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4 C’S OF DIAMOND
Four criteria are used to evaluate the quality of colorless diamonds in
the most objective manner possible: the 4 C's. These are Carat
(weight), Clarity (purity), Color, and Cut. In order to classify diamonds
in a clear and uniform way, laboratories and other international
certificating
bodies have agreed a common set of precise parameters to be used in
assessing each of these criteria. This classification is very important
as it influences the sales price of diamonds.
1. Carat (weight)
The value of stone increases exponentially with its weight. The weight of
a diamond is measured in carats: 1 carat is equal to 0.2 grams, and is
divided into 100 points. The word "carat" is derived, via Arabic and
Italian, from the Greek word "keration" (fruit of the carob). Because of
their
uniform weight, carob seeds were in the past used on precision scales, and
different countries each had their own carat. In 1907 the metric carat of
200 milligrams was adopted, and is universally used today.
Note: The "carat" used for gems is not the same as the "karat" used for
gold. The latter refers to the ratio of pure gold contained within a
metal. This ratio is calculated in twenty-fourths, i.e. pure gold will be
24 karats (24/24 = 100%) whereas 18 karat gold contains 18/24 of pure gold
(i.e. 75%).
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Here are several ways to express 1 carat :
1 ct.
200 milligrams
1/5 gram
100 cents
4 grainer
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Carat
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0.25
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0.50
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0.70
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0.90
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1.00
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Øm/ m
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4.1
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5.2
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5.8
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6.3
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6.5
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Carat
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1.25
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1.50
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2.00
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2.50
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3.00
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Øm/ m
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6.9
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7.4
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8.2
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8.8
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9.4
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2. Clarity
(purity)
This is a very important step in determining the value of a stone.
Specifying purity involves making an inventory of all the internal and
external impurities of the stone and evaluating the one that is the most
representative and the most important. The diamond is examined under a
microscope (30x) and with a magnifying glass (10x). Purity grades are (in
decreasing order):
IF (internally flawless) : completely pure diamonds
VVS1 - VVS2 (Very Very Small inclusions) : tiny inclusions can barely be
seen through a ten-power magnifying glass, even by a trained diamond
grader.
VS1 - VS2 (Very Small inclusions) : very small crystals, clouds, cracks or
pinpoints characterize this grade. These inclusions are not very visible
and have no impact on the sparkle of the diamond.
SI1 - SI2 (Small Inclusions) : impurities can be seen with a 10x
magnifying glass but are not visible to the naked eye.
I1 - I2 - I3 (GIA terminology) or P1 - P2 - P3 (HRD terminology) (Piqué) :
impurities are visible to the naked eye.
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Internally Flawless
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Very Very Slightly
Included
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Very Slightly Included
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Slightly Included
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Free from internal
blemishes visible under 10x magnification (small external details
tolerated).
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Inclusions and/or
external blemishes very difficult to locate under 10x magnification.
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Inclusions and external
blemishes difficult to locate under 10x magnification.
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Inclusions and external
blemishes easy to locate under 10x magnification.
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3. Color :
Colorless diamonds are assessed against a range of colors that goes from
colorless (D - for "Diamond") to light yellow or brown (P - the most
yellowish color). The color is observed through a uniform, Northern
daylight 65 light, and is compared to a set of reference master stones.
"+" or "-" signs are added in order to fine-tune the definition of the
color. A K- stone for example will have a color similar to but slightly
less yellow than a K stone.
Most diamonds are referred to as “colorless,” which in diamond terminology
ranges from really colorless to yellowish. A small percentage of diamonds
have a distinctive color—from yellow to black, through blue, green, pink
and even red. In this respect they resemble colored gemstones. These
so-called “fancy colors” are very rare and highly desirable. Since their
intense appearance is fashionable, color is sometimes produced
artificially using modern technology. Artificially colored diamonds are
less valuable than naturally colored diamonds.
D - J: colorless or white diamonds.
K - L : "tinted white" diamonds.
M - P : "tinted color" diamonds.
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4. Cut :
Almost 100 years ago, the Master cutter Marcel Tolkowski defined the ideal
proportions that govern the most popular cut: the brilliant (or round).
Indeed, the ideal brilliant has to be conceived and cut in such a way that
the light that enters the diamond through the sides of the crown is
amplified by the pavilion (which acts as a perfect mirror) and exits the
crown through the table. In order to obtain this effect, a number of
"ideal" parameters were defined which do leave some margin for maneuver:
the height of the stone in relation to its diameter, the depth of the
pavilion, the angle of the pavilion, the angle of the crown, the height of
the crown.
After having studied these various parameters, a grade is given to the cut
of the stone as a whole: VG (Very Good), G (Good), M (Medium) or P (Poor).
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In general, rough
diamond is not particularly attractive; it barely sparkles. The
diamond only achieves its characteristic, stunning brilliance after it
has been polished. The diamond’s unusual attractiveness and play of
color is due to its reflectivity and exceptionally high refractive
index, by which the light is optimally “broken”. The result is a
dispersion of the white light into all the colors of the rainbow. Of
course, all the facets of a polished diamond have to be oriented
properly for this effect to be obtained. Only then does the stone come
to life.
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How a diamond has been
cut, polished, and to what proportions and symmetry, are of utmost
importance since these factors determine the life, brilliance and
dispersion of the diamond. If these cutting factors fall below
standard, the appearance of the diamond will be adversely
affected. Execution of the design, the precision of the cutting
details and the quality of the polish
are collectively called the finish. |
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Shape
There's One more
Criteria Considered Besides 4 C’s of Diamond
Shapes: Besides Round or Brilliant Cut there are many Popular Shapes of
Diamond….
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Emerald cut:
Rectangular or square step cut with
diagonally cut corners and two, three, or four rows of facets parallel
to the girdle on the crown and pavilion. It is frequently used to
fashion emeralds. If the shape is square, it is called a square
emerald cut.
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Pear:
Variation of the brilliant cut with a pear-shaped girdle outline and
56 to 58 facets. Also called pendeloque or teardrop. |
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Marquise:
Elongated, boat-shaped brilliant cut with curving sides and pointed
ends, developed in France in the 1740s. Believed to have been named
after the Marquise de Pompadour, a mistress of King Louis XV. Also
called navette. |
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Heart:
Modified brilliant cut in the shape of a heart, with a table, 32 crown
facets, 24 pavilion facets, and a shield-shaped culet.
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Oval:
Brilliant cut with an elliptical girdle outline ; also called an oval
brilliant cut. Obsolete barrel-shaped cut, circular in section and
covered with triangular facets.
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Princess:
popular square or rectangular modified brilliant cut usually with 57
facets (21 crown facets, 32 pavilion facets, and four girdle facets)
but occasionally a rectangular/ square brilliant with 144 facets.
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