A microscopy-based screening system to identify natural and treated sapphires in the yellow to reddish-orange colour range

摘要

Features visible under a microscope of untreated, heat-treated and beryllium-diffusion-treated yellow, orange and reddish-orange sapphires, including padparadschas, are presented. A microscopy-based screening system for recognition and distinction of untreated, heat-treated and diffusion-treated sapphires combines structural features such as growth structures, colour zoning and inhomogeneous colour distribution patterns with the visual appearance of inclusions. Spectra and chemical compositions may be added to these microscopic characteristics and applied to an evaluation of samples of unknown origin and unknown treatment history. These properties combine to form a type of locality-specific data set, and are considered in the light of present knowledge about treatment techniques. The screening system allows the recognition of most untreated or heat-treated samples from Sri Lanka and Montana, U.S.A., and their distinction from beryllium-diffusion-treated samples from Sri Lanka, Montana, U.S.A., llakaka, Madagascar, and Songea, Tanzania.