Though stone treatment has gone on for centuries, new techniques and methods are now available and many of today's gemstones are treated to improve their appearance and make them more marketable. While it is common knowledge within the gem trade that stones are enhanced through treatment, the buying public has known little about the treatments until recently.



As long as the consumer realizes that the stone has been treated, and the value adjusted accordingly, this is not a deceptive or underhanded practice. Treatments can do such things as change or enhance color, make the stone more durable and enhance the character of the stone. Unless the stone is stated to be natural, we can almost always assume that the stone has been treated with the common treatments used on that type of gemstone. Natural precious stones with no treatment at all are a rarity and very expensive.

Treatment maybe as simple as the old treatment of soaking chalcedony in honey then ageing it on the roof of the house so the honey caramelized and changed the color. When the stone turned black, it was called Black Onyx. Gemstones can be treated with heat, laser treatment, radiation, bleaching, stabilization, putting in acid, applying pressure, oiling, impregnation, dyeing, or combinations of any of these techniques. Here are just a few examples of common stone treatments:

1. Chalcedony is treated with heat to become Carnelian, and when it is dyed black, we call it Black Onyx.

2. Aquamarine is sometimes heated at a low temperature to bring out the blues and lessen the naturally occurring yellows, which make greens appear in the stone.

3. Rubies are rarely available these days that have not been heat treated, but if you can find natural rubies, the value is at least 30% better than that of a treated stone.

4. Diamonds in colors have become quite popular. Many of these are treated with radiation or a combination of pressure and heat. Naturally colored diamonds are far more valuable than their treated counterparts.

5. Emeralds can be treated with oil or impregnated with polymers, even dyed polymers to enhance color.

6. Tanzanite is naturally brown and when it is treated with heat the characteristic blue with violet undertones becomes apparent.

7. Sapphires are sometimes heat treated at a high temperature to bring out the dark blues and enhance the clarity of the stones.

8. The Padparadscha Sapphire is most often treated with heat to enhance the brilliance of the color.

9. Pearls have been bleached, waxed, heated, dyed and irradiated to enhance their color and luster.

10. Citrine is frequently heat-treated amethyst or smoky quarts. Natural citrine is usually a light yellow.

11. Topaz is often irradiated or heated to bring out the brilliant blues. It is also sometimes sliced and layered by color to give an almost iridescent color. This topaz is usually called Mystic Topaz.

12. Turquoise can be dyed, stabilized, have the matrix enhanced and even backed with plastic when it is mounted.

If the price of any of these stones seems too good to be true, you are probably looking at a treated stone. If no deception is practiced and the buyer and seller are both happy with the transaction gemstone treatment is not an unethical or deceptive practice.