Diamonds are cut according to an exact mathematical formula. A finished diamond has 58 "facets," which are the small, flat polished planes cut into a diamond, so that the maximum amount of light is reflected back to the viewer's eye. This reflection is called "brilliance," and is extremely important in evaluating the quality of a diamond. The widest circumference of a diamond is the "girdle." Above the girdle are 32 facets plus the "table," the largest and topmost facet. Below the girdle there are 24 facets plus the "culet," or point.



Proper cut enhances a diamond's capacity to reflect light and makes it sparkle more. The width and depth have the greatest effect on how light travels within the diamond, and how it exits in the form of brilliance.

A diamond's depth, distance from top to bottom, should be about 58-61 percent of its width, which means the gem should be wider than it is tall. If the diamond is cut too shallow, light is lost out the sides causing the diamond to lose brilliance. But, if the diamond is cut too deep, light escapes out the bottom causing the diamond to appear dark and dull.


Cut quality commands a premium for two reasons: first, you are paying for a highly skilled diamond cutter's time, and it can take many hours to get all the proportions and angles to fall within the Ideal range; second, more of the diamond is lost in the cutting process.

Cut also deals with the shape of the diamond. Traditional shapes are round, princess, emerald, marquise, pear, oval and heart.
 

The Four C's - Color
Diamonds are found in all colors of the rainbow, from clear, colorless, transparent stones to ink black ones. The Gemological Institute of America (GIA) created the universal grading system in the early 1940’s to supersede all confusing grading systems in use at that time. The GIA color grading classification for white diamonds starts from the letter D, the finest color (colorless), and proceeds through the alphabet to Z getting progressively more yellow. The best color for a colorless diamond is, in fact, an absence of color.

Diamonds are graded for color only as loose, un-mounted stones in the top-down position (table down, pavilion up), and under very specific conditions of lighting and background. Colors D, E and F are essentially colorless diamonds and differ more in transparency. Colors G, H, I and sometimes J, will usually show little or no color in the face-up position (as set in jewelry) for most diamond shapes.

The grades D, E, F are exceptionally fine white diamonds being the only grades referred to as colorless. Although the color of two diamonds can be so slight as to only be detected in a controlled environment, the difference in price per carat between these diamonds, e.g., F and G, is significant at the wholesale level reflecting the rarity of the colorless diamonds in the market.

Diamond Color Chart

Four C's - Clarity

Clarity is a measure of the surface (blemishes) and internal (inclusions) characteristics of a polished diamond. Clarity, like color, has a major impact on the value of a diamond. The fewer clarity characteristics a stone has, the more rare, and therefore valuable, it is. A diamond with the highest clarity grade is flawless (Fl), which means when viewed under a 10x microscope it has no discernable blemishes or inclusions, a situation not frequently encountered. A diamond within the lowest clarity grades, I1-I3, has inclusions that are visible to the naked eye, i.e., without the use of a 10x microscope.

 

Internally Flawless No internal blemishes are visible under 10x magnification		Very Very Slightly Included No internal blemishes are visible under 10x magnification		Very Slightly Included Blemishes and inclusions difficult to locate under 10x magnification
Slightly Included Blemishes and inclusions easily viewed by 10x magnification		Imperfect Blemishes and inclusions easily viewed by 10x magnification and by the naked eye		Imperfect Blemishes and inclusions easily viewed by the naked eye

Diamond Clarity - Chart

Clarity grades are largely determined by the collective visual appearance that a stone's inclusions exhibit in relationship to the size and shape of the stone. After considering the size, position, number, color/contrast and nature of these inclusions, one may assess the final clarity grade. The higher clarity grades (Fl, IF, VVS1/2) are more difficult to distinguish than the lower (VS1/2, SI1/2, I1/2/3) because there are so few imperfections that more care must be given to avoid overlooking small characteristics.
 

Clarity	FL   IF	VVS1   VVS2	VS1   VS2	SI1   SI2	I1   I2   I3
Scale	Flawless-Internally Flawless	Very Very Slightly Imperfect	Very Slightly Imperfect	Slightly Imperfect	Imperfect

Generally, as the number of blemishes and inclusions in the stone decreases, the value of a diamond increases.


The Four C's - Carat Weight

The final “C” refers to the size of the diamond. Once you have decided what cut, color, and clarity grades you prefer in your diamond, determining the carat weight of diamond that will fit within your budget becomes very easy.  Diamonds are sold by carat, which is actually a unit of weight not size.  When exploring the exact size of a diamond, it is placed on a scale and weighed, as opposed to having its diameter or depth measured, which can provide only an approximate carat weight.

Below is an illustration of various diamond carat weights:

             

When rough diamonds are mined, the larger gems are discovered less often than the smaller ones, thus making the larger diamonds much more valuable.  In fact, diamond prices increase exponentially with carat weight.  For example, a 1-carat diamond of a given quality is always worth more than two 1/2-carat diamonds of the same quality.