced his work in 1902, publishing details outlining the process in 1904. Six years later, Verneuil's laboratory had expanded into a 30-furnace production facility, with annual gemstone production by the Verneuil process having reached 1,000 kg in 1907.
One of the most crucial factors in successfully crystallising an artificial gemstone is obtaining a starting material that is extremely pure. In the case of manufacturing Rubies this material is aluminium oxide. Depending on the desired colouration of the crystal, small quantities of various oxides are added, such as chromium oxide for a red Ruby. Alternatively, small, valueless crystals of the desired product can also be used. The resulting crystal is both chemically and physically identical to a real Ruby.
An extremely rare gemstone, natural Alexandrite is a vividly hued colour-changing gem first seen in the early 19th century in Russia. Great excitement grew around the gem as it was apparently named after the Tsar, but supplies were always limited even though it has since been found in other countries across the globe.
Synthetic alexandrite is an artificially grown crystalline variety of chrysoberyl, composed of beryllium aluminium oxide. Most true synthetic Alexandrite is grown by the Czochralski, or “pulled” method. Flux-grown Alexandrite stones are expensive to make and are grown in platinum crucibles and due to the high cost of this process, it is no longer used commercially. Czochralski Alexandrite is easy to identify because it is very “clean”. With magnification one can often see curved striations which are a well-known characteristic. Some stones manufactured by this method have been seen to change colour from blue to red – very similar to natural alexandrite from Brazil, Madagascar, and India.
Most gemstones that are described as “synthetic alexandrite” should really be called “simulated alexandrite”: Synthetic corundum is laced with vanadium to produce the colour change. This alexandrite-like material has been known for almost 100 years. It differs from real Alexandrite in that there is never any green colour change, just purple and mauve.
The oldest and most inexpensive process to synthesise Sapphires is known as flame fusion. The Verneuil process by which synthetic Rubies are made is also flame fusion. In this method a flame melts aluminium oxide powder, and the drops form into a long teardrop shape called a boule. The addition of traces of other minerals to the aluminium can create different colours of Sapphire. The Verneuil Process can create Sapphires much larger than those normally found in nature. The previously mentioned Czochralski process is also used to make synthetic Sapphires. It's not easy to tell the difference between lab grown Sapphires and natural, but there are some tell-tale signs that an expert can identify. Flame fusion processes can produce curved growth and colour bands not found in nature. The Czochralski process can produce gems with inclusions like bubbles and smoky veils, and Hydrothermal synthesis can have distinctive “nail head” inclusions.
Synthetic Rubies, Sapphires and Alexandrite are chemically and physically identical to the mined crystals, but because they are made in a laboratory, could be said to be an ethical choice, and of course are considerably cheaper than mined crystals. Indeed, sometimes it’s very difficult for even an expert to separate the laboratory manufactured from the mined gems.