Coral

Coral mined from the oceans. It grows underwater. Coral is used to create beautiful earrings, brooches, and pendants. Though coral rings are popular, be aware that coral scratches easily. Red coral jewelry is often dyed; white coral jewelry is usually bleached.
Organic Gems: Coral, Pearls, and Jet
Author: Margaret Burgon Klemp
Pearls, Corals and Jet are known as organic gems because they normally grow in the water. While they can be found in other habitats these gems are more at home in the oceans and lakes of the world. Pearl diving has been around for thousands of years with divers bringing clams and other sea mollusks up from the depths of the oceans in order to search them for pearls.
The story behind coral gems and jet is quite different. Coral is sometimes described as a sea plant with flowers but no roots. In 1723 the French biologist, G.A. Peyssonal researched and brought the mystery of corals to light. He surmised that coral colonies were made up of exoskeletal polyps. These polyps come from minute, small animals that create dendritic forms from calcite that is dissolved in sea water. It is from these forms that coral begins to grow and flourish. The habitat has to be just right. The water needs to be warm and, as a rule, about 10 to 45 feet deep. Some coral can be found at deeper levels but it is rare. It grows in branches that look like underwater trees.
Colors of coral range from white to red and sometimes pink and white. The most valuable coral are red, black and pink, and is created by coelenterate species. Most coral is quite soft and, therefore, needs to be handled carefully. Corallium rubrum is a red coral that forms tree-shaped colonies. Its' color is caused by a red calcium carbonate skeleton almost 20 inches (50 centimeters) tall. Hard rods are embedded in the outer part of its body. They also have feeding tubes or tentacles that can be drawn into the tissue. Other non-feeding tubes serve as sex organs. Red coral can be found in the Mediterranean and in the Atlantic Ocean coastal regions of Portugal and Northern Africa. Other types of coral can be found all over the world, including the Great Barrier Reef of the east coast of Australia. Red coral is one of the coral species that is not on the endangered list of plant and animal life. Most coral, because of their associations with the reefs hold a prominent place on the endangered list.
The red hues of coral have always been prized gems of artisans and craftsman. Coral jewelry has a long history, and is still made and worn in many parts of the world. Ancient civilizations used coral to make an ornament and then, very often, used gold to accent the piece. Coral has a secure place among ancient gems. In fact coral jewelry has been utilized since prehistoric times. Coral jewelry has been found from the Iron Age. Coral along with other gemstones holds a significant status in religious history. Ancient Phoenicians, Egyptians, and Romans all used coral as method of currency and trade. Some societies believed that ships needed to have coral on board as a defense against lightning. The gem was also supposed to drive hatred out of a home.
The Greek poet, Orpheus, called coral the gift of the goddess Minerva. He also claimed that it had special powers against witchcraft, poisons and invasions by robbers.
Greeks are credited with giving coral its' name. The word "coral" comes from the Greek word for pebble-korallion. Coral can be found on artifacts dating back to 3000 B.C. It was also used in China to decorate various articles of clothing, and it has been found in ancient Tibetan temples. Coral had religious significance for the lamas. Marco Polo wrote about the Chinese use of coral in his writings.
The organic gem Jet seemed to vanish from the market in the early 20th century, and is now making a comeback because of the popularity of black jewelry and jet is affordable. The color ranges of jet are from dark brown to black. Jet appears in irregular masses with a lenticular shape. It can be found embedded in black bituminous shale known as jet-rock. Originally, it was formed through the process of lithification of the driftwood that dwells in mud on ocean floors. Upon careful examination it was discovered that jet comes from a structure of coniferous wood. Scientists believe that wood from trees and other plants fell into rivers and were carried out to sea. Then the wood became water logged and sank down to the depths of the ocean and ended up in fine mud deposits where it eventually hardened and became embedded into shale. Jet dates from the lowermost group of the Jurassic strata known as the Upper "Lias" or layers. Under the pressure of the salt water and without any air the wood went through an unusual decomposition process which produced jet. While jet will burn, scratch, and damages easily there are harder forms of it that can be carved. It can be found over a large part of the world including: Germany, Spain, France, Poland, United States, England, Russia and India. Whilby, located on the North East Coast England is the major source of jet.
References:
Gems: A Lively Guide for the Casual Collector, by Daniel J. Dennis Jr., Henry N. Abrams, Incorporated, New York, New York
Gemstones: Symbols of Beauty and Power, by Eduard Gubelin and Franz-Xaver Erni, Geoscience Press, Tucson, Arizona
Gems in Myth, Legend and Lore, by Bruce G. Knuth, Jewelers Press, Thornton, Colorado
Wikipedia Information on Coral
Wikipedia Information on Jet
History, Sources and Properties of Coral from JJKent.com