Consumer Guide on Gemstones

Source: Federal Trade Commission

Gemstones
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, [name of manufacturer]-created, or synthetic, have essentially the same chemical, physical and visual properties as natural gemstones. Laboratory- created stones do not have the rarity of naturally colored stones and they are less expensive than naturally mined stones. By contrast, imitation stones look like natural stones in appearance only, and may be glass, plastic, or less costly stones. 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, 7x5 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.

Jewelers should tell you whether the gemstone you're considering has been treated when: the treatment is not permanent; the treated stone requires special care; or the treatment significantly affects the value of the gemstone.

Some common treatments that you may be told about and their effects include:

• Heating can lighten, darken or change the color of some gems, or improve a gemstone's clarity.
• Irradiation can add more color to colored diamonds, certain other gemstones and pearls.
• Impregnating some gems with colorless oils, wax or resins makes a variety of imperfections less visible and can improve the gemstones' clarity and appearance.
• Fracture filling hides cracks or fractures in gems by injecting colorless plastic or glass into the cracks and improves the gemstones' appearance and durability.
• Diffusion treatment adds color to the surface of colorless gems; the center of the stone remains colorless.
• Dyeing adds color and improves color uniformity in some gemstones and pearls.
• Bleaching lightens and whitens some gems, including jade and pearls.