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Home > Gemstones > Organic gemstone
Organic gemstone

The four organic gemstone groups are highly prized for their beauty and rarity. However, they are not as durable as gemstones from minerals:

[ Amber | Coral | Jet | Pearls | Cultured Pearls ]

It has hardness of 2 - 2.5 Mohs. It is formed of a mixture of hydrocarbons and its specific gravity is 1.05 - 1.096.

Amber is hard fossil resin or sap of ancient pine trees. They are usually amorphous (lacks crystalline structure). They are sometimes mined, sometimes gathered on seashores.

It varies from transparent to semitransparent and generally from light yellow to dark brown, but can also be orange, red, whitish, greenish-brown, blue, or violet and can be dyed in any color. Amber takes a fine polish and used mainly in making beads or other ornaments.

It has hardness of 3.5 - 4 Mohs. It is formed mainly of calcite (calcium carbonate) or conchiolin, a horny organic substance and its specific gravity is 2.60 - 2.70. Each coral polyp, a tiny marine animal that lives in enormous colonies, extracts calcium carbonate from the sea and exudes it to build a protective home around and above itself. Each generation of polyps dies in its protective home and each succeeding generation builds on top of its predecessor.

Gem coral ranges from semi translucent to opaque and occurs in white, pink, orange, red, blue, violet, golden, and black. The black and golden corals are largely horny organic substances, not calcium carbonate. The finest coral is used to make figurines, cameos, carvings, and beads. 

It has hardness of 2.5 - 4 Mohs. It is formed of carbon plus various hydrocarbon compounds and its specific gravity is 1.30 - 1.32. This compact velvet-black coal takes a good polish and is often cut into beads, bracelets, and a wide range of decorative and useful objects.

It has hardness of 2.5 - 4.5 Mohs. It is formed within a mollusk, such as an oyster, that deposits a substance called nacre around an irritant that entered the organism. Its specific gravity is 2.71. Pearl-bearing mollusks are found in both salt and fresh water. Salt-water pearls of gem quality are usually preferred for jewelry; they are produced almost entirely by the mollusk Pinctada. Various clams and mussels produce fresh-water pearls.

Natural pearls come in various shapes: round, pear, drop, egg, and others. They also come in various colors, such as white, cream, light rose, cream rose, black, gray, bronze, blue, dark blue, blue green, red, purple, yellow, and violet.

The quality of pearls is judged by the orient, which is the soft iridescence caused by the refraction of light by the layers of nacre, and luster, the reflectivity and shine of the surface. Fine pearls do not have any flaws or spots in the nacre: it has an even smooth texture. Other factors, which affect value, are the regularity of the shape, size, and color: rose tints are the most favored.

Cultured PearlsCultured Pearls
As pearls are so very rare and so very difficult to recover from the oceans depths, man invented the technique of "culturing" salt and fresh-water Pearls from oysters carefully seeded with irritants similar to those produced by nature. This painstaking effort of "culturing" is one of the most dramatic examples of mans quest to coax beauty from nature.

One of the earliest known methods to enhance a pearls color and luster required that a chicken swallow the Pearl. The belief at that time (400 AD) was that the chickens digestive system would soften the Pearls blemishes and even the color. Todays cultured; fresh and saltwater Pearls are often bleached to achieve a uniform color. They may also be polished in tumblers to make them round and lustrous.

Naturally colored pearls are in short supply. Some pearls are dyed and/or irradiated to achieve the rich blacks, grayish blues, pinks and golden hues that are now so much in demand. To care for your cultured Pearls, avoid using nail polish, abrasives, solvents and polish removers while wearing them. Ask your jeweler for further instructions regarding their care.

Cultured pearls and natural pearls can be distinguished from imitation pearls by a very simple test. Take the pearl and rub it (gently!) against the edge of a tooth. Cultured and natural pearls will feel slightly rough, like fine sandpaper, because of the texture of natural nacre. Imitations will feel as smooth as glass because the surface is molded or painted on a smooth bead.

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