The coral belongs to the small class of organic gems, which are formed from biological processes. The precious coral is a kind of coral which grows in rocky sea depths, commonly in dark environments, in the deep ends as well as in dark caves. The coral structure is consisting of hard calcium carbonate, coloured by carotenoid pigments. Coral colour ranges from salmon pink to deep red, for that reason the word coral is often used to describe such colours. Due to its beautiful appearance it has been harvested since the ancient times. Coral jewellery has been discovered in many ancient Egyptian and prehistoric European sites.
The majority of precious coral is gathered in the Mediterranean Sea. A lot of precious coral is also found in the Pacific.