Synthetic Emerald

Synthetic sapphire and ruby were first produced in volume by 1907, using the flame fusion method developed by the French chemist Verneuil. But this method could not be used to produce synthetic emerald. It took another 30 years before a commercially successful synthesis of emerald was invented by an American chemist, Carroll Chatham. Chatham was a brilliant chemist who developed an interest in synthetic gemstones at an early age.

As a teenager he tried to create diamonds in his garage laboratory, apparently by dissolving graphite in molten iron. When he tried to produce rapid cooling by immersing this solution in a vat of liquid nitrogen, the resulting explosion blew out windows around his San Francisco neighborhood. At urging of his father and the San Francisco police, he turned his attention to growing emerald crystals. By 1930 he had grown crystals of colorless beryl and then in 1935, he grew his first true emerald, a one carat crystal that is now in the Smithsonian Institution.

The reason that the Verneuil method would not work for emerald is because emerald is an aluminum beryllium silicate colored by chromium, and it is very difficult to melt all the component elements together -- some of them evaporate before others have even melted. The key to the Chatham process was a special solvent called a flux: a combination of chemicals such as lithium oxide, molybdenum oxide and vanadium oxide that stay liquid at high temperatures. Chatham's secret flux recipe solved the problem of how to melt all the components together. He suspended tiny seed crystals in the hot flux as the basis for growing new crystals. It can take up to a year to grow marketable stones in this environment.

Chatham's created emeralds are in some respects superior to the natural product. Since natural emerald tends to have many inclusions and fractures, it is not a particularly durable stone despite its very good hardness (8 on the Mohs scale). The Chatham emeralds suffer from none of the defects of natural emeralds.

Chatham was not only a brilliant scientist but an astute businessman. He built a company to sell his created emeralds, and he developed technology to create rubies, alexandrites, and blue and orange sapphires. Chatham died in 1983 but his son has carried on the business. Just a few years after Chatham's death the company finally realized his longtime dream of creating diamonds in the laboratory.