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Gems & Precious Metals

Posted by on Nov 16, 2010 in | 0 comments

Birthstones | The Healing Power of Jewelry


Natural gemstones are found in nature. Laboratory-created stones, as the name implies, are made in a laboratory. These stones, which also are referred to as laboratory-grown, manufacturer-created, or synthetic, have essentially the same chemical, physical, optical, and visual properties as natural gemstones. Laboratory- created stones do not have the rarity or value of natural colored gemstones. By contrast, imitation stones look like natural stones in appearance only, and may be a manmade or natural stone. Laboratory-created and imitation stones should be clearly identified as such.

Gemstones may be measured by weight, size, or both. The basic unit for weighing gemstones is the carat, which is equal to one-fifth (1/5th) of a gram. Carats are divided into 100 units, called points. For example, a half-carat gemstone would weigh .50 carats or 50 points. When gemstones are measured by dimensions, the size is expressed in millimeters (for example, 7×5 millimeters).

Gemstone treatments or enhancements refer to the way some gems are treated to improve their appearance or durability, or even change their color. Many gemstones are treated in some way. The effects of some treatments may lessen or change over time and some treated stones may require special care. Some enhancements also affect the value of a stone, when measured against a comparable untreated stone. Treatments and/or enhancements should always be disclosed by the seller.

A Word About Pearls.

Natural pearls are found in oysters and other mollusks. Cultured pearls also are grown in mollusks, but with human intervention; that is, an irritant introduced into the shells causes a pearl to grow. Imitation pearls are man-made with glass, plastic, or organic materials.

Because natural pearls are very rare, most pearls used in jewelry are either cultured or imitation pearls. Fine quality cultured pearls, because they are harvested from oysters or mollusks, are more expensive than imitation pearls. A cultured pearl’s value is largely based on its size, usually stated in millimeters, and the quality of its nacre coating, which gives it luster. The pearls color, blemish, type, and shape are also considered.

All That Glitters

The word gold, used by itself, means all gold or 24 karat (24K) gold. Because 24K gold is soft, it’s usually mixed with other metals to increase its hardness and durability. If a piece of jewelry is not 24 karat gold, the karat quality should accompany any claim that the item is gold.

The karat quality marking tells you what proportion of gold is mixed with the other metals. Fourteen-karat (14K) jewelry contains 14 parts of gold, mixed in throughout with 10 parts of an alloy metal. The higher the karat rating, the higher the proportion of gold in the piece of jewelry.

Most jewelry is marked with its karat quality, although marking is not required by law. Near the karat quality mark, you should see the name or the U.S. registered trademark of the company that will stand behind the mark. The trademark may be in the form of a name, symbol or initials. If you don’t see a trademark accompanying a quality mark on a piece of jewelry, look for another piece.

Platinum is a precious metal that costs more than gold. It usually is mixed with other similar metals, known as the platinum group metals: iridium, palladium, ruthenium, rhodium and osmium.

Different markings are used on platinum jewelry as compared with gold jewelry, based on the amount of pure platinum in the piece. The quality markings for platinum are based on parts per thousand. For example, the marking 900 Platinum means that 900 parts out of 1000 are pure platinum, or in other words, the item is 90% platinum and 10% other metals. The abbreviations for platinum – Plat. or Pt. – also can be used in marking jewelry.

The words silver or sterling silver describe a product that contains 92.5% silver. Silver products sometimes may be marked 925 which means that 925 parts per thousand are pure silver. Some jewelry may be described as silverplate: a layer of silver is bonded to a base metal. The mark coin silver is used for compounds that contain 90% silver. According to the law, quality-marked silver also must bear the name or a U.S. registered trademark of the company or person that will stand behind the mark.