Chatham, Knischka, and Lechleitner, as well as other manufacturers, are known to have treated Verneuil flame-fusion synthetic rubies by immersion in a flux melt to induce patterns like the “fingerprints” seen in some natural rubies. Some of these products are on the market and may require careful microscopic examination for identification. Also seen marketed as natural is a synthetic ruby of unknown manufacture with a distinctly different flux-induced pattern. This pattern—a continuous, three-dimensional, honeycomb-like cellular structure of flux-filled fractures—is easily recognizable with a gemological microscope.
