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Cut,
Clarity, Color & Carat
The 4-C's namely, Cut, Clarity, Color and Carat Weight
help to categorize and grade the diamond using universal terminology
which determines also the price and value of the
diamond. At the same time familiarity with the 4 C's helps individuals
to better understand the diamond's natural
characteristics and thus to decide knowledgeably which ombination is the
most suitable and most desirable for them
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CUT
Proportions and cut determine the brilliance
of a diamond. In order to maximize this brilliance, the diamond cutter
must place each of the diamond's facets, which
act as light-dispersing mirrors, in exact geometric relation to one another.
On a classic Round Brilliant cut diamond,
fifty eight (!) facets must be precisely aligned. Few diamonds are cut
to exacting standards since diamond cutters
try to maximize their returns on the raw material by leaving the stone
as large as possible with minimum waste. As
a result, the proportions, symmetry and perfection of the cut and shape
may be delegated to play a secondary role. The result
is usually a compromise between profit (e.g., size) and beauty (perfection
of cut, proportions and shape).
The most important criteria of the Cut is
the ratio of the depth to its diameter ( i.e. Depth/Diameter). In order
for the diamond to be considered within the
"Ideal" tolerance bracket the ratio should be between 58/100 and 62/100
or, "58%" and "62%" respectively (see illustration).
The measurements are taken in millimeters through the use of a Leveridge
Gauge or Micrometer "Table" diameter percentage
( see illustrations for definitions of the names of the different diamond
facets ) ; "Crown" angles and "Girdle" thickness
& symmetry are also important. Each of these proportion criteria have
tolerance ranges which, however, are less
crucial when violated than deviation from the above Depth/Diameter ratio
( "Percentage").
Marcel Tolkowsky is credited with calculating
in 1919 the ideal proportions and facet angles that create maximum brilliance
and fire. Unfortunately the "ideal cut" results in smaller weight yield
from the rough diamond crystal and is rarely practiced. Most cutters today
slightly compromise Tolkowsky's "ideal cut" but still create impressive
results.
When the diamond is well proportioned the
path of a beam of light is returned directly back to the eye instead of
escaping through the bottom or sides of the cut diamond, as a result the
diamond will be more lively and brilliant.
The Gemological Institute of America (GIA)
scale for the diamond's Cut (proportions) is described using the terms
"Excellent", "Very Good", "Good", "Fair", and "Poor" ("Recut").
CLARITY
Clarity refers to the inclusions and blemishes
in the crystal. Gemologists refer to these blemishes, rather, as identifying
characteristics avoiding any negative associations and connotations. One
must remember that a diamond is a natural substance and any inclusion or
pattern of inclusions can be considered as the diamonds unique natural
characteristic and "fingerprint". They can also help identify the diamond
making your diamond as unique as a snowflake, since no two are exactly
alike.
Diamonds are graded for clarity according
to the number, size, location and type of inclusion. Obviously, less numerous
and smaller inclusions that are less centrally located are more desirable
than the opposite. Examples of the type of internal inclusions
include: "pinpoints", included crystals that
are transparent, opaque or carbon . Groups of pinpoints are called "clouds"
and fractures are called "feathers". External blemishes include polishing
lines, grain lines ( mineral growth twinning planes), scratches,
chips, nicks and naturals (part of the rough
diamonds original surface or "skin").
Diamond Clarity Grading
Terminology :
As the value of a diamond is determined,
partially, by its "purity" or "clarity", standards for measuring the diamond's
clarity have been put into place . The clearer the diamond is the rarer
and therefore, the more valuable it is . The following terminology is used
by the industry. The letter abbreviations are sometimes confusing to the
novice but still are of high importance .
