Feature Gems & Gemology, Spring 2009, Volume 45, No. 1

Identification of the Endangered Pink-To-Red Stylaster Corals by Raman Spectroscopy

All corals within the Stylasteridae family (including the Stylaster genus) are listed in Appendix II of CITES; this means they are protected and their trade requires an export permit, unlike corals from the Corallium genus, which include most pink-to-red corals used in jewelry. Raman scattering demonstrates that corals from the Stylaster genus contain carotenoid pigments (polyenic pigments substituted with methyl groups), whereas those from the Corallium genus are colored by unmethylated polyenic pigments. Additionally, Stylaster corals are made of aragonite, whereas those from Corallium are composed of calcite. Through Raman scattering analysis, the fully protected Stylaster pink-to-red corals may be distinguished from this other type of gem coral.