Coral can be red, pink white, black or blue and is made of the calcified skeletal remains of marine animals called coral polyps. Unpolished coral is dull but can be polished to a glass like finish. The most valuable coral is red. Coral is listed in CITES Appendix II, which means it is threatened by trade – it may become endangered if trade is not controlled and monitored. Some legal harvesting of coral is allowed, but its current status is something to bear in mind when purchasing non-antique jewellery.