(via Gem & Jewellery News, Vol. 7, Number 2, March 1998) Harry Levy writes:
1998 started with an international alarm for the gem trade and jewelry markets. The scare began in Bangkok with news that quantities of radioactive chrysoberyl cat’s eyes were being sold there and exported all over the world.
A few gem species have been irradiated for a number of years now to improve or change their color. The stone most subjected to this treatment has been white topaz. The most common types of irradiation have been electron and neutron bombardment of the stones to produce various shades of blue.
Electron irradiation produces paler shades of blue, known in the trade as ‘sky blue’. In this instance rough or cut pieces of white topaz are exposed to electron irradiation and the longer the exposure the stronger is the color, but a saturation point is reached beyond which the color will not intensify. When the stones are annealed (heated and maintained at certain temperatures) they turn blue. On cooling the stones maintain their color and the color change is permanent as far as we know.
The dealer or cutter who has the stones irradiated determines the amount of radiation the stones should be exposed to; this is an economic decision, as the longer the stones are irradiated the higher is the cost charged by the laboratory. Different stones from different localities need different quantities of irradiation to obtain the optimum color, but the dealer cannot experiment with small quantities as the fee for irradiation is based on the time and strength of exposure for material in a chamber of fixed capacity, however full it is. The other popular method is to expose the stones to neutron irradiation and in this instance the blue color produced is known in the trade as ‘London blue’. The color known as ‘Swiss blue’ is obtained by applying both types of irradiation to the topazes.
Since the color changes produced in topaz have been so dramatic, other stones have been exposed to such treatments in the hope of producing similar changes and this has resulted in such stones as ‘hot pink’ tourmalines (the hotness referring to the color not the radioactivity), and various colors in diamonds.
Subjecting a stone to irradiation is not something that can be done in the back of a kitchen or in a shed at the bottom of the garden. Stones are irradiated in a nuclear accelerator at known nuclear plants, research institutions or universities. Normally they are subject to the most rigorous government controls and workers would never release material which was dangerously radioactive to anyone involved in the gem trade. The stones are only released from such establishments when they display acceptable levels of radioactivity.
Scares about radioactive gemstones have been circulating ever since it became known that they could be treated in this manner. We are all exposed to various levels of irradiation in our everyday lives. During one of the early discussions it was alleged that a single flight in Concorde exposed one to more radiation, due to the height of the flight path, than being covered in irradiated topaz for a lifetime.
Other scare stories have concerned irradiated topaz being stolen from various vaults in Brazil, where they had been put to cool, and sold on the international markets while they were still dangerously radioactive. A similar story emerged at one of the Hong Kong shows about such stones from China. The basis for such stories seems to be economic, where dealers from one center are more than keen to believe that stones coming cheaper from another source must be dangerous.
Dealers and others who handle such stones would never expose themselves, their families, their staff or their customers to such danger, although with rumors constantly circulating in the trade an increasing number of dealers are beginning to include an instrument for detecting radioactivity as part of their equipment. A simple Geiger counter registers most but not all the known rays that could be present, other instruments are needed to register the troublesome ones.
Coming back to our radioactive chysoberyls, the media picked up the story and television pictures were flashed round the world showing worried-looking dealers and jewelry shop owners in Bangkok being shown such stones next to ticking Geiger counters. This is a marvelous story for an investigative reporter and whole television programmes on this topic have been shown in such countries as Germany.
Unless the trade is very careful, a lay person watch such a programme will be told about radioactive chrysoberyl cat’s eyes, but will only remember radioactivity in association with gemstones in general, and continued media coverage will soon convince him and his ilk that every stone and every diamond is radioactive and hence all jewelry is dangerous to wear.
Of course, the public has rarely proved itself to be so fickle. They are aware that many things they come into contact with have been subjected to irradiation, but they trust the authorities and the traders to be responsible and not subject them to any danger. It again comes down to education and all those involved in the jewelry trade must make themselves aware of exactly what they are handling. It is not enough to have the ability to buy and sell something at a profit, because the trade should be the ones most able to educate the public, who are their customers, answer their questions and allay any fears they may come across. And the safest way to trade is to deal with reputable suppliers.
No comments:
Post a Comment