Coral is a semitransparent to opaque form of calcium carbonate. It occurs in a variety of colours including white, pink, orange and black. The rarest, and most expensive, variety is blood coral which has a deep red colour. Another valued variety is called “angel skin”; this is white in colour with a faint tinge of pink or peach.
It was believed that coral could cure madness, give wisdom, stop bleeding, calm storms and prevent sterility. To retain its powers it had to be kept uncut.
Coral is usually cabochon cut (i.e. dome shaped), or carved. It will be damaged by contact with any acid, including vinegar.