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Coral (precious)
Encyclopedia
Precious coral or red coral is the common name given to Corallium rubrum and several related species of marine coral
. The distinguishing characteristic of precious corals is their durable and intensely colored red or pink skeleton
, which is used for making jewelry.
. It grows at depths from 10 to 300 meters below sea level, although the shallower of these habitats have been largely depleted by harvesting. In the underwater caves of Alghero
, Sardinia
(the "Coral Riviera") it grows at depth from -4 mt to -35 mt. The same species is also found at Atlantic
sites near the Strait of Gibraltar
and at the Cape Verde
Islands. Other Corallium species are native to the western Pacific
, notably around Japan
(Corallium japonicum) and Taiwan
; these occur at depths of 350 to 1500 meters below sea level in areas with strong currents.
, colored in shades of red by carotenoid
pigments. In living specimens, the skeletal branches are overlaid with soft bright red integument, from which numerous retractable white polyp
s protrude. The polyps exhibit octameric radial symmetry.
The hard skeleton of red coral branches is naturally matte, but can be polished to a glassy shine. It exhibits a range of warm reddish pink colors from pale pink to deep red; the word coral
is also used to name such colors.
Owing to its intense and permanent coloration and glossiness, precious coral skeletons have been harvested since antiquity for decorative use. Coral jewelery has been found in ancient Egypt
ian and prehistoric Europe
an burials, and continues to be made to the present day.
Precious coral has relative density
of 3.86 and hardness 3.5 on the Mohs scale
. Due to its softness and opacity, coral is usually cut en cabochon
, or used to make bead
s.
and India
, where it was highly
esteemed as a substance endowed with mysterious sacred
properties. It is remarked by Pliny
that, previous to the
existence of the Indian demand, the Gauls were in the habit
of using it for the ornamentation of their weapons of war and
helmets; but in his day, so great was the Eastern demand, that
it was very rarely seen even in the regions which produced it.
Among the Romans branches of coral were hung around children's
necks to preserve them from danger, and the substance had
many medicinal virtues attributed to it. A belief in its potency
as a charm continued to be entertained throughout medieval
times; and even early in the 20th century in Italy was worn as a
preservative from the evil eye, and by females as a cure for
sterility.
From the Middle Ages upwards the securing of the right
to the coral fisheries on the African coasts was an object of
considerable rivalry among the Mediterranean communities of
Europe. Previous to the 16th century they were controlled by
the Italian republics. For a short period the Tunisian fisheries
were secured by Charles V to Spain; but the monopoly soon
fell into the hands of the French, who held the right till the
Revolutionary government in 1793 threw the trade open. For
a short period (about 1806) the British government controlled
the fisheries, but later returned to the hands of the French
authorities. Previous to the French Revolution
much of the coral
trade centred in Marseilles; but since that period, both the
procuring of the raw material and the working of it up into the
various forms in which it is used became peculiarly Italian
industries, centering largely in Naples, Rome and Genoa.
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
(in some variants the reeds) 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.
The Romans
believed coral could protect children from harm, as well as cure wounds made by snakes and scorpions and diagnose diseases by changing colour.
Coral
Corals are marine animals in class Anthozoa of phylum Cnidaria typically living in compact colonies of many identical individual "polyps". The group includes the important reef builders that inhabit tropical oceans and secrete calcium carbonate to form a hard skeleton.A coral "head" is a colony of...
. The distinguishing characteristic of precious corals is their durable and intensely colored red or pink skeleton
Skeleton
The skeleton is the body part that forms the supporting structure of an organism. There are two different skeletal types: the exoskeleton, which is the stable outer shell of an organism, and the endoskeleton, which forms the support structure inside the body.In a figurative sense, skeleton can...
, which is used for making jewelry.
Habitat
Red corals grow on rocky seabottom with low sedimentation, typically in dark environments—either in the depths or in dark caverns or crevices. The original species, C. rubrum, is found mainly in the Mediterranean SeaMediterranean Sea
The Mediterranean Sea is a sea connected to the Atlantic Ocean surrounded by the Mediterranean region and almost completely enclosed by land: on the north by Anatolia and Europe, on the south by North Africa, and on the east by the Levant...
. It grows at depths from 10 to 300 meters below sea level, although the shallower of these habitats have been largely depleted by harvesting. In the underwater caves of Alghero
Alghero
Alghero , is a town of about 44,000 inhabitants in Italy. It lies in the province of Sassari in northwestern Sardinia, next to the sea.-History:The area of today's Alghero has been settled since pre-historic times...
