Feature Gems & Gemology, Spring 2007, Volume 43, No. 1

Pink-to-Red Coral: A Guide to Determining Origin of Color

Pink-to-red coral has a long history as an ornamental gem material in jewelry, carvings, and sculptures. However, due to a variety of environmental and legal factors, the supply of high-quality, natural-color coral in this color range has dramatically decreased in recent years—and the quantity of dyed coral on the market has increased. From a study of more than 1,000 natural- and treated-color samples, this article summarizes the procedures that are useful to identify the color origin of pink-to-red coral. A variety of techniques—including magnification, exposure to acetone, and Raman analysis—can determine if the color of a piece of such coral is dyed. Although there are limitations to the use of magnification and acetone, Raman analysis can establish conclusively that the color is natural.