When purchasing something as unique and valuable as a diamond, it is necessary for one to have a basic background education regarding its quality and brilliance. Commonly referred to as the "Four C's", these consist of the diamond's: Cut, Color, Clarity, and Carat.

The cut of a diamond is what determines its shape (whether it will be round, oval, pear…). It also influences how well the diamond can reflect light and its ability to sparkle by its proportions. A well-cut diamond is symmetrical in both size and depth.

Cut is the factor that fuels a diamond’s fire, sparkle and brilliance. The traditional 58 facets in a round brilliant diamond, each precisely cut and defined, are as small as two millimeters in diameter. But without this precision, a diamond wouldn’t be nearly as beautiful. The allure of a particular diamond depends more on cut than anything else.

Though extremely difficult to analyze or quantify, the cut of any diamond has three attributes: brilliance (the total light reflected from a diamond), fire (the dispersion of light into the colors of the spectrum), and scintillation (the flashes of light, or sparkle, when a diamond is moved).

An understanding of diamond cut begins with the shape of a diamond. The standard round brilliant is the shape used in most diamond jewelry. All others are known as fancy shapes. Traditional fancy shapes include the marquise, pear, oval and emerald cuts. Hearts, cushions, triangles and a variety of others are also gaining popularity in diamond jewelry.

As a value factor, though, cut refers to a diamond’s proportions, symmetry and polish. For example, look at a side view of the standard round brilliant. The major components, from top to bottom, are the crown, girdle and pavilion. A round brilliant cut diamond has 57 or 58 facets, the 58th being a tiny flat facet at the bottom of the pavilion that’s known as the culet. The large, flat facet on the top is the table. The proportions of a diamond refer to the relationships between table size, crown angle and pavilion depth. A wide range of proportion combinations are possible, and these ultimately affect the stone’s interaction with light.

In early 2005, GIA unveiled a diamond cut grading system for standard round brilliants in the D-to-Z color range. This system, the product of more than 15 years of intensive research and testing, assigns an overall diamond cut grade ranging from Excellent to Poor.

How does pavilion depth affect a diamond's cut? The distance from the bottom of the girdle to the culet is the pavilion depth. A pavilion depth that’s too shallow or too deep will allow light to escape through the sides or the bottom of the stone. A well-cut diamond will direct more light through the crown.

Herein lies the astronomical difference in the prices of diamonds. A diamond with no inclusions or imperfections is worth more than one that has flaws, even though many of these inclusions cannot be seen with the naked eye. Since inclusions can interfere with the light passing through a diamond, clarity is something to consider for it will lessen the sparkle in the stone.

The color of a diamond depends on its capacity of absorbing light rays. In the absence of color, a diamond is absorbing the rays equally. Therefore, a colorless diamond is the most valuable. Diamonds range from colorless to yellow and are graded according to a letter scale: "D" being colorless and "K-Z" with hints of yellow to very yellow.

Carat refers to the weight of a diamond. Generally, larger diamonds are more expensive, however there are the other 3 C's to consider. Some smaller diamonds have better cut and clarity and are worth more than large, imperfect ones.