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.
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.
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. (See Diamond)
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
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.