Young Blonde Girl Wearing Little Corals Necklace On The White Couch

The two biogenic precious gemstones, coral and pearl, although drastically different in appearance, are chemically very similar. Both are mostly calcium carbonate deposited by marine invertebrates.
Another unrelated species, the Hawaiian black coral is sometimes used as an ornamental material. Its skeleton is not mineralized, consisting mostly of conchiolin.
In Hindu astrology red coral is associated with the planet Mars.
A branch of red coral figures prominently in the civic coat of arms of the town of Alghero, Italy.