Feature Gems & Gemology, Summer 2008, Volume 44, No. 2

Coloring of Topaz by Coating and Diffusion Processes: An X-Ray Photoemission Study of What Happens Beneath the Surface

Surface-treated topaz has become a viable alternative to topaz colored by irradiation.
Unlike irradiation, which modifies the entire gemstone, coloration by chemical modification is limited to the near-surface region. The treatment techniques are well established, but less is known about how the processes involved create the desired appearance. In this study, X-ray photoemission spectroscopy in combination with sputter depth profiling proved successful in characterizing two fundamentally different coloration mechanisms of chemically treated topaz: colored coatings and diffusion-induced coloration.