The cut of the diamond defines its sparkle. The shine of the diamond depends on how well it has been cut and how many facets it has. The better the cut, the better its shine. Because cut is so important, several grading methods have been developed to help consumers determine the cut of a particular diamond.
In general, these grades are: 1. Excellent 2. Very Good 3. Good 4. Fair & Poor
In a poorly cut diamond, the light that enters through the table reaches the facets and then 'leaks' out from the sides or bottom of the diamond rather than reflecting back to the eye. Less light reflected back to the eye means less brilliance. A better proportionately faceted diamond, the more the light gets reflected to the viewer's eye.
The size of the diamond. One carat is made up of 100 points and 5 carats make one gram. (Keep In Mind: Don't mix "carat weight" with "karat," the method of determining the purity of gold.) The process that forms a diamond happens only in very rare circumstances, and typically the natural materials required are found only in small amounts. That means that larger diamonds are uncovered less often than smaller ones. Thus, large diamonds are rare and have a greater value per carat. For that reason, the price of a diamond rises exponentially to its size.
This criterion tells us how the clear the stone is from impurities. Impurities like Crystal (bubbles), Feathers (cracks), Natts (Black inclusion), and etc. If you think about the incredible amount of pressure it takes to create a diamond, it's no surprise that most diamonds have flaws.Hence a chart is used to measure the clarity of the diamond.
F :Flawless: No internal or external flaws. Extremely rare.
IF :Internally Flawless: no internal flaws, but some surface flaws. Very rare.
VVS1-VVS2 :Very Very Slightly Included (two grades). Minute inclusions very difficult to detect under 10x magnification by a trained gemologist.
VS1-VS2 :Very Slightly Included (two grades). Minute inclusions seen only with difficulty under 10x magnification.
SI1-SI2 :Slightly Included (two grades). Minute inclusions more easily detected under 10x magnification.
I1-I2-I3 :Included (three grades). Inclusions visible under 10x magnification AS WELL AS to the human eye.
“Color” refers to the presence or absence of color in white diamonds. Color is a result of the composition of the diamond, and it never changes over time. The color of a diamond ranges from D to X, D being the whitest shade. Because a colorless diamond, like a clear window, allows more light to pass through it than a colored diamond, colorless diamonds emit more sparkle and fire. The formation process of a diamond ensures that only a few, rare diamonds are truly colorless. Thus the whiter a diamond's color, the greater its value.
(Keep In Mind: Fancy color diamonds do not follow this rule. These diamonds, which are very rare and very expensive, can be any color from blue to green to bright yellow. They are actually more valuable for their color.)
Diameter: The width of the diamond as measured through the girdle.
Table: This is the large, flat top facet of a diamond.
Crown: The upper portion of a cut gemstone, above the girdle.
Girdle: The narrow rim of a diamond that separates the crown from the pavilion. It is the largest diameter to any part of the stone.
Pavilion: The lower portion of the diamond, below the girdle. It is sometimes referred to as the base.
Culet: The tiny facet on the pointed bottom of the pavilion, which is the portion of a cut gem below the girdle.
Depth: The height of a gemstone, from the culet to the table.