A pearl starts growing when some irritating foreign substance such as a sand grain, bit of mud, parasite or other object becomes lodged in shell-producing gland called mantle. Pearls formed in soft flesh where nacre can be added on all sides are most likely to be spherical and most highly prized. By far great majority are flattened or variously distorted and have little value. Size, color, luster and freedom from flaws are other essential qualities. Unlike other gems, such as diamonds, pearls have an average life of only about 50 years. In time small amount of water in a pearl's make-up is lost and its surface cracks. Because they are mostly lime, necklaces which are worn often are injured by acid secretions of human skin.

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

Though, pearl is not technically a stone at all, it’s beauty has earned it a place in Big 5 of precious stones. Jewelry artists have long appreciated pearl and continue to utilize it’s charm in their creations.

Gemstone treatments or enhancements refer to 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 value of a stone, when measured against a comparable untreated stone.

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

Some common treatments that you may be told about and their effects include: • Heating can lighten, darken or change 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 gemstones’ clarity and appearance. • Fracture filling hides cracks or fractures in gems by injecting colorless plastic or glass into cracks and improves gemstones’ appearance and durability. • Diffusion treatment adds color to surface of colorless gems; center of 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.