The
sparkle and historical significance of semi precious
gem stones is unmatched. They are available in diverse
varieties and hues. Before making a purchase, a basic
understanding of the value of gems is essential.
Regardless of the gem variety, there are a few
constant rules to be kept in mind while selecting the
gems. Owing to the different types of natural,
synthetic and imitation stones in every color, shape
and size, it is necessary to get acquainted with the
specific semi precious gem stones. The prices are
guided by the desirability, quality and availability
of gemstones.
Color
The color is the most defining factor when evaluating
the colored gems. It is important to look at the hues,
tone and saturation, when deciding upon a gemstone
color. The more attractive the color, the higher is
the value. The highest quality gemstones have a pure
color and posses very slight shades of other colors.
Tone represents the depth of the color, which can
range from colorless to black. The tone of a gemstone
is described as “light”, “medium-light”, “medium”,
“medium-dark”, and “dark”. Bright, rich and intense
colors are valued over those that are too dark or
light. Colors that are dulled by tones of black, gray
or brown are regarded as less desirable. The
particular colors and shades of the gems affect the
prices of gems that is also affected by the personal
preferences as well.
Optical Effects
The brilliant colors displayed by some specific
gemstones are optical effects caused when white light
is split into its constituent colors. Some gems
exhibit unusual optical effects known as phenomena
that rare and beautiful and add immense value to the
gems. The Cat’s Eye Effect, the Star Effect and the
Color Change Effect are very popular phenomena.
Chatoyancy
Chatoyancy or the Cat’s Eye Effect is a reflection
effect appearing as a single bright band of light
across the gemstone's surface. It is generally found
in Chrysoberyl, Tourmaline and Tigers Eye.
Asterism
Asterism or the Star Effect appears as two or more
intersecting bands of light across the gem's surface.
The phenomenon is commonly found in Ruby, Sapphire and
Garnet.
Color Change
Color change gems have the capacity to distinctly
change their regular color when viewed under two
different light sources. The phenomenon commonly in
Alexandrite, Sapphire and Color Change Garnet.
Iridescence
Iridescence refers to the rainbow like color effects
as seen in some specific gems. It is generally found
in Opal, Ammonite and Moonstone.
Aventurescence
Aventurescent gems posses colorful play of glittering
reflections from small metallic inclusions. The
phenomenon is common in Sunstone, Aventurine Quartz
and Gold Stone.
Cut & Polish
The process of cutting and polishing gems is called
lapidary. A well-cut gemstone is symmetrical and
reflects light evenly across the surface and the
polish of the stone is smooth without any nicks. Owing
to the variable optical properties of colored gems,
the cuts are determined by the color saturation. There
is no ideal cut for gemstones that is geometrically
configured for brilliance like diamonds. A greater
color saturation requires a shallow cut, while less
color saturation requires a deeper cut. A well-cut
colored gem has even color, good brilliance, minimum
number of inclusions and a good symmetry and polish
conditions. Facets need to be aligned straight in
relation to the gem’s girdle and also to each other.
While choosing a gemstone, the polish must be flawless
with no visible surface pits and polishing lines.
The gem cutting styles are divided
into:
Faceted Gems- Those gems that have
geometrically shaped flat polished faces
Non-Faceted Gems- Those gems that do not have
geometrically shaped flat polished faces such as
cabochons
Carat Weight
Gemstone carat weight refers to its weight. Gems vary
in density and weight and not all gemstones look the
same in size. This unit of measurement originates from
the traditional use of carob seeds to weigh gems.
Carob seeds were used because of their consistent size
and shapes. One carat is equivalent to 0.20 Grams that
is further divided into 100 smaller units known as
Points. As the weight of a gemstone increases, its
price also increases.
Clarity
Each individual gemstone comprises of a combination of
trace minerals that create identifying marks or
inclusions in the gemstone itself. The tiny natural
features are most easily glimpsed under magnification.
For desired effects, inclusions need to interfere with
the brilliance, sparkle and fire of a gem. The best
value is found in gems that are lightly to moderately
included. The clarity of gems is determined by judging
the amount and location of inclusions seen. The higher
the clarity grade, the higher is the value of the gem.
Gems that have greater durability and resistance to
wear are more highly priced than those of lesser
durability.
Rarity
Generally, rare gems are more highly prized than more
common varieties. However, if a gem variety is so rare
that it is essentially unknown to the general public,
it is often classified as a "collector gem". Gems such
as Boracite, Childrenite and Simpsonite are extremely
rare, attractive and durable, but they are unlikely to
command prices appropriate to their rarity because
fewer people are aware of their existence.
Historical Connotations
The quality gems rich in history and lore have high
prices than the ones lacking a rich lore or history.
The variety of Ruby from “Mogok Valley in Burma” is
exclusive and paid for more than the Ruby from
elsewhere.
Gemstone Treatments
The gemstones are often treated to improve their
appearance. Some of these treatments are permanent
while others are not. Diffusion deepens the color of
the gemstone, but only within its outer layers. Oil
and waxes are used to fill-in surface-breaking
fractures. Treated gems can be a good choice to pay a
price that reflects a stone's true quality.
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