Feature
Gems & Gemology, Summer 1990, Vol. 26, No. 2

The Identification of Blue Diffusion-Treated Sapphires

Peer Reviewed Article
Robert E. Kane, Robert C. Kammerling, John I. Koivula, James E. Shigley, and Emmanuel Fritsch
Blue diffusion-treated sapphires are becoming more prevalent than ever before. The diffusion technique, which involves the addition of color-causing chemicals during heat treatment, results in a thin layer of color at the surface of colorless or light-colored sapphire. The color was found to be stable to routine cleaning procedures; however, it may be partially or completely removed if the stone is repolished or recut. Recently, significant quantities of so-called "deep" diffusion-treated sapphires have entered the market. This article documents the properties of these and other blue diffusion-treated sapphires, and presents means of identifying this method using simple gemological tests.

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