Gemstones have been subjected to various treatment processes, to improve their colour, clarity or durability, for thousands of years. There is evidence that ancient civilizations in the Middle East impregnated turquoise with wax to make it shinier and more durable and the ancient Romans knew how to make black onyx with carbonised sugar.
Modern treatments consist usually of a heating process, sometimes in the presence of a chemical agent and some times a period of irradiation. These techniques mimic what would happen to a gem stone in the Earth’s crust, only this time in man-made laboratory conditions. As these treatments are copying natural conditions, it can sometimes be very difficult to detect any treatment has taken place.
95% of all sapphires and nearly 99% of all rubies are routinely heat treated to improve their colour and clarity. So finding an attractive, ‘unheated’ sapphire or ruby can be very difficult and they can be very costly.
Some stones, like tanzanite and most of the blue topazes, are only the colour they are because they have been artificial treated.
At the other end of the scale, some treatments can be much less sophisticated and consist of nothing more than applying a coloured lacquer to the cut gem.
In recent years there has been a growing trend amongst designers and consumers to move away from these ‘man aided’ stones towards gem types where no interference has occurred. For example, there are no known treatments to improve garnet or spinel. So you know that if you buy one of these gems, they are exactly as nature intended… apart from cutting and polishing of course!