The G.I.A Clarity Scale:
| Flawless |
diamonds in this category are free from internal
and external imperfections when examined by skilled professionals under
natural or artificial light with a 10X loupe corrected for chromatic and
spherical aberration or with a 10X binocular microscope equipped with dark
field illumination. ( The following conditions still qualify a diamond
as flawless: an extra facet located on the pavilion which cannot be seen
from the face-up position; a natural that does not extend beyond the maximum
width of the girdle or break the symmetry of the girdle outline and is
not seen from the face-up position ) |
| Internally Flawless |
diamonds in this category are free from all internal
imperfections (inclusions) but do possess minor surface blemishes. Normally
these diamonds may be made flawless by minor repolishing with the exception
of surface grain lines. |
VVS1 and VVS2
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(Very Very Small Inclusions, level 1 or 2)
These grades contain minute inclusions so small
or insignificant that they are difficult to locate under 10X loop. When
these inclusions are very difficult to locate visible only from the pavilion
side or tiny enough to be easily removed by repolishing-the
first VVS grade applies. Pinpoints, faint clouds,
tiny feathers or bruises characterize the VVS grades. |
| VS1 and VS2 |
(Very Small Inclusion, level 1 or 2)
These grades imply minor inclusions of a size,
number and location that stand between those somewhat difficult to observe
and those somewhat easier to observe under 10X loop. Small included crystals,
small feathers, distinct clouds characterize the VS grades. |
| SI1 and SI2 |
(Small Inclusions levels 1,2)
These grades contain noticeable inclusions which
are easily visible under 10X loop. Normally these inclusions will be centrally
located and noticed immediately when the diamond is examined. diamonds
in these grades (particularly the SI2 grade) may
disclose inclusions to the unaided eye when placed
table down on a white background, but not when viewed face-up. |
| I1, I2 and I3 |
(observable Inclusions levels 1,2 & 3)
The "Imperfect Categories" contain obvious inclusions
when viewed under 10X loop and are visible to the unaided eye in the face-up
position. The grades vary from diamonds with inclusions that are difficult
to locate by the unaided eye to those with
severe inclusions that are easily noticeable. |
Though a diamond is said to be "flawless" if no inclusions
(internal or external) can be seen under 10 power magnification (triplet
loupe or binocular microscope) truly flawless diamonds are extremely rare.
The VS1 category is the cut-off point for what
is considered to be a fine clarity grade since the inclusions characteristic
of this grade are extremely small and difficult to see at 10X magnification.
To the left of the scale from the VS1 grade the differences between each
clarity grade are significantly smaller than clarity grades to the right
of the VS1 category, where the tolerances for each grade are larger. SI
grades are still considered to be very good to good, since their inclusions
are not eye visible, especially
when examined under normal lighting conditions.
Under gemological laboratory conditions where daylight is used the inclusions
in the SI2 grade are eye visible when viewed through the back of the diamond
(known as the "Pavilion View"). SI grades are considered good choices especially
when combined with good color and cut since the cost due to the clarity
is usually within popular price ranges and budgets.
COLOR
Paradoxically enough, the more colorless the diamond,
the greater is its rarity and value. Although many diamonds may appear
colorless to the untrained eye, the majority contain very slight traces
of yellow or brown. Color quality is critical because a diamond's value
increases dramatically the more colorless it is. Color determination consists
of comparison with Master-Color diamonds under daylight conditions. A single
increase in a diamonds color grade can boost a diamond's value by thousands
of dollars depending on the size and clarity grade combinations. diamonds
colors are graded from the letter "D" (Colorless) to "Z" (prominent hue).
CARAT
Diamonds are weighed on a carat scale. Trade legend
has it that the weight unit's name, "Carat", is derived from the measuring
unit of antiquity: the carob fruit seed... There are 100 points in one
carat. Therefore, weight can also be understood as a ratio (i.e. points/
100). A fifty point diamond -half a carat- is then 50/100's of a carat.
The size of a diamond measured in millimeters can also assist in determining
approximately the diamond's carat weight. by using the following formula
(not for the novice...):
[Average Diameter in mm. ] X [ Depth in mm. ]
X 0.0061 (whereby "X" stands for the mathematical operator "times" and
0.0061 is the Size/Weight conversion factor). It is however important to
understand that there is no direct relationship between size and weight
(i.e. a fifty point diamond is NOT twice as large (or wide) as a twenty
five point diamond, only twice as heavy). It is also important to
note that size alone is not enough to determine a diamond's value : One
has to consider also the cut and proportions of the diamond, its clarity
as well as its color. A large diamond holds little value if it lacks brilliance,
purity and good grade color. |
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