, Sardinia
Sardinia
Sardinia is the second-largest island in the Mediterranean Sea . It is an autonomous region of Italy, and the nearest land masses are the French island of Corsica, the Italian Peninsula, Sicily, Tunisia and the Spanish Balearic Islands.The name Sardinia is from the pre-Roman noun *sard[],...
(the "Coral Riviera") it grows at depth from -4 mt to -35 mt. The same species is also found at Atlantic
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
sites near the Strait of Gibraltar
Strait of Gibraltar
The Strait of Gibraltar is a narrow strait that connects the Atlantic Ocean to the Mediterranean Sea and separates Spain in Europe from Morocco in Africa. The name comes from Gibraltar, which in turn originates from the Arabic Jebel Tariq , albeit the Arab name for the Strait is Bab el-Zakat or...
and at the Cape Verde
Cape Verde
The Republic of Cape Verde is an island country, spanning an archipelago of 10 islands located in the central Atlantic Ocean, 570 kilometres off the coast of Western Africa...
Islands. Other Corallium species are native to the western Pacific
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
, notably around Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
(Corallium japonicum) and Taiwan
Taiwan
Taiwan , also known, especially in the past, as Formosa , is the largest island of the same-named island group of East Asia in the western Pacific Ocean and located off the southeastern coast of mainland China. The island forms over 99% of the current territory of the Republic of China following...
; these occur at depths of 350 to 1500 meters below sea level in areas with strong currents.
Anatomy
In common with other Gorgonacea, red corals have the shape of small leafless bushes and grow up to a meter in height. Their valuable skeleton is composed of intermeshed spicules of hard calcium carbonateCalcium carbonate
Calcium carbonate is a chemical compound with the formula CaCO3. It is a common substance found in rocks in all parts of the world, and is the main component of shells of marine organisms, snails, coal balls, pearls, and eggshells. Calcium carbonate is the active ingredient in agricultural lime,...
, colored in shades of red by carotenoid
Carotenoid
Carotenoids are tetraterpenoid organic pigments that are naturally occurring in the chloroplasts and chromoplasts of plants and some other photosynthetic organisms like algae, some bacteria, and some types of fungus. Carotenoids can be synthesized fats and other basic organic metabolic building...
pigments. In living specimens, the skeletal branches are overlaid with soft bright red integument, from which numerous retractable white polyp
Polyp
A polyp in zoology is one of two forms found in the phylum Cnidaria, the other being the medusa. Polyps are approximately cylindrical in shape and elongated at the axis of the body...
s protrude. The polyps exhibit octameric radial symmetry.
Species
The following are known species in the genus:- Corallium abyssale Bayer, 1956
- Corallium borneanse Bayer
- Corallium boshuense Kishinouye, 1903
- Corallium ducale Bayer
- Corallium elatius Ridley, 1882
- Corallium halmaheirense Hickson, 1907
- Corallium imperiale Bayer
- Corallium johnsoni Gray, 1860
- Corallium kishinouyei Bayer, 1996
- Corallium konojoi Kishinouye, 1903
- Corallium laauense Bayer, 1956
- Corallium maderense (Johnson, 1899)
- Corallium medea Bayer, 1964
- Corallium niobe Bayer, 1964
- Corallium niveum Bayer, 1956
- Corallium porcellanum Pasternak, 1981
- Corallium pusillum Kishinouye, 1903
- Corallium regale Bayer, 1956
- Corallium reginae Hickson, 1907
- Corallium rubrum (Linnaeus, 1758)
- Corallium secundum Dana, 1846
- Corallium sulcatum Kishinouye, 1903
- Corallium tricolor (Johnson, 1899)
- Corallium vanderbilti Boone, 1933
- Corallium variabile (Thomson & Henderson, 1906)
Coral as a gemstone
Coral (color)
The various tones of the color coral are representations of the wide range of colors of the class of cnidarians, also called corals. The complementary color of coral is teal.-Coral:The web color coral is a pinkish-orange color...
is also used to name such colors.
Owing to its intense and permanent coloration and glossiness, precious coral skeletons have been harvested since antiquity for decorative use. Coral jewelery has been found in ancient Egypt
Ancient Egypt
Ancient Egypt was an ancient civilization of Northeastern Africa, concentrated along the lower reaches of the Nile River in what is now the modern country of Egypt. Egyptian civilization coalesced around 3150 BC with the political unification of Upper and Lower Egypt under the first pharaoh...
ian and prehistoric Europe
Prehistoric Europe
Prehistoric Europe refers to the prehistorical period of Europe, usually taken to refer to human prehistory since the Lower Paleolithic, but in principle also extending to geological time scale - for which see Geological history of Europe....
an burials, and continues to be made to the present day.
