Community: Library

Gemstones

Natural stones are found in nature. Laboratory-created stones are made in a laboratory. These stones are also referred to as laboratory-grown, (name of manufacturer)-created, or synthetic. Laboratory-created stones are similar to natural stones, but they are different in two basic ways: 1) they are not as rare as natural gemstones and as such, 2) they are generally less expensive. Imitation stones resemble natural stones in appearance, and may be glass, plastic, or less costly stones. Laboratory-created and imitation stones must be identified as such.

Gemstones are 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 weighs .50 carats or 50 points. When gemstones are measured by dimensions, the size is expressed in millimeters.

Gemstone treatments or enhancements refer to the way some gems are altered or treated to improve their appearance or durability. The effects of some treatments may lesson or change over time and some treated stones may require special care. Sometimes, enhancements affect the value of the stone.

Some common treatments and their effects include:

Heating can lighten, darken, or change the color of some gems.
Irradiating can add more color to colored diamonds and certain other stones.
Impregnating some gems with colorless oils or wax masks a variety of imperfections, hides cracks, and improves color.
Fracture filling hides cracks or fractures in gems by injecting plastic resins into the cracks.
Diffusion treatment adds color to the surface of colorless gems; for some gems, the center of the stone remains colorless.
Dyeing adds color and improves color uniformity in some gems.
Bleaching lightens and whitens ivory and pearl.

Guidelines:

Identify whether stones are natural, laboratory-created, or imitation.
Provide the measurements of gemstones. Include the number of karats, points, and millimeters.
Describe fully the enhancements made to the stones. Specify whether the enhancements are permanent and if the treated stones require special care.

Source:

All That Glitters...The Jive on Jewelry, August 1998, FTC
Guides for the Jewelry, Precious Metals, and Pewter Industries, FTC
In the Loupe: Advertising Diamonds, Gemstones, and Pearls, August 1998, FTC