Gemological characteristics
|
|
The use of diamonds as gemstones of decorative value is the most
familiar use to most people today, and is also the earliest use,
with decorative use of diamonds stretching back into antiquity. The
dispersion of white light into a rainbow of colors, known in the
trade as fire, is the other primary characteristic of gem diamonds,
and has been highly prized throughout history. Over time, especially
since around 1900, experts in the field of gemology have developed
methods of characterizing diamonds and other gemstones based on the
characteristics most important to their value as a gem. Four
characteristics, known informally as the four Cs, are now commonly
used as the basic descriptors of diamonds: these are carat, clarity,
color, and cut.. |
Most gem diamonds are traded on the wholesale market based on single
values for each of the four Cs; for example knowing that a diamond
is rated as 1.5 carats, VS2 clarity, F color, excellent cut, is
enough to reasonably establish an expected price range. More
detailed information from within each characteristic can then be
used to determine actual market value for individual stones.
Consumers who purchase individual diamonds are often advised to use
the four Cs to pick the diamond that is "right" for them; to these
is sometimes added the "fifth C" of cost.
Other characteristics not described by the four Cs can and do
influence the value or appearance of a gem diamond. These
characteristics include physical characteristics such as the
presence of fluorescence, as well as data on a diamond's history
including its source and which gemological institute performed
evaluation services on the diamond. Cleanliness also dramatically
affects a diamond's beauty.
There are four major gemological associations which "certify"
diamonds: that is, define the four Cs of a diamond. While carat
weight and cut angles are mathematically defined, the clarity and
color are judged by the trained human eye and are therefore open to
slight variance in interpretation.
Gemological Institute of America (GIA) was the first laboratory to
issue modern diamond reports, and holds the highest reputation
amongst gemologists for its consistent, conservative grading.
American Gemological Society (AGS) is not as widely recognized nor
as old as the GIA, but garners an equally high reputation.
International Gemological Laboratory (IGL) is a generally respected
laboratory but suffers from a negative industry reputation for its
grading practices, which are perceived by critics as being either
less conservative or less consistent than the GIA and AGS.
European Gemological Laboratory (EGL) has a similar reputation to
the IGL.CaratThe carat weight measures the mass of a diamond. One carat is
defined as exactly 200 milligrams (about 0.007 ounce). The point
unit—equal to one one-hundredth of a carat (0.01 carat, or 2 mg)—is
commonly used for diamonds of less than one carat. All else being
equal, the value of a diamond increases exponentially in relation to
carat weight, since larger diamonds are both rarer and more
desirable for use as gemstones.
The price per carat does not increase smoothly with increasing size.
Instead, there are sharp jumps around milestone carat weights, as
demand is much higher for diamonds weighing just more than a
milestone than for those weighing just less. As an example, a 0.95
carat diamond may have a significantly lower price per carat than a
comparable 1.05 carat diamond, because of differences in demand.
A weekly price list published by Rapaport of New York, of diamond
prices per carat, for different diamond cuts, clarity and weights,
is currently considered the de-facto retail price baseline. Jewelers
often trade diamonds at negotiated discounts off the Rapaport price
(e.g., "R -3%").
In the wholesale trade of gem diamonds, carat is often used in
denominating lots of diamonds for sale. For example, a buyer may
place an order for 100 carats of 0.5 carat, D–F, VS2-SI1, excellent
cut diamonds, indicating he wishes to purchase 200 diamonds (100
carats total mass) of those approximate characteristics. Because of
this, diamond prices (particularly among wholesalers and other
industry professionals) are often quoted per carat, rather than per
stone.
Total carat weight (t.c.w.) is a phrase used to describe the total
mass of diamonds or other gemstone in a piece of jewelry, when more
than one gemstone is used. Diamond solitaire earrings, for example,
are usually quoted in t.c.w. when placed for sale, indicating the
mass of the diamonds in both earrings and not each individual
diamond. T.c.w. is also widely used for diamond necklaces, bracelets
and other similar jewelry pieces. |
 |
|
Nofeerentals.com Apartment rental NY NYC, Rental apartments in New York city Nofeerentals.com has rental apartments and provides no fee apartment rental in downtown Manhattan New York City near New York University and all Manhattan http://www.nofeerentals.com/index.asp
Notasinc.com Window Balconies, hand made carved wood balconies These handicrafts are a beautifully hand made wood balconies, crafted by in Colombia by artisans with quality materials and a distinct original design. The Wood is used in every part of each piece, including the individually carved roof tiles. http://www.notasinc.com/window_balconies.htm
Microsoft Gold
certified Partner Cisco authorized reseller HP Business partner
Microsoft Gold certified Partner Cisco authorized reseller HP Business partner
Microsoft small business specialist
http://www.lansend.com/partners.aspx
Plain Chai
Quik tea plain chai tea powder is made from the choicest blend of Assam &
Darjeeling Teas. Using patented technology allows Quik Tea to form "little ...
http://www.quiktea.com/index.php?p=product&id=2
|