Clarity Color Cut
Clarity is a measure of internal defects of a diamond called
inclusions. Inclusions may be crystals of a foreign material or
another diamond crystal, or structural imperfections such as
tiny cracks that can appear whitish or cloudy. The number, size,
color, relative location, orientation, and visibility of
inclusions can all affect the relative clarity of a diamond. The
Gemological Institute of America (GIA) and others have developed
systems to grade clarity, which are generally based on those
inclusions which are visible to a trained professional when a
diamond is viewed from above, under 10x magnification.
Diamonds become increasingly rare when considering higher
clarity gradings. Only about 20 percent of all diamonds mined
have a clarity rating high enough for the diamond to be
considered appropriate for use as a gemstone; the other 80
percent are relegated to industrial use. Of that top 20 percent,
a significant portion contains a visible inclusion or
inclusions. Those that do not have a visible inclusion are known
as "eye-clean" and are preferred by most buyers, although
visible inclusions can sometimes be hidden under the setting in
a piece of jewelry.
Most inclusions present in gem-quality diamonds do not affect
the diamonds' performance or structural integrity. However,
large clouds can affect a diamond's ability to transmit and
scatter light. Large cracks close to or breaking the surface may
reduce a diamond's resistance to fracture.
Diamonds are graded by the major societies on a scale ranging
from Flawless to Imperfect.
Color, A chemically pure and structurally perfect diamond is
perfectly transparent with no hue, or color. However, in reality
almost no gem-sized natural diamonds are absolutely perfect. The
color of a diamond may be affected by chemical impurities and/or
structural defects in the crystal lattice. Depending on the hue
and intensity of a diamond's coloration, a diamond's color can
either detract from or enhance its value. For example, most
white diamonds are discounted in price as more yellow hue is
detectable, while intense pink or blue diamonds (such as the
Hope Diamond) can be dramatically more valuable.
Most diamonds used as gemstones are basically transparent with
little tint, or white diamonds. The most common impurity,
nitrogen, replaces a small proportion of carbon atoms in a
diamond's structure and causes a yellowish to brownish tint.
This effect is present in almost all white diamonds; in only the
rarest diamonds is the coloration due to this effect
undetectable. The GIA has developed a rating system for color in
white diamonds, from "D" to "Z" (with D being "colorless" and Z
having a bright yellow coloration), which has been widely
adopted in the industry and is universally recognized,
superseding several older systems once used in different
countries. The system uses a benchmark set of either natural
diamonds of known color grade, or precision-crafted cubic
zirconia; test lighting conditions are also standardized and
carefully controlled. Diamonds with higher color grades are
rarer, in higher demand, and therefore more expensive, than
lower color grades. Oddly enough, diamonds graded Z are also
rare, and the bright yellow color is also highly valued.
Diamonds graded D-F are considered "colorless", G-J are
considered "near-colorless", K-M are "slightly colored". N-Y are
usually appear light yellow or brown.
In contrast to yellow or brown hues, diamonds of other colors
are much rarer and more valuable. While even a pale pink or blue
hue may increase the value of a diamond, more intense coloration
is usually considered more desirable and commands the highest
prices. A variety of impurities and structural imperfections
cause different colors in diamonds, including yellow, pink,
blue, red, green, brown, and other hues. Diamonds with unusual
or intense coloration are sometimes labeled "fancy" by the
diamond industry. Intense yellow coloration is considered one of
the fancy colors, and is separate from the color grades of white
diamonds. Gemologists have developed rating systems for fancy
colored diamonds, but they are not in common use because of the
relative rarity of colored diamonds.
Diamond cutting is the art and science of creating a gem-quality
diamond out of mined rough. The cut of a diamond describes the
manner in which a diamond has been shaped and polished from its
beginning form as a rough stone to its final gem proportions.
The cut of a diamond describes the quality of workmanship and
the angles to which a diamond is cut. Often diamond cut is
confused with "shape."
There are mathematical guidelines for the angles and length
ratios at which the diamond is supposed to cut at in order to
reflect the maximum amount of light. Round brilliant diamonds,
the most common, are guided by these specific guidelines, though
fancy cut stones are not able to be as accurately guided by
The techniques for cutting diamonds have been developed over
hundreds of years, with perhaps the greatest achievements made
in 1919 by mathematician and gem enthusiast Marcel Tolkowsky. He
developed the round brilliant cut by calculating the ideal shape
to return and scatter light when a diamond is viewed from above.
The modern round brilliant has 57 facets (polished faces),
counting 33 on the crown (the top half), and 24 on the pavilion
(the lower half). The girdle is the thin middle part. The
function of the crown is to diffuse light into various colors
and the pavilion's function to reflect light back through the
top of the diamond.
Tolkowsky defines the ideal dimensions to have:
Table percentage (table diameter divided by overall diameter) =
Depth percentage (Overall depth divided by the overall diameter)
Pavilion Angle (Angle between the girdle and the pavilion) =
Crown Angle (Angle between the girdle and the crown) = 34.5°
Pavilion Depth (Depth of pavilion divided by overall diameter) =
Crown Depth (Depth of crown divided by crown diameter) = 16.2%
The culet is the tiny point or facet at the bottom of the
diamond. This should be a negligible diameter, otherwise light
leaks out of the bottom. Tolkowsky's ideal dimensions did not
include a girdle. However, a thin girdle is required in reality
in order to prevent the diamond from easily chipping in the
setting. A normal girdle should be about 1%–2% of the overall
The further the diamond's characteristics are from Tolkowsky's
ideal, the less light will be reflected. However, there is a
small range in which the diamond can be considered "ideal."
Today, because of the relative importance of carat weight in
society, many diamonds are often intentionally cut poorly to
increase carat weight. There is a financial premium for a
diamond that weighs the magical 1.0 carat, so often the girdle
is made thicker or the depth is increased. Neither of these
tactics make the diamond appear any bigger, and they greatly
reduce the sparkle of the diamond. So a poorly cut 1.0 carat
diamond may have the same diameter and appear as large as a 0.85
carat diamond. The depth percentage is the overall quickest
indication of the quality of the cut of a round brilliant.
"Ideal" round brilliant diamonds should not have a depth
percentage greater than 62.5%. Another quick indication is the
overall diameter. Typically a round brilliant 1.0 carat diamond
should have a diameter of about 6.5 mm. Mathematically, the
diameter in millimeters of a round brilliant should
approximately equal 6.5 times the cube root of carat weight, or
11.1 times the cube root of gram weight.
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