24 Mart 2013 Pazar

Hawaii State Gemstone

Hawaii State Gemstone

Black Coral

Coral, like pearl, is a gemstone of organic origin, a product of the marine environment. Black coral is composed of a protein called conchiolin, unlike the more familiar red corals, which are mainly calcium carbonate. There are over 200 species of black coral. Black corals belong to the scientific order Antipatharia and are rarely black, but more often occur in white, red, yellow, green, or brown.
In March 2009, scientists dated a certain type of black coral to be over 4,200 years old, which puts it among the oldest continuously living organisms on the planet.
Of the more than 200 black coral species, Hawaii has more than 15. Although found at all depths, black corals can be a dominant feature of Hawaii’s unique deep coral reef environment. Particularly, black corals are very common in the Au’au Channel, between Maui and Lanai. This area is unique as it has a high abundance of black coral habitat and has been the basis of a coral fishery for almost 50 years.
In the Hawaiian language, black coral is called ‘ēkaha kū moana.Hawaii designated black coral its official state gemstone in 1987.
The word coral may come from the Greek κορáλλιον (korallion), which denotes the hard, calcareous skeleton of the coral animals. It has also been suggested that the word comes from an ancient Greek word pronounced kura-halos, meaning "mermaid," since the fine branches of the coral sometimes look like small figures. Alternatively, the word may be derived from the Hebrew גורל(goral), meaning lot or destiny, originally referring to objects used in the drawing of lots. Coral branches may well have been used in this way, since they were once used in oracles in Palestine, Asia Minor, and around the Mediterranean.
Coral is created from a protein secreted from tiny, cylindrical, underwater polyps that have tentacles and stinging cells. Corals live in colonies up to 6 feet (1.8 m) high. They grow into branches up to a height of 16 inches (40 cm), which are harvested by divers. Coral colonies create a habitat for crustaceans, bivalves, and fish.
Black corals can range in shape from small bushes to fans to single stalks. All black corals have a skeleton made of protein and chitin (the same material as an insect exoskeleton). In addition, black corals do not have symbiotic algae associated with them and do not require light, therefore allowing them to extend into depths where light is not present.
Corals grow all over the world at all depths, but the finest quality specimens are usually found in warmer waters. In Hawaii, they grow at depths of about 100–300 feet (30.5–91.4 m), shallow enough to harvest using scuba equipment. Many harvesters, however, have died in pursuit of coral trees at the deep end of this range.
  • Japan
  • Taiwan
  • Malaysian archipelago
  • Red Sea
  • Bay of Biscay
  • Canary Islands
  • Northeast Australia
  • Midway Islands
  • Hawaii
  • Tyrrhenian Sea, off the coast of Sardinia
  • Tunisia
  • Algeria
  • Former Yugoslavian republics
  • Turkey

Historical Uses
For centuries, coral has been harvested for a variety of uses, including idols, beads, cameos, medicine, and talismans. 
Modern Uses
Coral is often full of holes and cracks, but rare, high-quality coral is of an even color and lacks holes, cracks, blotches, and striations. Red coral, sometimes called fire coral, is the rarest and most valuable. The intense pink or red color of this species make it prized as a gem. To be used in jewelry, coral branches are cleaned, sorted, cut or filed, and polished from their natural matte finish to a high luster. It can take a few years for coral to grow large enough to be used in jewelry.
The Maui coral harvesting industry has been active since the 1950s. In 1998, surveys showed that the black coral population was sustainable. Since that time, however, two important changes have taken place. A large percentage of the population has been overgrown by an alien soft coral, snowflake coral, and larger colonies above 240 feet (73 m) have decreased due to fishing pressure. These factors contribute to a reduction in the number of juveniles, calling the sustainability of the population into question. Studies are underway to determine the future of black coral in the waters around Maui, and a five-year ban on harvesting was put in place to end in 2010.
The Romans believed coral had the power to protect children and heal wounds. In many cultures, coral is still worn to protect the wearer from evil spirits. The mineral is said to relieve tension, decrease fear, and improve one’s social life. Hawaiians traditionally ground black coral into a powder for medicinal purposes.
Artificial coral is made of glass, plastic, and porcelain.

State Gemstone
Black Coral
State Gemstone
Close-up of Black Coral
State Gemstone
Seeking Shelter in Black Coral
Kingdom: Animalia
Phylum: Cnidaria
Class: Anthozoa
Crystal Structure: Organic
Hardness (Mohs): 2.5-3
Color: Multiple colors, commonly white, red and black
Transparency: None
Luster: Waxy
Pleochroism: None
Refractive Index: 1.486-1.658
Density: 2.4-2.7
Cleavage: None

Some data courtesy of the Mineralogical Society of America
Author: World Trade Press

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