surface diffusion treatments.6, blue sapphire, corundum, gems, lattice diffusion

Although not exactly new to gemology, surface diffusion-treated corundums (SDTCs) have recently been creating quite a stir in world gem markets, particularly the important Bangkok corundum market. The following article examines the subject in detail, starting with the original Linde patents and continuing up to the present-day Deep Diffusion" treatment. Methods of identification are discussed, as well as much of the back-room politics and maneuvering which has surrounded this controversial treated gem material. Also included is a quick reference table giving a detailed summary of the key identifying features of all types of natural, treated and synthetic corundums."