Coral, the Stone That Was Alive

Coral used as a gem is not a mineral but the hard skeleton of colonial marine animals, principally Corallium species, built of calcium carbonate secreted by the living polyps; precious Mediterranean coral is the red Corallium rubrum. Because it is organic and only hardness 3 to 4, it is soft, sensitive to acid and to heat, and fades with wear.

Coral has one of the longest continuous runs in ornament and amulet of any material: it appears in Palaeolithic burials, was traded by the Romans as far as India, and was the classic apotropaic charm hung on European children against the evil eye and to ease teething, a use shown in Renaissance paintings of the Christ child. In modern usage the reef-conservation dimension has become part of the honest account of the material, since precious-coral harvesting depletes slow-growing colonies. See also Red Coral for the specifically astrological tradition.