4 C's of Diamonds
ColorWhen searching for white diamonds, people prefer them to be as clear as possible. When diamonds are composed purely of carbon, they are completely clear, but very few of them fall into that category. Since diamonds are formed by random natural processes in the Earth instead of in a sterile setting, most diamonds end up with foreign materials trapped in their structure during their creation. The most common of these materials is nitrogen, which introduces shades of brown or yellow. Because nitrogen is one of the most prevalent elements on the planet, it's very rare to find a completely colorless diamond, and the price of them reflects that fact.
GIA categorizes the color of diamonds with a D-Z scale, with "D" representing a colorless diamond and "Z" representing very yellow stones. Keep in mind, though, that when the saturation of yellow passes the Z mark, or the diamond has other colors like green or red, GIA labels these stones as "fancy" and has a different rating scale for them.
CutEveryday language tends to conflate the words "shape" and "cut" when it comes to diamonds, but those two terms mean different things here. The cut of a diamond refers to the quality that goes into planning and cutting the crown, girdle, and pavilion of a diamond to maximize its inner reflectivity. Diamantaires have used geometry and an understanding of physics to determine the proper dimensions and proportions for maximizing reflectivity in different shapes of diamonds, and a well-cut diamond has a remarkable fire and sparkle. The quality of cut can't be understated, since small imperfections can cause light to be lost and diamonds appear dark inside.
GIA grades cut from "excellent" to "poor," which uses a seven-point scale: brightness, fire (the rainbow effect of a diamond), scintillation (flashes of white light), weight ratio, polish, symmetry, and durability.
Carat Weight"Carat" refers to the weight of a diamond, rather than the colloquial understanding of the word as the size of the stone. One carat weighs exactly 0.2 grams, and each carat is divided into 100 points (0.002 grams each). So, for example, a 235-point diamond would be 2.35 carats, or 0.47 grams. Remember that while carat refers to weight, the shape of the diamond can change the way the carats look. Longer shapes, like emerald-cut and marquise-cut diamonds, will look significantly bigger than compact shapes of the same weight, like round-cut and princess-cut stones.
ClarityWhen talking about the clarity, it should be noted that the same origin which alters the color of diamonds can alter the clarity of the same stones. Since diamonds are created in natural, uncontrolled processes, their inner structures can be disrupted during formation. These disruptions are called "inclusions." Cracks, bubbles, voids, and other irregularities can be present, as well as foreign material inside the diamond, such as black carbon, iron, small garnet crystals, and sand. Most diamonds have some inclusions, but the amount, type, and visibility of inclusions can dramatically alter a diamond's clarity and cost.
GIA grades clarity on an 11-rank scale. At the top of the list is an F-category (flawless) diamond, which means that a certified grader can't find any internal flaws under 10x magnification. On the opposite end of the spectrum is an I3-category (extremely included) diamond, which has many inclusions that are visible to the naked eye.