The early history of beryllium diffusion in sapphire, starting with the 2001 appearance of large numbers of padparadscha sapphires in the Thai gem market.
The use of high-temperature lattice-diffusion heat treatment with beryllium to lighten the color of blue sapphires.
Surface ('bulk') diffusion-treated corundums (SDTCs) created a stir in the Bangkok market in 1990. This article looks at the original patents and continues through the so-called "Deep Diffusion" treatment. Identification methods are discussed, as well as the backroom politics of disclosure. At the end is a quick-reference table summarizing key identifying features of all types of natural, treated and synthetic corundums.
In 1991, titanium-diffused blue sapphires reappeared in the Bangkok market after an absence of many years. Touted as "deep diffusion," the stones proved to have no greater color penetration than the original Union Carbide product.