Wednesday, December 12, 2007

ESTATE JEWELRY VS IRRADIATED GEMSTONES

Frequently we are asked “what are irradiated gemstones?” and “should I be concerned about wearing irradiated gemstones?". "Is it better to wear antique jewelry or older estate jewelry gemstones that have not been irradiated?"

Gemstones are irradiated to enhance and deepen the color of the stone and to make it more valuable. Gemstones can be irradiated by neutron bombardment in a nuclear reactor, electron bombardment in an accelerator of by exposure to gamma rays in a cobalt irradiator. Gemstones have been irradiated since 1977.

Irradiation causes realignment of the inclusions in the gemstone which changes the way the stone channels light. How the inclusions or impurities will be realigned by irradiation is unknown. Some gemstones take on poorer colors or loose definition from the realignment of the impurities. As a result, the gemstones that are most often treated with irradiation are the cheaper stones. A large number of stones can be treated at one time even though only a few of these stones will show an improvement in color. The increase in the value of the poor quality stone from the treatment justifies the expense of the treatment of large numbers of stones. Topaz is the most commonly treated stone as subjecting topaz to irradiation often produces the more valuable blue colored topaz.

Treating a gemstone is not necessarily bad. For example, Tanzanite is heat treated to turn the stone the high prized blue/purple color. Without heat treatment, Tanzanite is a not too attractive brown color.

It is difficult to tell if a stone has been treated by irradiation. It is said that some highly skilled jewelers can determine that a stone has been irradiated. What these jewelers cannot tell is how the gemstone was treated. There have been some concerns over irradiation treatments and the possible exposure of the wearer to radiation. Generally, the longer the gemstone is exposed to radiation and the higher the intensity of the radiation treatment, the deeper and more attractive the resulting color of the stone. This also increases the possibility of the impurities and trace elements in the stone becoming radioactive. The treatment most likely to cause activation of radioactivity is treatment in a nuclear reactor although treatment in an accelerator can make gemstones radioactive. Gemstones are not made radioactive by treatment in a cobalt irradiator.

Testing by the Nuclear Regulatory Commission (NRC) has estimated that the exposure of a person wearing a blue topaz stone at the highest levels of radioactivity would be exposed to an annual dose of 1/200th of the radiation exposure generate by a chest X-ray. There is no reason to be concern that wearing a gemstone treated by irradiation will cause cancer or will be a health risk. There are no advisories concerning irradiated gemstones from the NRC.

Many consumers with concerns regarding irradiated gemstones have altered their jewelry buying patterns and now instead of buying “the new, the exceptionally clear, the bright colored irradiated gemstones” are choosing antique and older estate (pre-1977) jewelry pieces. These consumers say that estate jewelry is more desirable in respect to their environmental and health concerns. This group of new consumers are finding renewed beauty in old-mine cut diamonds, emeralds with visible inclusions and corundum (sapphires and rubies) that are not 100% transparent.