Garnet. A gem, usually deep red, of several varieties, including the almandite and pyrope. When cut en cabochon garnets are called carbuncles.
Garnet is found in nearly all colors but blue. Rarest of garnets is the green demantoid, found only in the Ural Mountains. Others come from Brazil, India, Sri Lanka, and the United States.

Amethyst. A transparent violet-to-purple quartz. Believed by the ancient Greeks to prevent intoxication.
Amethysts were used in both Greek and Roman jewelry. Under certain conditions the color of some amethysts may be improved by heating. Under other conditions heating may turn them yellow, then clear. Found in quantity in southern Brazil and northern Uruguay. Smaller amounts come from India, Sri Lanka, and Madagascar.

Aquamarine. Transparent sea-blue or sea-green beryl; of the same family as the emerald but far less valuable. Found in many parts of the world, particularly Brazil, Sri Lanka, India, and Madagascar, and in Maine, New Hampshire, Connecticut, and North Carolina. An aquamarine crystal found in Brazil in 1910 weighed about 240 pounds (110 kilograms).

Diamond. Pure crystallized carbon, the most highly esteemed of all gemstones. The fiery brilliance of the diamond has made it the world's favorite jewel. The word comes from the Greek term adamas, which means "unconquerable." The diamond is the hardest natural substance found on Earth. Diamond-tipped industrial tools can cut through granite as easily as a steel saw cuts through wood. Diamonds are crystals of pure carbon that have been subjected to tremendous pressure and heat. This process is believed to have taken place deep in the Earth. (See Diamond)

Pearl. Pearls can be black, brown, gray, rose, red, blue, green, purple, yellow, and white. No one knows exactly how pearls develop their color, since one oyster may produce pearls of several different hues simultaneously. The most valuable pearls are white and silvery-white saltwater pearls that form in the genus Pinctada. Black-lipped oysters from the South Pacific Ocean and the Gulf of Mexico sometimes produce naturally black pearls. Although natural pearls are found all over the world, most of the natural pearls now harvested come from the Persian Gulf, Sri Lanka, the Red Sea, and the Philippines. Smaller quantities come from the coast of Venezuela and from the Gulf of California. The cultured-pearl industry thrives in the seas of Japan and off the northwest coast of Australia, where few natural pearls are harvested. Japan produces more cultured pearls than any other country. Most cultured pearls are produced in underwater farms, with the mollusks suspended at the right depth in baskets. Historically, Japanese women divers, called ama, gathered the wild oysters.

Ruby. A transparent red corundum valued according to shade of color. Large rubies are often worth more than fine diamonds of the same size. Pigeon-blood (deep carmine-red) rubies, which seldom exceed three carats, are obtained from Myanmar. Darker rubies come from Thailand. Rubies also occur in Sri Lanka, Afghanistan, and North Carolina.

Sapphire. A transparent corundum, or aluminum oxide. Sapphires range from white through blue, violet, yellow, and green to near black. Blue star sapphires with six rays are favorite stones. Fine sapphires are equal in value to diamonds of equal size. Found in Myanmar, Thailand, Sri Lanka, and Jammu and Kashmir.

Tourmaline. A complex aluminum borosilicate occurring in great variety-colorless, rose red, green, blue, yellowish, green, honey yellow, violet, and dark blue. Most tourmaline is obtained from Brazil, Elba, Madagascar, and Maine, Connecticut, and California.