The 4 C's are four variables that are used to calculate the value of a diamond -- Clarity, Color, Cut, and Carat Weight.
Clarity describes the clearness or purity of a diamond. This is determined by the number, size, nature, and location of the internal (inclusions) and external (blemishes) imperfections.
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.
Be aware! 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.
Color describes 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.
| GIA | COLOR - COMMERCIAL GRADING |
| D | Colorless |
| J | Near Colorless |
| M | Faint Yellow |
| N,O,P,Q,R | Very Light Yellow |
| S,T,U,V, |
Be aware! 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.
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.
Cut refers 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 brilliance.
The proportions 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 as follows:
Table (%) = longest table measurement (in mm)
average girdle diameter (in mm)
And for depth percentage:
Depth (%) = depth (in mm)
average girdle diameter (in mm)
Without attention to quality cutting, light is lost and not returned to the eye.
Proportions Criteria are as shown below:
|
| "Premium Cut" | "Tolkowsky Ideal Cut" | "Excellent Ideal Cut" |
| Total Depth | 58.8% - 63.8% | 58.0% - 63.8% | 59.2% - 62.4% |
| Table Size | 58.0 - 61.0% | 53.0% - 58.0% | 52.5% - 58.4% |
| Crown Height | 13.0% - 17.0% | 14.2% - 16.2% | -------------- |
| Crown Angle | 32.7° - 36.3° | 33.7° - 35.8° | 32.5° - 35.4° |
| Pavilion Depth | 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.
Carat is 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 rarer.
