Out of all of the gemstone treatments currently on the market, there is one treatment that always raises questions. That treatment is irradiation.
When the word “irradiation” is whispered, the first thing that springs to mind is: is it safe? Good news: yes it is. We will explore why gemstones are irradiated and what the NRC (Nuclear Regulatory Commission) does to ensure your safety.
The gemstone that has caused the most much discussion is blue topaz. Since the 1980s, this gemstone has routinely undergone irradiation to give it the blue color we all know and love. There are two methods for irradiating blue topaz, and they both involve types of nuclear reactors.
The first method is to use a stream of electrons to induce the color. The second method is to use a stream of neutrons.
While the electron method produces topaz that does not pose a hazard to humans, topaz treated with the neutron method can continue to emit radiation for years. After extensive research from various bodies including the NRC, rigorous checks have been put in place to ensure all neutron-irradiated blue topaz that comes to market is safe to handle.
The list below gives examples of the gemstone colors that can be achieved with irradiation. This is not a complete list and other color variations are available.
Topaz: Colorless before treatment. Blue after treatment.
Diamond: Colorless to Green / Blue
Pearls: Light color to Gray-Blue
Tourmaline: Colorless to Yellow / Brown / Pink / Red
There are three main ways to irradiate gemstones. Each method uses a different facility and can have different effects on gemstones.
Neutron Bombardment – Use of a nuclear reactor
Electron (Beta) Bombardment – Use of an accelerator
Gamma Radiation – Use of a cobalt-60 facility (these facilities are commonly used to sterilize medical equipment)
The irradiation process can be thought of in terms of balls. The neutron method fires large tennis balls at the subject to induce the color. The electron method uses tiny balls to fire at the subject. Gamma radiation uses microscopic balls with huge amounts of energy to induce color.
The longer a gemstone is exposed to irradiation the more chance of the stone becoming radioactive. The reason why gemstones become radioactive is if impurities within the gemstone become active. Stones treated with either electron or neutron irradiation will remain radiaoactive for a period of time. Stones treated with gamma radiation will not become radiactive.
For stone treated with electron irradiation the radiation level of the material that comes out of the reactor is generally deemed safe to handle by the NRC. Even still there are strict guidelines in place to ensure that the Topaz is set aside for a number of months. Remember that radiation decays over time so if the stones are safe to handle straight out of the reactor they are safe to handle once they come to market.
Neutron radiation takes a longer period to become safe. According to the NRC the average time for freshly neutron irradiated Topas to become safe is 12 – 24 months.
Radiation is everywhere. It is a natural part of life and we actually can’t live without it. Let's do some quick comparisons. Radiation is measured by millirem or Radiation Absorbance Dose.
A 6-carat topaz worn for a year (assuming the radiation level is at the maximum the NRC deems safe) = 0.03 millirem
Now, let's compare that to some other common things, all based on 1-year exposure.
Porcelain Crown or False Teeth = 0.07 millirem (2.3x that of Topaz)
Chest X-ray = 10 millirem (333x that of Topaz)
Food and Water (yes, even these have natural radiation) = 30 millirem (1,000x that of Topaz)
Trans Atlantic Flight = 2.5 millirem (83x that of Topaz)
Watching TV = 1 millirem (33x that of Topaz)
This is a very complex subject, so let's break it down with some examples. We'll explain the two ways gemstones get their color: chromophores (impurities) and color centers (defects).
Chromophores are impurities in minerals that cause color.
Take sapphire for example. Pure sapphire is clear. Add in titanium as an impurity and it turns blue. Add in iron, it turns yellow. Add chromium, it turns pink. Add iron and chromium, you get orange/pink (padparadscha).
This is the most common way gems get their color. So, if you want to enhance a sapphire, you can diffuse titanium to it (through surface diffusion) and create a bluer stone.
Now, let's look at diamonds. All diamonds are pure carbon. So, how do they have pink diamonds, yellow diamonds, and red diamonds? The answer: a color center. This is a defect in the crystal structure of the gem, and this defect causes color.
How do you cause a defect? You smash the atoms inside the crystal. This is where the electron radiation and neutron radiation come in. You literally smash the gem with radiation to cause a defect that induces color.
These defects can be fixed by applying energy to the gem. In the case of kunzite, this energy is in the form of UV radiation from the sun. The energy from the sun repairs the crystal structure and removes the pink color from the gem.
You will see plenty of hiddenite in the market that has been irradiated. It has a color center induced, causing the green color. This color is sensitive to sunlight just like kunzite.
However, the color in topaz and tourmaline, for example, is stable. The process for creating the blue color in topaz involves irradiating the gemstone, then heating it. This heating process actually stabilizes the color, creating a gem that will not fade or deteriorate over time.
Some of the brown topaz you will see is the result of electron radiation. If this topaz is heated, it will turn blue and stabilise the color. However, a few years ago someone decided they would Irradiate topaz. But, when it turned brown with an orange tinge, they decided not to heat it to turn it blue but sell it as Imperial Topaz. Sites like Gem Rock Auctions do not allow these types of stones to be sold as Imperial Topaz.
Now that you know how safe irradiated gemstones are, it is time to decide if you really want to wear those false teeth. After all, would you rather have a set of false teeth or twice the number of topaz gemstones?
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