Precious coral has relative density
Relative density
Relative density, or specific gravity, is the ratio of the density of a substance to the density of a given reference material. Specific gravity usually means relative density with respect to water...
of 3.86 and hardness 3.5 on the Mohs scale
Mohs scale of mineral hardness
The Mohs scale of mineral hardness characterizes the scratch resistance of various minerals through the ability of a harder material to scratch a softer material. It was created in 1812 by the German geologist and mineralogist Friedrich Mohs and is one of several definitions of hardness in...
. Due to its softness and opacity, coral is usually cut en cabochon
Cabochon
A cabochon , from the Middle French caboche , is a gemstone which has been shaped and polished as opposed to faceted. The resulting form is usually a convex top with a flat bottom. Cutting en cabochon is usually applied to opaque gems, while faceting is usually applied to transparent stones...
, or used to make bead
Bead
A bead is a small, decorative object that is usually pierced for threading or stringing. Beads range in size from under to over in diameter. A pair of beads made from Nassarius sea snail shells, approximately 100,000 years old, are thought to be the earliest known examples of jewellery. Beadwork...
s.
History of trade in coral
At the beginning of the Christian era, there was a great trade carried on in coral between the MediterraneanMediterranean Basin
In biogeography, the Mediterranean Basin refers to the lands around the Mediterranean Sea that have a Mediterranean climate, with mild, rainy winters and hot, dry summers, which supports characteristic Mediterranean forests, woodlands, and scrub vegetation...
and India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
, where it was highly
esteemed as a substance endowed with mysterious sacred
properties. It is remarked by Pliny
Pliny the Elder
Gaius Plinius Secundus , better known as Pliny the Elder, was a Roman author, naturalist, and natural philosopher, as well as naval and army commander of the early Roman Empire, and personal friend of the emperor Vespasian...
that, previous to the
existence of the Indian demand, the Gauls were in the habit
of using it for the ornamentation of their weapons of war and
helmets; but in his day, so great was the Eastern demand, that
it was very rarely seen even in the regions which produced it.
Among the Romans branches of coral were hung around children's
necks to preserve them from danger, and the substance had
many medicinal virtues attributed to it. A belief in its potency
as a charm continued to be entertained throughout medieval
times; and even early in the 20th century in Italy was worn as a
preservative from the evil eye, and by females as a cure for
sterility.
From the Middle Ages upwards the securing of the right
to the coral fisheries on the African coasts was an object of
considerable rivalry among the Mediterranean communities of
Europe. Previous to the 16th century they were controlled by
the Italian republics. For a short period the Tunisian fisheries
were secured by Charles V to Spain; but the monopoly soon
fell into the hands of the French, who held the right till the
Revolutionary government in 1793 threw the trade open. For
a short period (about 1806) the British government controlled
the fisheries, but later returned to the hands of the French
authorities. Previous to the French Revolution
French Revolution
The French Revolution , sometimes distinguished as the 'Great French Revolution' , was a period of radical social and political upheaval in France and Europe. The absolute monarchy that had ruled France for centuries collapsed in three years...
much of the coral
trade centred in Marseilles; but since that period, both the
procuring of the raw material and the working of it up into the
various forms in which it is used became peculiarly Italian
industries, centering largely in Naples, Rome and Genoa.
Coral in mythology
The origin of coral is explained in Greek mythologyGreek mythology
Greek mythology is the body of myths and legends belonging to the ancient Greeks, concerning their gods and heroes, the nature of the world, and the origins and significance of their own cult and ritual practices. They were a part of religion in ancient Greece...
by the story of Perseus
Perseus
Perseus ,Perseos and Perseas are not used in English. the legendary founder of Mycenae and of the Perseid dynasty of Danaans there, was the first of the mythic heroes of Greek mythology whose exploits in defeating various archaic monsters provided the founding myths of the Twelve Olympians...
. Having petrified Cetus
Ceto
In ancient Greek, the word ketos - Latinized as cetus - denotes a large fish, a whale, a shark, or a sea monster. The sea monsters slain by Perseus and Heracles were each referred to as a cetus by ancient sources. The term cetacean originates from cetus. In Greek art, cetea were depicted as...
, the sea monster threatening Andromeda
Andromeda (mythology)
Andromeda is a princess from Greek mythology who, as divine punishment for her mother's bragging, the Boast of Cassiopeia, was chained to a rock as a sacrifice to a sea monster. She was saved from death by Perseus, her future husband. Her name is the Latinized form of the Greek Ἀνδρομέδη...
, Perseus placed Medusa
Medusa
In Greek mythology Medusa , " guardian, protectress") was a Gorgon, a chthonic monster, and a daughter of Phorcys and Ceto. The author Hyginus, interposes a generation and gives Medusa another chthonic pair as parents. Gazing directly upon her would turn onlookers to stone...
