The 4 C's are four variables that are used to calculate the value of
a diamond -- Clarity,
and Carat Weight.
the clearness or purity of a diamond. This is determined by the number,
size, nature, and location of the internal (inclusions) and external (blemishes)
The clarity scale
is broken down into the following grades:
The above clarity grading
scheme is in accordance with the GIA (Gemological
Institute of America). It is important to note that the GIA Grading
system is not static, and has changed slowly over time.
from all inclusions or blemishes.
inclusions visible at 10x magnification.
Very Slightly Included #1
that are extremely difficult to locate at 10x.
Very Slightly Included #2
that are very difficult to locate at 10x.
Slightly Included #1
inclusions that are difficult to locate at 10x.
Slightly Included #2
inclusions that are somewhat difficult to locate at 10x.
inclusions that are easy to locate at 10x.
inclusion that are very easy to locate at 10x.
inclusions. Somewhat easy to locate with the unaided eye.
inclusions. Easy to locate with the unaided eye.
inclusions. Very easy to locate with the unaided eye.
Two methods used to enhance the clarity grade given to a diamond are laser
drilling and fracture filling. Laser drilling is the process in which
a laser is used to drill a tiny hole into a diamond and the black of the
imperfection is then removed. The second treatment is fracture filling.
This method is not permanent and therefore not recommended. All clarity
treated diamonds must be disclosed as such prior to sale. The
Diamond Source USA does not deal with diamonds that have been clarity treated
in any way.
the amount of color the diamond contains. This can range from colorless
to yellow with slight tints of yellow, gray or brown. Colors can also range
from intense yellow to brown, blue, green, pink and red. These fancy colors
are rare and therefore more valuable.
It is possible to influence the color by irradiation treatment followed
by heat treatment. This method is not recommended for two reasons. The
first is the risk involved with exposure to irradiated objects. The second
is the risk of color change over time. All color treated diamonds must
be disclosed as such prior to sale. The Diamond Source USA does
not deal in diamonds that have been enhanced in any way.
- COMMERCIAL GRADING
The color of the
stone can be determined by using a GIA (Gemological Institute of
America) Certified set of master stones and/or the Colorimeter, a computer
which accurately grades the color of a polished diamond.
to the proportions, finish, symmetry, and polish of the diamond. These
factors determine the fire and brilliance of a diamond. Well
cut diamonds sell at a premium and poorly cut diamonds sell at discounted
prices. With the advent of technology, the cut of the diamond can be determined
through the use of the Dia-Mension system, a computerized system which
takes accurate measurements and proportions of a diamond in seconds, in
addition to the standard millimeter gauge.
As an example, a
round brilliant cut, which has 58 facets, is shown below. Since the
quality of the cut is directly responsible for the stone's beauty, the
precision with which the facets are arranged is of prime importance.
They determine the amount of light reflected to the eye, called
displayed by the stone are very significant. Two of the key factors
in the grading of cut quality -- table
percentage and depth
percentage -- are usually expressed on grading reports.
Measurement of three different parameters allows for easy calculation of
these percentages by using the formulas expressed below.
For example, for
a round brilliant cut diamond, table percentage is calculated
(%) = longest table measurement (in mm)
average girdle diameter (in mm)
And for depth
depth (in mm)
average girdle diameter (in mm)
to quality cutting, light is lost and not returned to the eye.
Proportions Criteria are as shown
"Tolkowsky Ideal Cut"
"Excellent Ideal Cut"
58.8% - 63.8%
58.0% - 63.8%
59.2% - 62.4%
58.0 - 61.0%
53.0% - 58.0%
52.5% - 58.4%
13.0% - 17.0%
14.2% - 16.2%
32.7° - 36.3°
33.7° - 35.8°
32.5° - 35.4°
41.7% - 45.0%
42.2% - 43.8%
41.5% - 44.4%
Each cut style above
represents, in the opinion of its respective designer, those proportions
which best balance the qualities of brilliance and dispersion ("fire")
within a round diamond.
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beauty is in the cutting!
It is where
the cutter truly expresses artistic skill, as the other 3 C's are determined
by nature alone.
the unit of weight for the diamond. A carat is further subdivided
in 100 points ( 0.01 carat = l point ). One carat is equal to 0.20 grams.
Value per carat increases with carat size, because larger rough diamonds
occur less frequently. In other words, 2 half-carat diamonds taken
together will not cost as much as 1 one-carat diamond, as the one-carat
stone is more rare.