Diamonds are graded by four criteria which measure a diamond’s color, clarity, cut, and carat weight. While these are great indicators for a diamond’s quality, it is important to keep in mind that there is much more to each diamond than just the 4Cs.
CARAT – Measures a Diamond’s Weight
Most people believe that “carat” refers to the size of a given diamond. In reality, it is a measure of weight. A diamond grading report will specify a diamond’s weight in “carats”. One carat is 0.2 grams, or 200 milligrams. Historically, the term comes from the use of carob seeds in Egypt, which weighed about that amount. The carat became a standard unit of weight in the early 20th century. In certificates, a diamond’s weight is always rounded to the nearest hundredth of a carat (0.01 carats).
Diamonds are also sometimes weighed in “points” instead of carats. A point is 0.01 carats, so a half-carat diamond would be 50 points. Not all diamonds that share the same weight will look the be the same size. This is because the cut of the diamond can affect its physical dimensions. Some diamonds may have extra weight at the pavilion (bottom part of a diamond), making the diameter appear smaller than that of a diamond which has less pavilion weight. Larger diamonds are much more rare than small ones, and it often takes hundreds of tons of rock and ore to find a single one-carat diamond.
However, size is not the most important factor when shopping for a diamond. There are many large diamonds on the market that are of inferior quality. The cut of the diamond, for example, is more critical to the visual brilliance and fire of a stone than its size. If the diamond size is the most important factor for you, be sure to not overlook the other three Cs (color, clarity, cut) when searching for a diamond.
COLOR – Measures a Diamond’s Tint
There are several scales used for judging the color of a diamond, but the most common is an alphabetic scale widely used in the US. The Gemological Institute of America (GIA) grades diamond colors from D (totally colorless, sometimes called “white”) to Z (yellow). A colorless diamond is graded as D, E, or F, but the difference between each grade is small and usually only obvious to a trained expert. The difference is much more noticeable when comparing an F color diamond with a J color diamond. The most common color range for diamonds used in engagement rings is G-J (near colorless).
An experienced gemologist grades a diamond’s color by first placing the diamond face-down on a white background. He then judges the level of color concentration by comparing it against a set of diamond masters. The gemologist then assigns a color grade represented by a letter to the stone, and this is recorded on the diamond’s certificate.
In nature, diamonds range in color from white (colorless) through slightly yellow or brownish. There are some stones that have chemical impurities that tint the diamond a different color such as blue, green or pink. These are called fancy diamonds and are rare and costly.
Diamonds with D, E or F color are considered colorless; G, H, I and J colors are near colorless; K, L, and M colors are a faint yellow; N through R have a light yellow tint; S through Z are light yellow. Once the color intensity surpasses Z, the diamond is considered “Fancy Yellow”, also known as Canary. The color of the stone can be affected by the mounting, so a slightly colored stone can appear colorless when properly mounted. A yellow gold mounting also makes very slight colors almost impossible to detect. Canary diamonds benefit from a yellow cup underneath, which raises their color intensity when set.
However, color alone does not make a diamond valuable. The other Cs (carat, clarity, cut) must also be considered. A colorless diamond with a poor cut is not as valuable as an ideal cut diamond that has some color of the same size.
CLARITY – Measures a Diamond’s Purity
Clarity judges how free the diamond is from imperfections. Clarity grades range from internally flawless (IF) to fairly included (I3). The higher the clarity grade, the higher the value of the diamond (and the more rare it is). Diamonds with no (or very few) inclusions are more highly valued than those with lower clarity, both because of their rarity and their visual appearance.
Flaws in diamonds come in many forms, some almost impossible to see and some visible to the naked eye. Typical flaws are:
• Pinpoint: A small white dot on the surface of the stone
• Carbons: A small black dot on the surface of the stone
• Feathers: Small cracks within the stone<