You might be surprised to find out that the “flawless” gemstone you’ve just purchased has been treated in a lab with heat in order to enhance its color. While it might sound like a process that would cause your gemstone to diminish in value, heat treatment is actually a very common practice among gem traders around the world. In fact, heat treatment can be dated all the way back to the time of Pliny the Elder, an ancient figure in Roman philosophy. For nearly as long as there have been gemstones for sale, traders have been treating their stones with heat.
Applying heat to a gemstone, usually in a kiln or oven between 200 and 2,000 degrees Celsius, gives the stone an extra kick to mature. Many gemstone traders say that it’s just like they are finishing the work that the earth’s heat would have done if the gemstone had stayed in the earth’s surface just a bit longer. Well, a number of years longer.
Some gems that are typically heat treated include amber, amethyst, aquamarine, citrine, ruby, sapphire, tanzanite, topaz, and colored diamonds.
Gems that are not treated are not always considered to be higher in value; in fact, you’d probably have a hard time finding a gemstone for sale that wasn’t slightly heat-treated. If you do, it might be a bit rarer and come with a tad higher price tag, but in general, heat treatment is an accepted practice. Typically, natural unheated rubies and sapphires are more valuable. Likewise in the case of non-oiled emeralds. The person who sells you a gem may be able to tell you whether or not it was heat treated, but it’s very difficult to detect whether or not a gemstone has been treated with heat. Only a certified gemstone laboratory would be able to definitively determine if heat was applied to a stone.
At Frank Pollak & Sons, we’ve been in the business of buying and selling fine jewelry since 1905. Interested in selling your gemstones jewelry? Stop in today for an evaluation from one of our fine jewelry professionals.