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The Nature of Gemstones

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					The Nature of Gemstones
Two thousand years ago, students of gemology classified gems by color
alone. They would have considered ruby and red spinel the same thing,
simply because they're the same color. But there is a tremendous
difference between the two gems.
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What is a gem?
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Some gems - like pearls, amber, coral, and ivory - are organic. This
means they come from plants or animals. But most gems are minerals:
natural, inorganic materials with specific chemical compositions. Most
have a characteristic structure, too. You probably already know the names
of some minerals commonly found in jewelry stores: topaz, sapphire,
emerald, and ruby, for example. Synthetic gems have become increasingly
popular like this titanium bracelet, which are exact repl icas of the real
gem with the strength of titanium.
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Three traits of all gems
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A substance isn't automatically considered a gem just because it's used
in jewelry or just because it falls in the mineral category. Items like
bones, seeds, and hair have all been used in jewelry, but that doesn't
place them in the same category as rubies, pearls, and amber. You will
some time find gems in tungsten carbide rings as well.
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To be a gem, a substance must share three important traits with all other
gems: beauty, rarity, and durability. Each trait, however, represents a
range, so all gems can possess different levels of all three traits.
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Beauty
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Throughout the centuries, humans have cherished the color of gleam of
finished gems. Mineral crystals brought up from the dark depths of the
earth, organic gems created by life processes - all gems worthy of the
name share the virtue of beauty.
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But because beauty is in the eye of the beholder, it isn't always easy to
categorize what's beautiful and what isn't. One accepted definition of
beauty holds that it's a combination of qualities that delight the senses
or appeal to the mind. In other words, a thing of beauty might not cause
everybody to react the same way, but it will cause everybody to react -
it will have visual appeal.
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In fashioned gemstones, visual appeal typically results from a
combination of color, symmetry, and surface appearance. Of these factors,
color is usually the most important for colored stones. From the deep
green of a fine emerald to the shifting colors in an opal, color is the
first thing you notice about a colored stone. For this reason, it's
usually the first consideration when you're viewing colored stones.
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Symmetry, the second factor, means balance and harmony of cu t. A stone is
most appealing when its shape and proportions are balanced, so certain
cut details enhance a gem's beauty.
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A gem's surface appearance, or luster, also influences its appeal. Most
gems are polished to a high luster, Pearls, which are not fashioned in
the same way most other gems are; owe part of their beauty to luster,
too.
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In addition to these three factors, transparency often plays a role in a
gem's beauty. Transparency describes how light passes through an object.
The more transparent an object, the more light passes through it. Many
gems are transparent, including emerald, garnet, and tanzanite. Light can
pass through them with little or no distortion.
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Opaque materials are on the other end of the transparency scale. An
opaque jewelry, like a tungsten carbide ring or stainless steel ring lets
no light through. Opaque colored stones include hematite and turquoise.
Some gems, like opal, have varying degrees of transparency in a range
from transparent to opaque.
Not all gemstones have the same combination of these elements: Jadeite
can be opaque - and beautiful. On the other hand, a ruby owes a good deal
of its beauty to the fact that it's transparent.
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Some people might like one gemstone more than any other, but remember
that ultimately, your choice is the most important. You will recognize
that each colored stone has at least one strong element of beauty, and
you will learn to appreciate it.
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Rarity
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Rarity, too, is a sliding scale, meaning some gems are rarer than others.
A few are so rare that they're considered collectors' items. Gem -
quality benitoite and red beryl - each found in only one place on earth -
are occasionally used in jewelry. Because they're not nearly as available
as gems like sapphire and amethyst, they're unknown to the majority of
consumers. Most gemstones are somewhere in the middle of the rarity
scale.
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Rarity doesn't always make a gem valuable. Pink spinel, for example, is
lovely, durable, and rare. Despite its virtues, pink spinel is generally
absent form consumer shopping lists. Few people know about it, so there's
very little demand for it.
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Demand is unpredictable. Amber, highly treasured in centuries past, is
less prized today, although rare specimens can still command high prices.
Similarly, jet - an opaque black organic gemstone - was extremely popular
in Victorian England, but is virtually unheard of in jewelry today.
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Often, shrewd marketing can sway consumer preference. If a major retailer
backs a gem with an expensive advertising campaign, it's more likely to
penetrate the market quickly, as was the case with tanzanite, the
striking violet-blue East African gem. But no matter how energetically
it's marketed, a gem must be beautiful and durable as well as rare to
merit popular success. And it must be available in sufficient quantities
to stay in public consciousness over the long haul.
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Durability
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Autumn leaves are lovely, with their rich, mottled wine reds and golden
yellows and their graceful, symmetrical shapes. A child who put a scarlet
leaf on a string to wear around her neck will soon find it brown and
shriveled. Leaves, unlike gems, lack durability. Leaves fade, change
shape, and decay. Gems endure.
Durability is a combination of three factors: hardness, toughness, and
stability. Hardness measures how well a gemstone resists scratching and
abrasion like the hardness of tungsten rings. Toughness is the ability to
withstand breaking, chipping, and cracking.
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Hardness and toughness are not the same thing. Topaz is a relatively hard
stone, but is has poor toughness. Jadeite is not as hard as topaz, but it
has exceptional toughness.
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Stability measures how well a gemstone resists the effects of light,
heat, and chemicals. The cleaning solutions that make sapphi re sparkle
can damage peridot. Likewise, everyday sunlight can fade kunzite over
time.
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Low durability is the reason that beautiful minerals like fluorite and
calcite are not usually used in jewelry. They can be polished, and most
people agree that both are beautiful. But they have very low hardness and
poor toughness, so they're rarely used in jewelry.
Kevin Jardim has been a Product Manager at Coppary Jewelry for over 5
years and has been in the jewelry business for over 15 years. He is
currently an Accredited Jewelry Professional earning his certificate form
the Gemological Institute of America. He is also affiliated with Jewelers
of America, the largest and most respected jewelry retailer association
in the U.S.

				
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posted:10/12/2010
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