Almost all gemstones are minerals with a crystalline structure. But not all. Some gems are not really gemstones. Rather their origin is organic -- they formed from biological processes, whether animal or vegetable.
The class of organic gems is small but includes a number of unusual varieties which are important in the gem trade: amber, coral, jet, ivory and pearl.
Amber is the fossilized hardened resin of the pine tree, formed approximately 50 million years ago. Amber has been used since prehistoric times for jewelry, amulets and religious objects. The most prized pieces contain inclusions of insects or plants or pyrites. The largest amber deposits in the world are near Kaliningrad, Russia, and there are large reserves in the seabed of the Baltic.
Coral is a branching skeleton-like structure built by small marine animals known as coral polyps. The gem-quality coral is related to the reef-forming corals, but the most valuable coral variety is found in the Mediterranean, the Red Sea and in coastal Japan. Colors range from bright to dark red to orange-red, orange-pink, pink, white, blue and black. Unworked coral is dull, but when polished it has an attractive vitreous luster.
Jet was extremely popular in the 19th century, but now is rarely found. Jet is actually a bituminous coal which can be polished. It was made famous by Queen Victoria of England, who wore jet as part of her mourning dress after the death of Prince Albert. Jet is extremely light and long necklaces of jet beads were very popular during the 1920's when women and would wear multiple strands of jet beads stretching from the neckline to the waist.
Ivory originally referred to the material of the elephant's tusk. Today ivory also comes from the teeth of hippopotamus, walrus, wild boar and other mammals. Like bones, ivory consists mainly of calcium phosphate. Before the invention of plastics, ivory was important for cutlery handles, musical instruments, billiard balls, and many other ornamental carved items. Due to the rapid decline in the populations of the animals that produce it, the importation and sale of ivory in many countries is banned or severely restricted.
Pearl is the most important of all the organic gems. Grown or cultivated in bivalve mollusks of the oyster type, pearls have been used for adornment for more than 6,000 years. By 2500 B.C. there was already a substantial pearl trade in China. One of the unique features of pearls in the gemstone world is that they do not require any processing -- in their natural state they show their full luster.
- First Published: May-29-2008
- Last Updated: November-15-2011
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