A gem, usually deep red, of several varieties, including
the almandite and pyrope. When cut on cabochon garnets are called
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.
A transparent violet-to-purple quartz. Believed by the ancient Greeks
to prevent intoxication.
Amethyst 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.
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).
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.
A deep-green brilliant emerald is one of the costliest of gems.
The emerald is a variety of beryl. The finest stones
come from Colombia. Other sources are Brazil, Egypt, Australia, Austria,
Norway, and North Carolina.
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.
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.
A yellowish green olivine. Found in St. John's Island (Red Sea), Australia,
Arizona, Hawaii, and, rarely, other places.
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.
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.
An aluminum fluosilicate occurring in tawny yellow, blue, green, reddish
violet, pink, and colorless varieties. Found in Brazil, Siberia, Sri
Lanka, and the United States.
A zirconium silicate usually occurring in brownish, gray, or brownish
red varieties, but sometimes in yellows and greens. Colorless and
blue varieties are usually produced by heating brown zircons. Zircons
come chiefly from Sri Lanka and Indochina.