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Evaluating
Gem Diamonds
The
principal localities for aquamarine are Brazil (notably
the region s Minas Gerais), South West Africa, India,
the Malaga say and the U.S.S.R. There are many United
States localities for I, but few are of gem significance.Cat's-eye
beryl (r.) is a curiosity seldom available commercially.
Morganite (below) is a lovely gem, and stones larger
than this 47.2-carat one are available.
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Morganite,
heliodor (golden beryl), and goshenite are not widely
known to the gem-buying public. Most gem material comes
from Brazil, although fine rough has been found in the
Malaga say Republic, South West Africa, and San Diego
County, California. Gem morganite of superb quality
has been mined in Pala, California, along with some
of the finest tourmaline crystals known. |
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Morganite was named after the New
York banker and gem collector, J. P. Morgan. The name heliodor
means "gift of the sun," which is appropriate for
the yellow color. Pale-green beryl, not colored by chromium,
is simply termed "green beryl." An unusual red beryl
is found in Utah, but has no gem signifi¬cance.
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DIAMONDS,
GEMSTONES & CRYSTALS
FACTS & FIGURES |
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most popular cutting style for emerald and most
of the other beryl's is a step-cut rectangle with
the corners truncated, yielding a characteristic
shape known as the emerald cut. Other popular
beryl cuts include the cushion cut, a simple rectangle;
the octagon, which is basically a square emerald
cut; and the round brilliant.
The
beryl's are all fairly tough gems, with the exception
of emerald. Because of its typically present inclusions
and flaws, emerald is a fragile deem and requires
care in mounting and wear. The hardness of beryl
is 71/2-8 on the Mohs scale, which is ample for
ring stones.
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Occasionally
a beryl contains fibrous inclusions, and a cabochon
! cut from such material will yield a weak cat's-eye.
Stones that resemble emerald, such as period,
tourmaline, green zircon, and dermatoid, can be
easily distinguished on the basis of optical properties. |
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But
to the waked eye even a glass imitation can sometimes be deceptive.
Consumer Tips-Many emeralds on the market have been treated
with , typically grape-seed oil. This oil, which may even
sometimes be bolo red green, seeps into fractures in the gems
and makes them far less obvious. The oil can usually be detected
with ultraviolet light. |
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