Coral Gem Identification: Natural Colour, Dye and Imitations

A red bead is not automatically natural-colour precious coral. Gem coral includes different animal skeleton materials, and the market also contains dyed products and imitations. Understanding the material and understanding its colour are two separate parts of identification.

Different corals have different structures

SSEF’s 2005 overview distinguishes calcitic precious coral, aragonitic blue coral and corals with horn-like organic skeletons. Their structures and physical properties differ. Fossilised coral may also have undergone mineral replacement, so it should not be treated as identical to recent coral.

Clues to dye and resin

Dye may collect in pores, fissures or other open spaces. Resin may appear as a different substance within these areas. Drill holes can sometimes expose useful clues that are hidden on a polished outer surface.

These observations are clues, not a complete home test. A clean-looking surface does not prove natural colour. SSEF describes combining microscopy with Raman spectroscopy to investigate the material and its colouring substances.

How shell can imitate coral

Dyed shell beads can resemble coral. Mineral identification helps distinguish aragonitic shell from calcitic precious coral, while layered structures can provide supporting evidence. Ask for the actual material name and a clear treatment description. A label such as red coral may leave both questions unanswered.

Sources and further reading

SSEF Swiss Gemmological Institute, Facette, issue 12, January 2005, pp. 6-7, “Coral en Vogue: Revival due to fashion trends”. Read the original SSEF PDF.

This independent educational article explains historical SSEF research in original, simple English. It is not an SSEF publication. No source photographs or illustrations are reproduced.