How do you heat-treat sapphires with beryllium?

Expert Columnists - Mary Johnson - Gemological Answers

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How do you heat-treat sapphires with beryllium?

By Mary L. Johnson

June 24, 2009

Mary Johnson has a doctorate in mineralogy and crystallography and is a former research and development manager at the Gemological Institute of America.

Questions often arise about treatments for colored gemstones. For this edition of "Gemological Answers," a reader wrote in with a question about beryllium-diffused blue sapphires, and a professor at the California Institute of Technology wrote in with a response to an earlier column on irradiated blue topaz.

Question: As expert lapidarists, wholesalers and exporters of all kinds of gemstones, my company specializes in yellow sapphires and beryllium-diffused heated yellow sapphires. I am very eager to learn about beryllium treatment in blue sapphires. I have searched in many places and cannot find the information I want.

I would like to learn more about how to heat-treat sapphires with beryllium to obtain a blue color.

Can you tell me what sort of chemicals and what type of heating system (i.e., how to supply heat and for what duration) to use for this treatment?

Answer: As far as I understand it, the same technology is used to diffuse beryllium into blue sapphires as is used for adding the yellow component to pink sapphires. Beryllium diffusion might lighten the color of some dark blue sapphires. The source of beryllium is usually chrysoberyl.

There is a book titled Beryllium-Treated Rubies and Sapphires, by Ted Themelis (Themelis.com), describing Themelis' experiments at treating corundum with beryllium. The temperatures involved are very high (1750 to 1850 degrees Celsius), so special furnaces might be needed.

I also tracked down some other references, including:

--"Beryllium-Treated Blue Sapphires," by Garry Du Toit, Richard W. Hughes and John I. Koivula. You can find the article on the Web site: AGTA-GTC.org/2006-03-29_be_sapphire.htm

--"Questions about treated sapphires from Thailand," from Pala International, (no specific author listed), are on the Web site: PalaGems.com/bulk_diffusion_sapphire.htm

--"Beryllium Diffusion of Ruby and Sapphire," by John L. Emmett and others, in the Summer 2003 Gems and Gemology, on the Web site: GIA.edu/gemsandgemology/18578/15202/1862/back_issue_article_detail.cfm

I hope these references help.

Update: Mineralogy professor George Rossman at the California Institute of Technology sent me some comments about my remarks on irradiated blue topaz. I had written the following: "Radiation is all around us, and it is impossible to make anything completely radiation-free." He agreed that this was a good way to state it, but found two of my written statements "a bit strident," so I'll share the back-and-forth between us below.

Johnson: "Irradiated topaz can contain certain isotopes that are hazardous to human health. In most but not all cases, this radiation decreases to 'safe' amounts within two years."

Rossman: In electron-irradiated topaz, radioactive sodium is the primary issue (if the electron energy is allowed to go above the normal beam energy used for irradiation). This radioactivity decays in days. Even in neutron-activated topaz, the levels of radioactive tantalum, iron, manganese, etc., are usually low compared with (for instance) the radioactivity in some natural zircons. Yes, it might take some years for these to decay the necessary number of half-lives to reach legal limits. However, "safe" is not the word I would use (given that although the topaz contains less radioactive material, they are, like everything else, never radiation-free).

Johnson: "Radiation damage can cause skin ulcers, cancer and cell death, and can lead to mandatory amputations or even death, but effects depend on the isotopes present and their amounts."

Rossman: To my knowledge, in even the worst cases of treated topaz ever described, the radioactivity and types of radiation dangers you mention are not present.

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