Irradiation of Gemstones
Colorless topaz after radiation to turn it blue, but before heating .
Light blue topaz before radiation.....topaz turns brown after radiation......after heating the topaz turns blue.
What is the story behind this treatment?: Irradiation is the process by which gemstones are exposed to various types of nuclear radiation to change some parts of the crystal structure. This change in crystal structure causes the gemstone to alter its color, either by the addition or subtraction of some part of the crystal structure. Did everybody understand that? No? OK, let's put it another way: Gemstones that are irradiated have their color changed due to being placed in a nuclear reactor which cooks the hell out of the stone until it changes color. Better? For me too. I do not really want to get into color centers and crystal lattices because its boring and hard to understand. But a gemstone having its color changed due to radioactive bombardment is pretty much a straight forward concept that everyone can grasp.
Can I wear it everyday?: Generally yes. Most radiated stones will have colors that are permanent. Mainly because the energy level that is present in the reactor is so high that it requires an equal energy level to undo the color change. So unless you are hanging around inside a nuclear reactor for a few days, the colors are generally permanent.
What does this treatment do to the stone?: Basically, the radiation bombards the atoms in the gemstones, knocking them either out of the stone, or moving them around inside the stone (you physics guys give me some latitude here). The removal from the stone, or relocation inside the stone, causes the stone to react to light differently, which causes the stone to offer a different color. For instance, as shown above, very light blue topaz is placed in a nuclear reactor which turns it brown. Basically by changing the crystal structure of the topaz (knocking some of the atoms out). The topaz turns brown as shown in the middle photograph above. Then, the stones are heated to bring out the blue color and get rid of the brown.
Does this treatment save money?:Oh Yeah! Without the radiation of gemstones there would be very little blue topaz and very few colored diamonds on the market, to name a couple of stones. Natural blue topaz jeweler as shown below would be virtually impossible to find, and would cost a fortune to own.
What do I need to know before going shopping?: First, if you are buying a colored diamond you should assume that it has been treated if it is green, brown, or yellow. If you are buying a colored diamond in these, or any, colors that are represented to be natural you should always ask for a certificate of origin of color from a major gemological institute. And I am not talking about the IGI in New York. I mean someone like the GIA, AGS or another major qualified gemological lab with a competent gemological staff.
IMPORTANT NOTE: Irradiated gemstones can be radioactive! Distribution of blue topaz is controlled in the United States by the Nuclear Regulatory Commission, due to the fact that radiated blue topaz stays radioactive for up to a year after treatment. And in 1970 a lot of "hot" blue topaz was sold on the world markets. Also, some diamonds also stay radioactive for many years after radiation treatment. One diamond recently tested in a major European laboratory was so radioactive that it would not be safe to be worn for 35,000 years. So be sure that if you are buying a gemstone that could possible be radiated, like blue topaz, colored diamonds, and even chrysoberyl cat's eyes, be sure and buy from a jeweler with a well trained gemologist who knows how to protect your interest of your purchase. This is not meant to scare anyone, but to let you be aware that a well trained gemologist can be an important person to know when shopping for gemstones.
Special Identifying Properties
and Tests: There are a
number of methods to identify irradiation. The best was to see
if a stone is still "hot" is with a Geiger counter.
One of the most fun is one of the old Victoreen CDV-700's from the
Cold War days in 1961. (Ref: Radioactivity
Demonstration in Teachers Interesting Demonstrations Page)
These units will measure small amounts of radiation, unlike the
later models that were only calibrated to measure large amounts
of radiation from a world war. Or there are other current models
available but near as much fun to own. The CDV-700 will identify
most types of radioactive gems and minerals so you can test your
blue topaz or chrysoberyl cat's eyes without needing to send them
to a lab. Diamonds are the same but you will also need to know
whether a diamond has been colored by radiation or is natural
in color. While there are a lot of basic gemological tests using
a spectroscope that can identify radiation color origin, I strongly
recommend that consumers and jewelers alike seek the services
of a major gemological laboratory.
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