|About Blue Topaz
This is not surprising. Topaz is a very hard material -- 8 on the Mohs hardness scale -- and blue topaz is a very pretty stone, available in a wide range of vivid hues with a striking vitreous luster. It is also a very affordable gem; we are usually able to sell it at prices under $6.00 a carat. If you compare that to the cost of aquamarine it makes blue topaz a tremendous value.
At the same time, blue topaz is a gem that is not well understood by many buyers, and some recent controversy in the USA has led some buyers to rethink their blue topaz purchases. But this is a case where a little knowledge will go a long way.
There are two important things to know about blue topaz. The first thing is that while topaz is very hard, it is not the most durable gemstone. That's because it has perfect cleavage, a property it shares with diamond. That means it can be chipped or split by a sharp blow, so it should be protected from hard knocks.
The second important thing is that topaz does not occur naturally in the deeply saturated blues you find in the market today. Blue topaz in nature is very rare indeed, and tends to a very pale blue. The vivid blues available in the market have all been produced by treating white topaz -- first with irradiation, then with heat. The color change is permanent and stable, but recently there has been some controversy about the safety of this treatment for the consumer.
There are 2 different irradiation methods used to produce blue topaz. One method, used to produce the lighter blue known as Sky Blue, uses gamma rays from Cobalt 60 sources or (more commonly) electrons produced by a linear accelerator, followed by heat treatment. The darker blue tones, known by the names Swiss Blue and London Blue, are achieved by bombardment from electrons produced in a nuclear reactor, followed by heat treatment.
Because of residual radioactivity, the irradiated topaz must be held in a secure facility for a period of time before it can be released for heating, cutting and polishing. The time varies from a few weeks for topaz irradiated in a linear accelerator to a few months for topaz irradiated in a nuclear reactor. There are very strict rules in place to protect not only consumers but also the cutters and gem dealers who handle these gems on a daily basis.
In July of 2007 the American Nuclear Regulatory Commission (NRC) reminded the gemstone and jewelry industry that current regulations require the initial importer of nuclear irradiated gems to be licensed by the NRC. Because there are currently no companies licensed by the NRC to import irradiated gems, several large jewelry chains in the US decided to remove blue topaz from their shelves since they could not assure the public that these gemstones were completely safe.
In August 2007 the NRC themselves tested 9 batches of irradiated blue topaz averaging 500 carats each and found that the topaz posed no health risk. They issued a Fact Sheet on Irradiated Gemstones to assure the public that these gemstones were quite safe. The NRC is now working with the industry to put a testing system in place that will include topaz treated in linear accelerators as well as those treated in nuclear reactors. Anything that can be done to assure the market that this very popular gemstone is safe is worth doing. But recent events have shown that there is not much ground for concern.
- First Published: October-17-2007
- Last Updated: October-06-2010
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