How Are Diamonds Irradiated?
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Electron Irradiation
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The colors produced by irradiation depend on the type of diamond used and the process which is performed on the diamond. The first method is produced by high energy electrons sent through linear accelerator at the diamond. The color is wholly dependent on the type of diamond used. This is the most common method and produces brilliant colors such as blue, green, yellow, brown and red brown. The color lies on the surface of the diamond in this process.
The diamond is placed in a chamber where a Van de Graaff generator shoot electrons at it for 15 to 500 hours. The beam of electrons contains 10 kilowatts to 500 kilowatts of power. The diamonds are then flushed with a coolant and removed from the chamber. In total the gem takes 4 to 25 gigarads of energy depending on the desired color. One gigarad is fatal to humans. After a few hours the diamond are no longer radioactive and can be used in jewelry. In order to produce yellow or brown diamonds the diamonds are heated or annealed at 300 to 1200 degrees centigrade.
Fast Neutrons
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The second process is use of sending fast neutrons at the diamond. This produces the black diamond. However this process carries the slight danger of producing a radioactive diamond. Similar to electron irradiation, diamonds are placed in a chamber and neutrons are fired at it via the piles in nuclear reactors. The stones are annealed at 500 to 900 degrees centigrade to add yellow to the diamond and make it green. Because of the danger of using this method, this process is banned in the United States.
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Cyclotron
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By using a cyclotron produces a green to black surface color on the diamond. It is used rarely but unlike the neutron method does not produce a radioactive diamond. The cyclotron is giant electro-magnet which generates a field that bombards the diamonds with protons and deuterons, the nucleus of a stable isotope of hydrogen, at high speeds. The diamond is then heated in a furnace to over 800 degrees centigrade to make the color permanent.
Gamma Radiation
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Producing a blue to green diamond, gamma radiation is the cheapest method of irradiating diamonds. The process is rarely used because it can take several months. Diamonds are chambered with cobalt-60 a radioactive isotope of cobalt, for several month. They are cool and removed. When exposed to sunlight the color can fade after a few months.
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