's head on the riverbank while he washed his hands. When he recovered her head, he saw that her blood had turned the seaweed
Seaweed
Seaweed is a loose, colloquial term encompassing macroscopic, multicellular, benthic marine algae. The term includes some members of the red, brown and green algae...
(in some variants the reeds) into red coral. Thus, the Greek word for coral is 'Gorgeia', as Medusa was one of the three Gorgons.
Poseidon
Poseidon
Poseidon was the god of the sea, and, as "Earth-Shaker," of the earthquakes in Greek mythology. The name of the sea-god Nethuns in Etruscan was adopted in Latin for Neptune in Roman mythology: both were sea gods analogous to Poseidon...
resided in a palace made of coral and gems, and Hephaestus
Hephaestus
Hephaestus was a Greek god whose Roman equivalent was Vulcan. He is the son of Zeus and Hera, the King and Queen of the Gods - or else, according to some accounts, of Hera alone. He was the god of technology, blacksmiths, craftsmen, artisans, sculptors, metals, metallurgy, fire and volcanoes...
first crafted his work from coral.
The Romans
Ancient Rome
Ancient Rome was a thriving civilization that grew on the Italian Peninsula as early as the 8th century BC. Located along the Mediterranean Sea and centered on the city of Rome, it expanded to one of the largest empires in the ancient world....
believed coral could protect children from harm, as well as cure wounds made by snakes and scorpions and diagnose diseases by changing colour.
Trivia
- The two biogenic precious gemstones, coral and pearlPearlA pearl is a hard object produced within the soft tissue of a living shelled mollusk. Just like the shell of a mollusk, a pearl is made up of calcium carbonate in minute crystalline form, which has been deposited in concentric layers. The ideal pearl is perfectly round and smooth, but many other...
, although drastically different in appearance, are chemically very similar. Both are mostly calcium carbonate deposited by marine invertebrateInvertebrateAn invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...
s. - Another unrelated species, the HawaiianHawaiian IslandsThe Hawaiian Islands are an archipelago of eight major islands, several atolls, numerous smaller islets, and undersea seamounts in the North Pacific Ocean, extending some 1,500 miles from the island of Hawaii in the south to northernmost Kure Atoll...
black coralBlack coralBlack corals are a group of deep water, tree-like corals related to sea anemones. They are also found in rare dark shallow water areas such as New Zealand's Milford Sound where they can be viewed from an underwater observatory. They normally occur in the tropics...
is sometimes used as an ornamental material. Its skeleton is not mineralized, consisting mostly of conchiolinConchiolinConchiolin and perlucin are complex proteins which are secreted by a mollusc's outer epithelium ....
. - In HinduHinduHindu refers to an identity associated with the philosophical, religious and cultural systems that are indigenous to the Indian subcontinent. As used in the Constitution of India, the word "Hindu" is also attributed to all persons professing any Indian religion...
astrologyAstrologyAstrology consists of a number of belief systems which hold that there is a relationship between astronomical phenomena and events in the human world...
red coral is associated with the planet MarsMarsMars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance...
or Graha-MangalaMangalaIn Jyotish astrology, Mangala is the name for Mars, the red planet. Mars is also called Angaraka In Jyotish astrology, Mangala (Devanagari: मंगल) is the name for Mars, the red planet. Mars is also called Angaraka In Jyotish astrology, Mangala (Devanagari: मंगल) is the name for Mars, the red...
and used for pleasing Mars. It should be worn in the ring finger. - A branch of red coral figures prominently in the civic coat of armsCoat of armsA coat of arms is a unique heraldic design on a shield or escutcheon or on a surcoat or tabard used to cover and protect armour and to identify the wearer. Thus the term is often stated as "coat-armour", because it was anciently displayed on the front of a coat of cloth...
of the town of AlgheroAlgheroAlghero , is a town of about 44,000 inhabitants in Italy. It lies in the province of Sassari in northwestern Sardinia, next to the sea.-History:The area of today's Alghero has been settled since pre-historic times...
, Italy.
External links
- International Colored Gemstone Association Extensive info on gemstone coral and jewelry photos (Accessed 2 February 2007)
- American Gem Trade Association Information on coral as a gemstone (Accessed 2 February 2007)
- Organic Gems: Red Coral Jewelry Photos of raw coral material and coral jewelry (Accessed 2 February 2007)
- Mediterranean red coral: research team International Research Team on Mediterranean red coral (Accessed 15 March 2007)
- The state of red coral (Corallium rubrum) populations in the N.W. Sardinian fishing grounds(Accessed 16 September 2010)
- FAO
- Gemstones Guide: Coral
- All about red Coral Carvings