Irradiation

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In 1904 William Crookes, a well known physicist discovers that diamonds turn green upon exposure to radium. The diamonds stayed radioactive and were therefore unfit to serve as jewelry stones. But… the concept of color change due to radiation had been discovered and people were on to it.


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During the 1930's Professor Ernest Lawrence who worked at Berkeley, California built the cyclotron; a device that could accelerate charged atomic particles to high velocities using a magnetic field. The invention of the cyclotron lead to experiments with diamond irradiation in the 40’s and 50’s.


Professor Lawrence next to his cyclotron


The colors that were induced were limited to the surface of the stones since the radiation couldn’t penetrate the whole stone which results in the tell tale ‘umbrella effect’ which indicates cyclotron irradiated diamonds. Encountering an umbrella effect tells us that the stone has been treated in the late 40’s or 50’s.

Halfway through the decade the first linear accelerators were built and, of course, diamonds were irradiated with it. These diamonds sometimes have a color concentration at the culet, visible from the side. When nuclear reactors became more common color change could be achieved throughout the the stone and radiation detection for simple gemologists stopped being easy.


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Nowadays a score of gemstones is treated with the aid of new irradiation techniques. Below follows a list of those stones, the effects and the date of the first reports in gemological literature:

Irradiation
Beryl Changing color 1947 (American Mineralogist, vol. 32, p 31-43 jan-feb 1947. Reported in G&G spring 1947)
Corundum Changing color 1947 (American Mineralogist, vol. 32, p 31-43 jan-feb 1947. Reported in G&G spring 1947)
Diamond Changing color

1914, Irradiated diamonds by immersion in radium bromide, (Pough & Schulke as reported in G&G spring 1951)
1938, Cyclotron irradiated diamonds (Hardy G&G summer 1949)

Pearl Darkening 1967, (R.T. Liddicoat G&G spring 1967)
Quartz Changing/introducing color 1949 (G&G winter 1949)
Spodumene Changing color 1947 (American Mineralogist, vol. 32, p 31-43 jan-feb 1947. Reported in G&G spring 1947)
Scapolite Changing/introducing color (American Mineralogist, vol. 32, p 31-43 jan-feb 1947. Reported in G&G spring 1947)
Topaz Changing color 1909 irradiation of pink topaz to orange (Pough & Rogers, 1947)


1957 stable blue color product of irradiation in combination with annealing, (Pough, 1957)

Tourmaline Changing color (American Mineralogist, vol. 32, p 31-43 jan-feb 1947. Reported in G&G spring 1947)
Zircon changing color (structure from crystalline to metamict) (American Mineralogist, vol. 32, p 31-43 jan-feb 1947. Reported in G&G spring 1947)
Lang Antiques
Lang Antiques