The use of radiation to color gemstones, especially diamonds (blue topaz is also common). Generally, nuclear reactors, linear accelerators, and gamma ray facilities are used to this end.

Green is the most common color sought by irradiation for diamonds simply because natural green diamonds, even in the rough, are nigh impossible to find.

Irradiation is very easy to detect, especially in faceted stones. The radiation only colors the surface of the stone, so if the stone is polished or abraded somehow, the color can sometimes wear off. In addition, in faceted stones, the color from irradiation will be more vivid near the culet since the gem is thinner there.

One of the first tests done to detect irradiation is a test to determine whether the stone is still "hot," or radioactive. Technological advances have helped to prevent radioactive stones from entering the market by allowing effective testing of the gemstones. However, blue topaz typically stays radioactive for a year after being treated, and diamonds can remain hot for several to several thousand years.

For other techniques of enhancing color and/or clarity, see Gem Enhancement.

Being the daughter of a nuclear physicist, I wanted to do a little explaining about the difference between "irradiated" and "radioactive".

Most people have only the vaguest idea of what radiation really is. Myths abound, like "if you get too many x-rays you'll glow in the dark". There is a difference between being irradiated and becoming radioactive. Radiation is nothing but waves (especially x-rays and microwaves) or particles (as in alpha, beta or gamma radiation). Being irradiated, i.e. exposed to radiation of either kind, will not make you or anything else radioactive. Ingesting or absorbing radioactive MATERIAL will. Thus, a hot dog that has been microwaved will not and cannot become radioactive; a hot dog that has been marinaded in plutonium will. Radiation can and does cause damage, but only when directly applied to whatever it is damaging. It cannot be transferred through an irradiated object.

Since someone asked a question about whether particle irradiation can cause things to become radioactive, I guess I'll have to explain that too. Actually, the particles themselves are not radioactive. The reason they do damage is that because of the radioactive decay of some radioactive compound they are kicked out of the nucleus at extremely high speed. They bash their way through the atoms (including those in the DNA) of your body, kind of like a bullet. The particles themselves are just photons, neutrons or electrons - which are not in and of themselves radioactive. The reason why radioactive decay can cause a chain reaction in a bomb or reactor is because the material surrounding it is unstable as well, but our bodies are composed of stable compounds which do not disintegrate because of a little extra energy.

Ir*ra`di*a"tion (?), n. [Cf. F. irradiation.]


Act of irradiating, or state of being irradiated.


Illumination; irradiance; brilliancy.

Sir W. Scott.


Fig.: Mental light or illumination.

Sir M. Hale.

4. Opt.

The apparent enlargement of a bright object seen upon a dark ground, due to the fact that the portions of the retina around the image are stimulated by the intense light; as when a dark spot on a white ground appears smaller, or a white spot on a dark ground larger, than it really is, esp. when a little out of focus.


© Webster 1913.

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