The word Coral is derived from the ancient Greek word "korallion" - coral. Historically, this word was used to describe the precious red coral from the Mediterranean.
The Coral is a branching skeleton-like structure built by polyp-bearing marine animals that live in colonies and are found throughout the world in the seas and oceans from freezing polar regions to equatorial reefs and at all depths. The branches are generally 20-40 cm in hight and up to 6 cm thick.
Precious coral, Corallium, is a gemstone quality variety of natural coral, closely related to reef-building 'stony' coral. Precious coral is a deep water coral that forms in rocky seabeds with low levels of sedimentation, typically in dark environments of over 500 feet deep, including caverns and crevices. Precious coral is slowly built by very small marine animals known as coral polyps. These tiny, soft-bodied creatures form with minute, hard shells that accumulate as the colony grows. Over time, the colony begins to form complex branches and skeletal structures composed of hardened calcium carbonate, and colored by carotenoid pigments. These biological formations grow very slowly, often as little as just 1 mm per year, ranging in size from small, hand-sized structures to enormous coral reefs. The distinguishing characteristic of precious corals is their durable and intensely colored red or pink-orange skeleton.
Most coral gemstones available today are varieties of Corallium rubrum, a very specific pink to red colored species of the coral genus. In the trade, Corallium rubrum is sometimes referred to as 'noble coral' and is considered to be the most desirable type of coral for jewelry. Noble coral also includes the popular 'angel skin coral', a pink to salmon colored coral.
The hard skeleton of red coral branches is naturally matte, but can be polished to a glassy shine. Owing to its intense and permanent coloration and glossiness, precious coral skeletons have been harvested since antiquity for decorative use.
Precious coral typically exhibits a range of warm pinkish to red colors, including light-red to salmon (momo coral), and medium-red (Sardegna coral) to deep ox-blood red (moro coral). Noble coral has the most desirable uniform color, but can often exhibit streaks or spots of white to pinkish red, especially angel skin coral. Precious coral can also be found in other colors such as gold, white, black and blue. Gold colored coral from Hawaii is extremely rare and highly desired for its slight chatoyancy. Black and blue coral is not often used for gems or jewelry as its trade is heavily regulated.
Coral jewellery has been found in ancient Egyptian and prehistoric European burials, and continues to be made to the present day. It was especially popular during the Victorian age. The Gauls used it for the ornamentation of their weapons and helmets; but by this period, so great was the Eastern demand, that it was very rarely seen even in the regions which produced it. The origin of coral is explained in Greek mythology by the story of Perseus. Having petrified Cetus, the sea monster threatening Andromeda, Perseus placed Medusa’s head on the riverbank while he washed his hands. When he recovered her head, he saw that her blood had turned the seaweed into red coral. Thus, the Greek word for coral is 'Gorgeia', as Medusa was one of the three Gorgons. Poseidon resided in a palace made of coral and gems, and Hephaestus first crafted his work from coral.
Coral is found only in tropical to subtropical saltwater environments. Though precious coral is found in locations all around the world, Torre del Greco (near Naples, Italy) has been the top coral trading center for over 200 years, processing nearly 75% of the entire world's supply of coral. Most of the precious coral available today is harvested from the Western Mediterranean Sea, especially in Sardinia. Notable deposits are also found in the Red Sea, the Bay of Biscay, the Malaysian Archipelago, the Midway Islands, Japan, Taiwan, Australia and the Hawaiian Islands.